Feature/node settings apy playground (#1677 ) (#2738 )

* initial ui for test my node use svg for node path add stories for test my node * add initial rewards calculation * update validation for rewards playground * init playground with default values * get node uptime * get mixnode reward estimation * calculate saturation calculate stake saturation * Make ComputeRewardEstParam derive Debug * set active set to be always true Co-authored-by: Jon Häggblad <jon.haggblad@gmail.com> Co-authored-by: Jon Häggblad <jon.haggblad@gmail.com>
updating changelogs
2022-12-21 12:56:40 +00:00 · 2022-12-20 12:33:20 +01:00 · 2022-12-20 12:28:13 +01:00 · 2022-12-20 12:14:05 +01:00 · 2022-12-20 12:10:21 +01:00 · 2022-12-20 12:04:24 +01:00
475 changed files with 24514 additions and 6910 deletions
@@ -5,7 +5,7 @@ on:
    - cron: '5 9 * * *'
 jobs:
  cargo-deny:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - name: Checkout repository code
        uses: actions/checkout@v2
@@ -26,7 +26,7 @@ jobs:
          path: .github/workflows/support-files/notifications/deny.message
  notification:
    needs: cargo-deny
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - name: Check out repository code
        uses: actions/checkout@v2
@@ -1,6 +1,6 @@
 [
  {
-    "os":"ubuntu-latest",
+    "os":"ubuntu-20.04",
    "rust":"stable",
    "runOnEvent":"always"
  },
@@ -6,7 +6,7 @@ on:

 jobs:
  build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - uses: actions/checkout@v2
      
@@ -10,7 +10,7 @@ on:

 jobs:
  matrix_prep:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}
    steps:
@@ -24,7 +24,7 @@ jobs:
  contracts:
    # since it's going to be compiled into wasm, there's absolutely
    # no point in running CI on different OS-es
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    continue-on-error: ${{ matrix.rust == 'nightly' }}
    needs: matrix_prep
    strategy:
@@ -13,7 +13,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest]
+        platform: [ubuntu-20.04]

    runs-on: ${{ matrix.platform }}
    steps:
@@ -5,7 +5,7 @@ on:
    - cron: '14 1 * * *'
 jobs:
  matrix_prep:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}
    steps:
@@ -25,7 +25,7 @@ jobs:
    steps:
      - name: Install Dependencies (Linux)
        run: sudo apt-get update && sudo apt-get install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev libudev-dev squashfs-tools
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-20.04'

      - name: Check out repository code
        uses: actions/checkout@v2
@@ -96,7 +96,7 @@ jobs:

      - name: Reclaim some disk space
        uses: actions-rs/cargo@v1
-        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-20.04' }}
        with:
          command: clean

@@ -160,7 +160,7 @@ jobs:

  notification:
    needs: build
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - name: Collect jobs status
        uses: technote-space/workflow-conclusion-action@v2
@@ -1,6 +1,6 @@
 [
  {
-    "os":"ubuntu-latest",
+    "os":"ubuntu-20.04",
    "rust":"stable",
    "runOnEvent":"schedule"
  },
@@ -17,7 +17,7 @@
  },

  {
-    "os":"ubuntu-latest",
+    "os":"ubuntu-20.04",
    "rust":"beta",
    "runOnEvent":"schedule"
  },
@@ -33,7 +33,7 @@
  },

  {
-    "os":"ubuntu-latest",
+    "os":"ubuntu-20.04",
    "rust":"nightly",
    "runOnEvent":"schedule"
  },
@@ -5,7 +5,7 @@ on:
    - cron: '14 2 * * *'
 jobs:
  matrix_prep:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}
    steps:
@@ -17,7 +17,7 @@ jobs:
          inputFile: '.github/workflows/nightly_build_matrix_includes.json'
          filter: '[?runOnEvent==`${{ github.event_name }}` || runOnEvent==`always`]'
  get_release:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    needs: matrix_prep
    outputs:
      output1: ${{ steps.step2.outputs.latest_release }}
@@ -38,7 +38,7 @@ jobs:
    steps:
      - name: Install Dependencies (Linux)
        run: sudo apt-get update && sudo apt-get install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev libudev-dev squashfs-tools
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-20.04'

      - name: Check out latest release branch
        uses: actions/checkout@v3
@@ -111,7 +111,7 @@ jobs:

      - name: Reclaim some disk space
        uses: actions-rs/cargo@v1
-        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-20.04' }}
        with:
          command: clean

@@ -175,7 +175,7 @@ jobs:

  notification:
    needs: [build,get_release]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - name: Collect jobs status
        uses: technote-space/workflow-conclusion-action@v2
@@ -192,7 +192,7 @@ jobs:
          NYM_PROJECT_NAME: "Nym nightly build on latest release"
          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
          GIT_COMMIT_MESSAGE: "${{ github.event.head_commit.message }}"
-          GIT_BRANCH: "https://github.com/nymtech/nym/tree/${{needs.get_release.outputs.output1}}"
+          GIT_BRANCH_NAME: "${{needs.get_release.outputs.output1}}"
          KEYBASE_NYMBOT_USERNAME: "${{ secrets.KEYBASE_NYMBOT_USERNAME }}"
          KEYBASE_NYMBOT_PAPERKEY: "${{ secrets.KEYBASE_NYMBOT_PAPERKEY }}"
          KEYBASE_NYMBOT_TEAM: "${{ secrets.KEYBASE_NYMBOT_TEAM }}"
@@ -5,7 +5,7 @@ on:
    - cron: '24 2 * * *'
 jobs:
  matrix_prep:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}
    steps:
@@ -17,7 +17,7 @@ jobs:
          inputFile: '.github/workflows/nightly_build_matrix_includes.json'
          filter: '[?runOnEvent==`${{ github.event_name }}` || runOnEvent==`always`]'
  get_release:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    needs: matrix_prep
    outputs:
      output1: ${{ steps.step2.outputs.latest_release }}
@@ -38,7 +38,7 @@ jobs:
    steps:
      - name: Install Dependencies (Linux)
        run: sudo apt-get update && sudo apt-get install libwebkit2gtk-4.0-dev build-essential curl wget libssl-dev libgtk-3-dev libudev-dev squashfs-tools
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-20.04'

      - name: Check out latest release branch
        uses: actions/checkout@v3
@@ -111,7 +111,7 @@ jobs:

      - name: Reclaim some disk space
        uses: actions-rs/cargo@v1
-        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.os == 'windows-latest' || matrix.os == 'ubuntu-20.04' }}
        with:
          command: clean

@@ -175,7 +175,7 @@ jobs:

  notification:
    needs: [build,get_release]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - name: Collect jobs status
        uses: technote-space/workflow-conclusion-action@v2
@@ -192,7 +192,7 @@ jobs:
          NYM_PROJECT_NAME: "Nym nightly build on latest release"
          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
          GIT_COMMIT_MESSAGE: "${{ github.event.head_commit.message }}"
-          GIT_BRANCH: "https://github.com/nymtech/nym/tree/${{needs.get_release.outputs.output1}}"
+          GIT_BRANCH_NAME: "${{needs.get_release.outputs.output1}}"
          KEYBASE_NYMBOT_USERNAME: "${{ secrets.KEYBASE_NYMBOT_USERNAME }}"
          KEYBASE_NYMBOT_PAPERKEY: "${{ secrets.KEYBASE_NYMBOT_PAPERKEY }}"
          KEYBASE_NYMBOT_TEAM: "${{ secrets.KEYBASE_NYMBOT_TEAM }}"
@@ -13,7 +13,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest, windows-latest, macos-latest]
+        platform: [ubuntu-20.04, windows-latest, macos-latest]

    runs-on: ${{ matrix.platform }}
    steps:
@@ -13,7 +13,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest]
+        platform: [ubuntu-20.04]

    runs-on: ${{ matrix.platform }}
    steps:
@@ -19,7 +19,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest]
+        platform: [ubuntu-20.04]

    runs-on: ${{ matrix.platform }}
    steps:
@@ -12,7 +12,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest]
+        platform: [ubuntu-20.04]

    runs-on: ${{ matrix.platform }}
    steps:
@@ -12,7 +12,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        platform: [ubuntu-latest]
+        platform: [ubuntu-20.04]
    runs-on: ${{ matrix.platform }}
    steps:
      - uses: actions/checkout@v2
@@ -12,7 +12,7 @@ defaults:
 jobs:
  test:
    name: wallet tests
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - uses: actions/checkout@v2

@@ -85,7 +85,7 @@ async function getMessageBody(context) {
            ...
          ],
          check_run_url: 'https://api.github.com/repos/nymtech/nym/check-runs/5182940024',
-          labels: [ 'ubuntu-latest' ],
+          labels: [ 'ubuntu-20.04' ],
          runner_id: 1,
          runner_name: 'Hosted Agent',
          runner_group_id: 2,
@@ -7,7 +7,7 @@ on:

 jobs:
  wasm:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
    steps:
      - uses: actions/checkout@v2

@@ -37,4 +37,5 @@ validator-config
 *.patch
 validator-api-config.toml
 dist
-storybook-static
+storybook-static
+envs/qwerty.env
@@ -2,12 +2,58 @@

 Post 1.0.0 release, the changelog format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

-## Unreleased
+## [Unreleased]

-### Added
+## [v1.1.4] (2022-12-20)

- socks5-client/network-requester: add support for socks4a protocol
+This release adds multiple Single Use Reply Blocks (SURBs) to allow arbitrarily-sized anonymized replies. 
+At the moment this is turned off by default, but available for use by application developers. 
+We will need to wait for network-requesters to upgrade to this new release, after which multi-SURB anonymization will become the default setting for the SOCKS proxy clients. 

+The release also include some additional work for distributed key generation in the Coconut signing authority nodes. 
+
+### Changed
+
+- Feature/dkg contract threshold by @neacsu in https://github.com/nymtech/nym/pull/1885
+- Multi-surbs by @jstuczyn in https://github.com/nymtech/nym/pull/2667
+- Fix multi-surb backwards compatibility in pre 1.1.4 client config files by @jstuczyn in https://github.com/nymtech/nym/pull/2703
+- fix: ignore corrupted surb storage and instead create fresh one by @jstuczyn in https://github.com/nymtech/nym/pull/2711
+- socks5: rework waiting in inbound.rs by @octol in https://github.com/nymtech/nym/pull/1880
+
+## [v1.1.3] (2022-12-13)
+
+### Changed
+
+- validator-api: can recover from shutdown during DKG process ([#1872])
+- clients: deduplicate gateway inititialization, part of work towards a rust-sdk
+- clients: keep all transmission lanes going at all times by making priority probabilistic
+- clients: ability to use multi-reply SURBs to send arbitrarily long messages fully anonymously whilst requesting additional reply blocks whenever they're about to run out ([#1796], [#1801], [#1804], [#1835], [#1858], [#1883]))
+
+### Fixed
+
+- network-requester: fix bug where websocket connection disconnect resulted in success error code
+- clients: fix a few panics handling the gateway-client
+- mixnode, gateway, validator-api: Use mainnet values as defaults for URLs and mixnet contract  ([#1884])
+- socks5: fixed bug where connections sometimes where closed too early
+- clients: improve message logging when received message fails to get reconstructed ([#1803])
+
+[#1796]: https://github.com/nymtech/nym/pull/1796
+[#1801]: https://github.com/nymtech/nym/pull/1801
+[#1803]: https://github.com/nymtech/nym/pull/1803
+[#1804]: https://github.com/nymtech/nym/pull/1804
+[#1835]: https://github.com/nymtech/nym/pull/1835
+[#1858]: https://github.com/nymtech/nym/pull/1858
+[#1872]: https://github.com/nymtech/nym/pull/1872
+[#1883]: https://github.com/nymtech/nym/pull/1883
+[#1884]: https://github.com/nymtech/nym/pull/1884
+
+## [v1.1.2]
+
+### Changed
+
+- gateway: Renamed flag from `enabled/disabled_credentials_mode` to `only-coconut-credentials`
+- "Family" feature for node families + layers
+- Initial coconut functionality including credentials and distributed key generation 

 ## [v1.1.1](https://github.com/nymtech/nym/tree/v1.1.1) (2022-11-29)

@@ -131,9 +131,9 @@ dependencies = [

 [[package]]
 name = "async-trait"
-version = "0.1.53"
+version = "0.1.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed6aa3524a2dfcf9fe180c51eae2b58738348d819517ceadf95789c51fff7600"
+checksum = "1e805d94e6b5001b651426cf4cd446b1ab5f319d27bab5c644f61de0a804360c"
 dependencies = [
 "proc-macro2",
 "quote",
@@ -586,11 +586,13 @@ dependencies = [

 [[package]]
 name = "client-core"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
+ "async-trait",
 "client-connections",
 "config",
 "crypto",
+ "dashmap 5.4.0",
 "dirs",
 "futures",
 "gateway-client",
@@ -603,11 +605,13 @@ dependencies = [
 "pemstore",
 "rand 0.7.3",
 "serde",
- "sled",
+ "serde_json",
+ "sqlx 0.6.2",
 "tap",
 "task",
 "tempfile",
 "thiserror",
+ "time 0.3.17",
 "tokio",
 "tokio-stream",
 "topology",
@@ -616,6 +620,7 @@ dependencies = [
 "wasm-bindgen",
 "wasm-bindgen-futures",
 "wasm-timer",
+ "wasm-utils",
 ]

 [[package]]
@@ -781,7 +786,7 @@ dependencies = [
 "rand 0.8.5",
 "sha2 0.10.2",
 "subtle 2.4.1",
- "time 0.3.14",
+ "time 0.3.17",
 "version_check",
 ]

@@ -924,7 +929,6 @@ dependencies = [
 name = "credential"
 version = "0.1.0"
 dependencies = [
- "async-trait",
 "bip39",
 "cfg-if 0.1.10",
 "clap 3.2.8",
@@ -936,7 +940,6 @@ dependencies = [
 "crypto",
 "network-defaults",
 "pemstore",
- "pickledb",
 "rand 0.7.3",
 "serde",
 "thiserror",
@@ -1351,6 +1354,19 @@ dependencies = [
 "num_cpus",
 ]

+[[package]]
+name = "dashmap"
+version = "5.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "907076dfda823b0b36d2a1bb5f90c96660a5bbcd7729e10727f07858f22c4edc"
+dependencies = [
+ "cfg-if 1.0.0",
+ "hashbrown 0.12.3",
+ "lock_api",
+ "once_cell",
+ "parking_lot_core 0.9.4",
+]
+
 [[package]]
 name = "der"
 version = "0.5.1"
@@ -1799,16 +1815,6 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c8cbd1169bd7b4a0a20d92b9af7a7e0422888bd38a6f5ec29c1fd8c1558a272e"

-[[package]]
-name = "fs2"
-version = "0.4.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9564fc758e15025b46aa6643b1b77d047d1a56a1aea6e01002ac0c7026876213"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "fuchsia-cprng"
 version = "0.1.1"
@@ -1921,15 +1927,6 @@ dependencies = [
 "slab",
 ]

-[[package]]
-name = "fxhash"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c31b6d751ae2c7f11320402d34e41349dd1016f8d5d45e48c4312bc8625af50c"
-dependencies = [
- "byteorder",
-]
-
 [[package]]
 name = "gateway-client"
 version = "0.1.0"
@@ -2275,13 +2272,14 @@ checksum = "7ebdb29d2ea9ed0083cd8cece49bbd968021bd99b0849edb4a9a7ee0fdf6a4e0"

 [[package]]
 name = "hidapi"
-version = "1.4.2"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d26e1151deaab68f34fbfd16d491a2a0170cf98d69d3efa23873b567a4199e1"
+checksum = "798154e4b6570af74899d71155fb0072d5b17e6aa12f39c8ef22c60fb8ec99e7"
 dependencies = [
 "cc",
 "libc",
 "pkg-config",
+ "winapi",
 ]

 [[package]]
@@ -2612,9 +2610,9 @@ dependencies = [

 [[package]]
 name = "js-sys"
-version = "0.3.55"
+version = "0.3.60"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7cc9ffccd38c451a86bf13657df244e9c3f37493cce8e5e21e940963777acc84"
+checksum = "49409df3e3bf0856b916e2ceaca09ee28e6871cf7d9ce97a692cacfdb2a25a47"
 dependencies = [
 "wasm-bindgen",
 ]
@@ -2670,7 +2668,7 @@ checksum = "fe435806c197dfeaa5efcded5e623c4b8230fd28fdf1e91e7a86e40ef2acbf90"
 dependencies = [
 "arrayref",
 "no-std-compat",
- "snafu 0.7.1",
+ "snafu",
 ]

 [[package]]
@@ -2746,12 +2744,6 @@ dependencies = [
 "vcpkg",
 ]

-[[package]]
-name = "linked-hash-map"
-version = "0.5.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fb9b38af92608140b86b693604b9ffcc5824240a484d1ecd4795bacb2fe88f3"
-
 [[package]]
 name = "lioness"
 version = "0.1.2"
@@ -2766,9 +2758,9 @@ dependencies = [

 [[package]]
 name = "lock_api"
-version = "0.4.7"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "327fa5b6a6940e4699ec49a9beae1ea4845c6bab9314e4f84ac68742139d8c53"
+checksum = "435011366fe56583b16cf956f9df0095b405b82d76425bc8981c0e22e60ec4df"
 dependencies = [
 "autocfg 1.1.0",
 "scopeguard",
@@ -2920,7 +2912,7 @@ dependencies = [
 "serde_json",
 "serde_repr",
 "thiserror",
- "time 0.3.14",
+ "time 0.3.17",
 "ts-rs",
 ]

@@ -3097,15 +3089,6 @@ dependencies = [
 "libc",
 ]

-[[package]]
-name = "num_threads"
-version = "0.1.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aba1801fb138d8e85e11d0fc70baf4fe1cdfffda7c6cd34a854905df588e5ed0"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "nym-bity-integration"
 version = "0.1.0"
@@ -3123,7 +3106,7 @@ dependencies = [

 [[package]]
 name = "nym-cli"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "anyhow",
 "base64",
@@ -3168,7 +3151,7 @@ dependencies = [
 "serde_json",
 "tap",
 "thiserror",
- "time 0.3.14",
+ "time 0.3.17",
 "toml",
 "url",
 "validator-client",
@@ -3177,7 +3160,7 @@ dependencies = [

 [[package]]
 name = "nym-client"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "clap 3.2.8",
 "client-connections",
@@ -3201,7 +3184,6 @@ dependencies = [
 "rand 0.7.3",
 "serde",
 "serde_json",
- "sled",
 "tap",
 "task",
 "thiserror",
@@ -3217,7 +3199,7 @@ dependencies = [

 [[package]]
 name = "nym-gateway"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "anyhow",
 "async-trait",
@@ -3230,7 +3212,7 @@ dependencies = [
 "config",
 "credentials",
 "crypto",
- "dashmap",
+ "dashmap 4.0.2",
 "dirs",
 "dotenv",
 "futures",
@@ -3264,7 +3246,7 @@ dependencies = [

 [[package]]
 name = "nym-mixnode"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "anyhow",
 "bs58",
@@ -3306,7 +3288,7 @@ dependencies = [

 [[package]]
 name = "nym-network-requester"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "async-trait",
 "clap 3.2.8",
@@ -3338,7 +3320,7 @@ dependencies = [

 [[package]]
 name = "nym-network-statistics"
-version = "1.0.2"
+version = "1.1.4"
 dependencies = [
 "dirs",
 "log",
@@ -3354,7 +3336,7 @@ dependencies = [

 [[package]]
 name = "nym-socks5-client"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "clap 3.2.8",
 "client-connections",
@@ -3380,7 +3362,7 @@ dependencies = [
 "proxy-helpers",
 "rand 0.7.3",
 "serde",
- "snafu 0.6.10",
+ "serde_json",
 "socks5-requests",
 "tap",
 "task",
@@ -3421,7 +3403,7 @@ dependencies = [

 [[package]]
 name = "nym-validator-api"
-version = "1.1.1"
+version = "1.1.4"
 dependencies = [
 "anyhow",
 "async-trait",
@@ -3471,7 +3453,7 @@ dependencies = [
 "tap",
 "task",
 "thiserror",
- "time 0.3.14",
+ "time 0.3.17",
 "tokio",
 "tokio-stream",
 "topology",
@@ -3544,6 +3526,7 @@ dependencies = [
 "nymsphinx-types",
 "rand 0.7.3",
 "rand_distr",
+ "thiserror",
 "tokio",
 "topology",
 ]
@@ -3569,6 +3552,7 @@ dependencies = [
 "nymsphinx-types",
 "rand 0.7.3",
 "serde",
+ "thiserror",
 ]

 [[package]]
@@ -3582,7 +3566,9 @@ dependencies = [
 "nymsphinx-types",
 "rand 0.7.3",
 "serde",
+ "thiserror",
 "topology",
+ "wasm-bindgen",
 ]

 [[package]]
@@ -3594,6 +3580,7 @@ dependencies = [
 "nymsphinx-params",
 "nymsphinx-types",
 "rand 0.7.3",
+ "thiserror",
 ]

 [[package]]
@@ -3608,6 +3595,7 @@ dependencies = [
 "nymsphinx-params",
 "nymsphinx-types",
 "rand 0.7.3",
+ "thiserror",
 "topology",
 ]

@@ -3659,9 +3647,9 @@ dependencies = [

 [[package]]
 name = "once_cell"
-version = "1.13.0"
+version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18a6dbe30758c9f83eb00cbea4ac95966305f5a7772f3f42ebfc7fc7eddbd8e1"
+checksum = "86f0b0d4bf799edbc74508c1e8bf170ff5f41238e5f8225603ca7caaae2b7860"

 [[package]]
 name = "oorandom"
@@ -3763,7 +3751,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "87f5ec2493a61ac0506c0f4199f99070cbe83857b0337006a30f3e6719b8ef58"
 dependencies = [
 "lock_api",
- "parking_lot_core 0.9.2",
+ "parking_lot_core 0.9.4",
 ]

 [[package]]
@@ -3782,15 +3770,15 @@ dependencies = [

 [[package]]
 name = "parking_lot_core"
-version = "0.9.2"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "995f667a6c822200b0433ac218e05582f0e2efa1b922a3fd2fbaadc5f87bab37"
+checksum = "4dc9e0dc2adc1c69d09143aff38d3d30c5c3f0df0dad82e6d25547af174ebec0"
 dependencies = [
 "cfg-if 1.0.0",
 "libc",
 "redox_syscall",
 "smallvec 1.8.0",
- "windows-sys 0.34.0",
+ "windows-sys 0.42.0",
 ]

 [[package]]
@@ -3935,19 +3923,6 @@ dependencies = [
 "indexmap",
 ]

-[[package]]
-name = "pickledb"
-version = "0.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9161694d67f6c5163519d42be942ae36bbdb55f439460144f105bc4f9f7d1d61"
-dependencies = [
- "bincode",
- "serde",
- "serde_cbor",
- "serde_json",
- "serde_yaml",
-]
-
 [[package]]
 name = "pin-project"
 version = "1.0.10"
@@ -4079,11 +4054,11 @@ dependencies = [

 [[package]]
 name = "proc-macro2"
-version = "1.0.37"
+version = "1.0.47"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ec757218438d5fda206afc041538b2f6d889286160d649a86a24d37e1235afd1"
+checksum = "5ea3d908b0e36316caf9e9e2c4625cdde190a7e6f440d794667ed17a1855e725"
 dependencies = [
- "unicode-xid",
+ "unicode-ident",
 ]

 [[package]]
@@ -4642,7 +4617,7 @@ dependencies = [
 "serde_json",
 "state",
 "tempfile",
- "time 0.3.14",
+ "time 0.3.17",
 "tokio",
 "tokio-stream",
 "tokio-util 0.7.3",
@@ -4704,7 +4679,7 @@ dependencies = [
 "smallvec 1.8.0",
 "stable-pattern",
 "state",
- "time 0.3.14",
+ "time 0.3.17",
 "tokio",
 "uncased",
 ]
@@ -5026,9 +5001,9 @@ dependencies = [

 [[package]]
 name = "serde_json"
-version = "1.0.83"
+version = "1.0.89"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "38dd04e3c8279e75b31ef29dbdceebfe5ad89f4d0937213c53f7d49d01b3d5a7"
+checksum = "020ff22c755c2ed3f8cf162dbb41a7268d934702f3ed3631656ea597e08fc3db"
 dependencies = [
 "itoa 1.0.1",
 "ryu",
@@ -5058,18 +5033,6 @@ dependencies = [
 "serde",
 ]

-[[package]]
-name = "serde_yaml"
-version = "0.8.23"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a4a521f2940385c165a24ee286aa8599633d162077a54bdcae2a6fd5a7bfa7a0"
-dependencies = [
- "indexmap",
- "ryu",
- "serde",
- "yaml-rust",
-]
-
 [[package]]
 name = "sha-1"
 version = "0.8.2"
@@ -5197,22 +5160,6 @@ version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eb703cfe953bccee95685111adeedb76fabe4e97549a58d16f03ea7b9367bb32"

-[[package]]
-name = "sled"
-version = "0.34.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f96b4737c2ce5987354855aed3797279def4ebf734436c6aa4552cf8e169935"
-dependencies = [
- "crc32fast",
- "crossbeam-epoch",
- "crossbeam-utils",
- "fs2",
- "fxhash",
- "libc",
- "log",
- "parking_lot 0.11.2",
-]
-
 [[package]]
 name = "smallvec"
 version = "0.6.14"
@@ -5230,40 +5177,19 @@ checksum = "f2dd574626839106c320a323308629dcb1acfc96e32a8cba364ddc61ac23ee83"

 [[package]]
 name = "snafu"
-version = "0.6.10"
+version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eab12d3c261b2308b0d80c26fffb58d17eba81a4be97890101f416b478c79ca7"
+checksum = "a152ba99b054b22972ee794cf04e5ef572da1229e33b65f3c57abbff0525a454"
 dependencies = [
 "doc-comment",
- "snafu-derive 0.6.10",
-]
-
-[[package]]
-name = "snafu"
-version = "0.7.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5177903bf45656592d9eb5c0e22f408fc023aae51dbe2088889b71633ba451f2"
-dependencies = [
- "doc-comment",
- "snafu-derive 0.7.1",
+ "snafu-derive",
 ]

 [[package]]
 name = "snafu-derive"
-version = "0.6.10"
+version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1508efa03c362e23817f96cde18abed596a25219a8b2c66e8db33c03543d315b"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "snafu-derive"
-version = "0.7.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "410b26ed97440d90ced3e2488c868d56a86e2064f5d7d6f417909b286afe25e5"
+checksum = "d5e79cdebbabaebb06a9bdbaedc7f159b410461f63611d4d0e3fb0fab8fed850"
 dependencies = [
 "heck 0.4.0",
 "proc-macro2",
@@ -5292,7 +5218,7 @@ dependencies = [
 [[package]]
 name = "sphinx"
 version = "0.1.0"
-source = "git+https://github.com/nymtech/sphinx?rev=c494250f2a78bed33a618d470792418eee932859#c494250f2a78bed33a618d470792418eee932859"
+source = "git+https://github.com/nymtech/sphinx?rev=e05a1992522ed0afd3c6fcac160313ffc9bb306a#e05a1992522ed0afd3c6fcac160313ffc9bb306a"
 dependencies = [
 "aes 0.7.5",
 "arrayref",
@@ -5650,13 +5576,13 @@ dependencies = [

 [[package]]
 name = "syn"
-version = "1.0.91"
+version = "1.0.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b683b2b825c8eef438b77c36a06dc262294da3d5a5813fac20da149241dcd44d"
+checksum = "4ae548ec36cf198c0ef7710d3c230987c2d6d7bd98ad6edc0274462724c585ce"
 dependencies = [
 "proc-macro2",
 "quote",
- "unicode-xid",
+ "unicode-ident",
 ]

 [[package]]
@@ -5700,6 +5626,8 @@ dependencies = [
 "log",
 "thiserror",
 "tokio",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
 ]

 [[package]]
@@ -5743,7 +5671,7 @@ dependencies = [
 "subtle 2.4.1",
 "subtle-encoding",
 "tendermint-proto",
- "time 0.3.14",
+ "time 0.3.17",
 "zeroize",
 ]

@@ -5776,7 +5704,7 @@ dependencies = [
 "serde",
 "serde_bytes",
 "subtle-encoding",
- "time 0.3.14",
+ "time 0.3.17",
 ]

 [[package]]
@@ -5804,7 +5732,7 @@ dependencies = [
 "tendermint-config",
 "tendermint-proto",
 "thiserror",
- "time 0.3.14",
+ "time 0.3.17",
 "tokio",
 "tracing",
 "url",
@@ -5878,22 +5806,31 @@ dependencies = [

 [[package]]
 name = "time"
-version = "0.3.14"
+version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3c3f9a28b618c3a6b9251b6908e9c99e04b9e5c02e6581ccbb67d59c34ef7f9b"
+checksum = "a561bf4617eebd33bca6434b988f39ed798e527f51a1e797d0ee4f61c0a38376"
 dependencies = [
 "itoa 1.0.1",
- "libc",
- "num_threads",
+ "js-sys",
 "serde",
+ "time-core",
 "time-macros",
 ]

 [[package]]
-name = "time-macros"
-version = "0.2.4"
+name = "time-core"
+version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "42657b1a6f4d817cda8e7a0ace261fe0cc946cf3a80314390b22cc61ae080792"
+checksum = "2e153e1f1acaef8acc537e68b44906d2db6436e2b35ac2c6b42640fff91f00fd"
+
+[[package]]
+name = "time-macros"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d967f99f534ca7e495c575c62638eebc2898a8c84c119b89e250477bc4ba16b2"
+dependencies = [
+ "time-core",
+]

 [[package]]
 name = "tinytemplate"
@@ -5907,9 +5844,9 @@ dependencies = [

 [[package]]
 name = "tokio"
-version = "1.21.2"
+version = "1.22.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a9e03c497dc955702ba729190dc4aac6f2a0ce97f913e5b1b5912fc5039d9099"
+checksum = "d76ce4a75fb488c605c54bf610f221cea8b0dafb53333c1a67e8ee199dcd2ae3"
 dependencies = [
 "autocfg 1.1.0",
 "bytes",
@@ -6121,6 +6058,7 @@ dependencies = [
 "nymsphinx-addressing",
 "nymsphinx-types",
 "rand 0.7.3",
+ "thiserror",
 "version-checker",
 ]

@@ -6380,6 +6318,12 @@ version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1a01404663e3db436ed2746d9fefef640d868edae3cceb81c3b8d5732fda678f"

+[[package]]
+name = "unicode-ident"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ceab39d59e4c9499d4e5a8ee0e2735b891bb7308ac83dfb4e80cad195c9f6f3"
+
 [[package]]
 name = "unicode-normalization"
 version = "0.1.9"
@@ -6550,7 +6494,7 @@ dependencies = [
 "rustc_version 0.4.0",
 "rustversion",
 "thiserror",
- "time 0.3.14",
+ "time 0.3.17",
 ]

 [[package]]
@@ -6568,7 +6512,7 @@ checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"

 [[package]]
 name = "vesting-contract"
-version = "1.1.0"
+version = "1.1.2"
 dependencies = [
 "contracts-common",
 "cosmwasm-std",
@@ -6823,19 +6767,6 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"

-[[package]]
-name = "windows-sys"
-version = "0.34.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5acdd78cb4ba54c0045ac14f62d8f94a03d10047904ae2a40afa1e99d8f70825"
-dependencies = [
- "windows_aarch64_msvc 0.34.0",
- "windows_i686_gnu 0.34.0",
- "windows_i686_msvc 0.34.0",
- "windows_x86_64_gnu 0.34.0",
- "windows_x86_64_msvc 0.34.0",
-]
-
 [[package]]
 name = "windows-sys"
 version = "0.36.1"
@@ -6850,10 +6781,25 @@ dependencies = [
 ]

 [[package]]
-name = "windows_aarch64_msvc"
-version = "0.34.0"
+name = "windows-sys"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "17cffbe740121affb56fad0fc0e421804adf0ae00891205213b5cecd30db881d"
+checksum = "5a3e1820f08b8513f676f7ab6c1f99ff312fb97b553d30ff4dd86f9f15728aa7"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc 0.42.0",
+ "windows_i686_gnu 0.42.0",
+ "windows_i686_msvc 0.42.0",
+ "windows_x86_64_gnu 0.42.0",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc 0.42.0",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41d2aa71f6f0cbe00ae5167d90ef3cfe66527d6f613ca78ac8024c3ccab9a19e"

 [[package]]
 name = "windows_aarch64_msvc"
@@ -6862,10 +6808,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"

 [[package]]
-name = "windows_i686_gnu"
-version = "0.34.0"
+name = "windows_aarch64_msvc"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2564fde759adb79129d9b4f54be42b32c89970c18ebf93124ca8870a498688ed"
+checksum = "dd0f252f5a35cac83d6311b2e795981f5ee6e67eb1f9a7f64eb4500fbc4dcdb4"

 [[package]]
 name = "windows_i686_gnu"
@@ -6874,10 +6820,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"

 [[package]]
-name = "windows_i686_msvc"
-version = "0.34.0"
+name = "windows_i686_gnu"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9cd9d32ba70453522332c14d38814bceeb747d80b3958676007acadd7e166956"
+checksum = "fbeae19f6716841636c28d695375df17562ca208b2b7d0dc47635a50ae6c5de7"

 [[package]]
 name = "windows_i686_msvc"
@@ -6886,10 +6832,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"

 [[package]]
-name = "windows_x86_64_gnu"
-version = "0.34.0"
+name = "windows_i686_msvc"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cfce6deae227ee8d356d19effc141a509cc503dfd1f850622ec4b0f84428e1f4"
+checksum = "84c12f65daa39dd2babe6e442988fc329d6243fdce47d7d2d155b8d874862246"

 [[package]]
 name = "windows_x86_64_gnu"
@@ -6898,10 +6844,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"

 [[package]]
-name = "windows_x86_64_msvc"
-version = "0.34.0"
+name = "windows_x86_64_gnu"
+version = "0.42.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d19538ccc21819d01deaf88d6a17eae6596a12e9aafdbb97916fb49896d89de9"
+checksum = "bf7b1b21b5362cbc318f686150e5bcea75ecedc74dd157d874d754a2ca44b0ed"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09d525d2ba30eeb3297665bd434a54297e4170c7f1a44cad4ef58095b4cd2028"

 [[package]]
 name = "windows_x86_64_msvc"
@@ -6909,6 +6861,12 @@ version = "0.36.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"

+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.42.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40009d85759725a34da6d89a94e63d7bdc50a862acf0dbc7c8e488f1edcb6f5"
+
 [[package]]
 name = "winreg"
 version = "0.10.1"
@@ -6939,15 +6897,6 @@ dependencies = [
 "zeroize",
 ]

-[[package]]
-name = "yaml-rust"
-version = "0.4.5"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
-dependencies = [
- "linked-hash-map",
-]
-
 [[package]]
 name = "yansi"
 version = "0.5.1"
@@ -1,23 +1,26 @@
 [package]
 name = "client-core"
-version = "1.1.1"
+version = "1.1.4"
 authors = ["Dave Hrycyszyn <futurechimp@users.noreply.github.com>"]
 edition = "2021"

 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

 [dependencies]
+async-trait = { version = "0.1.58" }
 dirs = "4.0"
+dashmap = "5.4.0"
 futures = "0.3"
 humantime-serde = "1.0"
 log = "0.4"
 rand = { version = "0.7.3", features = ["wasm-bindgen"] }
 serde = { version = "1.0", features = ["derive"] }
-sled = { version = "0.34", optional = true }
+serde_json = "1.0.89"
 tap = "1.0.1"
 thiserror = "1.0.34"
 url = { version ="2.2", features = ["serde"] }
-tokio = { version = "1.21.2", features = ["time", "macros"]}
+tokio = { version = "1.21.2", features = ["macros"]}
+time = "0.3.17"

 # internal
 config = { path = "../../common/config" }
@@ -37,6 +40,15 @@ task = { path = "../../common/task" }
 version = "0.1.9"
 features = ["time"]

+[target."cfg(not(target_arch = \"wasm32\"))".dependencies.tokio]
+version = "1.21.2"
+features = ["time"]
+
+[target."cfg(not(target_arch = \"wasm32\"))".dependencies.sqlx]
+version = "0.6.2"
+features = ["runtime-tokio-rustls", "sqlite", "macros", "migrate"]
+optional = true
+
 [target."cfg(target_arch = \"wasm32\")".dependencies.wasm-bindgen-futures]
 version = "0.4"

@@ -51,15 +63,23 @@ rev = "b9d1a54ad514c2f230a026afe0dde341e98cd7b6"
 version = "0.2.4"
 features = ["futures"]

-#[target."cfg(not(target_arch = \"wasm32\"))".dependencies.task]
-#path = "../../common/task"
+[target."cfg(target_arch = \"wasm32\")".dependencies.wasm-utils]
+path = "../../common/wasm-utils"
+
+[target."cfg(target_arch = \"wasm32\")".dependencies.time]
+version = "0.3.17"
+features = ["wasm-bindgen"]

 [dev-dependencies]
 tempfile = "3.1.0"

+[build-dependencies]
+tokio = { version = "1.21.2", features = ["rt-multi-thread", "macros"] }
+sqlx = { version = "0.6.2", features = ["runtime-tokio-rustls", "sqlite", "macros", "migrate"] }
+
 [features]
-default = ["reply-surb"]
+default = []
+fs-surb-storage = ["sqlx"]
 wasm = ["gateway-client/wasm"]
 coconut = ["gateway-client/coconut", "gateway-requests/coconut"]
-reply-surb = ["sled"]

@@ -0,0 +1,31 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+#[tokio::main]
+async fn main() {
+    #[cfg(feature = "fs-surb-storage")]
+    {
+        use sqlx::{Connection, SqliteConnection};
+        use std::env;
+
+        let out_dir = env::var("OUT_DIR").unwrap();
+        let database_path = format!("{}/fs-surbs-example.sqlite", out_dir);
+
+        let mut conn = SqliteConnection::connect(&format!("sqlite://{}?mode=rwc", database_path))
+            .await
+            .expect("Failed to create SQLx database connection");
+
+        sqlx::migrate!("./fs_surbs_migrations")
+            .run(&mut conn)
+            .await
+            .expect("Failed to perform SQLx migrations");
+
+        #[cfg(target_family = "unix")]
+        println!("cargo:rustc-env=DATABASE_URL=sqlite://{}", &database_path);
+
+        #[cfg(target_family = "windows")]
+        // for some strange reason we need to add a leading `/` to the windows path even though it's
+        // not a valid windows path... but hey, it works...
+        println!("cargo:rustc-env=DATABASE_URL=sqlite:///{}", &database_path);
+    }
+}
@@ -0,0 +1,40 @@
+CREATE TABLE status
+(
+    flush_in_progress        INTEGER NOT NULL,
+    previous_flush_timestamp INTEGER NOT NULL,
+    client_in_use            INTEGER NOT NULL
+);
+
+CREATE TABLE reply_surb_storage_metadata
+(
+    min_reply_surb_threshold INTEGER NOT NULL,
+    max_reply_surb_threshold INTEGER NOT NULL
+);
+
+CREATE TABLE sender_tag
+(
+    recipient BLOB NOT NULL UNIQUE,
+    tag       BLOB NOT NULL UNIQUE
+);
+
+CREATE TABLE reply_key
+(
+    key_digest        BLOB    NOT NULL UNIQUE,
+    reply_key         BLOB    NOT NULL UNIQUE,
+    sent_at_timestamp INTEGER NOT NULL
+);
+
+CREATE TABLE reply_surb_sender
+(
+    id                  INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+    last_sent_timestamp INTEGER NOT NULL,
+    tag                 BLOB    NOT NULL UNIQUE
+);
+
+CREATE TABLE reply_surb
+(
+    reply_surb_sender_id INTEGER NOT NULL,
+    reply_surb           BLOB    NOT NULL,
+
+    FOREIGN KEY (reply_surb_sender_id) REFERENCES reply_surb_sender (id)
+);
@@ -10,33 +10,37 @@ use crate::client::real_messages_control::RealMessagesController;
 use crate::client::received_buffer::{
    ReceivedBufferRequestReceiver, ReceivedBufferRequestSender, ReceivedMessagesBufferController,
 };
+use crate::client::replies::reply_controller;
+use crate::client::replies::reply_controller::{ReplyControllerReceiver, ReplyControllerSender};
+use crate::client::replies::reply_storage::{
+    CombinedReplyStorage, PersistentReplyStorage, ReplyStorageBackend, SentReplyKeys,
+};
 use crate::client::topology_control::{
    TopologyAccessor, TopologyRefresher, TopologyRefresherConfig,
 };
 use crate::config::{Config, DebugConfig, GatewayEndpointConfig};
 use crate::error::ClientCoreError;
+use crate::spawn_future;
 use client_connections::{ConnectionCommandReceiver, ConnectionCommandSender, LaneQueueLengths};
-use crypto::asymmetric::identity;
+use crypto::asymmetric::{encryption, identity};
 use futures::channel::mpsc;
 use gateway_client::bandwidth::BandwidthController;
 use gateway_client::{
    AcknowledgementReceiver, AcknowledgementSender, GatewayClient, MixnetMessageReceiver,
    MixnetMessageSender,
 };
-use log::info;
+use log::{debug, info};
+use nymsphinx::acknowledgements::AckKey;
 use nymsphinx::addressing::clients::Recipient;
 use nymsphinx::addressing::nodes::NodeIdentity;
-#[cfg(feature = "reply-surb")]
-use std::path::PathBuf;
-#[cfg(feature = "reply-surb")]
+use std::sync::Arc;
+use std::time::Duration;
 use tap::TapFallible;
 use task::{ShutdownListener, ShutdownNotifier};
 use url::Url;

-// it's fine to do this disgusting compilation flag business here as this problem
-// is going to go away in 1.2.0
-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorage;
+#[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+pub mod non_wasm_helpers;

 pub struct ClientInput {
    pub shared_lane_queue_lengths: LaneQueueLengths,
@@ -76,35 +80,36 @@ impl ClientOutputStatus {
    }
 }

-pub struct BaseClientBuilder<'a> {
+pub struct BaseClientBuilder<'a, B> {
    // due to wasm limitations I had to split it like this : (
    gateway_config: &'a GatewayEndpointConfig,
    debug_config: &'a DebugConfig,
    disabled_credentials: bool,
    validator_api_endpoints: Vec<Url>,
-
-    #[cfg(feature = "reply-surb")]
-    reply_surb_keys_store_path: PathBuf,
+    reply_storage_backend: B,

    bandwidth_controller: Option<BandwidthController>,
    key_manager: KeyManager,
 }

-impl<'a> BaseClientBuilder<'a> {
+impl<'a, B> BaseClientBuilder<'a, B>
+where
+    B: ReplyStorageBackend + Send + Sync + 'static,
+{
    pub fn new_from_base_config<T>(
        base_config: &'a Config<T>,
        key_manager: KeyManager,
        bandwidth_controller: Option<BandwidthController>,
-    ) -> BaseClientBuilder<'a> {
+        reply_storage_backend: B,
+    ) -> BaseClientBuilder<'a, B> {
        BaseClientBuilder {
            gateway_config: base_config.get_gateway_endpoint_config(),
            debug_config: base_config.get_debug_config(),
            disabled_credentials: base_config.get_disabled_credentials_mode(),
            validator_api_endpoints: base_config.get_validator_api_endpoints(),
            bandwidth_controller,
+            reply_storage_backend,
            key_manager,
-            #[cfg(feature = "reply-surb")]
-            reply_surb_keys_store_path: base_config.get_reply_encryption_key_store_path(),
        }
    }

@@ -113,19 +118,18 @@ impl<'a> BaseClientBuilder<'a> {
        debug_config: &'a DebugConfig,
        key_manager: KeyManager,
        bandwidth_controller: Option<BandwidthController>,
+        reply_storage_backend: B,
        disabled_credentials: bool,
        validator_api_endpoints: Vec<Url>,
-        #[cfg(feature = "reply-surb")] reply_surb_keys_store_path: PathBuf,
-    ) -> BaseClientBuilder<'a> {
+    ) -> BaseClientBuilder<'a, B> {
        BaseClientBuilder {
            gateway_config,
            debug_config,
            disabled_credentials,
            validator_api_endpoints,
            bandwidth_controller,
+            reply_storage_backend,
            key_manager,
-            #[cfg(feature = "reply-surb")]
-            reply_surb_keys_store_path,
        }
    }

@@ -142,7 +146,9 @@ impl<'a> BaseClientBuilder<'a> {
    // future constantly pumping loop cover traffic at some specified average rate
    // the pumped traffic goes to the MixTrafficController
    fn start_cover_traffic_stream(
-        &self,
+        debug_config: &DebugConfig,
+        ack_key: Arc<AckKey>,
+        self_address: Recipient,
        topology_accessor: TopologyAccessor,
        mix_tx: BatchMixMessageSender,
        shutdown: ShutdownListener,
@@ -150,16 +156,16 @@ impl<'a> BaseClientBuilder<'a> {
        info!("Starting loop cover traffic stream...");

        let mut stream = LoopCoverTrafficStream::new(
-            self.key_manager.ack_key(),
-            self.debug_config.average_ack_delay,
-            self.debug_config.average_packet_delay,
-            self.debug_config.loop_cover_traffic_average_delay,
+            ack_key,
+            debug_config.average_ack_delay,
+            debug_config.average_packet_delay,
+            debug_config.loop_cover_traffic_average_delay,
            mix_tx,
-            self.as_mix_recipient(),
+            self_address,
            topology_accessor,
        );

-        if let Some(size) = self.debug_config.use_extended_packet_size {
+        if let Some(size) = debug_config.use_extended_packet_size {
            log::debug!("Setting extended packet size: {:?}", size);
            stream.set_custom_packet_size(size.into());
        }
@@ -169,32 +175,18 @@ impl<'a> BaseClientBuilder<'a> {

    #[allow(clippy::too_many_arguments)]
    fn start_real_traffic_controller(
-        &self,
+        controller_config: real_messages_control::Config,
        topology_accessor: TopologyAccessor,
        ack_receiver: AcknowledgementReceiver,
        input_receiver: InputMessageReceiver,
        mix_sender: BatchMixMessageSender,
+        reply_storage: CombinedReplyStorage,
+        reply_controller_sender: ReplyControllerSender,
+        reply_controller_receiver: ReplyControllerReceiver,
        lane_queue_lengths: LaneQueueLengths,
        client_connection_rx: ConnectionCommandReceiver,
        shutdown: ShutdownListener,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
    ) {
-        let mut controller_config = real_messages_control::Config::new(
-            self.key_manager.ack_key(),
-            self.debug_config.ack_wait_multiplier,
-            self.debug_config.ack_wait_addition,
-            self.debug_config.average_ack_delay,
-            self.debug_config.message_sending_average_delay,
-            self.debug_config.average_packet_delay,
-            self.debug_config.disable_main_poisson_packet_distribution,
-            self.as_mix_recipient(),
-        );
-
-        if let Some(size) = self.debug_config.use_extended_packet_size {
-            log::debug!("Setting extended packet size: {:?}", size);
-            controller_config.set_custom_packet_size(size.into());
-        }
-
        info!("Starting real traffic stream...");

        RealMessagesController::new(
@@ -203,10 +195,11 @@ impl<'a> BaseClientBuilder<'a> {
            input_receiver,
            mix_sender,
            topology_accessor,
+            reply_storage,
+            reply_controller_sender,
+            reply_controller_receiver,
            lane_queue_lengths,
            client_connection_rx,
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage,
        )
        .start_with_shutdown(shutdown);
    }
@@ -214,19 +207,20 @@ impl<'a> BaseClientBuilder<'a> {
    // buffer controlling all messages fetched from provider
    // required so that other components would be able to use them (say the websocket)
    fn start_received_messages_buffer_controller(
-        &self,
+        local_encryption_keypair: Arc<encryption::KeyPair>,
        query_receiver: ReceivedBufferRequestReceiver,
        mixnet_receiver: MixnetMessageReceiver,
+        reply_key_storage: SentReplyKeys,
+        reply_controller_sender: ReplyControllerSender,
        shutdown: ShutdownListener,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
    ) {
        info!("Starting received messages buffer controller...");
        ReceivedMessagesBufferController::new(
-            self.key_manager.encryption_keypair(),
+            local_encryption_keypair,
            query_receiver,
            mixnet_receiver,
-            #[cfg(feature = "reply-surb")]
            reply_key_storage,
+            reply_controller_sender,
        )
        .start_with_shutdown(shutdown)
    }
@@ -236,22 +230,22 @@ impl<'a> BaseClientBuilder<'a> {
        mixnet_message_sender: MixnetMessageSender,
        ack_sender: AcknowledgementSender,
        shutdown: ShutdownListener,
-    ) -> GatewayClient {
+    ) -> Result<GatewayClient, ClientCoreError<B>> {
        let gateway_id = self.gateway_config.gateway_id.clone();
        if gateway_id.is_empty() {
-            panic!("The identity of the gateway is unknown - did you run `nym-client` init?")
+            return Err(ClientCoreError::GatewayIdUnknown);
        }
        let gateway_owner = self.gateway_config.gateway_owner.clone();
        if gateway_owner.is_empty() {
-            panic!("The owner of the gateway is unknown - did you run `nym-client` init?")
+            return Err(ClientCoreError::GatewayOwnerUnknown);
        }
        let gateway_address = self.gateway_config.gateway_listener.clone();
        if gateway_address.is_empty() {
-            panic!("The address of the gateway is unknown - did you run `nym-client` init?")
+            return Err(ClientCoreError::GatwayAddressUnknown);
        }

        let gateway_identity = identity::PublicKey::from_base58_string(gateway_id)
-            .expect("provided gateway id is invalid!");
+            .map_err(ClientCoreError::UnableToCreatePublicKeyFromGatewayId)?;

        // disgusting wasm workaround since there's no key persistence there (nor `client init`)
        let shared_key = if self.key_manager.gateway_key_set() {
@@ -270,7 +264,7 @@ impl<'a> BaseClientBuilder<'a> {
            ack_sender,
            self.debug_config.gateway_response_timeout,
            self.bandwidth_controller.take(),
-            Some(shutdown),
+            shutdown,
        );

        gateway_client.set_disabled_credentials_mode(self.disabled_credentials);
@@ -278,21 +272,23 @@ impl<'a> BaseClientBuilder<'a> {
        gateway_client
            .authenticate_and_start()
            .await
-            .expect("could not authenticate and start up the gateway connection");
-
-        gateway_client
+            .tap_err(|err| {
+                log::error!("Could not authenticate and start up the gateway connection - {err}")
+            })?;
+        Ok(gateway_client)
    }

    // future responsible for periodically polling directory server and updating
    // the current global view of topology
    async fn start_topology_refresher(
-        &mut self,
+        validator_api_urls: Vec<Url>,
+        refresh_rate: Duration,
        topology_accessor: TopologyAccessor,
        shutdown: ShutdownListener,
-    ) -> Result<(), ClientCoreError> {
+    ) -> Result<(), ClientCoreError<B>> {
        let topology_refresher_config = TopologyRefresherConfig::new(
-            self.validator_api_endpoints.clone(),
-            self.debug_config.topology_refresh_rate,
+            validator_api_urls,
+            refresh_rate,
            env!("CARGO_PKG_VERSION").to_string(),
        );
        let mut topology_refresher =
@@ -302,13 +298,12 @@ impl<'a> BaseClientBuilder<'a> {
        info!("Obtaining initial network topology");
        topology_refresher.refresh().await;

-        // TODO: a slightly more graceful termination here
-        if !topology_refresher.is_topology_routable().await {
+        if let Err(err) = topology_refresher.ensure_topology_is_routable().await {
            log::error!(
                "The current network topology seem to be insufficient to route any packets through \
-                - check if enough nodes and a gateway are online"
+                - check if enough nodes and a gateway are online - source: {err}"
            );
-            return Err(ClientCoreError::InsufficientNetworkTopology);
+            return Err(ClientCoreError::InsufficientNetworkTopology(err));
        }

        info!("Starting topology refresher...");
@@ -330,7 +325,27 @@ impl<'a> BaseClientBuilder<'a> {
        mix_tx
    }

-    pub async fn start_base(mut self) -> Result<BaseClient, ClientCoreError> {
+    async fn setup_persistent_reply_storage(
+        backend: B,
+        shutdown: ShutdownListener,
+    ) -> Result<CombinedReplyStorage, ClientCoreError<B>> {
+        let persistent_storage = PersistentReplyStorage::new(backend);
+        let mem_store = persistent_storage
+            .load_state_from_backend()
+            .await
+            .map_err(|err| ClientCoreError::SurbStorageError { source: err })?;
+
+        let store_clone = mem_store.clone();
+        spawn_future(async move {
+            persistent_storage
+                .flush_on_shutdown(store_clone, shutdown)
+                .await
+        });
+
+        Ok(mem_store)
+    }
+
+    pub async fn start_base(mut self) -> Result<BaseClient, ClientCoreError<B>> {
        info!("Starting nym client");
        // channels for inter-component communication
        // TODO: make the channels be internally created by the relevant components
@@ -351,31 +366,41 @@ impl<'a> BaseClientBuilder<'a> {
        let (ack_sender, ack_receiver) = mpsc::unbounded();
        let shared_topology_accessor = TopologyAccessor::new();

-        #[cfg(feature = "reply-surb")]
-        let reply_key_storage =
-            ReplyKeyStorage::load(&self.reply_surb_keys_store_path).tap_err(|err| {
-                log::error!("Failed to load reply key storage - is it perhaps already in use?");
-                log::error!("{:?}", err);
-            })?;
-
        // Shutdown notifier for signalling tasks to stop
        let shutdown = ShutdownNotifier::default();

+        // channels responsible for dealing with reply-related fun
+        let (reply_controller_sender, reply_controller_receiver) =
+            reply_controller::new_control_channels();
+
+        let self_address = self.as_mix_recipient();
+
        // the components are started in very specific order. Unless you know what you are doing,
        // do not change that.
-        self.start_topology_refresher(shared_topology_accessor.clone(), shutdown.subscribe())
-            .await?;
-        self.start_received_messages_buffer_controller(
-            received_buffer_request_receiver,
-            mixnet_messages_receiver,
-            shutdown.subscribe(),
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage.clone(),
-        );
-
        let gateway_client = self
            .start_gateway_client(mixnet_messages_sender, ack_sender, shutdown.subscribe())
-            .await;
+            .await?;
+
+        let reply_storage =
+            Self::setup_persistent_reply_storage(self.reply_storage_backend, shutdown.subscribe())
+                .await?;
+
+        Self::start_topology_refresher(
+            self.validator_api_endpoints.clone(),
+            self.debug_config.topology_refresh_rate,
+            shared_topology_accessor.clone(),
+            shutdown.subscribe(),
+        )
+        .await?;
+
+        Self::start_received_messages_buffer_controller(
+            self.key_manager.encryption_keypair(),
+            received_buffer_request_receiver,
+            mixnet_messages_receiver,
+            reply_storage.key_storage(),
+            reply_controller_sender.clone(),
+            shutdown.subscribe(),
+        );

        // The sphinx_message_sender is the transmitter for any component generating sphinx packets
        // that are to be sent to the mixnet. They are used by cover traffic stream and real
@@ -392,28 +417,44 @@ impl<'a> BaseClientBuilder<'a> {
        // primarily to throttle incoming connections (e.g socks5 for attached network-requesters)
        let shared_lane_queue_lengths = LaneQueueLengths::new();

-        self.start_real_traffic_controller(
+        let mut controller_config = real_messages_control::Config::new(
+            self.debug_config,
+            self.key_manager.ack_key(),
+            self_address,
+        );
+
+        if let Some(size) = self.debug_config.use_extended_packet_size {
+            log::debug!("Setting extended packet size: {:?}", size);
+            controller_config.set_custom_packet_size(size.into());
+        }
+
+        Self::start_real_traffic_controller(
+            controller_config,
            shared_topology_accessor.clone(),
            ack_receiver,
            input_receiver,
            sphinx_message_sender.clone(),
+            reply_storage,
+            reply_controller_sender,
+            reply_controller_receiver,
            shared_lane_queue_lengths.clone(),
            client_connection_rx,
            shutdown.subscribe(),
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage,
        );

        if !self.debug_config.disable_loop_cover_traffic_stream {
-            self.start_cover_traffic_stream(
+            Self::start_cover_traffic_stream(
+                self.debug_config,
+                self.key_manager.ack_key(),
+                self_address,
                shared_topology_accessor,
                sphinx_message_sender,
                shutdown.subscribe(),
            );
        }

-        info!("Client startup finished!");
-        info!("The address of this client is: {}", self.as_mix_recipient());
+        debug!("Core client startup finished!");
+        debug!("The address of this client is: {self_address}");

        Ok(BaseClient {
            client_input: ClientInputStatus::AwaitingProducer {
@@ -0,0 +1,83 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::{
+    fs_backend, CombinedReplyStorage, ReplyStorageBackend,
+};
+use crate::config::DebugConfig;
+use crate::error::ClientCoreError;
+use log::{error, info};
+use std::path::Path;
+use std::{fs, io};
+use time::OffsetDateTime;
+
+async fn setup_fresh_backend<P: AsRef<Path>>(
+    db_path: P,
+    debug_config: &DebugConfig,
+) -> Result<fs_backend::Backend, ClientCoreError<fs_backend::Backend>> {
+    info!("creating fresh surb database");
+    let mut storage_backend = match fs_backend::Backend::init(db_path).await {
+        Ok(backend) => backend,
+        Err(err) => {
+            error!("failed to setup persistent storage backend for our reply needs: {err}");
+            return Err(ClientCoreError::SurbStorageError { source: err });
+        }
+    };
+
+    // while I kinda hate that we're going to be creating `CombinedReplyStorage` twice,
+    // it will only be happening on the very first run and in practice won't incur huge
+    // costs since the storage is going to be empty
+    let mem_store = CombinedReplyStorage::new(
+        debug_config.minimum_reply_surb_storage_threshold,
+        debug_config.maximum_reply_surb_storage_threshold,
+    );
+    storage_backend
+        .init_fresh(&mem_store)
+        .await
+        .map_err(|err| ClientCoreError::SurbStorageError { source: err })?;
+
+    Ok(storage_backend)
+}
+
+fn archive_corrupted_database<P: AsRef<Path>>(db_path: P) -> io::Result<()> {
+    let db_path = db_path.as_ref();
+    debug_assert!(db_path.exists());
+
+    let now = OffsetDateTime::now_utc().unix_timestamp();
+
+    let suffix = format!("_{now}.corrupted");
+
+    let new_extension =
+        if let Some(existing_extension) = db_path.extension().and_then(|ext| ext.to_str()) {
+            format!("{existing_extension}.{}", suffix)
+        } else {
+            suffix
+        };
+
+    let mut renamed = db_path.to_owned();
+    renamed.set_extension(new_extension);
+
+    fs::rename(db_path, renamed)
+}
+
+pub async fn setup_fs_reply_surb_backend<P: AsRef<Path>>(
+    db_path: P,
+    debug_config: &DebugConfig,
+) -> Result<fs_backend::Backend, ClientCoreError<fs_backend::Backend>> {
+    // if the database file doesnt exist, initialise fresh storage, otherwise attempt to load the existing one
+    let db_path = db_path.as_ref();
+    if db_path.exists() {
+        info!("loading existing surb database");
+        match fs_backend::Backend::try_load(db_path).await {
+            Ok(backend) => Ok(backend),
+            Err(err) => {
+                error!("failed to setup persistent storage backend for our reply needs: {err}. We're going to create a fresh database instead. This behaviour might change in the future");
+
+                archive_corrupted_database(db_path)?;
+                setup_fresh_backend(db_path, debug_config).await
+            }
+        }
+    } else {
+        setup_fresh_backend(db_path, debug_config).await
+    }
+}
@@ -161,15 +161,16 @@ impl LoopCoverTrafficStream<OsRng> {
        // poisson delay, but is it really a problem?
        let topology_permit = self.topology_access.get_read_permit().await;
        // the ack is sent back to ourselves (and then ignored)
-        let topology_ref_option = topology_permit.try_get_valid_topology_ref(
+        let topology_ref = match topology_permit.try_get_valid_topology_ref(
            &self.our_full_destination,
            Some(&self.our_full_destination),
-        );
-        if topology_ref_option.is_none() {
-            warn!("No valid topology detected - won't send any loop cover message this time");
-            return;
-        }
-        let topology_ref = topology_ref_option.unwrap();
+        ) {
+            Ok(topology) => topology,
+            Err(err) => {
+                warn!("We're not going to send any loop cover message this time, as the current topology seem to be invalid - {err}");
+                return;
+            }
+        };

        let cover_message = generate_loop_cover_packet(
            &mut self.rng,
@@ -191,7 +192,7 @@ impl LoopCoverTrafficStream<OsRng> {
                    // However it's still useful to alert the user that the gateway or the link to
                    // the gateway can't keep up. Either due to insufficient bandwidth on the
                    // client side, or that the gateway is overloaded.
-                    log::warn!("Failed to send: gateway appears to not keep up");
+                    log::warn!("Failed to send sphinx packet - gateway or connection to gatway can't keep up");
                }
                TrySendError::Closed(_) => {
                    log::warn!("Failed to send cover message - channel closed");
@@ -241,19 +242,4 @@ impl LoopCoverTrafficStream<OsRng> {
            log::debug!("LoopCoverTrafficStream: Exiting");
        })
    }
-
-    pub fn start(mut self) {
-        // we should set initial delay only when we actually start the stream
-        let sampled =
-            sample_poisson_duration(&mut self.rng, self.average_cover_message_sending_delay);
-        self.set_next_delay(sampled);
-
-        spawn_future(async move {
-            debug!("Started LoopCoverTrafficStream without graceful shutdown support");
-
-            while self.next().await.is_some() {
-                self.on_new_message().await;
-            }
-        })
-    }
 }
@@ -1,40 +1,80 @@
 use client_connections::TransmissionLane;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;

 pub type InputMessageSender = tokio::sync::mpsc::Sender<InputMessage>;
 pub type InputMessageReceiver = tokio::sync::mpsc::Receiver<InputMessage>;

 #[derive(Debug)]
 pub enum InputMessage {
-    Fresh {
+    /// The simplest message variant where no additional information is attached.
+    /// You're simply sending your `data` to specified `recipient` without any tagging.
+    ///
+    /// Ends up with `NymMessage::Plain` variant
+    Regular {
        recipient: Recipient,
        data: Vec<u8>,
-        with_reply_surb: bool,
        lane: TransmissionLane,
    },
-    Reply {
-        reply_surb: ReplySurb,
+
+    /// Creates a message used for a duplex anonymous communication where the recipient
+    /// will never learn of our true identity. This is achieved by carefully sending `reply_surbs`.
+    ///
+    /// Note that if reply_surbs is set to zero then
+    /// this variant requires the client having sent some reply_surbs in the past
+    /// (and thus the recipient also knowing our sender tag).
+    ///
+    /// Ends up with `NymMessage::Repliable` variant
+    Anonymous {
+        recipient: Recipient,
        data: Vec<u8>,
+        reply_surbs: u32,
+        lane: TransmissionLane,
+    },
+
+    /// Attempt to use our internally received and stored `ReplySurb` to send the message back
+    /// to specified recipient whilst not knowing its full identity (or even gateway).
+    ///
+    /// Ends up with `NymMessage::Reply` variant
+    Reply {
+        recipient_tag: AnonymousSenderTag,
+        data: Vec<u8>,
+        lane: TransmissionLane,
    },
 }

 impl InputMessage {
-    pub fn new_fresh(
-        recipient: Recipient,
-        data: Vec<u8>,
-        with_reply_surb: bool,
-        lane: TransmissionLane,
-    ) -> Self {
-        InputMessage::Fresh {
+    pub fn new_regular(recipient: Recipient, data: Vec<u8>, lane: TransmissionLane) -> Self {
+        InputMessage::Regular {
            recipient,
            data,
-            with_reply_surb,
            lane,
        }
    }

-    pub fn new_reply(reply_surb: ReplySurb, data: Vec<u8>) -> Self {
-        InputMessage::Reply { reply_surb, data }
+    pub fn new_anonymous(
+        recipient: Recipient,
+        data: Vec<u8>,
+        reply_surbs: u32,
+        lane: TransmissionLane,
+    ) -> Self {
+        InputMessage::Anonymous {
+            recipient,
+            data,
+            reply_surbs,
+            lane,
+        }
+    }
+
+    pub fn new_reply(
+        recipient_tag: AnonymousSenderTag,
+        data: Vec<u8>,
+        lane: TransmissionLane,
+    ) -> Self {
+        InputMessage::Reply {
+            recipient_tag,
+            data,
+            lane,
+        }
    }
 }
@@ -91,14 +91,4 @@ impl MixTrafficController {
            log::debug!("MixTrafficController: Exiting");
        })
    }
-
-    pub fn start(mut self) {
-        spawn_future(async move {
-            debug!("Started MixTrafficController without graceful shutdown support");
-
-            while let Some(mix_packets) = self.mix_rx.recv().await {
-                self.on_messages(mix_packets).await;
-            }
-        })
-    }
 }
@@ -8,6 +8,5 @@ pub mod key_manager;
 pub mod mix_traffic;
 pub mod real_messages_control;
 pub mod received_buffer;
-#[cfg(feature = "reply-surb")]
-pub mod reply_key_storage;
+pub mod replies;
 pub mod topology_control;
@@ -1,7 +1,7 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use super::action_controller::{Action, ActionSender};
+use super::action_controller::{AckActionSender, Action};
 use futures::StreamExt;
 use gateway_client::AcknowledgementReceiver;
 use log::*;
@@ -16,14 +16,14 @@ use std::sync::Arc;
 pub(super) struct AcknowledgementListener {
    ack_key: Arc<AckKey>,
    ack_receiver: AcknowledgementReceiver,
-    action_sender: ActionSender,
+    action_sender: AckActionSender,
 }

 impl AcknowledgementListener {
    pub(super) fn new(
        ack_key: Arc<AckKey>,
        ack_receiver: AcknowledgementReceiver,
-        action_sender: ActionSender,
+        action_sender: AckActionSender,
    ) -> Self {
        AcknowledgementListener {
            ack_key,
@@ -49,11 +49,6 @@ impl AcknowledgementListener {
        if frag_id == COVER_FRAG_ID {
            trace!("Received an ack for a cover message - no need to do anything");
            return;
-        } else if frag_id.is_reply() {
-            info!("Received an ack for a reply message - no need to do anything! (don't know what to do!)");
-            // TODO: probably there will need to be some extra procedure here, something to notify
-            // user that his reply reached the recipient (since we got an ack)
-            return;
        }

        trace!("Received {} from the mix network", frag_id);
@@ -90,14 +85,4 @@ impl AcknowledgementListener {
        shutdown.recv_timeout().await;
        log::debug!("AcknowledgementListener: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started AcknowledgementListener without graceful shutdown support");
-
-        while let Some(acks) = self.ack_receiver.next().await {
-            self.handle_ack_receiver_item(acks).await
-        }
-    }
 }
@@ -3,7 +3,7 @@

 use super::PendingAcknowledgement;
 use crate::client::real_messages_control::acknowledgement_control::RetransmissionRequestSender;
-use futures::channel::mpsc::{self, UnboundedReceiver, UnboundedSender};
+use futures::channel::mpsc;
 use futures::StreamExt;
 use log::*;
 use nonexhaustive_delayqueue::{Expired, NonExhaustiveDelayQueue, QueueKey};
@@ -13,7 +13,8 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use std::time::Duration;

-pub(crate) type ActionSender = UnboundedSender<Action>;
+pub(crate) type AckActionSender = mpsc::UnboundedSender<Action>;
+pub(crate) type AckActionReceiver = mpsc::UnboundedReceiver<Action>;

 // The actual data being sent off as well as potential key to the delay queue
 type PendingAckEntry = (Arc<PendingAcknowledgement>, Option<QueueKey>);
@@ -95,7 +96,7 @@ pub(super) struct ActionController {
    pending_acks_timers: NonExhaustiveDelayQueue<FragmentIdentifier>,

    /// Channel for receiving `Action`s from other modules.
-    incoming_actions: UnboundedReceiver<Action>,
+    incoming_actions: AckActionReceiver,

    /// Channel for notifying `RetransmissionRequestListener` about expired acknowledgements.
    retransmission_sender: RetransmissionRequestSender,
@@ -105,18 +106,15 @@ impl ActionController {
    pub(super) fn new(
        config: Config,
        retransmission_sender: RetransmissionRequestSender,
-    ) -> (Self, ActionSender) {
-        let (sender, receiver) = mpsc::unbounded();
-        (
-            ActionController {
-                config,
-                pending_acks_data: HashMap::new(),
-                pending_acks_timers: NonExhaustiveDelayQueue::new(),
-                incoming_actions: receiver,
-                retransmission_sender,
-            },
-            sender,
-        )
+        incoming_actions: AckActionReceiver,
+    ) -> Self {
+        ActionController {
+            config,
+            pending_acks_data: HashMap::new(),
+            pending_acks_timers: NonExhaustiveDelayQueue::new(),
+            incoming_actions,
+            retransmission_sender,
+        }
    }

    fn handle_insert(&mut self, pending_acks: Vec<PendingAcknowledgement>) {
@@ -138,13 +136,18 @@ impl ActionController {
        trace!("{} is starting its timer", frag_id);

        if let Some((pending_ack_data, queue_key)) = self.pending_acks_data.get_mut(&frag_id) {
-            if queue_key.is_some() {
-                // this branch should be IMPOSSIBLE under ANY condition. It would imply starting
-                // timer TWICE for the SAME PendingAcknowledgement
-                panic!("Tried to start an already started ack timer!")
-            }
-            let timeout = (pending_ack_data.delay.clone() * self.config.ack_wait_multiplier)
-                .to_duration()
+            // the fact that this branch is now POSSIBLE is a sign of a need to refactor this whole
+            // retransmission procedure
+            //
+            // (it can happen as timer is started when ack expires to make sure it's not stuck in memory
+            // and the second instance can be fired when we finally get reply surbs for data we failed to retransmit)
+
+            // if queue_key.is_some() {
+            //     // this branch should be IMPOSSIBLE under ANY condition. It would imply starting
+            //     // timer TWICE for the SAME PendingAcknowledgement
+            //     panic!("Tried to start an already started ack timer!")
+            // }
+            let timeout = (pending_ack_data.delay * self.config.ack_wait_multiplier).to_duration()
                + self.config.ack_wait_addition;

            let new_queue_key = self.pending_acks_timers.insert(frag_id, timeout);
@@ -192,7 +195,8 @@ impl ActionController {
        trace!("{} is updating its delay", frag_id);
        // TODO: is it possible to solve this without either locking or temporarily removing the value?
        if let Some((pending_ack_data, queue_key)) = self.pending_acks_data.remove(&frag_id) {
-            // this Action is triggered by `RetransmissionRequestListener` which held the other potential
+            // this Action is triggered by `RetransmissionRequestListener` (for 'normal' packets)
+            // or `ReplyController` (for 'reply' packets) which held the other potential
            // reference to this Arc. HOWEVER, before the Action was pushed onto the queue, the reference
            // was dropped hence this unwrap is safe.
            let mut inner_data = Arc::try_unwrap(pending_ack_data).unwrap();
@@ -277,17 +281,4 @@ impl ActionController {
            .expect("Task stopped without shutdown called");
        log::debug!("ActionController: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started ActionController without graceful shutdown support");
-
-        loop {
-            tokio::select! {
-                action = self.incoming_actions.next() => self.process_action(action.unwrap()),
-                expired_ack = self.pending_acks_timers.next() => self.handle_expired_ack_timer(expired_ack.unwrap())
-            }
-        }
-    }
 }
@@ -1,23 +1,14 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use super::action_controller::{Action, ActionSender};
-use super::PendingAcknowledgement;
-use crate::client::{
-    inbound_messages::{InputMessage, InputMessageReceiver},
-    real_messages_control::real_traffic_stream::{BatchRealMessageSender, RealMessage},
-    topology_control::TopologyAccessor,
-};
+use crate::client::inbound_messages::{InputMessage, InputMessageReceiver};
+use crate::client::real_messages_control::message_handler::MessageHandler;
+use crate::client::replies::reply_controller::ReplyControllerSender;
 use client_connections::TransmissionLane;
 use log::*;
-use nymsphinx::anonymous_replies::ReplySurb;
-use nymsphinx::preparer::MessagePreparer;
-use nymsphinx::{acknowledgements::AckKey, addressing::clients::Recipient};
+use nymsphinx::addressing::clients::Recipient;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use rand::{CryptoRng, Rng};
-use std::sync::Arc;
-
-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorage;

 /// Module responsible for dealing with the received messages: splitting them, creating acknowledgements,
 /// putting everything into sphinx packets, etc.
@@ -26,15 +17,9 @@ pub(super) struct InputMessageListener<R>
 where
    R: CryptoRng + Rng,
 {
-    ack_key: Arc<AckKey>,
-    ack_recipient: Recipient,
    input_receiver: InputMessageReceiver,
-    message_preparer: MessagePreparer<R>,
-    action_sender: ActionSender,
-    real_message_sender: BatchRealMessageSender,
-    topology_access: TopologyAccessor,
-    #[cfg(feature = "reply-surb")]
-    reply_key_storage: ReplyKeyStorage,
+    message_handler: MessageHandler<R>,
+    reply_controller_sender: ReplyControllerSender,
 }

 impl<R> InputMessageListener<R>
@@ -45,153 +30,83 @@ where
    // some considerable refactoring
    #[allow(clippy::too_many_arguments)]
    pub(super) fn new(
-        ack_key: Arc<AckKey>,
-        ack_recipient: Recipient,
        input_receiver: InputMessageReceiver,
-        message_preparer: MessagePreparer<R>,
-        action_sender: ActionSender,
-        real_message_sender: BatchRealMessageSender,
-        topology_access: TopologyAccessor,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
+        message_handler: MessageHandler<R>,
+        reply_controller_sender: ReplyControllerSender,
    ) -> Self {
        InputMessageListener {
-            ack_key,
-            ack_recipient,
            input_receiver,
-            message_preparer,
-            action_sender,
-            real_message_sender,
-            topology_access,
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage,
+            message_handler,
+            reply_controller_sender,
        }
    }

-    // we require topology for replies to generate surb_acks
-    async fn handle_reply(&mut self, reply_surb: ReplySurb, data: Vec<u8>) -> Option<RealMessage> {
-        let topology_permit = self.topology_access.get_read_permit().await;
-        let topology = match topology_permit.try_get_valid_topology_ref(&self.ack_recipient, None) {
-            Some(topology_ref) => topology_ref,
-            None => {
-                warn!("Could not process the message - the network topology is invalid");
-                return None;
-            }
-        };
-
-        match self
-            .message_preparer
-            .prepare_reply_for_use(data, reply_surb, topology, &self.ack_key)
-            .await
-        {
-            Ok((mix_packet, reply_id)) => {
-                // TODO: later probably write pending ack here
-                // and deal with them....
-                // ... somehow
-                Some(RealMessage::new(mix_packet, reply_id))
-            }
-            Err(err) => {
-                // TODO: should we have some mechanism to indicate to the user that the `reply_surb`
-                // could be reused since technically it wasn't used up here?
-                warn!("failed to deal with received reply surb - {:?}", err);
-                None
-            }
-        }
+    async fn handle_reply(
+        &mut self,
+        recipient_tag: AnonymousSenderTag,
+        data: Vec<u8>,
+        lane: TransmissionLane,
+    ) {
+        // offload reply handling to the dedicated task
+        self.reply_controller_sender
+            .send_reply(recipient_tag, data, lane)
    }

-    async fn handle_fresh_message(
+    async fn handle_plain_message(
        &mut self,
        recipient: Recipient,
        content: Vec<u8>,
-        with_reply_surb: bool,
-    ) -> Option<Vec<RealMessage>> {
-        log::trace!("handling msg size: {}", content.len());
-        let topology_permit = self.topology_access.get_read_permit().await;
-        let topology = match topology_permit
-            .try_get_valid_topology_ref(&self.ack_recipient, Some(&recipient))
+        lane: TransmissionLane,
+    ) {
+        if let Err(err) = self
+            .message_handler
+            .try_send_plain_message(recipient, content, lane)
+            .await
        {
-            Some(topology_ref) => topology_ref,
-            None => {
-                warn!("Could not process the message - the network topology is invalid");
-                return None;
-            }
-        };
-
-        // split the message, attach optional reply surb
-        let (split_message, reply_key) = self
-            .message_preparer
-            .prepare_and_split_message(content, with_reply_surb, topology)
-            .expect("somehow the topology was invalid after all!");
-
-        #[cfg(feature = "reply-surb")]
-        if let Some(reply_key) = reply_key {
-            self.reply_key_storage
-                .insert_encryption_key(reply_key)
-                .expect("Failed to insert surb reply key to the store!")
+            warn!("failed to send a plain message - {err}")
        }
+    }

-        #[cfg(not(feature = "reply-surb"))]
-        let _reply_key = reply_key;
-
-        // encrypt chunks, put them inside sphinx packets and generate acks
-        let mut pending_acks = Vec::with_capacity(split_message.len());
-        let mut real_messages = Vec::with_capacity(split_message.len());
-        for message_chunk in split_message {
-            // we need to clone it because we need to keep it in memory in case we had to retransmit
-            // it. And then we'd need to recreate entire ACK again.
-            let chunk_clone = message_chunk.clone();
-            let prepared_fragment = self
-                .message_preparer
-                .prepare_chunk_for_sending(chunk_clone, topology, &self.ack_key, &recipient)
-                .unwrap();
-
-            real_messages.push(RealMessage::new(
-                prepared_fragment.mix_packet,
-                message_chunk.fragment_identifier(),
-            ));
-
-            pending_acks.push(PendingAcknowledgement::new(
-                message_chunk,
-                prepared_fragment.total_delay,
-                recipient,
-            ));
+    async fn handle_repliable_message(
+        &mut self,
+        recipient: Recipient,
+        content: Vec<u8>,
+        reply_surbs: u32,
+        lane: TransmissionLane,
+    ) {
+        if let Err(err) = self
+            .message_handler
+            .try_send_message_with_reply_surbs(recipient, content, reply_surbs, lane)
+            .await
+        {
+            warn!("failed to send a repliable message - {err}")
        }
-
-        // tells the controller to put this into the hashmap
-        self.action_sender
-            .unbounded_send(Action::new_insert(pending_acks))
-            .unwrap();
-
-        Some(real_messages)
    }

    async fn on_input_message(&mut self, msg: InputMessage) {
-        let (real_messages, lane) = match msg {
-            InputMessage::Fresh {
+        match msg {
+            InputMessage::Regular {
                recipient,
                data,
-                with_reply_surb,
                lane,
-            } => (
-                self.handle_fresh_message(recipient, data, with_reply_surb)
-                    .await,
+            } => self.handle_plain_message(recipient, data, lane).await,
+            InputMessage::Anonymous {
+                recipient,
+                data,
+                reply_surbs,
                lane,
-            ),
-            InputMessage::Reply { reply_surb, data } => (
-                self.handle_reply(reply_surb, data)
+            } => {
+                self.handle_repliable_message(recipient, data, reply_surbs, lane)
                    .await
-                    .map(|message| vec![message]),
-                TransmissionLane::Reply,
-            ),
+            }
+            InputMessage::Reply {
+                recipient_tag,
+                data,
+                lane,
+            } => {
+                self.handle_reply(recipient_tag, data, lane).await;
+            }
        };
-
-        // there's no point in trying to send nothing
-        if let Some(real_messages) = real_messages {
-            // tells real message sender (with the poisson timer) to send this to the mix network
-            self.real_message_sender
-                .send((real_messages, lane))
-                .await
-                .expect("BatchRealMessageReceiver has stopped receiving!");
-        }
    }

    pub(super) async fn run_with_shutdown(&mut self, mut shutdown: task::ShutdownListener) {
@@ -216,13 +131,4 @@ where
        shutdown.recv_timeout().await;
        log::debug!("InputMessageListener: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started InputMessageListener without graceful shutdown support");
-        while let Some(input_msg) = self.input_receiver.recv().await {
-            self.on_input_message(input_msg).await;
-        }
-    }
 }
@@ -7,18 +7,20 @@ use self::{
    retransmission_request_listener::RetransmissionRequestListener,
    sent_notification_listener::SentNotificationListener,
 };
-use super::real_traffic_stream::BatchRealMessageSender;
-use crate::client::{inbound_messages::InputMessageReceiver, topology_control::TopologyAccessor};
+use crate::client::inbound_messages::InputMessageReceiver;
+use crate::client::real_messages_control::message_handler::MessageHandler;
+use crate::client::replies::reply_controller::ReplyControllerSender;
 use crate::spawn_future;
+use action_controller::AckActionReceiver;
 use futures::channel::mpsc;
 use gateway_client::AcknowledgementReceiver;
 use log::*;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use nymsphinx::params::PacketSize;
 use nymsphinx::{
    acknowledgements::AckKey,
    addressing::clients::Recipient,
    chunking::fragment::{Fragment, FragmentIdentifier},
-    preparer::MessagePreparer,
    Delay as SphinxDelay,
 };
 use rand::{CryptoRng, Rng};
@@ -27,8 +29,7 @@ use std::{
    time::Duration,
 };

-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorage;
+pub(crate) use action_controller::{AckActionSender, Action};

 mod acknowledgement_listener;
 mod action_controller;
@@ -50,24 +51,64 @@ pub(super) type SentPacketNotificationSender = mpsc::UnboundedSender<FragmentIde
 /// that it is about to be sent to the mix network and its timeout timer should be started.
 type SentPacketNotificationReceiver = mpsc::UnboundedReceiver<FragmentIdentifier>;

+#[derive(Debug)]
+pub(crate) enum PacketDestination {
+    Anonymous {
+        recipient_tag: AnonymousSenderTag,
+        // special flag to indicate whether this was an ack for requesting additional surbs,
+        // in that case we have to do everything we can to get it through, even if it means going
+        // below our stored reply surb threshold
+        extra_surb_request: bool,
+    },
+    KnownRecipient(Box<Recipient>),
+}
+
 /// Structure representing a data `Fragment` that is on-route to the specified `Recipient`
 #[derive(Debug)]
 pub(crate) struct PendingAcknowledgement {
    message_chunk: Fragment,
    delay: SphinxDelay,
-    recipient: Recipient,
+    destination: PacketDestination,
 }

 impl PendingAcknowledgement {
    /// Creates new instance of `PendingAcknowledgement` using the provided data.
-    fn new(message_chunk: Fragment, delay: SphinxDelay, recipient: Recipient) -> Self {
+    pub(crate) fn new_known(
+        message_chunk: Fragment,
+        delay: SphinxDelay,
+        recipient: Recipient,
+    ) -> Self {
        PendingAcknowledgement {
            message_chunk,
            delay,
-            recipient,
+            destination: PacketDestination::KnownRecipient(recipient.into()),
        }
    }

+    pub(crate) fn new_anonymous(
+        message_chunk: Fragment,
+        delay: SphinxDelay,
+        recipient_tag: AnonymousSenderTag,
+        extra_surb_request: bool,
+    ) -> Self {
+        PendingAcknowledgement {
+            message_chunk,
+            delay,
+            destination: PacketDestination::Anonymous {
+                recipient_tag,
+                extra_surb_request,
+            },
+        }
+    }
+
+    pub(crate) fn inner_fragment_identifier(&self) -> FragmentIdentifier {
+        self.message_chunk.fragment_identifier()
+    }
+
+    pub(crate) fn fragment_data(&self) -> Fragment {
+        self.message_chunk.clone()
+    }
+
    fn update_delay(&mut self, new_delay: SphinxDelay) {
        self.delay = new_delay;
    }
@@ -76,10 +117,6 @@ impl PendingAcknowledgement {
 /// AcknowledgementControllerConnectors represents set of channels for communication with
 /// other parts of the system in order to support acknowledgements and retransmission.
 pub(super) struct AcknowledgementControllerConnectors {
-    /// Channel used for forwarding prepared sphinx messages into the poisson sender
-    /// to be sent to the mix network.
-    real_message_sender: BatchRealMessageSender,
-
    /// Channel used for receiving raw messages from a client. The messages need to be put
    /// into sphinx packets first.
    input_receiver: InputMessageReceiver,
@@ -91,20 +128,28 @@ pub(super) struct AcknowledgementControllerConnectors {

    /// Channel used for receiving acknowledgements from the mix network.
    ack_receiver: AcknowledgementReceiver,
+
+    /// Channel used for sending request to `ActionController` to deal with anything ack-related,
+    ack_action_sender: AckActionSender,
+
+    /// Channel used for receiving request by `ActionController` to deal with anything ack-related,
+    ack_action_receiver: AckActionReceiver,
 }

 impl AcknowledgementControllerConnectors {
    pub(super) fn new(
-        real_message_sender: BatchRealMessageSender,
        input_receiver: InputMessageReceiver,
        sent_notifier: SentPacketNotificationReceiver,
        ack_receiver: AcknowledgementReceiver,
+        ack_action_sender: AckActionSender,
+        ack_action_receiver: AckActionReceiver,
    ) -> Self {
        AcknowledgementControllerConnectors {
-            real_message_sender,
            input_receiver,
            sent_notifier,
            ack_receiver,
+            ack_action_sender,
+            ack_action_receiver,
        }
    }
 }
@@ -117,28 +162,15 @@ pub(super) struct Config {
    /// Given ack timeout in the form a * BASE_DELAY + b, it specifies the multiplier `a`
    ack_wait_multiplier: f64,

-    /// Average delay an acknowledgement packet is going to get delayed at a single mixnode.
-    average_ack_delay: Duration,
-
-    /// Average delay a data packet is going to get delayed at a single mixnode.
-    average_packet_delay: Duration,
-
    /// Predefined packet size used for the encapsulated messages.
    packet_size: PacketSize,
 }

 impl Config {
-    pub(super) fn new(
-        ack_wait_addition: Duration,
-        ack_wait_multiplier: f64,
-        average_ack_delay: Duration,
-        average_packet_delay: Duration,
-    ) -> Self {
+    pub(super) fn new(ack_wait_addition: Duration, ack_wait_multiplier: f64) -> Self {
        Config {
            ack_wait_addition,
            ack_wait_multiplier,
-            average_ack_delay,
-            average_packet_delay,
            packet_size: Default::default(),
        }
    }
@@ -162,68 +194,51 @@ where

 impl<R> AcknowledgementController<R>
 where
-    R: 'static + CryptoRng + Rng + Clone + Send,
+    R: 'static + CryptoRng + Rng + Clone + Send + Sync,
 {
-    #[allow(clippy::too_many_arguments)]
    pub(super) fn new(
        config: Config,
-        rng: R,
-        topology_access: TopologyAccessor,
        ack_key: Arc<AckKey>,
-        ack_recipient: Recipient,
        connectors: AcknowledgementControllerConnectors,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
+        message_handler: MessageHandler<R>,
+        reply_controller_sender: ReplyControllerSender,
    ) -> Self {
        let (retransmission_tx, retransmission_rx) = mpsc::unbounded();

        let action_config =
            action_controller::Config::new(config.ack_wait_addition, config.ack_wait_multiplier);
-        let (action_controller, action_sender) =
-            ActionController::new(action_config, retransmission_tx);
-
-        let message_preparer = MessagePreparer::new(
-            rng,
-            ack_recipient,
-            config.average_packet_delay,
-            config.average_ack_delay,
-        )
-        .with_custom_real_message_packet_size(config.packet_size);
+        let action_controller = ActionController::new(
+            action_config,
+            retransmission_tx,
+            connectors.ack_action_receiver,
+        );

        // will listen for any acks coming from the network
        let acknowledgement_listener = AcknowledgementListener::new(
            Arc::clone(&ack_key),
            connectors.ack_receiver,
-            action_sender.clone(),
+            connectors.ack_action_sender.clone(),
        );

        // will listen for any new messages from the client
        let input_message_listener = InputMessageListener::new(
-            Arc::clone(&ack_key),
-            ack_recipient,
            connectors.input_receiver,
-            message_preparer.clone(),
-            action_sender.clone(),
-            connectors.real_message_sender.clone(),
-            topology_access.clone(),
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage,
+            message_handler.clone(),
+            reply_controller_sender.clone(),
        );

        // will listen for any ack timeouts and trigger retransmission
        let retransmission_request_listener = RetransmissionRequestListener::new(
-            Arc::clone(&ack_key),
-            ack_recipient,
-            message_preparer,
-            action_sender.clone(),
-            connectors.real_message_sender,
+            connectors.ack_action_sender.clone(),
+            message_handler,
            retransmission_rx,
-            topology_access,
+            reply_controller_sender,
        );

        // will listen for events indicating the packet was sent through the network so that
        // the retransmission timer should be started.
        let sent_notification_listener =
-            SentNotificationListener::new(connectors.sent_notifier, action_sender);
+            SentNotificationListener::new(connectors.sent_notifier, connectors.ack_action_sender);

        AcknowledgementController {
            acknowledgement_listener,
@@ -278,35 +293,4 @@ where
            debug!("The controller has finished execution!");
        });
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) fn start(self) {
-        let mut acknowledgement_listener = self.acknowledgement_listener;
-        let mut input_message_listener = self.input_message_listener;
-        let mut retransmission_request_listener = self.retransmission_request_listener;
-        let mut sent_notification_listener = self.sent_notification_listener;
-        let mut action_controller = self.action_controller;
-
-        spawn_future(async move {
-            acknowledgement_listener.run().await;
-            error!("The acknowledgement listener has finished execution!");
-        });
-        spawn_future(async move {
-            input_message_listener.run().await;
-            error!("The input listener has finished execution!");
-        });
-        spawn_future(async move {
-            retransmission_request_listener.run().await;
-            error!("The retransmission request listener has finished execution!");
-        });
-        spawn_future(async move {
-            sent_notification_listener.run().await;
-            error!("The sent notification listener has finished execution!");
-        });
-        spawn_future(async move {
-            action_controller.run().await;
-            error!("The controller has finished execution!");
-        });
-    }
 }
@@ -1,82 +1,101 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 use super::{
-    action_controller::{Action, ActionSender},
+    action_controller::{AckActionSender, Action},
    PendingAcknowledgement, RetransmissionRequestReceiver,
 };
-use crate::client::{
-    real_messages_control::real_traffic_stream::{BatchRealMessageSender, RealMessage},
-    topology_control::TopologyAccessor,
-};
-
+use crate::client::real_messages_control::acknowledgement_control::PacketDestination;
+use crate::client::real_messages_control::message_handler::{MessageHandler, PreparationError};
+use crate::client::real_messages_control::real_traffic_stream::RealMessage;
+use crate::client::replies::reply_controller::ReplyControllerSender;
 use client_connections::TransmissionLane;
 use futures::StreamExt;
 use log::*;
-use nymsphinx::{
-    acknowledgements::AckKey, addressing::clients::Recipient, preparer::MessagePreparer,
-};
+use nymsphinx::addressing::clients::Recipient;
+use nymsphinx::chunking::fragment::Fragment;
+use nymsphinx::preparer::PreparedFragment;
 use rand::{CryptoRng, Rng};
 use std::sync::{Arc, Weak};

 // responsible for packet retransmission upon fired timer
-pub(super) struct RetransmissionRequestListener<R>
-where
-    R: CryptoRng + Rng,
-{
-    ack_key: Arc<AckKey>,
-    ack_recipient: Recipient,
-    message_preparer: MessagePreparer<R>,
-    action_sender: ActionSender,
-    real_message_sender: BatchRealMessageSender,
+pub(super) struct RetransmissionRequestListener<R> {
+    action_sender: AckActionSender,
+    message_handler: MessageHandler<R>,
    request_receiver: RetransmissionRequestReceiver,
-    topology_access: TopologyAccessor,
+    reply_controller_sender: ReplyControllerSender,
 }

 impl<R> RetransmissionRequestListener<R>
 where
    R: CryptoRng + Rng,
 {
-    #[allow(clippy::too_many_arguments)]
    pub(super) fn new(
-        ack_key: Arc<AckKey>,
-        ack_recipient: Recipient,
-        message_preparer: MessagePreparer<R>,
-        action_sender: ActionSender,
-        real_message_sender: BatchRealMessageSender,
+        action_sender: AckActionSender,
+        message_handler: MessageHandler<R>,
        request_receiver: RetransmissionRequestReceiver,
-        topology_access: TopologyAccessor,
+        reply_controller_sender: ReplyControllerSender,
    ) -> Self {
        RetransmissionRequestListener {
-            ack_key,
-            ack_recipient,
-            message_preparer,
            action_sender,
-            real_message_sender,
+            message_handler,
            request_receiver,
-            topology_access,
+            reply_controller_sender,
        }
    }

-    async fn on_retransmission_request(&mut self, timed_out_ack: Weak<PendingAcknowledgement>) {
-        let timed_out_ack = match timed_out_ack.upgrade() {
+    async fn prepare_normal_retransmission_chunk(
+        &mut self,
+        packet_recipient: Recipient,
+        chunk_data: Fragment,
+    ) -> Result<PreparedFragment, PreparationError> {
+        debug!("retransmitting normal packet...");
+
+        self.message_handler
+            .try_prepare_single_chunk_for_sending(packet_recipient, chunk_data)
+            .await
+    }
+
+    async fn on_retransmission_request(
+        &mut self,
+        weak_timed_out_ack: Weak<PendingAcknowledgement>,
+    ) {
+        let timed_out_ack = match weak_timed_out_ack.upgrade() {
            Some(timed_out_ack) => timed_out_ack,
            None => {
                debug!("We received an ack JUST as we were about to retransmit [1]");
                return;
            }
        };
-        let packet_recipient = &timed_out_ack.recipient;
-        let chunk_clone = timed_out_ack.message_chunk.clone();
-        let frag_id = chunk_clone.fragment_identifier();

-        let topology_permit = self.topology_access.get_read_permit().await;
-        let topology_ref = match topology_permit
-            .try_get_valid_topology_ref(&self.ack_recipient, Some(packet_recipient))
-        {
-            Some(topology_ref) => topology_ref,
-            None => {
-                warn!("Could not retransmit the packet - the network topology is invalid");
+        let maybe_prepared_fragment = match &timed_out_ack.destination {
+            PacketDestination::Anonymous {
+                recipient_tag,
+                extra_surb_request,
+            } => {
+                // if this is retransmission for reply, offload it to the dedicated task
+                // that deals with all the surbs
+                return self.reply_controller_sender.send_retransmission_data(
+                    *recipient_tag,
+                    weak_timed_out_ack,
+                    *extra_surb_request,
+                );
+            }
+            PacketDestination::KnownRecipient(recipient) => {
+                self.prepare_normal_retransmission_chunk(
+                    **recipient,
+                    timed_out_ack.message_chunk.clone(),
+                )
+                .await
+            }
+        };
+
+        let frag_id = timed_out_ack.message_chunk.fragment_identifier();
+
+        let prepared_fragment = match maybe_prepared_fragment {
+            Ok(prepared_fragment) => prepared_fragment,
+            Err(err) => {
+                warn!("Could not retransmit the packet - {err}");
                // we NEED to start timer here otherwise we will have this guy permanently stuck in memory
                self.action_sender
                    .unbounded_send(Action::new_start_timer(frag_id))
@@ -85,11 +104,6 @@ where
            }
        };

-        let prepared_fragment = self
-            .message_preparer
-            .prepare_chunk_for_sending(chunk_clone, topology_ref, &self.ack_key, packet_recipient)
-            .unwrap();
-
        // if we have the ONLY strong reference to the ack data, it means it was removed from the
        // pending acks
        if Arc::strong_count(&timed_out_ack) == 1 {
@@ -101,7 +115,6 @@ where
        // we no longer need the reference - let's drop it so that if somehow `UpdateTimer` action
        // reached the controller before this function terminated, the controller would not panic.
        drop(timed_out_ack);
-
        let new_delay = prepared_fragment.total_delay;

        // We know this update will be reflected by the `StartTimer` Action performed when this
@@ -116,13 +129,12 @@ where
            .unwrap();

        // send to `OutQueueControl` to eventually send to the mix network
-        self.real_message_sender
-            .send((
+        self.message_handler
+            .forward_messages(
                vec![RealMessage::new(prepared_fragment.mix_packet, frag_id)],
                TransmissionLane::Retransmission,
-            ))
+            )
            .await
-            .expect("BatchRealMessageReceiver has stopped receiving!");
    }

    pub(super) async fn run_with_shutdown(&mut self, mut shutdown: task::ShutdownListener) {
@@ -145,14 +157,4 @@ where
        shutdown.recv_timeout().await;
        log::debug!("RetransmissionRequestListener: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started RetransmissionRequestListener without graceful shutdown support");
-
-        while let Some(timed_out_ack) = self.request_receiver.next().await {
-            self.on_retransmission_request(timed_out_ack).await;
-        }
-    }
 }
@@ -1,7 +1,7 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use super::action_controller::{Action, ActionSender};
+use super::action_controller::{AckActionSender, Action};
 use super::SentPacketNotificationReceiver;
 use futures::StreamExt;
 use log::*;
@@ -13,13 +13,13 @@ use nymsphinx::chunking::fragment::{FragmentIdentifier, COVER_FRAG_ID};
 /// accidentally fire retransmission way quicker than we should have.
 pub(super) struct SentNotificationListener {
    sent_notifier: SentPacketNotificationReceiver,
-    action_sender: ActionSender,
+    action_sender: AckActionSender,
 }

 impl SentNotificationListener {
    pub(super) fn new(
        sent_notifier: SentPacketNotificationReceiver,
-        action_sender: ActionSender,
+        action_sender: AckActionSender,
    ) -> Self {
        SentNotificationListener {
            sent_notifier,
@@ -31,11 +31,6 @@ impl SentNotificationListener {
        if frag_id == COVER_FRAG_ID {
            trace!("sent off a cover message - no need to start retransmission timer!");
            return;
-        } else if frag_id.is_reply() {
-            debug!("sent off a reply message - no need to start retransmission timer!");
-            // TODO: probably there will need to be some extra procedure here, like it would
-            // be nice to know that our reply actually reached the recipient (i.e. we got the ack)
-            return;
        }
        self.action_sender
            .unbounded_send(Action::new_start_timer(frag_id))
@@ -64,14 +59,4 @@ impl SentNotificationListener {
        assert!(shutdown.is_shutdown_poll());
        log::debug!("SentNotificationListener: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started SentNotificationListener without graceful shutdown support");
-
-        while let Some(frag_id) = self.sent_notifier.next().await {
-            self.on_sent_message(frag_id).await;
-        }
-    }
 }
@@ -0,0 +1,548 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::real_messages_control::acknowledgement_control::PendingAcknowledgement;
+use crate::client::real_messages_control::real_traffic_stream::{
+    BatchRealMessageSender, RealMessage,
+};
+use crate::client::real_messages_control::{AckActionSender, Action};
+use crate::client::replies::reply_storage::{ReceivedReplySurbsMap, SentReplyKeys, UsedSenderTags};
+use crate::client::topology_control::{TopologyAccessor, TopologyReadPermit};
+use client_connections::TransmissionLane;
+use log::{debug, error, info, trace, warn};
+use nymsphinx::acknowledgements::AckKey;
+use nymsphinx::addressing::clients::Recipient;
+use nymsphinx::anonymous_replies::requests::{AnonymousSenderTag, RepliableMessage, ReplyMessage};
+use nymsphinx::anonymous_replies::{ReplySurb, SurbEncryptionKey};
+use nymsphinx::chunking::fragment::{Fragment, FragmentIdentifier};
+use nymsphinx::message::NymMessage;
+use nymsphinx::params::{PacketSize, DEFAULT_NUM_MIX_HOPS};
+use nymsphinx::preparer::{MessagePreparer, PreparedFragment};
+use nymsphinx::Delay;
+use rand::{CryptoRng, Rng};
+use std::sync::Arc;
+use std::time::Duration;
+use thiserror::Error;
+use topology::{NymTopology, NymTopologyError};
+
+// TODO: move that error elsewhere since it seems to be contaminating different files
+#[derive(Debug, Clone, Error)]
+pub enum PreparationError {
+    #[error(transparent)]
+    NymTopologyError(#[from] NymTopologyError),
+
+    #[error("The received message cannot be sent using a single reply surb. It ended up getting split into {fragments} fragments.")]
+    MessageTooLongForSingleSurb { fragments: usize },
+
+    #[error("Not enough reply SURBs to send the message. We have {available} available and require at least {required}.")]
+    NotEnoughSurbs { available: usize, required: usize },
+}
+
+impl PreparationError {
+    fn return_surbs(self, returned_surbs: Vec<ReplySurb>) -> SurbWrappedPreparationError {
+        SurbWrappedPreparationError {
+            source: self,
+            returned_surbs: Some(returned_surbs),
+        }
+    }
+}
+
+#[derive(Debug, Error)]
+#[error("Failed to prepare packets - {source}. {} reply surbs will be returned", .returned_surbs.as_ref().map(|s| s.len()).unwrap_or_default())]
+pub struct SurbWrappedPreparationError {
+    #[source]
+    source: PreparationError,
+
+    returned_surbs: Option<Vec<ReplySurb>>,
+}
+
+impl<T> From<T> for SurbWrappedPreparationError
+where
+    T: Into<PreparationError>,
+{
+    fn from(err: T) -> Self {
+        SurbWrappedPreparationError {
+            source: err.into(),
+            returned_surbs: None,
+        }
+    }
+}
+
+impl SurbWrappedPreparationError {
+    pub(crate) fn return_unused_surbs(
+        self,
+        surb_storage: &ReceivedReplySurbsMap,
+        target: &AnonymousSenderTag,
+    ) -> PreparationError {
+        if let Some(reply_surbs) = self.returned_surbs {
+            surb_storage.insert_surbs(target, reply_surbs)
+        }
+        self.source
+    }
+}
+
+#[derive(Clone)]
+pub(crate) struct Config {
+    /// Key used to decrypt contents of received SURBAcks
+    ack_key: Arc<AckKey>,
+
+    /// Address of this client which also represent an address to which all acknowledgements
+    /// and surb-based are going to be sent.
+    sender_address: Recipient,
+
+    /// Average delay a data packet is going to get delay at a single mixnode.
+    average_packet_delay: Duration,
+
+    /// Average delay an acknowledgement packet is going to get delay at a single mixnode.
+    average_ack_delay: Duration,
+
+    /// Number of mix hops each packet ('real' message, ack, reply) is expected to take.
+    /// Note that it does not include gateway hops.
+    num_mix_hops: u8,
+
+    /// Predefined packet size used for the encapsulated messages.
+    packet_size: PacketSize,
+}
+
+impl Config {
+    pub fn new(
+        ack_key: Arc<AckKey>,
+        sender_address: Recipient,
+        average_packet_delay: Duration,
+        average_ack_delay: Duration,
+    ) -> Self {
+        Config {
+            ack_key,
+            sender_address,
+            average_packet_delay,
+            average_ack_delay,
+            num_mix_hops: DEFAULT_NUM_MIX_HOPS,
+            packet_size: PacketSize::default(),
+        }
+    }
+
+    /// Allows setting non-default number of expected mix hops in the network.
+    #[allow(dead_code)]
+    pub fn with_mix_hops(mut self, hops: u8) -> Self {
+        self.num_mix_hops = hops;
+        self
+    }
+
+    /// Allows setting non-default size of the sphinx packets sent out.
+    pub fn with_custom_packet_size(mut self, packet_size: PacketSize) -> Self {
+        self.packet_size = packet_size;
+        self
+    }
+}
+
+#[derive(Clone)]
+pub(crate) struct MessageHandler<R> {
+    config: Config,
+    rng: R,
+    message_preparer: MessagePreparer<R>,
+    action_sender: AckActionSender,
+    real_message_sender: BatchRealMessageSender,
+    topology_access: TopologyAccessor,
+    reply_key_storage: SentReplyKeys,
+    tag_storage: UsedSenderTags,
+}
+
+impl<R> MessageHandler<R>
+where
+    R: CryptoRng + Rng,
+{
+    pub(crate) fn new(
+        config: Config,
+        rng: R,
+        action_sender: AckActionSender,
+        real_message_sender: BatchRealMessageSender,
+        topology_access: TopologyAccessor,
+        reply_key_storage: SentReplyKeys,
+        tag_storage: UsedSenderTags,
+    ) -> Self
+    where
+        R: Copy,
+    {
+        let message_preparer = MessagePreparer::new(
+            rng,
+            config.sender_address,
+            config.average_packet_delay,
+            config.average_ack_delay,
+        )
+        .with_custom_real_message_packet_size(config.packet_size)
+        .with_mix_hops(config.num_mix_hops);
+
+        MessageHandler {
+            config,
+            rng,
+            message_preparer,
+            action_sender,
+            real_message_sender,
+            topology_access,
+            reply_key_storage,
+            tag_storage,
+        }
+    }
+
+    fn get_or_create_sender_tag(&mut self, recipient: &Recipient) -> AnonymousSenderTag {
+        if let Some(existing) = self.tag_storage.try_get_existing(recipient) {
+            trace!("we already had sender tag for {recipient}");
+            existing
+        } else {
+            info!("creating new sender tag for {recipient}");
+            let new_tag = AnonymousSenderTag::new_random(&mut self.rng);
+            self.tag_storage.insert_new(recipient, new_tag);
+            info!("we'll be using {new_tag} for all anonymous messages sent to {recipient}");
+            new_tag
+        }
+    }
+
+    fn get_topology<'a>(
+        &self,
+        permit: &'a TopologyReadPermit<'a>,
+    ) -> Result<&'a NymTopology, PreparationError> {
+        match permit.try_get_valid_topology_ref(&self.config.sender_address, None) {
+            Ok(topology_ref) => Ok(topology_ref),
+            Err(err) => {
+                warn!("Could not process the packet - the network topology is invalid - {err}");
+                Err(err.into())
+            }
+        }
+    }
+
+    async fn generate_reply_surbs_with_keys(
+        &mut self,
+        amount: usize,
+    ) -> Result<(Vec<ReplySurb>, Vec<SurbEncryptionKey>), PreparationError> {
+        let topology_permit = self.topology_access.get_read_permit().await;
+        let topology = self.get_topology(&topology_permit)?;
+
+        let reply_surbs = self
+            .message_preparer
+            .generate_reply_surbs(amount, topology)?;
+
+        let reply_keys = reply_surbs
+            .iter()
+            .map(|s| *s.encryption_key())
+            .collect::<Vec<_>>();
+
+        Ok((reply_surbs, reply_keys))
+    }
+
+    pub(crate) async fn try_send_single_surb_message(
+        &mut self,
+        target: AnonymousSenderTag,
+        message: ReplyMessage,
+        reply_surb: ReplySurb,
+        is_extra_surb_request: bool,
+    ) -> Result<(), SurbWrappedPreparationError> {
+        let mut fragment = self
+            .message_preparer
+            .pad_and_split_message(NymMessage::new_reply(message));
+        if fragment.len() > 1 {
+            // well, it's not a single surb message
+            return Err(SurbWrappedPreparationError {
+                source: PreparationError::MessageTooLongForSingleSurb {
+                    fragments: fragment.len(),
+                },
+                returned_surbs: Some(vec![reply_surb]),
+            });
+        }
+
+        let chunk = fragment.pop().unwrap();
+        let chunk_clone = chunk.clone();
+        let prepared_fragment = self
+            .try_prepare_single_reply_chunk_for_sending(reply_surb, chunk_clone)
+            .await?;
+
+        let real_messages =
+            RealMessage::new(prepared_fragment.mix_packet, chunk.fragment_identifier());
+        let delay = prepared_fragment.total_delay;
+        let pending_ack =
+            PendingAcknowledgement::new_anonymous(chunk, delay, target, is_extra_surb_request);
+
+        let lane = if is_extra_surb_request {
+            TransmissionLane::ReplySurbRequest
+        } else {
+            TransmissionLane::General
+        };
+
+        self.forward_messages(vec![real_messages], lane).await;
+        self.insert_pending_acks(vec![pending_ack]);
+        Ok(())
+    }
+
+    pub(crate) async fn try_request_additional_reply_surbs(
+        &mut self,
+        from: AnonymousSenderTag,
+        reply_surb: ReplySurb,
+        amount: u32,
+    ) -> Result<(), SurbWrappedPreparationError> {
+        debug!("requesting {amount} reply SURBs from {from:?}");
+
+        let surbs_request =
+            ReplyMessage::new_surb_request_message(self.config.sender_address, amount);
+        self.try_send_single_surb_message(from, surbs_request, reply_surb, true)
+            .await
+    }
+
+    // // TODO: this will require additional argument to make it use different variant of `ReplyMessage`
+    pub(crate) fn split_reply_message(&mut self, message: Vec<u8>) -> Vec<Fragment> {
+        self.message_preparer
+            .pad_and_split_message(NymMessage::new_reply(ReplyMessage::new_data_message(
+                message,
+            )))
+    }
+
+    // the only difference between this method and `try_send_reply_chunks` is that
+    // here we are not creating acks as acks are already in memory waiting to get cleared.
+    // we are only updating their existing delays
+    pub(crate) async fn try_send_retransmission_reply_chunks(
+        &mut self,
+        fragments: Vec<Fragment>,
+        reply_surbs: Vec<ReplySurb>,
+        lane: TransmissionLane,
+    ) -> Result<(), SurbWrappedPreparationError> {
+        let prepared_fragments = self
+            .prepare_reply_chunks_for_sending(fragments.clone(), reply_surbs)
+            .await?;
+
+        let mut real_messages = Vec::with_capacity(prepared_fragments.len());
+
+        for prepared in prepared_fragments {
+            self.update_ack_delay(prepared.fragment_identifier, prepared.total_delay);
+            real_messages.push(prepared.into())
+        }
+
+        self.forward_messages(real_messages, lane).await;
+        Ok(())
+    }
+
+    pub(crate) async fn try_send_reply_chunks(
+        &mut self,
+        target: AnonymousSenderTag,
+        fragments: Vec<Fragment>,
+        reply_surbs: Vec<ReplySurb>,
+        lane: TransmissionLane,
+    ) -> Result<(), SurbWrappedPreparationError> {
+        let prepared_fragments = self
+            .prepare_reply_chunks_for_sending(fragments.clone(), reply_surbs)
+            .await?;
+
+        let mut pending_acks = Vec::with_capacity(fragments.len());
+        let mut real_messages = Vec::with_capacity(fragments.len());
+
+        for (raw, prepared) in fragments.into_iter().zip(prepared_fragments.into_iter()) {
+            let real_message = RealMessage::new(prepared.mix_packet, prepared.fragment_identifier);
+            let delay = prepared.total_delay;
+            let pending_ack = PendingAcknowledgement::new_anonymous(raw, delay, target, false);
+
+            real_messages.push(real_message);
+            pending_acks.push(pending_ack);
+        }
+
+        self.forward_messages(real_messages, lane).await;
+        self.insert_pending_acks(pending_acks);
+        Ok(())
+    }
+
+    pub(crate) async fn try_send_plain_message(
+        &mut self,
+        recipient: Recipient,
+        message: Vec<u8>,
+        lane: TransmissionLane,
+    ) -> Result<(), PreparationError> {
+        let message = NymMessage::new_plain(message);
+        self.try_split_and_send_non_reply_message(message, recipient, lane)
+            .await
+    }
+
+    pub(crate) async fn try_split_and_send_non_reply_message(
+        &mut self,
+        message: NymMessage,
+        recipient: Recipient,
+        lane: TransmissionLane,
+    ) -> Result<(), PreparationError> {
+        // TODO: I really dislike existence of this assertion, it implies code has to be re-organised
+        debug_assert!(!matches!(message, NymMessage::Reply(_)));
+
+        // TODO2: it's really annoying we have to get topology permit again here due to borrow-checker
+        let topology_permit = self.topology_access.get_read_permit().await;
+        let topology = self.get_topology(&topology_permit)?;
+
+        let fragments = self.message_preparer.pad_and_split_message(message);
+
+        let mut pending_acks = Vec::with_capacity(fragments.len());
+        let mut real_messages = Vec::with_capacity(fragments.len());
+        for fragment in fragments {
+            // we need to clone it because we need to keep it in memory in case we had to retransmit
+            // it. And then we'd need to recreate entire ACK again.
+            let chunk_clone = fragment.clone();
+            let prepared_fragment = self.message_preparer.prepare_chunk_for_sending(
+                chunk_clone,
+                topology,
+                &self.config.ack_key,
+                &recipient,
+            )?;
+
+            let real_message =
+                RealMessage::new(prepared_fragment.mix_packet, fragment.fragment_identifier());
+            let delay = prepared_fragment.total_delay;
+            let pending_ack = PendingAcknowledgement::new_known(fragment, delay, recipient);
+
+            real_messages.push(real_message);
+            pending_acks.push(pending_ack);
+        }
+
+        self.insert_pending_acks(pending_acks);
+        self.forward_messages(real_messages, lane).await;
+
+        Ok(())
+    }
+
+    pub(crate) async fn try_send_additional_reply_surbs(
+        &mut self,
+        recipient: Recipient,
+        amount: u32,
+    ) -> Result<(), PreparationError> {
+        let sender_tag = self.get_or_create_sender_tag(&recipient);
+        let (reply_surbs, reply_keys) =
+            self.generate_reply_surbs_with_keys(amount as usize).await?;
+
+        let message = NymMessage::new_repliable(RepliableMessage::new_additional_surbs(
+            sender_tag,
+            reply_surbs,
+        ));
+
+        self.try_split_and_send_non_reply_message(
+            message,
+            recipient,
+            TransmissionLane::AdditionalReplySurbs,
+        )
+        .await?;
+
+        log::trace!("storing {} reply keys", reply_keys.len());
+        self.reply_key_storage.insert_multiple(reply_keys);
+
+        Ok(())
+    }
+
+    pub(crate) async fn try_send_message_with_reply_surbs(
+        &mut self,
+        recipient: Recipient,
+        message: Vec<u8>,
+        num_reply_surbs: u32,
+        lane: TransmissionLane,
+    ) -> Result<(), SurbWrappedPreparationError> {
+        let sender_tag = self.get_or_create_sender_tag(&recipient);
+        let (reply_surbs, reply_keys) = self
+            .generate_reply_surbs_with_keys(num_reply_surbs as usize)
+            .await?;
+
+        let message =
+            NymMessage::new_repliable(RepliableMessage::new_data(message, sender_tag, reply_surbs));
+
+        self.try_split_and_send_non_reply_message(message, recipient, lane)
+            .await?;
+
+        log::trace!("storing {} reply keys", reply_keys.len());
+        self.reply_key_storage.insert_multiple(reply_keys);
+
+        Ok(())
+    }
+
+    pub(crate) async fn try_prepare_single_chunk_for_sending(
+        &mut self,
+        recipient: Recipient,
+        chunk: Fragment,
+    ) -> Result<PreparedFragment, PreparationError> {
+        let topology_permit = self.topology_access.get_read_permit().await;
+        let topology = self.get_topology(&topology_permit)?;
+
+        let prepared_fragment = self
+            .message_preparer
+            .prepare_chunk_for_sending(chunk, topology, &self.config.ack_key, &recipient)
+            .unwrap();
+
+        Ok(prepared_fragment)
+    }
+
+    async fn prepare_reply_chunks_for_sending(
+        &mut self,
+        fragments: Vec<Fragment>,
+        reply_surbs: Vec<ReplySurb>,
+    ) -> Result<Vec<PreparedFragment>, SurbWrappedPreparationError> {
+        debug_assert_ne!(
+            fragments.len(),
+            reply_surbs.len(),
+            "attempted to send {} fragments with {} reply surbs",
+            fragments.len(),
+            reply_surbs.len()
+        );
+
+        let topology_permit = self.topology_access.get_read_permit().await;
+        let topology = match self.get_topology(&topology_permit) {
+            Ok(topology) => topology,
+            Err(err) => return Err(err.return_surbs(reply_surbs)),
+        };
+
+        Ok(fragments
+            .into_iter()
+            .zip(reply_surbs.into_iter())
+            .map(|(fragment, reply_surb)| {
+                // unwrap here is fine as we know we have a valid topology
+                self.message_preparer
+                    .prepare_reply_chunk_for_sending(
+                        fragment,
+                        topology,
+                        &self.config.ack_key,
+                        reply_surb,
+                    )
+                    .unwrap()
+            })
+            .collect())
+    }
+
+    pub(crate) async fn try_prepare_single_reply_chunk_for_sending(
+        &mut self,
+        reply_surb: ReplySurb,
+        chunk: Fragment,
+    ) -> Result<PreparedFragment, SurbWrappedPreparationError> {
+        let topology_permit = self.topology_access.get_read_permit().await;
+        let topology = match self.get_topology(&topology_permit) {
+            Ok(topology) => topology,
+            Err(err) => return Err(err.return_surbs(vec![reply_surb])),
+        };
+
+        let prepared_fragment = self
+            .message_preparer
+            .prepare_reply_chunk_for_sending(chunk, topology, &self.config.ack_key, reply_surb)
+            .unwrap();
+
+        Ok(prepared_fragment)
+    }
+
+    pub(crate) fn update_ack_delay(&self, id: FragmentIdentifier, new_delay: Delay) {
+        self.action_sender
+            .unbounded_send(Action::UpdateDelay(id, new_delay))
+            .expect("action control task has died")
+    }
+
+    pub(crate) fn insert_pending_acks(&self, pending_acks: Vec<PendingAcknowledgement>) {
+        self.action_sender
+            .unbounded_send(Action::new_insert(pending_acks))
+            .expect("action control task has died")
+    }
+
+    // tells real message sender (with the poisson timer) to send this to the mix network
+    pub(crate) async fn forward_messages(
+        &self,
+        messages: Vec<RealMessage>,
+        transmission_lane: TransmissionLane,
+    ) {
+        self.real_message_sender
+            .send((messages, transmission_lane))
+            .await
+            .expect("real message receiver task (OutQueueControl) has died");
+    }
+}
@@ -8,6 +8,11 @@
 use self::{
    acknowledgement_control::AcknowledgementController, real_traffic_stream::OutQueueControl,
 };
+use crate::client::real_messages_control::message_handler::MessageHandler;
+use crate::client::replies::reply_controller::{
+    ReplyController, ReplyControllerReceiver, ReplyControllerSender,
+};
+use crate::client::replies::reply_storage::CombinedReplyStorage;
 use crate::{
    client::{
        inbound_messages::InputMessageReceiver, mix_traffic::BatchMixMessageSender,
@@ -27,11 +32,13 @@ use rand::{rngs::OsRng, CryptoRng, Rng};
 use std::sync::Arc;
 use std::time::Duration;

-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorage;
+use crate::client::replies::reply_controller;
+use crate::config;
+pub(crate) use acknowledgement_control::{AckActionSender, Action};

-mod acknowledgement_control;
-mod real_traffic_stream;
+pub(crate) mod acknowledgement_control;
+pub(crate) mod message_handler;
+pub(crate) mod real_traffic_stream;

 // TODO: ack_key and self_recipient shouldn't really be part of this config
 pub struct Config {
@@ -62,31 +69,102 @@ pub struct Config {

    /// Predefined packet size used for the encapsulated messages.
    packet_size: PacketSize,
+
+    /// Defines the minimum number of reply surbs the client would request.
+    minimum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs the client would request.
+    maximum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs a remote party is allowed to request from this client at once.
+    maximum_allowed_reply_surb_request_size: u32,
+
+    /// Defines maximum amount of time the client is going to wait for reply surbs before explicitly asking
+    /// for more even though in theory they wouldn't need to.
+    maximum_reply_surb_waiting_period: Duration,
+
+    /// Defines maximum amount of time given reply surb is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    maximum_reply_surb_age: Duration,
+
+    /// Defines maximum amount of time given reply key is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    maximum_reply_key_age: Duration,
+}
+
+impl<'a> From<&'a Config> for acknowledgement_control::Config {
+    fn from(cfg: &'a Config) -> Self {
+        acknowledgement_control::Config::new(cfg.ack_wait_addition, cfg.ack_wait_multiplier)
+            .with_custom_packet_size(cfg.packet_size)
+    }
+}
+
+impl<'a> From<&'a Config> for real_traffic_stream::Config {
+    fn from(cfg: &'a Config) -> Self {
+        real_traffic_stream::Config::new(
+            Arc::clone(&cfg.ack_key),
+            cfg.self_recipient,
+            cfg.average_ack_delay_duration,
+            cfg.average_packet_delay_duration,
+            cfg.average_message_sending_delay,
+            cfg.disable_main_poisson_packet_distribution,
+        )
+        .with_custom_cover_packet_size(cfg.packet_size)
+    }
+}
+
+impl<'a> From<&'a Config> for reply_controller::Config {
+    fn from(cfg: &'a Config) -> Self {
+        reply_controller::Config::new(
+            cfg.minimum_reply_surb_request_size,
+            cfg.maximum_reply_surb_request_size,
+            cfg.maximum_allowed_reply_surb_request_size,
+            cfg.maximum_reply_surb_waiting_period,
+            cfg.maximum_reply_surb_age,
+            cfg.maximum_reply_key_age,
+        )
+    }
+}
+
+impl<'a> From<&'a Config> for message_handler::Config {
+    fn from(cfg: &'a Config) -> Self {
+        message_handler::Config::new(
+            Arc::clone(&cfg.ack_key),
+            cfg.self_recipient,
+            cfg.average_packet_delay_duration,
+            cfg.average_ack_delay_duration,
+        )
+        .with_custom_packet_size(cfg.packet_size)
+    }
 }

 impl Config {
-    // TODO: change the config into a builder
-    #[allow(clippy::too_many_arguments)]
    pub fn new(
+        base_client_debug_config: &config::DebugConfig,
        ack_key: Arc<AckKey>,
-        ack_wait_multiplier: f64,
-        ack_wait_addition: Duration,
-        average_ack_delay_duration: Duration,
-        average_message_sending_delay: Duration,
-        average_packet_delay_duration: Duration,
-        disable_main_poisson_packet_distribution: bool,
        self_recipient: Recipient,
    ) -> Self {
        Config {
            ack_key,
-            ack_wait_addition,
-            ack_wait_multiplier,
            self_recipient,
-            average_message_sending_delay,
-            average_packet_delay_duration,
-            average_ack_delay_duration,
-            disable_main_poisson_packet_distribution,
            packet_size: Default::default(),
+            ack_wait_addition: base_client_debug_config.ack_wait_addition,
+            ack_wait_multiplier: base_client_debug_config.ack_wait_multiplier,
+            average_message_sending_delay: base_client_debug_config.message_sending_average_delay,
+            average_packet_delay_duration: base_client_debug_config.average_packet_delay,
+            average_ack_delay_duration: base_client_debug_config.average_ack_delay,
+            disable_main_poisson_packet_distribution: base_client_debug_config
+                .disable_main_poisson_packet_distribution,
+            minimum_reply_surb_request_size: base_client_debug_config
+                .minimum_reply_surb_request_size,
+            maximum_reply_surb_request_size: base_client_debug_config
+                .maximum_reply_surb_request_size,
+            maximum_allowed_reply_surb_request_size: base_client_debug_config
+                .maximum_allowed_reply_surb_request_size,
+            maximum_reply_surb_waiting_period: base_client_debug_config
+                .maximum_reply_surb_waiting_period,
+            maximum_reply_surb_age: base_client_debug_config.maximum_reply_surb_age,
+            maximum_reply_key_age: base_client_debug_config.maximum_reply_key_age,
        }
    }

@@ -95,75 +173,84 @@ impl Config {
    }
 }

-pub struct RealMessagesController<R>
+pub(crate) struct RealMessagesController<R>
 where
    R: CryptoRng + Rng,
 {
    out_queue_control: OutQueueControl<R>,
    ack_control: AcknowledgementController<R>,
+    reply_control: ReplyController<R>,
 }

 // obviously when we finally make shared rng that is on 'higher' level, this should become
 // generic `R`
 impl RealMessagesController<OsRng> {
    #[allow(clippy::too_many_arguments)]
-    pub fn new(
+    pub(crate) fn new(
        config: Config,
        ack_receiver: AcknowledgementReceiver,
        input_receiver: InputMessageReceiver,
        mix_sender: BatchMixMessageSender,
        topology_access: TopologyAccessor,
+        reply_storage: CombinedReplyStorage,
+        // so much refactoring needed, but this is temporary just to test things out
+        reply_controller_sender: ReplyControllerSender,
+        reply_controller_receiver: ReplyControllerReceiver,
        lane_queue_lengths: LaneQueueLengths,
        client_connection_rx: ConnectionCommandReceiver,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
    ) -> Self {
        let rng = OsRng;

+        // create channels for inter-task communication
        let (real_message_sender, real_message_receiver) = tokio::sync::mpsc::channel(1);
        let (sent_notifier_tx, sent_notifier_rx) = mpsc::unbounded();
-
+        let (ack_action_tx, ack_action_rx) = mpsc::unbounded();
        let ack_controller_connectors = AcknowledgementControllerConnectors::new(
-            real_message_sender,
            input_receiver,
            sent_notifier_rx,
            ack_receiver,
+            ack_action_tx.clone(),
+            ack_action_rx,
        );

-        let ack_control_config = acknowledgement_control::Config::new(
-            config.ack_wait_addition,
-            config.ack_wait_multiplier,
-            config.average_ack_delay_duration,
-            config.average_packet_delay_duration,
-        )
-        .with_custom_packet_size(config.packet_size);
+        // create all configs for the components
+        let ack_control_config = (&config).into();
+        let out_queue_config = (&config).into();
+        let reply_controller_config = (&config).into();
+        let message_handler_config = (&config).into();
+
+        // create the actual components
+        let message_handler = MessageHandler::new(
+            message_handler_config,
+            rng,
+            ack_action_tx,
+            real_message_sender,
+            topology_access.clone(),
+            reply_storage.key_storage(),
+            reply_storage.tags_storage(),
+        );

        let ack_control = AcknowledgementController::new(
            ack_control_config,
-            rng,
-            topology_access.clone(),
            Arc::clone(&config.ack_key),
-            config.self_recipient,
            ack_controller_connectors,
-            #[cfg(feature = "reply-surb")]
-            reply_key_storage,
+            message_handler.clone(),
+            reply_controller_sender,
        );

-        let out_queue_config = real_traffic_stream::Config::new(
-            config.average_ack_delay_duration,
-            config.average_packet_delay_duration,
-            config.average_message_sending_delay,
-            config.disable_main_poisson_packet_distribution,
-        )
-        .with_custom_cover_packet_size(config.packet_size);
+        let reply_control = ReplyController::new(
+            reply_controller_config,
+            message_handler,
+            reply_storage,
+            reply_controller_receiver,
+        );

        let out_queue_control = OutQueueControl::new(
            out_queue_config,
-            Arc::clone(&config.ack_key),
+            rng,
            sent_notifier_tx,
            mix_sender,
            real_message_receiver,
-            rng,
-            config.self_recipient,
            topology_access,
            lane_queue_lengths,
            client_connection_rx,
@@ -172,30 +259,26 @@ impl RealMessagesController<OsRng> {
        RealMessagesController {
            out_queue_control,
            ack_control,
+            reply_control,
        }
    }

    pub fn start_with_shutdown(self, shutdown: task::ShutdownListener) {
        let mut out_queue_control = self.out_queue_control;
        let ack_control = self.ack_control;
+        let mut reply_control = self.reply_control;

        let shutdown_handle = shutdown.clone();
        spawn_future(async move {
            out_queue_control.run_with_shutdown(shutdown_handle).await;
            debug!("The out queue controller has finished execution!");
        });
+        let shutdown_handle = shutdown.clone();
+        spawn_future(async move {
+            reply_control.run_with_shutdown(shutdown_handle).await;
+            debug!("The reply controller has finished execution!");
+        });
+
        ack_control.start_with_shutdown(shutdown);
    }
-
-    #[cfg(target_arch = "wasm32")]
-    pub fn start(self) {
-        let mut out_queue_control = self.out_queue_control;
-        let ack_control = self.ack_control;
-
-        spawn_future(async move {
-            out_queue_control.run().await;
-            debug!("The out queue controller has finished execution!");
-        });
-        ack_control.start();
-    }
 }
@@ -16,6 +16,7 @@ use nymsphinx::chunking::fragment::FragmentIdentifier;
 use nymsphinx::cover::generate_loop_cover_packet;
 use nymsphinx::forwarding::packet::MixPacket;
 use nymsphinx::params::PacketSize;
+use nymsphinx::preparer::PreparedFragment;
 use nymsphinx::utils::sample_poisson_duration;
 use rand::{CryptoRng, Rng};
 use std::pin::Pin;
@@ -47,6 +48,12 @@ fn get_time_now() -> wasm_timer::Instant {

 /// Configurable parameters of the `OutQueueControl`
 pub(crate) struct Config {
+    /// Key used to encrypt and decrypt content of an ACK packet.
+    ack_key: Arc<AckKey>,
+
+    /// Represents full address of this client.
+    our_full_destination: Recipient,
+
    /// Average delay an acknowledgement packet is going to get delay at a single mixnode.
    average_ack_delay: Duration,

@@ -66,12 +73,16 @@ pub(crate) struct Config {

 impl Config {
    pub(crate) fn new(
+        ack_key: Arc<AckKey>,
+        our_full_destination: Recipient,
        average_ack_delay: Duration,
        average_packet_delay: Duration,
        average_message_sending_delay: Duration,
        disable_poisson_packet_distribution: bool,
    ) -> Self {
        Config {
+            ack_key,
+            our_full_destination,
            average_ack_delay,
            average_packet_delay,
            average_message_sending_delay,
@@ -93,9 +104,6 @@ where
    /// Configurable parameters of the `ActionController`
    config: Config,

-    /// Key used to encrypt and decrypt content of an ACK packet.
-    ack_key: Arc<AckKey>,
-
    /// Channel used for notifying of a real packet being sent out. Used to start up retransmission timer.
    sent_notifier: SentPacketNotificationSender,

@@ -119,9 +127,6 @@ where
    /// before being sent out into the network.
    real_receiver: BatchRealMessageReceiver,

-    /// Represents full address of this client.
-    our_full_destination: Recipient,
-
    /// Instance of a cryptographically secure random number generator.
    rng: R,

@@ -144,6 +149,16 @@ where
 pub(crate) struct RealMessage {
    mix_packet: MixPacket,
    fragment_id: FragmentIdentifier,
+    // TODO: add info about it being constructed with reply-surb
+}
+
+impl From<PreparedFragment> for RealMessage {
+    fn from(fragment: PreparedFragment) -> Self {
+        RealMessage {
+            mix_packet: fragment.mix_packet,
+            fragment_id: fragment.fragment_identifier,
+        }
+    }
 }

 impl RealMessage {
@@ -175,25 +190,21 @@ where
    #[allow(clippy::too_many_arguments)]
    pub(crate) fn new(
        config: Config,
-        ack_key: Arc<AckKey>,
+        rng: R,
        sent_notifier: SentPacketNotificationSender,
        mix_tx: BatchMixMessageSender,
        real_receiver: BatchRealMessageReceiver,
-        rng: R,
-        our_full_destination: Recipient,
        topology_access: TopologyAccessor,
        lane_queue_lengths: LaneQueueLengths,
        client_connection_rx: ConnectionCommandReceiver,
    ) -> Self {
        OutQueueControl {
            config,
-            ack_key,
            sent_notifier,
            next_delay: None,
            sending_delay_controller: Default::default(),
            mix_tx,
            real_receiver,
-            our_full_destination,
            rng,
            topology_access,
            transmission_buffer: Default::default(),
@@ -220,24 +231,23 @@ where
                // poisson delay, but is it really a problem?
                let topology_permit = self.topology_access.get_read_permit().await;
                // the ack is sent back to ourselves (and then ignored)
-                let topology_ref_option = topology_permit.try_get_valid_topology_ref(
-                    &self.our_full_destination,
-                    Some(&self.our_full_destination),
-                );
-                if topology_ref_option.is_none() {
-                    warn!(
-                        "No valid topology detected - won't send any loop cover message this time"
-                    );
-                    return;
-                }
-                let topology_ref = topology_ref_option.unwrap();
+                let topology_ref = match topology_permit.try_get_valid_topology_ref(
+                    &self.config.our_full_destination,
+                    Some(&self.config.our_full_destination),
+                ) {
+                    Ok(topology) => topology,
+                    Err(err) => {
+                        warn!("We're not going to send any loop cover message this time, as the current topology seem to be invalid - {err}");
+                        return;
+                    }
+                };

                (
                    generate_loop_cover_packet(
                        &mut self.rng,
                        topology_ref,
-                        &self.ack_key,
-                        &self.our_full_destination,
+                        &self.config.ack_key,
+                        &self.config.our_full_destination,
                        self.config.average_ack_delay,
                        self.config.average_packet_delay,
                        self.config.cover_packet_size,
@@ -459,7 +469,9 @@ where
    }

    #[cfg(not(target_arch = "wasm32"))]
-    fn log_status(&self) {
+    fn log_status(&self, shutdown: &mut task::ShutdownListener) {
+        use crate::error::ClientCoreStatusMessage;
+
        let packets = self.transmission_buffer.total_size();
        let backlog = self.transmission_buffer.total_size_in_bytes() as f64 / 1024.0;
        let lanes = self.transmission_buffer.num_lanes();
@@ -483,13 +495,20 @@ where
        } else {
            log::debug!("{status_str}");
        }
+
+        // Send status message to whoever is listening (possibly UI)
+        if mult == self.sending_delay_controller.max_multiplier() {
+            shutdown.send_status_msg(Box::new(ClientCoreStatusMessage::GatewayIsVerySlow));
+        } else if mult > self.sending_delay_controller.min_multiplier() {
+            shutdown.send_status_msg(Box::new(ClientCoreStatusMessage::GatewayIsSlow));
+        }
    }

    #[cfg(not(target_arch = "wasm32"))]
    fn log_status_infrequent(&self) {
        if self.sending_delay_controller.current_multiplier() > 1 {
            log::warn!(
-                "Unable to send packets fast enough - sending delay multiplier set to: {}",
+                "Unable to send packets at the default rate - rate reduced by setting the delay multiplier set to: {}",
                self.sending_delay_controller.current_multiplier()
            );
        }
@@ -510,7 +529,7 @@ where
                        log::trace!("OutQueueControl: Received shutdown");
                    }
                    _ = status_timer.tick() => {
-                        self.log_status();
+                        self.log_status(&mut shutdown);
                    }
                    _ = infrequent_status_timer.tick() => {
                        self.log_status_infrequent();
@@ -547,16 +566,6 @@ where
        }
        log::debug!("OutQueueControl: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    pub(super) async fn run(&mut self) {
-        debug!("Started OutQueueControl without graceful shutdown support");
-
-        while let Some(next_message) = self.next().await {
-            self.on_message(next_message).await;
-        }
-    }
 }

 impl<R> Stream for OutQueueControl<R>
@@ -77,6 +77,14 @@ impl SendingDelayController {
        self.current_multiplier
    }

+    pub(crate) fn min_multiplier(&self) -> u32 {
+        self.lower_bound
+    }
+
+    pub(crate) fn max_multiplier(&self) -> u32 {
+        self.upper_bound
+    }
+
    pub(crate) fn increase_delay_multiplier(&mut self) {
        if self.current_multiplier < self.upper_bound {
            self.current_multiplier =
@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: Apache-2.0

 use client_connections::TransmissionLane;
-use rand::seq::SliceRandom;
+use rand::{seq::SliceRandom, Rng};
 use std::{
    collections::{HashMap, HashSet, VecDeque},
    time::Duration,
@@ -17,7 +17,7 @@ use wasm_timer;
 use super::{get_time_now, RealMessage};

 // The number of lanes included in the oldest set. Used when we need to prioritize traffic.
-const OLDEST_LANE_SET_SIZE: usize = 5;
+const OLDEST_LANE_SET_SIZE: usize = 4;
 // As a way of prune connections we also check for timeouts.
 const MSG_CONSIDERED_STALE_AFTER_SECS: u64 = 10 * 60;

@@ -116,9 +116,15 @@ impl TransmissionBuffer {
        lanes.choose(&mut rand::thread_rng()).copied()
    }

+    // 2/3 chance to pick from the old lanes
    fn pick_random_old_lane(&self) -> Option<TransmissionLane> {
-        let lanes = self.get_oldest_set();
-        lanes.choose(&mut rand::thread_rng()).copied()
+        let rand = &mut rand::thread_rng();
+        if rand.gen_ratio(2, 3) {
+            let lanes = self.get_oldest_set();
+            lanes.choose(rand).copied()
+        } else {
+            self.pick_random_lane().copied()
+        }
    }

    fn pop_front_from_lane(&mut self, lane: &TransmissionLane) -> Option<RealMessage> {
@@ -1,26 +1,26 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

+use crate::client::replies::reply_controller::ReplyControllerSender;
+use crate::client::replies::reply_storage::SentReplyKeys;
 use crate::spawn_future;
 use crypto::asymmetric::encryption;
+use crypto::Digest;
 use futures::channel::mpsc;
 use futures::lock::Mutex;
 use futures::StreamExt;
 use gateway_client::MixnetMessageReceiver;
 use log::*;
+use nymsphinx::anonymous_replies::requests::{
+    RepliableMessage, RepliableMessageContent, ReplyMessage, ReplyMessageContent,
+};
+use nymsphinx::anonymous_replies::{encryption_key::EncryptionKeyDigest, SurbEncryptionKey};
+use nymsphinx::message::{NymMessage, PlainMessage};
+use nymsphinx::params::ReplySurbKeyDigestAlgorithm;
 use nymsphinx::receiver::{MessageReceiver, MessageRecoveryError, ReconstructedMessage};
 use std::collections::HashSet;
 use std::sync::Arc;

-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorage;
-#[cfg(feature = "reply-surb")]
-use crypto::{symmetric::stream_cipher, Digest};
-#[cfg(feature = "reply-surb")]
-use nymsphinx::anonymous_replies::{encryption_key::EncryptionKeyDigest, SurbEncryptionKey};
-#[cfg(feature = "reply-surb")]
-use nymsphinx::params::{ReplySurbEncryptionAlgorithm, ReplySurbKeyDigestAlgorithm};
-
 // Buffer Requests to say "hey, send any reconstructed messages to this channel"
 // or to say "hey, I'm going offline, don't send anything more to me. Just buffer them instead"
 pub type ReceivedBufferRequestSender = mpsc::UnboundedSender<ReceivedBufferMessage>;
@@ -46,26 +46,15 @@ struct ReceivedMessagesBufferInner {
 }

 impl ReceivedMessagesBufferInner {
-    fn process_received_fragment(&mut self, raw_fragment: Vec<u8>) -> Option<ReconstructedMessage> {
-        let fragment_data = match self
-            .message_receiver
-            .recover_plaintext(self.local_encryption_keypair.private_key(), raw_fragment)
-        {
-            Err(e) => {
-                warn!("failed to recover fragment data: {:?}. The whole underlying message might be corrupted and unrecoverable!", e);
-                return None;
-            }
-            Ok(frag_data) => frag_data,
-        };
-
-        if nymsphinx::cover::is_cover(&fragment_data) {
+    fn recover_from_fragment(&mut self, fragment_data: &[u8]) -> Option<NymMessage> {
+        if nymsphinx::cover::is_cover(fragment_data) {
            trace!("The message was a loop cover message! Skipping it");
            return None;
        }

-        let fragment = match self.message_receiver.recover_fragment(&fragment_data) {
-            Err(e) => {
-                warn!("failed to recover fragment from raw data: {:?}. The whole underlying message might be corrupted and unrecoverable!", e);
+        let fragment = match self.message_receiver.recover_fragment(fragment_data) {
+            Err(err) => {
+                warn!("failed to recover fragment from raw data: {err}. The whole underlying message might be corrupted and unrecoverable!");
                return None;
            }
            Ok(frag) => frag,
@@ -79,9 +68,10 @@ impl ReceivedMessagesBufferInner {
        // if we returned an error the underlying message is malformed in some way
        match self.message_receiver.insert_new_fragment(fragment) {
            Err(err) => match err {
-                MessageRecoveryError::MalformedReconstructedMessage(message_sets) => {
+                MessageRecoveryError::MalformedReconstructedMessage { source, used_sets } => {
+                    error!("message reconstruction failed - {source}. Attempting to re-use the message sets...");
                    // TODO: should we really insert reconstructed sets? could this be abused for some attack?
-                    for set_id in message_sets {
+                    for set_id in used_sets {
                        if !self.recently_reconstructed.insert(set_id) {
                            // or perhaps we should even panic at this point?
                            error!("Reconstructed another message containing already used set id!")
@@ -107,6 +97,34 @@ impl ReceivedMessagesBufferInner {
            },
        }
    }
+
+    fn process_received_reply(
+        &mut self,
+        reply_ciphertext: &mut [u8],
+        reply_key: SurbEncryptionKey,
+    ) -> Option<NymMessage> {
+        // note: this performs decryption IN PLACE without extra allocation
+        self.message_receiver
+            .recover_plaintext_from_reply(reply_ciphertext, reply_key);
+        let fragment_data = reply_ciphertext;
+
+        self.recover_from_fragment(fragment_data)
+    }
+
+    fn process_received_regular_packet(&mut self, mut raw_fragment: Vec<u8>) -> Option<NymMessage> {
+        let fragment_data = match self.message_receiver.recover_plaintext_from_regular_packet(
+            self.local_encryption_keypair.private_key(),
+            &mut raw_fragment,
+        ) {
+            Err(err) => {
+                warn!("failed to recover fragment data: {err}. The whole underlying message might be corrupted and unrecoverable!");
+                return None;
+            }
+            Ok(frag_data) => frag_data,
+        };
+
+        self.recover_from_fragment(fragment_data)
+    }
 }

 #[derive(Debug, Clone)]
@@ -114,17 +132,15 @@ impl ReceivedMessagesBufferInner {
 // You should always use .clone() to create additional instances
 struct ReceivedMessagesBuffer {
    inner: Arc<Mutex<ReceivedMessagesBufferInner>>,
-
-    /// Storage containing keys to all [`ReplySURB`]s ever sent out that we did not receive back.
-    // There's no need to put it behind a Mutex since it's already properly concurrent
-    #[cfg(feature = "reply-surb")]
-    reply_key_storage: ReplyKeyStorage,
+    reply_key_storage: SentReplyKeys,
+    reply_controller_sender: ReplyControllerSender,
 }

 impl ReceivedMessagesBuffer {
    fn new(
        local_encryption_keypair: Arc<encryption::KeyPair>,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
+        reply_key_storage: SentReplyKeys,
+        reply_controller_sender: ReplyControllerSender,
    ) -> Self {
        ReceivedMessagesBuffer {
            inner: Arc::new(Mutex::new(ReceivedMessagesBufferInner {
@@ -134,8 +150,8 @@ impl ReceivedMessagesBuffer {
                message_sender: None,
                recently_reconstructed: HashSet::new(),
            })),
-            #[cfg(feature = "reply-surb")]
            reply_key_storage,
+            reply_controller_sender,
        }
    }

@@ -177,34 +193,139 @@ impl ReceivedMessagesBuffer {
        guard.message_sender = Some(sender);
    }

-    async fn add_reconstructed_messages(&mut self, msgs: Vec<ReconstructedMessage>) {
-        debug!("Adding {:?} new messages to the buffer!", msgs.len());
-        trace!("Adding new messages to the buffer! {:?}", msgs);
-        self.inner.lock().await.messages.extend(msgs)
+    fn handle_reconstructed_plain_messages(
+        &mut self,
+        msgs: Vec<PlainMessage>,
+    ) -> Vec<ReconstructedMessage> {
+        msgs.into_iter().map(Into::into).collect()
    }

-    #[cfg(feature = "reply-surb")]
-    fn process_received_reply(
-        reply_ciphertext: &[u8],
-        reply_key: SurbEncryptionKey,
-    ) -> Option<ReconstructedMessage> {
-        let zero_iv = stream_cipher::zero_iv::<ReplySurbEncryptionAlgorithm>();
+    fn handle_reconstructed_repliable_messages(
+        &mut self,
+        msgs: Vec<RepliableMessage>,
+    ) -> Vec<ReconstructedMessage> {
+        let mut reconstructed = Vec::new();
+        for msg in msgs {
+            let (reply_surbs, from_surb_request) = match msg.content {
+                RepliableMessageContent::Data {
+                    message,
+                    reply_surbs,
+                } => {
+                    trace!(
+                        "received message that also contained additional {} reply surbs from {:?}!",
+                        reply_surbs.len(),
+                        msg.sender_tag
+                    );

-        let mut reply_msg = stream_cipher::decrypt::<ReplySurbEncryptionAlgorithm>(
-            reply_key.inner(),
-            &zero_iv,
-            reply_ciphertext,
-        );
-        if let Err(err) = MessageReceiver::remove_padding(&mut reply_msg) {
-            warn!("Received reply had malformed padding! - {:?}", err);
-            None
-        } else {
-            // TODO: perhaps having to say it doesn't have a surb an indication the type should be changed?
-            Some(ReconstructedMessage {
-                message: reply_msg,
-                reply_surb: None,
-            })
+                    reconstructed.push(ReconstructedMessage::new(message, msg.sender_tag));
+
+                    (reply_surbs, false)
+                }
+                RepliableMessageContent::AdditionalSurbs { reply_surbs } => {
+                    trace!(
+                        "received additional {} reply surbs from {:?}!",
+                        reply_surbs.len(),
+                        msg.sender_tag
+                    );
+                    (reply_surbs, true)
+                }
+                RepliableMessageContent::Heartbeat {
+                    additional_reply_surbs,
+                } => {
+                    error!("received a repliable heartbeat message - we don't know how to handle it yet (and we won't know until future PRs)");
+                    (additional_reply_surbs, false)
+                }
+            };
+
+            self.reply_controller_sender.send_additional_surbs(
+                msg.sender_tag,
+                reply_surbs,
+                from_surb_request,
+            )
        }
+        reconstructed
+    }
+
+    fn handle_reconstructed_reply_messages(
+        &mut self,
+        msgs: Vec<ReplyMessage>,
+    ) -> Vec<ReconstructedMessage> {
+        let mut reconstructed = Vec::new();
+        for msg in msgs {
+            match msg.content {
+                ReplyMessageContent::Data { message } => reconstructed.push(message.into()),
+                ReplyMessageContent::SurbRequest { recipient, amount } => {
+                    debug!("received request for {amount} additional reply SURBs from {recipient}");
+                    self.reply_controller_sender
+                        .send_additional_surbs_request(*recipient, amount);
+                }
+            }
+        }
+        reconstructed
+    }
+
+    async fn handle_reconstructed_messages(&mut self, msgs: Vec<NymMessage>) {
+        if msgs.is_empty() {
+            return;
+        }
+
+        let mut plain_messages = Vec::new();
+        let mut repliable_messages = Vec::new();
+        let mut reply_messages = Vec::new();
+
+        for msg in msgs {
+            match msg {
+                NymMessage::Plain(plain) => plain_messages.push(plain),
+                NymMessage::Repliable(repliable) => repliable_messages.push(repliable),
+                NymMessage::Reply(reply) => reply_messages.push(reply),
+            }
+        }
+
+        let mut reconstructed_messages = self.handle_reconstructed_plain_messages(plain_messages);
+        reconstructed_messages
+            .append(&mut self.handle_reconstructed_repliable_messages(repliable_messages));
+        reconstructed_messages
+            .append(&mut self.handle_reconstructed_reply_messages(reply_messages));
+
+        let mut inner_guard = self.inner.lock().await;
+        debug!(
+            "Adding {:?} new messages to the buffer!",
+            reconstructed_messages.len()
+        );
+
+        if let Some(sender) = &inner_guard.message_sender {
+            trace!("Sending reconstructed messages to announced sender");
+            if let Err(err) = sender.unbounded_send(reconstructed_messages) {
+                warn!("The reconstructed message receiver went offline without explicit notification (relevant error: - {err})");
+                inner_guard.message_sender = None;
+                inner_guard.messages.extend(err.into_inner());
+            }
+        } else {
+            trace!("No sender available - buffering reconstructed messages");
+            inner_guard.messages.extend(reconstructed_messages)
+        }
+    }
+
+    // this function doesn't really belong here...
+    fn get_reply_key<'a>(
+        &self,
+        raw_message: &'a mut [u8],
+    ) -> Option<(SurbEncryptionKey, &'a mut [u8])> {
+        let reply_surb_digest_size = ReplySurbKeyDigestAlgorithm::output_size();
+        if raw_message.len() < reply_surb_digest_size {
+            return None;
+        }
+
+        let possible_key_digest =
+            EncryptionKeyDigest::clone_from_slice(&raw_message[..reply_surb_digest_size]);
+        self.reply_key_storage
+            .try_pop(possible_key_digest)
+            .map(|reply_encryption_key| {
+                (
+                    *reply_encryption_key,
+                    &mut raw_message[reply_surb_digest_size..],
+                )
+            })
    }

    async fn handle_new_received(&mut self, msgs: Vec<Vec<u8>>) {
@@ -217,69 +338,27 @@ impl ReceivedMessagesBuffer {
        let mut inner_guard = self.inner.lock().await;

        // first check if this is a reply or a chunked message
-        // TODO: verify with @AP if this way of doing it is safe or whether it could
-        // cause some attacks due to, I don't know, stupid edge case collisions?
-        // Update: this DOES introduce a possible leakage: https://github.com/nymtech/nym/issues/296
-        for msg in msgs {
-            // TODO:
-            // 1. make it nicer
-            // 2. make it not feature-locked
-
-            #[cfg(feature = "reply-surb")]
-            {
-                let reply_surb_digest_size = ReplySurbKeyDigestAlgorithm::output_size();
-
-                let possible_key_digest =
-                    EncryptionKeyDigest::clone_from_slice(&msg[..reply_surb_digest_size]);
-
-                // check first `HasherOutputSize` bytes if they correspond to known encryption key
-                // if yes - this is a reply message
-
-                // TODO: this might be a bottleneck - since the keys are stored on disk we, presumably,
-                // are doing a disk operation every single received fragment
-                if let Some(reply_encryption_key) = self
-                    .reply_key_storage
-                    .get_and_remove_encryption_key(possible_key_digest)
-                    .expect("storage operation failed!")
-                {
-                    if let Some(completed_message) = Self::process_received_reply(
-                        &msg[reply_surb_digest_size..],
-                        reply_encryption_key,
-                    ) {
-                        completed_messages.push(completed_message)
-                    }
+        // note: there's a possible information leakage associated with this check https://github.com/nymtech/nym/issues/296
+        for mut msg in msgs {
+            // check first `HasherOutputSize` bytes if they correspond to known encryption key
+            // if yes - this is a reply message
+            let completed_message =
+                if let Some((reply_key, reply_message)) = self.get_reply_key(&mut msg) {
+                    inner_guard.process_received_reply(reply_message, reply_key)
                } else {
-                    // otherwise - it's a 'normal' message
-                    if let Some(completed_message) = inner_guard.process_received_fragment(msg) {
-                        completed_messages.push(completed_message)
-                    }
-                }
-            }
+                    inner_guard.process_received_regular_packet(msg)
+                };

-            #[cfg(not(feature = "reply-surb"))]
-            if let Some(completed_message) = inner_guard.process_received_fragment(msg) {
-                completed_messages.push(completed_message)
+            if let Some(completed) = completed_message {
+                info!("received {completed}");
+                completed_messages.push(completed)
            }
        }

+        drop(inner_guard);
+
        if !completed_messages.is_empty() {
-            if let Some(sender) = &inner_guard.message_sender {
-                trace!("Sending reconstructed messages to announced sender");
-                if let Err(err) = sender.unbounded_send(completed_messages) {
-                    warn!("The reconstructed message receiver went offline without explicit notification (relevant error: - {:?})", err);
-                    // make sure to drop the lock to not deadlock
-                    // (it is required by `add_reconstructed_messages`)
-                    inner_guard.message_sender = None;
-                    drop(inner_guard);
-                    self.add_reconstructed_messages(err.into_inner()).await;
-                }
-            } else {
-                // make sure to drop the lock to not deadlock
-                // (it is required by `add_reconstructed_messages`)
-                drop(inner_guard);
-                trace!("No sender available - buffering reconstructed messages");
-                self.add_reconstructed_messages(completed_messages).await;
-            }
+            self.handle_reconstructed_messages(completed_messages).await
        }
    }
 }
@@ -342,16 +421,6 @@ impl RequestReceiver {
        shutdown.recv_timeout().await;
        log::debug!("RequestReceiver: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    async fn run(&mut self) {
-        debug!("Started RequestReceiver without graceful shutdown support");
-
-        while let Some(message) = self.query_receiver.next().await {
-            self.handle_message(message).await
-        }
-    }
 }

 struct FragmentedMessageReceiver {
@@ -391,34 +460,25 @@ impl FragmentedMessageReceiver {
        shutdown.recv_timeout().await;
        log::debug!("FragmentedMessageReceiver: Exiting");
    }
-
-    // todo: think whether this is still required
-    #[allow(dead_code)]
-    async fn run(&mut self) {
-        debug!("Started FragmentedMessageReceiver without graceful shutdown support");
-
-        while let Some(new_messages) = self.mixnet_packet_receiver.next().await {
-            self.received_buffer.handle_new_received(new_messages).await;
-        }
-    }
 }

-pub struct ReceivedMessagesBufferController {
+pub(crate) struct ReceivedMessagesBufferController {
    fragmented_message_receiver: FragmentedMessageReceiver,
    request_receiver: RequestReceiver,
 }

 impl ReceivedMessagesBufferController {
-    pub fn new(
+    pub(crate) fn new(
        local_encryption_keypair: Arc<encryption::KeyPair>,
        query_receiver: ReceivedBufferRequestReceiver,
        mixnet_packet_receiver: MixnetMessageReceiver,
-        #[cfg(feature = "reply-surb")] reply_key_storage: ReplyKeyStorage,
+        reply_key_storage: SentReplyKeys,
+        reply_controller_sender: ReplyControllerSender,
    ) -> Self {
        let received_buffer = ReceivedMessagesBuffer::new(
            local_encryption_keypair,
-            #[cfg(feature = "reply-surb")]
            reply_key_storage,
+            reply_controller_sender,
        );

        ReceivedMessagesBufferController {
@@ -444,16 +504,4 @@ impl ReceivedMessagesBufferController {
            request_receiver.run_with_shutdown(shutdown).await;
        });
    }
-
-    #[cfg(target_arch = "wasm32")]
-    pub fn start(self) {
-        let mut fragmented_message_receiver = self.fragmented_message_receiver;
-        let mut request_receiver = self.request_receiver;
-        spawn_future(async move {
-            fragmented_message_receiver.run().await;
-        });
-        spawn_future(async move {
-            request_receiver.run().await;
-        });
-    }
 }
@@ -0,0 +1,5 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+pub mod reply_controller;
+pub mod reply_storage;
@@ -0,0 +1,928 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::real_messages_control::acknowledgement_control::PendingAcknowledgement;
+use crate::client::real_messages_control::message_handler::{MessageHandler, PreparationError};
+use crate::client::replies::reply_storage::CombinedReplyStorage;
+use client_connections::TransmissionLane;
+use futures::channel::mpsc;
+use futures::StreamExt;
+use log::{debug, error, info, trace, warn};
+use nymsphinx::addressing::clients::Recipient;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
+use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::chunking::fragment::{Fragment, FragmentIdentifier};
+use rand::{CryptoRng, Rng};
+use std::cmp::{max, min};
+use std::collections::btree_map::Entry;
+use std::collections::{BTreeMap, HashMap, VecDeque};
+use std::sync::{Arc, Weak};
+use std::time::Duration;
+use time::OffsetDateTime;
+
+#[cfg(not(target_arch = "wasm32"))]
+type IntervalStream = tokio_stream::wrappers::IntervalStream;
+
+#[cfg(target_arch = "wasm32")]
+type IntervalStream = gloo_timers::future::IntervalStream;
+
+pub(crate) fn new_control_channels() -> (ReplyControllerSender, ReplyControllerReceiver) {
+    let (tx, rx) = mpsc::unbounded();
+    (tx.into(), rx)
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct ReplyControllerSender(mpsc::UnboundedSender<ReplyControllerMessage>);
+
+impl From<mpsc::UnboundedSender<ReplyControllerMessage>> for ReplyControllerSender {
+    fn from(inner: mpsc::UnboundedSender<ReplyControllerMessage>) -> Self {
+        ReplyControllerSender(inner)
+    }
+}
+
+impl ReplyControllerSender {
+    pub(crate) fn send_retransmission_data(
+        &self,
+        recipient: AnonymousSenderTag,
+        timed_out_ack: Weak<PendingAcknowledgement>,
+        extra_surb_request: bool,
+    ) {
+        self.0
+            .unbounded_send(ReplyControllerMessage::RetransmitReply {
+                recipient,
+                timed_out_ack,
+                extra_surb_request,
+            })
+            .expect("ReplyControllerReceiver has died!")
+    }
+
+    pub(crate) fn send_reply(
+        &self,
+        recipient: AnonymousSenderTag,
+        message: Vec<u8>,
+        lane: TransmissionLane,
+    ) {
+        self.0
+            .unbounded_send(ReplyControllerMessage::SendReply {
+                recipient,
+                message,
+                lane,
+            })
+            .expect("ReplyControllerReceiver has died!")
+    }
+
+    pub(crate) fn send_additional_surbs(
+        &self,
+        sender_tag: AnonymousSenderTag,
+        reply_surbs: Vec<ReplySurb>,
+        from_surb_request: bool,
+    ) {
+        self.0
+            .unbounded_send(ReplyControllerMessage::AdditionalSurbs {
+                sender_tag,
+                reply_surbs,
+                from_surb_request,
+            })
+            .expect("ReplyControllerReceiver has died!")
+    }
+
+    pub(crate) fn send_additional_surbs_request(&self, recipient: Recipient, amount: u32) {
+        self.0
+            .unbounded_send(ReplyControllerMessage::AdditionalSurbsRequest {
+                recipient: Box::new(recipient),
+                amount,
+            })
+            .expect("ReplyControllerReceiver has died!")
+    }
+}
+
+pub(crate) type ReplyControllerReceiver = mpsc::UnboundedReceiver<ReplyControllerMessage>;
+
+#[derive(Debug)]
+pub(crate) enum ReplyControllerMessage {
+    RetransmitReply {
+        recipient: AnonymousSenderTag,
+        timed_out_ack: Weak<PendingAcknowledgement>,
+        extra_surb_request: bool,
+    },
+
+    SendReply {
+        recipient: AnonymousSenderTag,
+        message: Vec<u8>,
+        lane: TransmissionLane,
+    },
+
+    AdditionalSurbs {
+        sender_tag: AnonymousSenderTag,
+        reply_surbs: Vec<ReplySurb>,
+        from_surb_request: bool,
+    },
+
+    // Should this also be handled in here? it's technically a completely different side of the pipe
+    // let's see how it works when combined, might split it before creating PR
+    AdditionalSurbsRequest {
+        recipient: Box<Recipient>,
+        amount: u32,
+    },
+}
+
+pub struct Config {
+    min_surb_request_size: u32,
+    max_surb_request_size: u32,
+    maximum_allowed_reply_surb_request_size: u32,
+    max_surb_waiting_period: Duration,
+    max_reply_surb_age: Duration,
+    max_reply_key_age: Duration,
+}
+
+impl Config {
+    pub(crate) fn new(
+        min_surb_request_size: u32,
+        max_surb_request_size: u32,
+        maximum_allowed_reply_surb_request_size: u32,
+        max_surb_waiting_period: Duration,
+        max_reply_surb_age: Duration,
+        max_reply_key_age: Duration,
+    ) -> Self {
+        Self {
+            min_surb_request_size,
+            max_surb_request_size,
+            maximum_allowed_reply_surb_request_size,
+            max_surb_waiting_period,
+            max_reply_surb_age,
+            max_reply_key_age,
+        }
+    }
+}
+
+// the purpose of this task:
+// - buffers split messages from input message listener if there were insufficient surbs to send them
+// - upon getting extra surbs, resends them
+// - so I guess it will handle all 'RepliableMessage' and requests from 'ReplyMessage'
+// - replies to "give additional surbs" requests
+// - will reply to future heartbeats
+
+// TODO: this should be split into ingress and egress controllers
+// because currently its trying to perform two distinct jobs
+pub struct ReplyController<R> {
+    config: Config,
+
+    // TODO: incorporate that field at some point
+    // and use binomial distribution to determine the expected required number
+    // of surbs required to send the message through
+    // expected_reliability: f32,
+    request_receiver: ReplyControllerReceiver,
+    pending_replies: HashMap<AnonymousSenderTag, VecDeque<Fragment>>,
+
+    /// Retransmission packets that have already timed out and are waiting for additional reply SURBs
+    /// so that they could be sent back to the network. Once we receive more SURBs, we should send them ASAP.
+    // TODO: when purging stale entries, we must take extra care to also purge all pending ACK data!!
+    pending_retransmissions:
+        HashMap<AnonymousSenderTag, BTreeMap<FragmentIdentifier, Weak<PendingAcknowledgement>>>,
+
+    message_handler: MessageHandler<R>,
+    full_reply_storage: CombinedReplyStorage,
+}
+
+impl<R> ReplyController<R>
+where
+    R: CryptoRng + Rng,
+{
+    pub(crate) fn new(
+        config: Config,
+        message_handler: MessageHandler<R>,
+        full_reply_storage: CombinedReplyStorage,
+        request_receiver: ReplyControllerReceiver,
+    ) -> Self {
+        ReplyController {
+            config,
+            request_receiver,
+            pending_replies: HashMap::new(),
+            pending_retransmissions: HashMap::new(),
+            message_handler,
+            full_reply_storage,
+        }
+    }
+
+    /// Inserts the pending replies into the BACK of the queue fn insert_pending_replies<V: Into<VecDeque<Fragment>>>(
+    fn insert_pending_replies<V: Into<VecDeque<Fragment>>>(
+        &mut self,
+        recipient: &AnonymousSenderTag,
+        fragments: V,
+    ) {
+        if let Some(existing) = self.pending_replies.get_mut(recipient) {
+            existing.append(&mut fragments.into())
+        } else {
+            self.pending_replies.insert(*recipient, fragments.into());
+        }
+    }
+
+    fn re_insert_pending_retransmission(
+        &mut self,
+        recipient: &AnonymousSenderTag,
+        data: Vec<Arc<PendingAcknowledgement>>,
+    ) {
+        // the underlying entry MUST exist as we've just got data from there
+        let map_entry = self
+            .pending_retransmissions
+            .get_mut(recipient)
+            .expect("our pending retransmission entry is somehow gone!");
+
+        for pending in data {
+            // if it's 0, we don't need to do anything - we just got that ack!
+            if Arc::strong_count(&pending) > 1 {
+                let id = pending.inner_fragment_identifier();
+                let downgraded = Arc::downgrade(&pending);
+                map_entry.insert(id, downgraded);
+            }
+        }
+    }
+
+    fn should_request_more_surbs(&self, target: &AnonymousSenderTag) -> bool {
+        trace!("checking if we should request more surbs from {:?}", target);
+
+        let pending_queue_size = self
+            .pending_replies
+            .get(target)
+            .map(|pending_queue| pending_queue.len())
+            .unwrap_or_default();
+
+        let retransmission_queue = self
+            .pending_retransmissions
+            .get(target)
+            .map(|pending_queue| pending_queue.len())
+            .unwrap_or_default();
+
+        let total_queue = pending_queue_size + retransmission_queue;
+
+        // simple as that - there's absolutely nothing to retransmit
+        if total_queue == 0 {
+            return false;
+        }
+
+        let available_surbs = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .available_surbs(target);
+        let pending_surbs = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .pending_reception(target) as usize;
+        let min_surbs_threshold = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .min_surb_threshold();
+        let max_surbs_threshold = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .max_surb_threshold();
+
+        debug!("total queue size: {total_queue} = pending data {pending_queue_size} + pending retransmission {retransmission_queue}, available surbs: {available_surbs} pending surbs: {pending_surbs} threshold range: {min_surbs_threshold}..{max_surbs_threshold}");
+
+        (pending_surbs + available_surbs) < max_surbs_threshold
+            && (pending_surbs + available_surbs) < (total_queue + min_surbs_threshold)
+    }
+
+    async fn handle_send_reply(
+        &mut self,
+        recipient_tag: AnonymousSenderTag,
+        data: Vec<u8>,
+        lane: TransmissionLane,
+    ) {
+        if !self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .contains_surbs_for(&recipient_tag)
+        {
+            warn!("received reply request for {:?} but we don't have any surbs stored for that recipient!", recipient_tag);
+            return;
+        }
+
+        trace!("handling reply to {:?}", recipient_tag);
+        let fragments = self.message_handler.split_reply_message(data);
+
+        let required_surbs = fragments.len();
+        trace!("This reply requires {:?} SURBs", required_surbs);
+
+        // TODO: edge case:
+        // we're making a lot of requests and have to request a lot of surbs
+        // (but at some point we run out of surbs for surb requests)
+
+        let (surbs, _surbs_left) = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .get_reply_surbs(&recipient_tag, required_surbs);
+
+        if let Some(reply_surbs) = surbs {
+            if let Err(err) = self
+                .message_handler
+                .try_send_reply_chunks(recipient_tag, fragments, reply_surbs, lane)
+                .await
+            {
+                let err = err.return_unused_surbs(
+                    self.full_reply_storage.surbs_storage_ref(),
+                    &recipient_tag,
+                );
+                warn!("failed to send reply to {:?} - {err}", recipient_tag);
+
+                // TODO: should we buffer that data to try again?
+            }
+        } else {
+            // we don't have enough surbs for this reply
+            self.insert_pending_replies(&recipient_tag, fragments);
+
+            if self.should_request_more_surbs(&recipient_tag) {
+                self.request_reply_surbs_for_queue_clearing(recipient_tag)
+                    .await;
+            }
+        }
+    }
+
+    async fn request_additional_reply_surbs(
+        &mut self,
+        target: AnonymousSenderTag,
+        amount: u32,
+    ) -> Result<(), PreparationError> {
+        let reply_surb = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .get_reply_surb_ignoring_threshold(&target)
+            .and_then(|(reply_surb, _)| reply_surb)
+            .ok_or(PreparationError::NotEnoughSurbs {
+                available: 0,
+                required: 1,
+            })?;
+
+        if let Err(err) = self
+            .message_handler
+            .try_request_additional_reply_surbs(target, reply_surb, amount)
+            .await
+        {
+            let err = err.return_unused_surbs(self.full_reply_storage.surbs_storage_ref(), &target);
+            warn!(
+                "failed to request additional surbs from {:?} - {err}",
+                target
+            );
+            return Err(err);
+        } else {
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .increment_pending_reception(&target, amount);
+        }
+
+        Ok(())
+    }
+
+    async fn try_clear_pending_retransmission(&mut self, target: AnonymousSenderTag) {
+        trace!("trying to clear pending retransmission queue");
+        let available_surbs = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .available_surbs(&target);
+        let min_surbs_threshold = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .min_surb_threshold();
+
+        let max_to_clear = if available_surbs > min_surbs_threshold {
+            available_surbs - min_surbs_threshold
+        } else {
+            trace!("we don't have enough surbs for retransmission queue clearing...");
+            return;
+        };
+        trace!("we can clear up to {max_to_clear} entries");
+
+        let Some(pending) = self.pending_retransmissions.get_mut(&target) else {
+            trace!("there are no pending retransmissions for {target}!");
+            return;
+        };
+
+        let mut to_take = Vec::new();
+        let mut to_remove = Vec::new();
+
+        // TODO: once rust 1.66.0 is stabilised on 15.12.22, just change it to
+        // `.pop_front()` to directly take ownership
+        for (k, data) in pending.iter() {
+            let upgraded = match data.upgrade() {
+                Some(upgraded) => upgraded,
+                None => {
+                    // we got the ack while the data was waiting in the queue
+                    to_remove.push(*k);
+                    continue;
+                }
+            };
+
+            to_take.push(upgraded);
+
+            // we have taken as many entries as we could have
+            if to_take.len() >= max_to_clear {
+                break;
+            }
+            // TODO: use if upgraded.is_extra_surb_request() to bypass the limit
+        }
+
+        for ack in &to_take {
+            pending.remove(&ack.inner_fragment_identifier());
+        }
+
+        for id in to_remove {
+            pending.remove(&id);
+        }
+
+        if to_take.is_empty() {
+            // no need to do anything
+            return;
+        }
+
+        let (surbs_for_reply, _) = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .get_reply_surbs(&target, to_take.len());
+
+        let Some(surbs_for_reply) = surbs_for_reply else {
+            error!("somehow different task has stolen our reply surbs! - this should have been impossible");
+            self.re_insert_pending_retransmission(&target, to_take);
+            return;
+        };
+
+        let to_send_vec = to_take.iter().map(|ack| ack.fragment_data()).collect();
+
+        if let Err(err) = self
+            .message_handler
+            .try_send_retransmission_reply_chunks(
+                to_send_vec,
+                surbs_for_reply,
+                TransmissionLane::Retransmission,
+            )
+            .await
+        {
+            let err = err.return_unused_surbs(self.full_reply_storage.surbs_storage_ref(), &target);
+            self.re_insert_pending_retransmission(&target, to_take);
+
+            warn!(
+                "failed to clear pending retransmission queue for {:?} - {err}",
+                target
+            );
+        }
+    }
+
+    fn pop_at_most_pending_replies(
+        &mut self,
+        from: &AnonymousSenderTag,
+        amount: usize,
+    ) -> Option<VecDeque<Fragment>> {
+        // if possible, pop all pending replies, if not, pop only entries for which we'd have a reply surb
+        let total = self.pending_replies.get(from)?.len();
+        trace!("pending queue has {total} elements");
+        if total == 0 {
+            return None;
+        }
+        if total < amount {
+            self.pending_replies.remove(from)
+        } else {
+            Some(
+                self.pending_replies
+                    .get_mut(from)?
+                    .drain(..amount)
+                    .collect(),
+            )
+        }
+    }
+
+    async fn try_clear_pending_queue(&mut self, target: AnonymousSenderTag) {
+        trace!("trying to clear pending queue");
+        let available_surbs = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .available_surbs(&target);
+        let min_surbs_threshold = self
+            .full_reply_storage
+            .surbs_storage_ref()
+            .min_surb_threshold();
+
+        let max_to_clear = if available_surbs > min_surbs_threshold {
+            available_surbs - min_surbs_threshold
+        } else {
+            trace!("we don't have enough surbs for queue clearing...");
+            return;
+        };
+        trace!("we can clear up to {max_to_clear} entries");
+
+        // we're guaranteed to not get more entries than we have reply surbs for
+        if let Some(to_send) = self.pop_at_most_pending_replies(&target, max_to_clear) {
+            let to_send_vec = to_send.iter().cloned().collect::<Vec<_>>();
+
+            if to_send_vec.is_empty() {
+                panic!(
+                    "please let the devs know if you ever see this message (reply_controller.rs)"
+                );
+            }
+
+            let (surbs_for_reply, _) = self
+                .full_reply_storage
+                .surbs_storage_ref()
+                .get_reply_surbs(&target, to_send_vec.len());
+
+            let Some(surbs_for_reply) = surbs_for_reply else {
+                error!("somehow different task has stolen our reply surbs! - this should have been impossible");
+                self.insert_pending_replies(&target, to_send);
+                return;
+            };
+
+            if let Err(err) = self
+                .message_handler
+                .try_send_reply_chunks(
+                    target,
+                    to_send_vec,
+                    surbs_for_reply,
+                    TransmissionLane::General,
+                )
+                .await
+            {
+                let err =
+                    err.return_unused_surbs(self.full_reply_storage.surbs_storage_ref(), &target);
+                self.insert_pending_replies(&target, to_send);
+                warn!("failed to clear pending queue for {:?} - {err}", target);
+            }
+        } else {
+            trace!("the pending queue is empty");
+        }
+    }
+
+    async fn handle_received_surbs(
+        &mut self,
+        from: AnonymousSenderTag,
+        reply_surbs: Vec<ReplySurb>,
+        from_surb_request: bool,
+    ) {
+        trace!("handling received surbs");
+
+        // clear the requesting flag since we should have been asking for surbs
+        self.full_reply_storage
+            .surbs_storage_ref()
+            .reset_surbs_last_received_at(&from);
+        if from_surb_request {
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .decrement_pending_reception(&from, reply_surbs.len() as u32);
+        }
+
+        // store received surbs
+        self.full_reply_storage
+            .surbs_storage_ref()
+            .insert_surbs(&from, reply_surbs);
+
+        // use as many as we can for clearing pending retransmission queue
+        self.try_clear_pending_retransmission(from).await;
+
+        // use as many as we can for clearing pending 'normal' queue
+        self.try_clear_pending_queue(from).await;
+
+        // if we have to, request more
+        if self.should_request_more_surbs(&from) {
+            self.request_reply_surbs_for_queue_clearing(from).await;
+        }
+    }
+
+    async fn handle_surb_request(&mut self, recipient: Recipient, mut amount: u32) {
+        // 1. check whether we sent any surbs in the past to this recipient, otherwise
+        // they have no business in asking for more
+        if !self
+            .full_reply_storage
+            .tags_storage_ref()
+            .exists(&recipient)
+        {
+            warn!("{recipient} asked us for reply SURBs even though we never sent them any anonymous messages before!");
+            return;
+        }
+
+        // 2. check whether the requested amount is within sane range
+        if amount > self.config.maximum_allowed_reply_surb_request_size {
+            warn!("The requested reply surb amount is larger than our maximum allowed ({amount} > {}). Lowering it to a more sane value...", self.config.maximum_allowed_reply_surb_request_size);
+            amount = self.config.maximum_allowed_reply_surb_request_size;
+        }
+
+        // 3. construct and send the surbs away
+        // (send them in smaller batches to make the experience a bit smoother
+        let mut remaining = amount;
+        while remaining > 0 {
+            let to_send = min(remaining, 100);
+            if let Err(err) = self
+                .message_handler
+                .try_send_additional_reply_surbs(recipient, to_send)
+                .await
+            {
+                warn!("failed to send additional surbs to {recipient} - {err}");
+            } else {
+                trace!("sent {to_send} reply SURBs to {recipient}");
+            }
+
+            remaining -= to_send;
+        }
+    }
+
+    fn buffer_pending_ack(
+        &mut self,
+        recipient: AnonymousSenderTag,
+        ack_ref: Arc<PendingAcknowledgement>,
+        weak_ack_ref: Weak<PendingAcknowledgement>,
+    ) {
+        let frag_id = ack_ref.inner_fragment_identifier();
+        if let Some(existing) = self.pending_retransmissions.get_mut(&recipient) {
+            if let Entry::Vacant(e) = existing.entry(frag_id) {
+                e.insert(weak_ack_ref);
+            } else {
+                warn!("we're already trying to retransmit {frag_id}. We must be really behind in surbs!");
+            }
+        } else {
+            let mut inner = BTreeMap::new();
+            inner.insert(frag_id, weak_ack_ref);
+            self.pending_retransmissions.insert(recipient, inner);
+        }
+    }
+
+    async fn handle_reply_retransmission(
+        &mut self,
+        recipient_tag: AnonymousSenderTag,
+        timed_out_ack: Weak<PendingAcknowledgement>,
+        extra_surbs_request: bool,
+    ) {
+        // seems we got the ack in the end
+        let ack_ref = match timed_out_ack.upgrade() {
+            Some(ack) => ack,
+            None => {
+                debug!("we received the ack for one of the reply packets as we were putting it in the retransmission queue");
+                return;
+            }
+        };
+
+        // if this is retransmission for obtaining additional reply surbs,
+        // we can dip below the storage threshold
+        let (maybe_reply_surb, _) = if extra_surbs_request {
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .get_reply_surb_ignoring_threshold(&recipient_tag)
+        } else {
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .get_reply_surb(&recipient_tag)
+        }
+        .expect("attempted to retransmit a packet to an unknown recipient - we shouldn't have sent the original packet in the first place!");
+
+        if let Some(reply_surb) = maybe_reply_surb {
+            match self
+                .message_handler
+                .try_prepare_single_reply_chunk_for_sending(reply_surb, ack_ref.fragment_data())
+                .await
+            {
+                Ok(prepared) => {
+                    // drop the ack ref so that controller would not panic on `UpdateTimer` if that task
+                    // got to handle the action before this function terminated (which is very much
+                    // possible if `forward_messages` takes a while)
+                    drop(ack_ref);
+
+                    self.message_handler
+                        .update_ack_delay(prepared.fragment_identifier, prepared.total_delay);
+                    self.message_handler
+                        .forward_messages(vec![prepared.into()], TransmissionLane::Retransmission)
+                        .await;
+                }
+                Err(err) => {
+                    let err = err.return_unused_surbs(
+                        self.full_reply_storage.surbs_storage_ref(),
+                        &recipient_tag,
+                    );
+                    warn!("failed to prepare message for retransmission - {err}");
+                    // we buffer that packet and to try another day
+                    self.buffer_pending_ack(recipient_tag, ack_ref, timed_out_ack);
+
+                    if self.should_request_more_surbs(&recipient_tag) {
+                        self.request_reply_surbs_for_queue_clearing(recipient_tag)
+                            .await;
+                    }
+                }
+            };
+        } else {
+            self.buffer_pending_ack(recipient_tag, ack_ref, timed_out_ack);
+
+            if self.should_request_more_surbs(&recipient_tag) {
+                self.request_reply_surbs_for_queue_clearing(recipient_tag)
+                    .await;
+            }
+        }
+    }
+
+    async fn handle_request(&mut self, request: ReplyControllerMessage) {
+        match request {
+            ReplyControllerMessage::RetransmitReply {
+                recipient,
+                timed_out_ack,
+                extra_surb_request,
+            } => {
+                self.handle_reply_retransmission(recipient, timed_out_ack, extra_surb_request)
+                    .await
+            }
+            ReplyControllerMessage::SendReply {
+                recipient,
+                message,
+                lane,
+            } => self.handle_send_reply(recipient, message, lane).await,
+            ReplyControllerMessage::AdditionalSurbs {
+                sender_tag,
+                reply_surbs,
+                from_surb_request,
+            } => {
+                self.handle_received_surbs(sender_tag, reply_surbs, from_surb_request)
+                    .await
+            }
+            ReplyControllerMessage::AdditionalSurbsRequest { recipient, amount } => {
+                self.handle_surb_request(*recipient, amount).await
+            }
+        }
+    }
+
+    async fn request_reply_surbs_for_queue_clearing(&mut self, target: AnonymousSenderTag) {
+        trace!("requesting surbs for queues clearing");
+
+        let pending_queue_size = self
+            .pending_replies
+            .get(&target)
+            .map(|pending_queue| pending_queue.len())
+            .unwrap_or_default();
+
+        let retransmission_queue = self
+            .pending_retransmissions
+            .get(&target)
+            .map(|pending_queue| pending_queue.len())
+            .unwrap_or_default();
+
+        let total_queue = (pending_queue_size + retransmission_queue) as u32;
+
+        if total_queue == 0 {
+            trace!("the pending queues for {:?} are already empty", target);
+            return;
+        }
+
+        let request_size = min(
+            self.config.max_surb_request_size,
+            max(total_queue, self.config.min_surb_request_size),
+        );
+
+        if let Err(err) = self
+            .request_additional_reply_surbs(target, request_size)
+            .await
+        {
+            warn!("failed to request additional surbs... - {err}")
+        }
+    }
+
+    async fn inspect_stale_entries(&mut self) {
+        let mut to_request = Vec::new();
+        let mut to_remove = Vec::new();
+
+        let now = OffsetDateTime::now_utc();
+        for (pending_reply_target, vals) in &self.pending_replies {
+            if vals.is_empty() {
+                continue;
+            }
+
+            let Some(last_received) = self.full_reply_storage.surbs_storage_ref().surbs_last_received_at(pending_reply_target) else {
+                error!("we have {} pending replies for {pending_reply_target}, but we somehow never received any reply surbs from them!", vals.len());
+                to_remove.push(*pending_reply_target);
+                continue;
+            };
+
+            // this should never ever happen (famous last words, eh?), but in case it DOES happen eventually
+            // purge that malformed data
+            let Ok(last_received_time) = OffsetDateTime::from_unix_timestamp(last_received) else {
+                error!("somehow our stored timestamp ({last_received}) for surbs from {pending_reply_target} is corrupted!. Going to remove all the associated entries");
+                to_remove.push(*pending_reply_target);
+                continue;
+            };
+
+            let diff = now - last_received_time;
+
+            if diff > self.config.max_surb_waiting_period {
+                warn!("We haven't received any surbs in {:?} from {pending_reply_target}. Going to explicitly ask for more", diff);
+                to_request.push(*pending_reply_target);
+            }
+        }
+
+        for pending_reply_target in to_request {
+            self.request_reply_surbs_for_queue_clearing(pending_reply_target)
+                .await;
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .reset_pending_reception(&pending_reply_target)
+        }
+        for to_remove in to_remove {
+            self.pending_replies.remove(&to_remove);
+        }
+    }
+
+    async fn invalidate_old_data(&self) {
+        let now = OffsetDateTime::now_utc();
+
+        let mut to_remove_surbs = Vec::new();
+        let mut to_remove_keys = Vec::new();
+        for map_ref in self.full_reply_storage.surbs_storage_ref().as_raw_iter() {
+            let (sender, received) = map_ref.pair();
+            // TODO: handle the following edge case:
+            // there's a malicious client sending us exactly one reply surb just before we should have invalidated
+            // the data thus making us keep everything in memory
+            // possible solution: keep timestamp PER reply surb (but that seems like an overkill)
+            // but I doubt this is ever going to be a problem...
+            // ...
+            // However, if you're reading this message, it probably became a legit problem,
+            // so I guess add timestamp per surb then? chop-chop.
+
+            let last_received = received.surbs_last_received_at();
+            // this should never ever happen (famous last words, eh?), but in case it DOES happen eventually
+            // purge that malformed data
+            let Ok(last_received_time) = OffsetDateTime::from_unix_timestamp(last_received) else {
+                error!("somehow our stored timestamp ({last_received}) for surbs from {sender} is corrupted!. Going to remove all the associated entries");
+                to_remove_surbs.push(*sender);
+                continue;
+            };
+            let diff = now - last_received_time;
+
+            if diff > self.config.max_reply_surb_age {
+                info!("it's been {diff:?} since we last received any reply surb from {sender}. Going to remove all stored entries...");
+
+                to_remove_surbs.push(*sender);
+            }
+        }
+
+        for map_ref in self.full_reply_storage.key_storage_ref().as_raw_iter() {
+            let (digest, reply_key) = map_ref.pair();
+
+            // this should never ever happen (famous last words, eh?), but in case it DOES happen eventually
+            // purge that malformed data
+            let Ok(sent_at) = OffsetDateTime::from_unix_timestamp(reply_key.sent_at_timestamp) else {
+                error!("somehow our stored timestamp ({}) for one of our reply key is corrupted!. Going to remove all the entry", reply_key.sent_at_timestamp);
+                to_remove_keys.push(*digest);
+                continue;
+            };
+
+            let diff = now - sent_at;
+
+            if diff > self.config.max_reply_key_age {
+                debug!("it's been {diff:?} since we created this reply key. it's probably never going to get used, so we're going to purge it...");
+                to_remove_keys.push(*digest);
+            }
+        }
+
+        for to_remove in to_remove_surbs {
+            self.full_reply_storage
+                .surbs_storage_ref()
+                .remove(&to_remove);
+        }
+
+        for to_remove in to_remove_keys {
+            self.full_reply_storage.key_storage().remove(to_remove)
+        }
+    }
+
+    fn create_interval_stream(polling_rate: Duration) -> IntervalStream {
+        #[cfg(not(target_arch = "wasm32"))]
+        return tokio_stream::wrappers::IntervalStream::new(tokio::time::interval(polling_rate));
+
+        #[cfg(target_arch = "wasm32")]
+        return gloo_timers::future::IntervalStream::new(polling_rate.as_millis() as u32);
+    }
+
+    pub(crate) async fn run_with_shutdown(&mut self, mut shutdown: task::ShutdownListener) {
+        debug!("Started ReplyController with graceful shutdown support");
+
+        let polling_rate = Duration::from_secs(5);
+        let mut stale_inspection = Self::create_interval_stream(polling_rate);
+
+        // this is in the order of hours/days so we don't have to poll it that often
+        let polling_rate = Duration::from_secs(self.config.max_reply_surb_age.as_secs() / 10);
+        let mut invalidation_inspection = Self::create_interval_stream(polling_rate);
+
+        while !shutdown.is_shutdown() {
+            tokio::select! {
+                biased;
+                _ = shutdown.recv() => {
+                    log::trace!("ReplyController: Received shutdown");
+                },
+                req = self.request_receiver.next() => match req {
+                    Some(req) => self.handle_request(req).await,
+                    None => {
+                        log::trace!("ReplyController: Stopping since channel closed");
+                        break;
+                    }
+                },
+                _ = stale_inspection.next() => {
+                    self.inspect_stale_entries().await
+                },
+                _ = invalidation_inspection.next() => {
+                    self.invalidate_old_data().await
+                }
+            }
+        }
+        assert!(shutdown.is_shutdown_poll());
+        log::debug!("ReplyController: Exiting");
+    }
+}
@@ -0,0 +1,43 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::backend::Empty;
+use crate::client::replies::reply_storage::{CombinedReplyStorage, ReplyStorageBackend};
+use async_trait::async_trait;
+
+// well, right now we don't have the browser storage : (
+// so we keep everything in memory
+pub struct Backend {
+    empty: Empty,
+}
+
+impl Backend {
+    pub fn new(min_surb_threshold: usize, max_surb_threshold: usize) -> Self {
+        Backend {
+            empty: Empty {
+                min_surb_threshold,
+                max_surb_threshold,
+            },
+        }
+    }
+}
+
+#[async_trait]
+impl ReplyStorageBackend for Backend {
+    type StorageError = <Empty as ReplyStorageBackend>::StorageError;
+
+    async fn flush_surb_storage(
+        &mut self,
+        storage: &CombinedReplyStorage,
+    ) -> Result<(), Self::StorageError> {
+        self.empty.flush_surb_storage(storage).await
+    }
+
+    async fn init_fresh(&mut self, fresh: &CombinedReplyStorage) -> Result<(), Self::StorageError> {
+        self.empty.init_fresh(fresh).await
+    }
+
+    async fn load_surb_storage(&self) -> Result<CombinedReplyStorage, Self::StorageError> {
+        self.empty.load_surb_storage().await
+    }
+}
@@ -0,0 +1,53 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use std::io;
+use std::path::PathBuf;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum StorageError {
+    #[error("the provided database path doesn't have a filename defined")]
+    DatabasePathWithoutFilename { provided_path: PathBuf },
+
+    #[error("failed to rename our databse file - {source}")]
+    DatabaseRenameError {
+        #[source]
+        source: io::Error,
+    },
+
+    #[error("failed to rename our old databse file - {source}")]
+    DatabaseOldFileRemoveError {
+        #[source]
+        source: io::Error,
+    },
+
+    #[error("failed to perform sqlx migration: {source}")]
+    MigrationError {
+        #[source]
+        #[from]
+        source: sqlx::migrate::MigrateError,
+    },
+
+    #[error("failed to connect to the underlying connection pool: {source}")]
+    DatabaseConnectionError {
+        #[source]
+        source: sqlx::error::Error,
+    },
+
+    #[error("failed to run the SQL query: {source}")]
+    QueryError {
+        #[source]
+        #[from]
+        source: sqlx::error::Error,
+    },
+
+    #[error("The loaded data is inconsistent - it seems that on the last shutdown the client hasn't finished the data flush. You may have to remove the entire storage manually")]
+    IncompleteDataFlush,
+
+    #[error("data retrieved from the underlying storage is corrupted: {details}")]
+    CorruptedData {
+        details: String,
+        // err: Option<Box<dyn std::error::Error>>
+    },
+}
@@ -0,0 +1,257 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::backend::fs_backend::error::StorageError;
+use crate::client::replies::reply_storage::backend::fs_backend::models::{
+    ReplySurbStorageMetadata, StoredReplyKey, StoredReplySurb, StoredSenderTag, StoredSurbSender,
+};
+use log::{error, info};
+use sqlx::ConnectOptions;
+use std::path::Path;
+
+#[derive(Debug, Clone)]
+pub(crate) struct StorageManager {
+    pub(crate) connection_pool: sqlx::SqlitePool,
+}
+
+// all SQL goes here
+impl StorageManager {
+    pub(crate) async fn init<P: AsRef<Path>>(
+        database_path: P,
+        fresh: bool,
+    ) -> Result<Self, StorageError> {
+        let mut opts = sqlx::sqlite::SqliteConnectOptions::new()
+            .filename(database_path)
+            .create_if_missing(fresh);
+
+        opts.disable_statement_logging();
+
+        let connection_pool = match sqlx::SqlitePool::connect_with(opts).await {
+            Ok(pool) => pool,
+            Err(err) => {
+                error!("Failed to connect to SQLx database: {err}");
+                return Err(StorageError::DatabaseConnectionError { source: err });
+            }
+        };
+
+        if let Err(err) = sqlx::migrate!("./fs_surbs_migrations")
+            .run(&connection_pool)
+            .await
+        {
+            error!("Failed to initialize SQLx database: {err}");
+            return Err(err.into());
+        }
+
+        info!("Database migration finished!");
+        Ok(StorageManager { connection_pool })
+    }
+
+    #[allow(dead_code)]
+    pub(crate) async fn status_table_exists(&self) -> Result<bool, sqlx::Error> {
+        sqlx::query!("SELECT name FROM sqlite_master WHERE type='table' AND name='status'")
+            .fetch_optional(&self.connection_pool)
+            .await
+            .map(|r| r.is_some())
+    }
+
+    pub(crate) async fn create_status_table(&self) -> Result<(), sqlx::Error> {
+        sqlx::query!("INSERT INTO status(flush_in_progress, previous_flush_timestamp, client_in_use) VALUES (0, 0, 1)")
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_flush_status(&self) -> Result<bool, sqlx::Error> {
+        sqlx::query!("SELECT flush_in_progress FROM status;")
+            .fetch_one(&self.connection_pool)
+            .await
+            .map(|r| r.flush_in_progress > 0)
+    }
+
+    pub(crate) async fn set_previous_flush_timestamp(
+        &self,
+        timestamp: i64,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query!("UPDATE status SET previous_flush_timestamp = ?", timestamp)
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_previous_flush_timestamp(&self) -> Result<i64, sqlx::Error> {
+        sqlx::query!("SELECT previous_flush_timestamp FROM status;")
+            .fetch_one(&self.connection_pool)
+            .await
+            .map(|r| r.previous_flush_timestamp)
+    }
+
+    pub(crate) async fn set_flush_status(&self, in_progress: bool) -> Result<(), sqlx::Error> {
+        let in_progress_int = i64::from(in_progress);
+        sqlx::query!("UPDATE status SET flush_in_progress = ?", in_progress_int)
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_client_in_use_status(&self) -> Result<bool, sqlx::Error> {
+        sqlx::query!("SELECT client_in_use FROM status;")
+            .fetch_one(&self.connection_pool)
+            .await
+            .map(|r| r.client_in_use > 0)
+    }
+
+    pub(crate) async fn set_client_in_use_status(&self, in_use: bool) -> Result<(), sqlx::Error> {
+        let in_use_int = i64::from(in_use);
+        sqlx::query!("UPDATE status SET client_in_use = ?", in_use_int)
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn delete_all_tags(&self) -> Result<(), sqlx::Error> {
+        sqlx::query!("DELETE FROM sender_tag;")
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_tags(&self) -> Result<Vec<StoredSenderTag>, sqlx::Error> {
+        sqlx::query_as!(StoredSenderTag, "SELECT * FROM sender_tag;",)
+            .fetch_all(&self.connection_pool)
+            .await
+    }
+
+    pub(crate) async fn insert_tag(&self, stored_tag: StoredSenderTag) -> Result<(), sqlx::Error> {
+        sqlx::query!(
+            r#"
+                INSERT INTO sender_tag(recipient, tag) VALUES (?, ?);
+            "#,
+            stored_tag.recipient,
+            stored_tag.tag
+        )
+        .execute(&self.connection_pool)
+        .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn delete_all_reply_keys(&self) -> Result<(), sqlx::Error> {
+        sqlx::query!("DELETE FROM reply_key;")
+            .execute(&self.connection_pool)
+            .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_reply_keys(&self) -> Result<Vec<StoredReplyKey>, sqlx::Error> {
+        sqlx::query_as!(StoredReplyKey, "SELECT * FROM reply_key;",)
+            .fetch_all(&self.connection_pool)
+            .await
+    }
+
+    pub(crate) async fn insert_reply_key(
+        &self,
+        stored_reply_key: StoredReplyKey,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query!(
+            r#"
+                INSERT INTO reply_key(key_digest, reply_key, sent_at_timestamp) VALUES (?, ?, ?);
+            "#,
+            stored_reply_key.key_digest,
+            stored_reply_key.reply_key,
+            stored_reply_key.sent_at_timestamp
+        )
+        .execute(&self.connection_pool)
+        .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_surb_senders(&self) -> Result<Vec<StoredSurbSender>, sqlx::Error> {
+        sqlx::query_as!(StoredSurbSender, "SELECT * FROM reply_surb_sender;",)
+            .fetch_all(&self.connection_pool)
+            .await
+    }
+
+    pub(crate) async fn insert_surb_sender(
+        &self,
+        stored_surb_sender: StoredSurbSender,
+    ) -> Result<i64, sqlx::Error> {
+        let id = sqlx::query!(
+            r#"
+                INSERT INTO reply_surb_sender(tag, last_sent_timestamp) VALUES (?, ?);
+            "#,
+            stored_surb_sender.tag,
+            stored_surb_sender.last_sent_timestamp
+        )
+        .execute(&self.connection_pool)
+        .await?
+        .last_insert_rowid();
+        Ok(id)
+    }
+
+    pub(crate) async fn get_reply_surbs(
+        &self,
+        sender_id: i64,
+    ) -> Result<Vec<StoredReplySurb>, sqlx::Error> {
+        sqlx::query_as!(
+            StoredReplySurb,
+            "SELECT * FROM reply_surb WHERE reply_surb_sender_id = ?",
+            sender_id
+        )
+        .fetch_all(&self.connection_pool)
+        .await
+    }
+
+    pub(crate) async fn delete_all_reply_surb_data(&self) -> Result<(), sqlx::Error> {
+        sqlx::query!("DELETE FROM reply_surb;")
+            .execute(&self.connection_pool)
+            .await?;
+
+        sqlx::query!("DELETE FROM reply_surb_sender;")
+            .execute(&self.connection_pool)
+            .await?;
+
+        Ok(())
+    }
+
+    pub(crate) async fn insert_reply_surb(
+        &self,
+        stored_reply_surb: StoredReplySurb,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query!(
+            r#"
+                INSERT INTO reply_surb(reply_surb_sender_id, reply_surb) VALUES (?, ?);
+            "#,
+            stored_reply_surb.reply_surb_sender_id,
+            stored_reply_surb.reply_surb
+        )
+        .execute(&self.connection_pool)
+        .await?;
+        Ok(())
+    }
+
+    pub(crate) async fn get_reply_surb_storage_metadata(
+        &self,
+    ) -> Result<ReplySurbStorageMetadata, sqlx::Error> {
+        sqlx::query_as!(
+            ReplySurbStorageMetadata,
+             r#"
+                SELECT min_reply_surb_threshold as "min_reply_surb_threshold: u32", max_reply_surb_threshold as "max_reply_surb_threshold: u32" FROM reply_surb_storage_metadata;
+             "#,
+        )
+            .fetch_one(&self.connection_pool)
+            .await
+    }
+
+    pub(crate) async fn insert_reply_surb_storage_metadata(
+        &self,
+        metadata: ReplySurbStorageMetadata,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query!(r#"
+            INSERT INTO reply_surb_storage_metadata(min_reply_surb_threshold, max_reply_surb_threshold)
+            VALUES (?, ?);
+        "#,
+            metadata.min_reply_surb_threshold,
+            metadata.max_reply_surb_threshold,
+        ).execute(&self.connection_pool).await?;
+        Ok(())
+    }
+}
@@ -0,0 +1,348 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::backend::fs_backend::manager::StorageManager;
+use crate::client::replies::reply_storage::backend::fs_backend::models::{
+    ReplySurbStorageMetadata, StoredReplyKey, StoredReplySurb, StoredSenderTag, StoredSurbSender,
+};
+use crate::client::replies::reply_storage::surb_storage::ReceivedReplySurbs;
+use crate::client::replies::reply_storage::{
+    CombinedReplyStorage, ReceivedReplySurbsMap, ReplyStorageBackend, SentReplyKeys, UsedSenderTags,
+};
+use async_trait::async_trait;
+use log::{error, info, warn};
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
+use std::fs;
+use std::path::{Path, PathBuf};
+use time::OffsetDateTime;
+
+pub use self::error::StorageError;
+
+mod error;
+mod manager;
+mod models;
+
+#[derive(Debug)]
+pub struct Backend {
+    temporary_old_path: Option<PathBuf>,
+    database_path: PathBuf,
+    manager: StorageManager,
+}
+
+impl Backend {
+    const OLD_EXTENSION: &'static str = "old";
+
+    pub async fn init<P: AsRef<Path>>(database_path: P) -> Result<Self, StorageError> {
+        let owned_path: PathBuf = database_path.as_ref().into();
+        if owned_path.file_name().is_none() {
+            return Err(StorageError::DatabasePathWithoutFilename {
+                provided_path: owned_path,
+            });
+        }
+
+        let backend = Backend {
+            temporary_old_path: None,
+            database_path: owned_path,
+            manager: StorageManager::init(database_path, true).await?,
+        };
+
+        backend.manager.create_status_table().await?;
+
+        Ok(backend)
+    }
+
+    pub async fn try_load<P: AsRef<Path>>(database_path: P) -> Result<Self, StorageError> {
+        let owned_path: PathBuf = database_path.as_ref().into();
+        if owned_path.file_name().is_none() {
+            return Err(StorageError::DatabasePathWithoutFilename {
+                provided_path: owned_path,
+            });
+        }
+
+        let manager = StorageManager::init(database_path, false).await?;
+
+        // the database flush wasn't fully finished and thus the data is in inconsistent state
+        // (we don't really know what's properly saved or what's not)
+        if manager.get_flush_status().await? {
+            return Err(StorageError::IncompleteDataFlush);
+        }
+
+        let last_flush_timestamp = manager.get_previous_flush_timestamp().await?;
+        if last_flush_timestamp == 0 {
+            // either this client has been running since 1970 or the flush failed
+            return Err(StorageError::IncompleteDataFlush);
+        }
+
+        // the process has gone down without full graceful shutdown,
+        // meaning the database doesn't contain valid data anymore
+        // so we have to purge it
+        if manager.get_client_in_use_status().await? {
+            error!("the client hasn't undergone through graceful shutdown the last time it's gone down - we can't trust its reply surbs or stored encryption keys. They shall get purged");
+            manager.delete_all_reply_surb_data().await?;
+            manager.delete_all_reply_keys().await?;
+        }
+
+        if let Err(err) = manager.get_reply_surb_storage_metadata().await {
+            // we can't recover here, we HAVE TO initialise fresh (because we don't know correct starting metadata)
+            error!("it seems the client has been shutdown gracefully - we're missing valid surb data dump. the existing database cannot be used");
+            return Err(err.into());
+        }
+
+        let last_flush = match OffsetDateTime::from_unix_timestamp(last_flush_timestamp) {
+            Ok(last_flush) => last_flush,
+            Err(err) => {
+                return Err(StorageError::CorruptedData {
+                    details: format!("failed to parse stored timestamp - {err}"),
+                });
+            }
+        };
+
+        // in theory clients can use our reply surbs whenever they want, even a year in the future
+        // (assuming no key rotation has happened)
+        // but the way it's currently coded, everyone will purge old data
+        let since_last_flush = OffsetDateTime::now_utc() - last_flush;
+        if since_last_flush.whole_days() > 0 {
+            info!("it's been over {} days and {} hours since we last used our data store. our reply surbs are already outdated - we're going to purge them now.", since_last_flush.whole_days(), since_last_flush.whole_hours());
+            manager.delete_all_reply_surb_data().await?;
+        }
+
+        if since_last_flush.whole_days() > 1 {
+            info!("it's been over {} days and {} hours since we last used our data store. our reply keys are already outdated - we're going to purge them now.", since_last_flush.whole_days(), since_last_flush.whole_hours());
+            manager.delete_all_reply_keys().await?;
+        }
+
+        if since_last_flush.whole_days() > 2 {
+            info!("it's been over {} days and {} hours since we last used our data store. our used sender tags are already outdated - we're going to purge them now.", since_last_flush.whole_days(), since_last_flush.whole_hours());
+            manager.delete_all_tags().await?;
+        }
+
+        Ok(Backend {
+            temporary_old_path: None,
+            database_path: owned_path,
+            manager,
+        })
+    }
+
+    async fn close_pool(&mut self) {
+        self.manager.connection_pool.close().await;
+    }
+
+    async fn rotate(&mut self) -> Result<(), StorageError> {
+        self.close_pool().await;
+
+        let new_extension = if let Some(existing_extension) =
+            self.database_path.extension().and_then(|ext| ext.to_str())
+        {
+            format!("{existing_extension}.{}", Self::OLD_EXTENSION)
+        } else {
+            Self::OLD_EXTENSION.to_string()
+        };
+
+        let mut temp_old = self.database_path.clone();
+        temp_old.set_extension(new_extension);
+
+        fs::rename(&self.database_path, &temp_old)
+            .map_err(|err| StorageError::DatabaseRenameError { source: err })?;
+        self.manager = StorageManager::init(&self.database_path, true).await?;
+        self.manager.create_status_table().await?;
+
+        self.temporary_old_path = Some(temp_old);
+        Ok(())
+    }
+
+    fn remove_old(&mut self) -> Result<(), StorageError> {
+        if let Some(old_path) = self.temporary_old_path.take() {
+            fs::remove_file(old_path)
+                .map_err(|err| StorageError::DatabaseOldFileRemoveError { source: err })
+        } else {
+            warn!("the old database file doesn't seem to exist!");
+            Ok(())
+        }
+    }
+
+    async fn start_storage_flush(&self) -> Result<(), StorageError> {
+        Ok(self.manager.set_flush_status(true).await?)
+    }
+
+    async fn end_storage_flush(&self) -> Result<(), StorageError> {
+        self.manager
+            .set_previous_flush_timestamp(OffsetDateTime::now_utc().unix_timestamp())
+            .await?;
+        Ok(self.manager.set_flush_status(false).await?)
+    }
+
+    async fn start_client_use(&self) -> Result<(), StorageError> {
+        Ok(self.manager.set_client_in_use_status(true).await?)
+    }
+
+    async fn stop_client_use(&self) -> Result<(), StorageError> {
+        Ok(self.manager.set_client_in_use_status(false).await?)
+    }
+
+    async fn get_stored_tags(&self) -> Result<UsedSenderTags, StorageError> {
+        let stored = self.manager.get_tags().await?;
+
+        // stop at the first instance of corruption. if even a single entry is malformed,
+        // something weird has happened and we can't trust the rest of the data
+        let raw = stored
+            .into_iter()
+            .map(TryInto::try_into)
+            .collect::<Result<_, _>>()?;
+
+        Ok(UsedSenderTags::from_raw(raw))
+    }
+
+    async fn dump_sender_tags(&self, tags: &UsedSenderTags) -> Result<(), StorageError> {
+        for map_ref in tags.as_raw_iter() {
+            let (recipient, tag) = map_ref.pair();
+            self.manager
+                .insert_tag(StoredSenderTag::new(*recipient, *tag))
+                .await?;
+        }
+        Ok(())
+    }
+
+    async fn get_stored_reply_keys(&self) -> Result<SentReplyKeys, StorageError> {
+        let stored = self.manager.get_reply_keys().await?;
+
+        // stop at the first instance of corruption. if even a single entry is malformed,
+        // something weird has happened and we can't trust the rest of the data
+        let raw = stored
+            .into_iter()
+            .map(TryInto::try_into)
+            .collect::<Result<_, _>>()?;
+
+        Ok(SentReplyKeys::from_raw(raw))
+    }
+
+    async fn dump_sender_reply_keys(&self, reply_keys: &SentReplyKeys) -> Result<(), StorageError> {
+        for map_ref in reply_keys.as_raw_iter() {
+            let (digest, key) = map_ref.pair();
+            self.manager
+                .insert_reply_key(StoredReplyKey::new(*digest, *key))
+                .await?;
+        }
+        Ok(())
+    }
+
+    async fn get_stored_reply_surbs(&self) -> Result<ReceivedReplySurbsMap, StorageError> {
+        let surb_senders = self.manager.get_surb_senders().await?;
+
+        let metadata = self.get_reply_surb_storage_metadata().await?;
+        let mut received_surbs = Vec::with_capacity(surb_senders.len());
+        for sender in surb_senders {
+            let sender_id = sender.id;
+            let (sender_tag, surbs_last_received_at_timestamp): (AnonymousSenderTag, i64) =
+                sender.try_into()?;
+            let stored_surbs = self
+                .manager
+                .get_reply_surbs(sender_id)
+                .await?
+                .into_iter()
+                .map(|raw| raw.try_into())
+                .collect::<Result<_, _>>()?;
+
+            received_surbs.push((
+                sender_tag,
+                ReceivedReplySurbs::new_retrieved(stored_surbs, surbs_last_received_at_timestamp),
+            ))
+        }
+
+        Ok(ReceivedReplySurbsMap::from_raw(
+            metadata.min_reply_surb_threshold as usize,
+            metadata.max_reply_surb_threshold as usize,
+            received_surbs,
+        ))
+    }
+
+    async fn dump_reply_surbs(
+        &self,
+        reply_surbs: &ReceivedReplySurbsMap,
+    ) -> Result<(), StorageError> {
+        for map_ref in reply_surbs.as_raw_iter() {
+            let (tag, received_surbs) = map_ref.pair();
+            let sender_id = self
+                .manager
+                .insert_surb_sender(StoredSurbSender::new(
+                    *tag,
+                    received_surbs.surbs_last_received_at(),
+                ))
+                .await?;
+
+            for reply_surb in received_surbs.surbs_ref() {
+                self.manager
+                    .insert_reply_surb(StoredReplySurb::new(sender_id, reply_surb))
+                    .await?
+            }
+        }
+        Ok(())
+    }
+
+    async fn get_reply_surb_storage_metadata(
+        &self,
+    ) -> Result<ReplySurbStorageMetadata, StorageError> {
+        self.manager
+            .get_reply_surb_storage_metadata()
+            .await
+            .map_err(Into::into)
+    }
+
+    async fn dump_reply_surb_storage_metadata(
+        &self,
+        reply_surbs: &ReceivedReplySurbsMap,
+    ) -> Result<(), StorageError> {
+        self.manager
+            .insert_reply_surb_storage_metadata(ReplySurbStorageMetadata::new(
+                reply_surbs.min_surb_threshold(),
+                reply_surbs.max_surb_threshold(),
+            ))
+            .await
+            .map_err(Into::into)
+    }
+}
+
+#[async_trait]
+impl ReplyStorageBackend for Backend {
+    type StorageError = error::StorageError;
+
+    async fn start_storage_session(&self) -> Result<(), Self::StorageError> {
+        self.start_client_use().await
+    }
+
+    async fn flush_surb_storage(
+        &mut self,
+        storage: &CombinedReplyStorage,
+    ) -> Result<(), Self::StorageError> {
+        // close all connections (there should be none! and rename the file to contain .old extension)
+        self.rotate().await?;
+        self.start_storage_flush().await?;
+
+        self.dump_sender_tags(storage.tags_storage_ref()).await?;
+        self.dump_sender_reply_keys(storage.key_storage_ref())
+            .await?;
+        let surbs_ref = storage.surbs_storage_ref();
+        self.dump_reply_surb_storage_metadata(surbs_ref).await?;
+        self.dump_reply_surbs(surbs_ref).await?;
+
+        self.remove_old()?;
+        self.end_storage_flush().await
+    }
+
+    async fn init_fresh(&mut self, fresh: &CombinedReplyStorage) -> Result<(), Self::StorageError> {
+        // for now nothing more to do apart from dumping the metadata
+        self.dump_reply_surb_storage_metadata(fresh.surbs_storage_ref())
+            .await
+    }
+
+    async fn load_surb_storage(&self) -> Result<CombinedReplyStorage, Self::StorageError> {
+        let reply_keys = self.get_stored_reply_keys().await?;
+        let tags = self.get_stored_tags().await?;
+        let reply_surbs = self.get_stored_reply_surbs().await?;
+
+        Ok(CombinedReplyStorage::load(reply_keys, reply_surbs, tags))
+    }
+
+    async fn stop_storage_session(self) -> Result<(), Self::StorageError> {
+        self.stop_client_use().await
+    }
+}
@@ -0,0 +1,185 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::backend::fs_backend::error::StorageError;
+use crate::client::replies::reply_storage::key_storage::UsedReplyKey;
+use crypto::generic_array::typenum::Unsigned;
+use crypto::Digest;
+use nymsphinx::addressing::clients::{Recipient, RecipientBytes};
+use nymsphinx::anonymous_replies::encryption_key::EncryptionKeyDigest;
+use nymsphinx::anonymous_replies::requests::{AnonymousSenderTag, SENDER_TAG_SIZE};
+use nymsphinx::anonymous_replies::{ReplySurb, SurbEncryptionKey, SurbEncryptionKeySize};
+use nymsphinx::params::ReplySurbKeyDigestAlgorithm;
+
+#[derive(Debug, Clone)]
+pub(crate) struct StoredSenderTag {
+    pub(crate) recipient: Vec<u8>,
+    pub(crate) tag: Vec<u8>,
+}
+
+impl StoredSenderTag {
+    pub(crate) fn new(recipient: RecipientBytes, tag: AnonymousSenderTag) -> StoredSenderTag {
+        StoredSenderTag {
+            recipient: recipient.to_vec(),
+            tag: tag.to_bytes().to_vec(),
+        }
+    }
+}
+
+impl TryFrom<StoredSenderTag> for (RecipientBytes, AnonymousSenderTag) {
+    type Error = StorageError;
+
+    fn try_from(value: StoredSenderTag) -> Result<Self, Self::Error> {
+        let recipient_len = value.recipient.len();
+        let Ok(recipient_bytes) = value.recipient.try_into() else {
+            return Err(StorageError::CorruptedData {
+                details: format!(
+                    "the retrieved recipient has length of {recipient_len} while {} was expected",
+                    Recipient::LEN
+                ),
+            });
+        };
+
+        let tag_len = value.tag.len();
+        let Ok(sender_tag_bytes) = value.tag.try_into() else {
+            return Err(StorageError::CorruptedData {
+                details: format!(
+                    "the retrieved sender tag has length of {tag_len} while {} was expected",
+                    SENDER_TAG_SIZE
+                ),
+            });
+        };
+
+        Ok((
+            recipient_bytes,
+            AnonymousSenderTag::from_bytes(sender_tag_bytes),
+        ))
+    }
+}
+
+#[derive(Debug, Clone)]
+pub(crate) struct StoredReplyKey {
+    pub(crate) key_digest: Vec<u8>,
+    pub(crate) reply_key: Vec<u8>,
+    pub(crate) sent_at_timestamp: i64,
+}
+
+impl StoredReplyKey {
+    pub(crate) fn new(key_digest: EncryptionKeyDigest, reply_key: UsedReplyKey) -> StoredReplyKey {
+        StoredReplyKey {
+            key_digest: key_digest.to_vec(),
+            reply_key: (*reply_key).to_bytes(),
+            sent_at_timestamp: reply_key.sent_at_timestamp,
+        }
+    }
+}
+
+impl TryFrom<StoredReplyKey> for (EncryptionKeyDigest, UsedReplyKey) {
+    type Error = StorageError;
+
+    fn try_from(value: StoredReplyKey) -> Result<Self, Self::Error> {
+        let expected_reply_key_digest_size = ReplySurbKeyDigestAlgorithm::output_size();
+        let reply_key_digest_size = value.key_digest.len();
+
+        let Some(digest) = EncryptionKeyDigest::from_exact_iter(value.key_digest) else {
+            return Err(StorageError::CorruptedData {
+                details: format!(
+                    "the reply surb digest has length of {reply_key_digest_size} while {expected_reply_key_digest_size} was expected",
+                ),
+            });
+        };
+
+        let reply_key_len = value.reply_key.len();
+        let Ok(reply_key) = SurbEncryptionKey::try_from_bytes(&value.reply_key) else {
+            return Err(StorageError::CorruptedData {
+                details: format!(
+                    "the reply key has length of {reply_key_len} while {} was expected",
+                    SurbEncryptionKeySize::USIZE
+                ),
+            });
+        };
+
+        Ok((
+            digest,
+            UsedReplyKey::new(reply_key, value.sent_at_timestamp),
+        ))
+    }
+}
+
+pub(crate) struct StoredSurbSender {
+    pub(crate) id: i64,
+    pub(crate) tag: Vec<u8>,
+    pub(crate) last_sent_timestamp: i64,
+}
+
+impl StoredSurbSender {
+    pub(crate) fn new(tag: AnonymousSenderTag, last_sent_timestamp: i64) -> Self {
+        StoredSurbSender {
+            // for the purposes of STORING data,
+            // we ignore that field anyway
+            id: 0,
+            tag: tag.to_bytes().to_vec(),
+            last_sent_timestamp,
+        }
+    }
+}
+
+impl TryFrom<StoredSurbSender> for (AnonymousSenderTag, i64) {
+    type Error = StorageError;
+
+    fn try_from(value: StoredSurbSender) -> Result<Self, Self::Error> {
+        let tag_len = value.tag.len();
+        let Ok(sender_tag_bytes) = value.tag.try_into() else {
+            return Err(StorageError::CorruptedData {
+                details: format!(
+                    "the retrieved sender tag has length of {tag_len} while {} was expected",
+                    SENDER_TAG_SIZE
+                ),
+            });
+        };
+
+        Ok((
+            AnonymousSenderTag::from_bytes(sender_tag_bytes),
+            value.last_sent_timestamp,
+        ))
+    }
+}
+
+pub(crate) struct StoredReplySurb {
+    pub(crate) reply_surb_sender_id: i64,
+    pub(crate) reply_surb: Vec<u8>,
+}
+
+impl StoredReplySurb {
+    pub(crate) fn new(reply_surb_sender_id: i64, reply_surb: &ReplySurb) -> Self {
+        StoredReplySurb {
+            reply_surb_sender_id,
+            reply_surb: reply_surb.to_bytes(),
+        }
+    }
+}
+
+impl TryFrom<StoredReplySurb> for ReplySurb {
+    type Error = StorageError;
+
+    fn try_from(value: StoredReplySurb) -> Result<Self, Self::Error> {
+        ReplySurb::from_bytes(&value.reply_surb).map_err(|err| StorageError::CorruptedData {
+            details: format!("failed to recover the reply surb: {err}"),
+        })
+    }
+}
+
+#[derive(Copy, Clone)]
+pub(crate) struct ReplySurbStorageMetadata {
+    pub(crate) min_reply_surb_threshold: u32,
+    pub(crate) max_reply_surb_threshold: u32,
+}
+
+impl ReplySurbStorageMetadata {
+    pub(crate) fn new(min_reply_surb_threshold: usize, max_reply_surb_threshold: usize) -> Self {
+        Self {
+            min_reply_surb_threshold: min_reply_surb_threshold as u32,
+            max_reply_surb_threshold: max_reply_surb_threshold as u32,
+        }
+    }
+}
@@ -0,0 +1,78 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::CombinedReplyStorage;
+use async_trait::async_trait;
+use std::error::Error;
+use thiserror::Error;
+
+#[cfg(target_arch = "wasm32")]
+pub mod browser_backend;
+
+#[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+pub mod fs_backend;
+
+// #[cfg(all(test, feature = "std"))]
+// third case: node with actual filesystem
+
+#[derive(Debug, Error)]
+#[error("no information provided")]
+pub struct UndefinedError;
+
+pub struct Empty {
+    // we need to keep 'basic' metadata here to "load" the CombinedReplyStorage
+    min_surb_threshold: usize,
+    max_surb_threshold: usize,
+}
+
+#[async_trait]
+impl ReplyStorageBackend for Empty {
+    type StorageError = UndefinedError;
+
+    async fn flush_surb_storage(
+        &mut self,
+        _storage: &CombinedReplyStorage,
+    ) -> Result<(), Self::StorageError> {
+        Ok(())
+    }
+
+    async fn init_fresh(
+        &mut self,
+        _fresh: &CombinedReplyStorage,
+    ) -> Result<(), Self::StorageError> {
+        Ok(())
+    }
+
+    async fn load_surb_storage(&self) -> Result<CombinedReplyStorage, Self::StorageError> {
+        Ok(CombinedReplyStorage::new(
+            self.min_surb_threshold,
+            self.max_surb_threshold,
+        ))
+    }
+}
+
+#[async_trait]
+pub trait ReplyStorageBackend: Sized {
+    type StorageError: Error + 'static;
+
+    async fn start_storage_session(&self) -> Result<(), Self::StorageError> {
+        Ok(())
+    }
+
+    // reply keys and surbs would need additional field set when data is loaded
+    // so if there's some failure, we'd trash it all
+    async fn flush_surb_storage(
+        &mut self,
+        storage: &CombinedReplyStorage,
+    ) -> Result<(), Self::StorageError>;
+
+    /// The purpose of this call is to save any metadata that might be present.
+    /// (such as surb thresholds)
+    async fn init_fresh(&mut self, fresh: &CombinedReplyStorage) -> Result<(), Self::StorageError>;
+
+    async fn load_surb_storage(&self) -> Result<CombinedReplyStorage, Self::StorageError>;
+
+    async fn stop_storage_session(self) -> Result<(), Self::StorageError> {
+        Ok(())
+    }
+}
@@ -0,0 +1,60 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use crate::client::replies::reply_storage::{ReceivedReplySurbsMap, SentReplyKeys, UsedSenderTags};
+
+#[derive(Debug, Clone)]
+pub struct CombinedReplyStorage {
+    sent_reply_keys: SentReplyKeys,
+    received_reply_surbs: ReceivedReplySurbsMap,
+    used_tags: UsedSenderTags,
+}
+
+impl CombinedReplyStorage {
+    pub fn new(min_surb_threshold: usize, max_surb_threshold: usize) -> CombinedReplyStorage {
+        CombinedReplyStorage {
+            sent_reply_keys: SentReplyKeys::new(),
+            received_reply_surbs: ReceivedReplySurbsMap::new(
+                min_surb_threshold,
+                max_surb_threshold,
+            ),
+            used_tags: UsedSenderTags::new(),
+        }
+    }
+
+    pub fn load(
+        sent_reply_keys: SentReplyKeys,
+        received_reply_surbs: ReceivedReplySurbsMap,
+        used_tags: UsedSenderTags,
+    ) -> Self {
+        CombinedReplyStorage {
+            sent_reply_keys,
+            received_reply_surbs,
+            used_tags,
+        }
+    }
+
+    pub fn key_storage(&self) -> SentReplyKeys {
+        self.sent_reply_keys.clone()
+    }
+
+    pub fn surbs_storage(&self) -> ReceivedReplySurbsMap {
+        self.received_reply_surbs.clone()
+    }
+
+    pub fn tags_storage(&self) -> UsedSenderTags {
+        self.used_tags.clone()
+    }
+
+    pub fn key_storage_ref(&self) -> &SentReplyKeys {
+        &self.sent_reply_keys
+    }
+
+    pub fn surbs_storage_ref(&self) -> &ReceivedReplySurbsMap {
+        &self.received_reply_surbs
+    }
+
+    pub fn tags_storage_ref(&self) -> &UsedSenderTags {
+        &self.used_tags
+    }
+}
@@ -0,0 +1,86 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use dashmap::iter::Iter;
+use dashmap::DashMap;
+use nymsphinx::anonymous_replies::encryption_key::EncryptionKeyDigest;
+use nymsphinx::anonymous_replies::SurbEncryptionKey;
+use std::ops::Deref;
+use std::sync::Arc;
+use time::OffsetDateTime;
+
+#[derive(Debug, Clone)]
+pub struct SentReplyKeys {
+    inner: Arc<SentReplyKeysInner>,
+}
+
+#[derive(Debug)]
+struct SentReplyKeysInner {
+    data: DashMap<EncryptionKeyDigest, UsedReplyKey>,
+}
+
+impl SentReplyKeys {
+    pub(crate) fn new() -> SentReplyKeys {
+        SentReplyKeys {
+            inner: Arc::new(SentReplyKeysInner {
+                data: DashMap::new(),
+            }),
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn from_raw(raw: Vec<(EncryptionKeyDigest, UsedReplyKey)>) -> SentReplyKeys {
+        SentReplyKeys {
+            inner: Arc::new(SentReplyKeysInner {
+                data: raw.into_iter().collect(),
+            }),
+        }
+    }
+
+    pub(crate) fn as_raw_iter(&self) -> Iter<'_, EncryptionKeyDigest, UsedReplyKey> {
+        self.inner.data.iter()
+    }
+
+    pub(crate) fn insert_multiple(&self, keys: Vec<SurbEncryptionKey>) {
+        let now = OffsetDateTime::now_utc().unix_timestamp();
+        for key in keys {
+            self.insert(UsedReplyKey::new(key, now))
+        }
+    }
+
+    pub(crate) fn insert(&self, key: UsedReplyKey) {
+        self.inner.data.insert(key.compute_digest(), key);
+    }
+
+    pub(crate) fn try_pop(&self, digest: EncryptionKeyDigest) -> Option<UsedReplyKey> {
+        self.inner.data.remove(&digest).map(|(_k, v)| v)
+    }
+
+    pub(crate) fn remove(&self, digest: EncryptionKeyDigest) {
+        self.inner.data.remove(&digest);
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct UsedReplyKey {
+    key: SurbEncryptionKey,
+    // the purpose of this field is to perform invalidation at relatively very long intervals
+    pub(crate) sent_at_timestamp: i64,
+}
+
+impl UsedReplyKey {
+    pub(crate) fn new(key: SurbEncryptionKey, sent_at_timestamp: i64) -> Self {
+        UsedReplyKey {
+            key,
+            sent_at_timestamp,
+        }
+    }
+}
+
+impl Deref for UsedReplyKey {
+    type Target = SurbEncryptionKey;
+
+    fn deref(&self) -> &Self::Target {
+        &self.key
+    }
+}
@@ -0,0 +1,64 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+pub use crate::client::replies::reply_storage::combined::CombinedReplyStorage;
+pub use crate::client::replies::reply_storage::key_storage::SentReplyKeys;
+pub use crate::client::replies::reply_storage::surb_storage::ReceivedReplySurbsMap;
+pub use crate::client::replies::reply_storage::tag_storage::UsedSenderTags;
+pub use backend::*;
+
+mod backend;
+mod combined;
+mod key_storage;
+mod surb_storage;
+mod tag_storage;
+
+// only really exists to get information about shutdown and save data to the backing storage
+pub struct PersistentReplyStorage<T = backend::Empty>
+where
+    T: ReplyStorageBackend,
+{
+    backend: T,
+}
+
+impl<T> PersistentReplyStorage<T>
+where
+    T: ReplyStorageBackend + Send + Sync,
+{
+    pub fn new(backend: T) -> Self {
+        PersistentReplyStorage { backend }
+    }
+
+    pub async fn load_state_from_backend(&self) -> Result<CombinedReplyStorage, T::StorageError> {
+        self.backend.load_surb_storage().await
+    }
+
+    // this will have to get enabled after merging develop
+    pub async fn flush_on_shutdown(
+        mut self,
+        mem_state: CombinedReplyStorage,
+        mut shutdown: task::ShutdownListener,
+    ) {
+        use log::{debug, error, info, warn};
+
+        debug!("Started PersistentReplyStorage");
+        if let Err(err) = self.backend.start_storage_session().await {
+            error!("failed to start the storage session - {err}");
+            return;
+        }
+
+        shutdown.recv().await;
+
+        info!("PersistentReplyStorage is flushing all reply-related data to underlying storage");
+        warn!("you MUST NOT forcefully shutdown now or you risk data corruption!");
+        if let Err(err) = self.backend.flush_surb_storage(&mem_state).await {
+            error!("failed to flush our reply-related data to the persistent storage: {err}")
+        } else {
+            info!("Data flush is complete")
+        }
+
+        if let Err(err) = self.backend.stop_storage_session().await {
+            error!("failed to properly stop the storage session - {err}. We might not be able to smoothly restore it")
+        }
+    }
+}
@@ -0,0 +1,278 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use dashmap::iter::Iter;
+use dashmap::DashMap;
+use log::trace;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
+use nymsphinx::anonymous_replies::ReplySurb;
+use std::collections::VecDeque;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+use time::OffsetDateTime;
+
+#[derive(Debug, Clone)]
+pub struct ReceivedReplySurbsMap {
+    inner: Arc<ReceivedReplySurbsMapInner>,
+}
+
+#[derive(Debug)]
+struct ReceivedReplySurbsMapInner {
+    data: DashMap<AnonymousSenderTag, ReceivedReplySurbs>,
+
+    // the minimum amount of surbs that have to be kept in storage for requests for more surbs
+    min_surb_threshold: AtomicUsize,
+
+    // the maximum amount of surbs that we want to keep in storage so that we don't over-request them
+    max_surb_threshold: AtomicUsize,
+}
+
+impl ReceivedReplySurbsMap {
+    pub(crate) fn new(
+        min_surb_threshold: usize,
+        max_surb_threshold: usize,
+    ) -> ReceivedReplySurbsMap {
+        ReceivedReplySurbsMap {
+            inner: Arc::new(ReceivedReplySurbsMapInner {
+                data: DashMap::new(),
+                min_surb_threshold: AtomicUsize::new(min_surb_threshold),
+                max_surb_threshold: AtomicUsize::new(max_surb_threshold),
+            }),
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn from_raw(
+        min_surb_threshold: usize,
+        max_surb_threshold: usize,
+        raw: Vec<(AnonymousSenderTag, ReceivedReplySurbs)>,
+    ) -> ReceivedReplySurbsMap {
+        ReceivedReplySurbsMap {
+            inner: Arc::new(ReceivedReplySurbsMapInner {
+                data: raw.into_iter().collect(),
+                min_surb_threshold: AtomicUsize::new(min_surb_threshold),
+                max_surb_threshold: AtomicUsize::new(max_surb_threshold),
+            }),
+        }
+    }
+
+    pub(crate) fn as_raw_iter(&self) -> Iter<'_, AnonymousSenderTag, ReceivedReplySurbs> {
+        self.inner.data.iter()
+    }
+
+    pub(crate) fn remove(&self, target: &AnonymousSenderTag) {
+        self.inner.data.remove(target);
+    }
+
+    pub(crate) fn reset_surbs_last_received_at(&self, target: &AnonymousSenderTag) {
+        if let Some(mut entry) = self.inner.data.get_mut(target) {
+            entry.surbs_last_received_at_timestamp = OffsetDateTime::now_utc().unix_timestamp();
+        }
+    }
+
+    pub(crate) fn surbs_last_received_at(&self, target: &AnonymousSenderTag) -> Option<i64> {
+        self.inner
+            .data
+            .get(target)
+            .map(|e| e.surbs_last_received_at())
+    }
+
+    pub(crate) fn pending_reception(&self, target: &AnonymousSenderTag) -> u32 {
+        self.inner
+            .data
+            .get(target)
+            .map(|e| e.pending_reception())
+            .unwrap_or_default()
+    }
+
+    pub(crate) fn increment_pending_reception(
+        &self,
+        target: &AnonymousSenderTag,
+        amount: u32,
+    ) -> Option<u32> {
+        self.inner
+            .data
+            .get_mut(target)
+            .map(|mut e| e.increment_pending_reception(amount))
+    }
+
+    pub(crate) fn decrement_pending_reception(
+        &self,
+        target: &AnonymousSenderTag,
+        amount: u32,
+    ) -> Option<u32> {
+        self.inner
+            .data
+            .get_mut(target)
+            .map(|mut e| e.decrement_pending_reception(amount))
+    }
+
+    pub(crate) fn reset_pending_reception(&self, target: &AnonymousSenderTag) {
+        if let Some(mut e) = self.inner.data.get_mut(target) {
+            e.reset_pending_reception()
+        }
+    }
+
+    pub(crate) fn min_surb_threshold(&self) -> usize {
+        self.inner.min_surb_threshold.load(Ordering::Relaxed)
+    }
+
+    pub(crate) fn max_surb_threshold(&self) -> usize {
+        self.inner.max_surb_threshold.load(Ordering::Relaxed)
+    }
+
+    pub(crate) fn available_surbs(&self, target: &AnonymousSenderTag) -> usize {
+        self.inner
+            .data
+            .get(target)
+            .map(|entry| entry.items_left())
+            .unwrap_or_default()
+    }
+
+    pub(crate) fn contains_surbs_for(&self, target: &AnonymousSenderTag) -> bool {
+        self.inner.data.contains_key(target)
+    }
+
+    pub(crate) fn get_reply_surbs(
+        &self,
+        target: &AnonymousSenderTag,
+        amount: usize,
+    ) -> (Option<Vec<ReplySurb>>, usize) {
+        if let Some(mut entry) = self.inner.data.get_mut(target) {
+            let surbs_left = entry.items_left();
+            if surbs_left < self.min_surb_threshold() + amount {
+                (None, surbs_left)
+            } else {
+                entry.get_reply_surbs(amount)
+            }
+        } else {
+            (None, 0)
+        }
+    }
+
+    pub(crate) fn get_reply_surb_ignoring_threshold(
+        &self,
+        target: &AnonymousSenderTag,
+    ) -> Option<(Option<ReplySurb>, usize)> {
+        self.inner
+            .data
+            .get_mut(target)
+            .map(|mut s| s.get_reply_surb())
+    }
+
+    pub(crate) fn get_reply_surb(
+        &self,
+        target: &AnonymousSenderTag,
+    ) -> Option<(Option<ReplySurb>, usize)> {
+        self.inner.data.get_mut(target).map(|mut entry| {
+            let surbs_left = entry.items_left();
+            if surbs_left < self.min_surb_threshold() {
+                (None, surbs_left)
+            } else {
+                entry.get_reply_surb()
+            }
+        })
+    }
+
+    pub(crate) fn insert_surbs<I: IntoIterator<Item = ReplySurb>>(
+        &self,
+        target: &AnonymousSenderTag,
+        surbs: I,
+    ) {
+        if let Some(mut existing_data) = self.inner.data.get_mut(target) {
+            existing_data.insert_reply_surbs(surbs)
+        } else {
+            let new_entry = ReceivedReplySurbs::new(surbs.into_iter().collect());
+            self.inner.data.insert(*target, new_entry);
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct ReceivedReplySurbs {
+    // in the future we'd probably want to put extra data here to indicate when the SURBs got received
+    // so we could invalidate entries from the previous key rotations
+    data: VecDeque<ReplySurb>,
+
+    pending_reception: u32,
+    surbs_last_received_at_timestamp: i64,
+}
+
+impl ReceivedReplySurbs {
+    fn new(initial_surbs: VecDeque<ReplySurb>) -> Self {
+        ReceivedReplySurbs {
+            data: initial_surbs,
+            pending_reception: 0,
+            surbs_last_received_at_timestamp: OffsetDateTime::now_utc().unix_timestamp(),
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn new_retrieved(
+        surbs: Vec<ReplySurb>,
+        surbs_last_received_at_timestamp: i64,
+    ) -> ReceivedReplySurbs {
+        ReceivedReplySurbs {
+            data: surbs.into(),
+            pending_reception: 0,
+            surbs_last_received_at_timestamp,
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn surbs_ref(&self) -> &VecDeque<ReplySurb> {
+        &self.data
+    }
+
+    pub(crate) fn surbs_last_received_at(&self) -> i64 {
+        self.surbs_last_received_at_timestamp
+    }
+
+    pub(crate) fn pending_reception(&self) -> u32 {
+        self.pending_reception
+    }
+
+    pub(crate) fn increment_pending_reception(&mut self, amount: u32) -> u32 {
+        self.pending_reception += amount;
+        self.pending_reception
+    }
+
+    pub(crate) fn decrement_pending_reception(&mut self, amount: u32) -> u32 {
+        self.pending_reception = self.pending_reception.saturating_sub(amount);
+        self.pending_reception
+    }
+
+    pub(crate) fn reset_pending_reception(&mut self) {
+        self.pending_reception = 0;
+    }
+
+    pub(crate) fn get_reply_surbs(&mut self, amount: usize) -> (Option<Vec<ReplySurb>>, usize) {
+        if self.items_left() < amount {
+            (None, self.items_left())
+        } else {
+            let surbs = self.data.drain(..amount).collect();
+            (Some(surbs), self.items_left())
+        }
+    }
+
+    pub(crate) fn get_reply_surb(&mut self) -> (Option<ReplySurb>, usize) {
+        (self.pop_surb(), self.items_left())
+    }
+
+    fn pop_surb(&mut self) -> Option<ReplySurb> {
+        self.data.pop_front()
+    }
+
+    fn items_left(&self) -> usize {
+        self.data.len()
+    }
+
+    // realistically we're always going to be getting multiple surbs at once
+    pub(crate) fn insert_reply_surbs<I: IntoIterator<Item = ReplySurb>>(&mut self, surbs: I) {
+        let mut v = surbs.into_iter().collect::<VecDeque<_>>();
+        trace!("storing {} surbs in the storage", v.len());
+        self.data.append(&mut v);
+        self.surbs_last_received_at_timestamp = OffsetDateTime::now_utc().unix_timestamp();
+        trace!("we now have {} surbs!", self.data.len());
+    }
+}
@@ -0,0 +1,59 @@
+// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use dashmap::DashMap;
+use nymsphinx::addressing::clients::{Recipient, RecipientBytes};
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
+use std::sync::Arc;
+
+#[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+use dashmap::iter::Iter;
+
+#[derive(Debug, Clone)]
+pub struct UsedSenderTags {
+    inner: Arc<UsedSenderTagsInner>,
+}
+
+#[derive(Debug)]
+struct UsedSenderTagsInner {
+    data: DashMap<RecipientBytes, AnonymousSenderTag>,
+}
+
+impl UsedSenderTags {
+    pub(crate) fn new() -> UsedSenderTags {
+        UsedSenderTags {
+            inner: Arc::new(UsedSenderTagsInner {
+                data: DashMap::new(),
+            }),
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn from_raw(raw: Vec<(RecipientBytes, AnonymousSenderTag)>) -> UsedSenderTags {
+        UsedSenderTags {
+            inner: Arc::new(UsedSenderTagsInner {
+                data: raw.into_iter().collect(),
+            }),
+        }
+    }
+
+    #[cfg(all(not(target_arch = "wasm32"), feature = "fs-surb-storage"))]
+    pub(crate) fn as_raw_iter(&self) -> Iter<'_, RecipientBytes, AnonymousSenderTag> {
+        self.inner.data.iter()
+    }
+
+    pub(crate) fn insert_new(&self, recipient: &Recipient, tag: AnonymousSenderTag) {
+        self.inner.data.insert(recipient.to_bytes(), tag);
+    }
+
+    pub(crate) fn try_get_existing(&self, recipient: &Recipient) -> Option<AnonymousSenderTag> {
+        self.inner
+            .data
+            .get(&recipient.to_bytes())
+            .map(|r| *r.value())
+    }
+
+    pub(crate) fn exists(&self, recipient: &Recipient) -> bool {
+        self.inner.data.contains_key(&recipient.to_bytes())
+    }
+}
@@ -1,97 +0,0 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
-// SPDX-License-Identifier: Apache-2.0
-
-use crypto::generic_array::typenum::Unsigned;
-use log::*;
-use nymsphinx::anonymous_replies::{
-    encryption_key::EncryptionKeyDigest, SurbEncryptionKey, SurbEncryptionKeySize,
-};
-use std::path::Path;
-
-#[derive(Debug, thiserror::Error)]
-pub enum ReplyKeyStorageError {
-    #[error("DB Read Error: {0}")]
-    DbReadError(sled::Error),
-    #[error("DB Write Error: {0}")]
-    DbWriteError(sled::Error),
-    #[error("DB Open Error: {0}")]
-    DbOpenError(sled::Error),
-}
-
-/// Permanent storage for keys in all sent [`ReplySURB`]
-///
-/// Each sent out [`ReplySURB`] has a new key associated with it that is going to be used for
-/// payload encryption. In order to -decrypt whatever reply we receive, we need to know which
-/// key to use for that purpose. We do it based on received `H(t)` which has to be included
-/// with each reply.
-/// Moreover, there is no restriction when the [`ReplySURB`] might get used so we need to
-/// have a permanent storage for all the keys that we might ever see in the future.
-#[derive(Debug, Clone)]
-pub struct ReplyKeyStorage {
-    db: sled::Db,
-}
-
-impl ReplyKeyStorage {
-    pub fn load<P: AsRef<Path>>(path: P) -> Result<Self, ReplyKeyStorageError> {
-        let db = match sled::open(path) {
-            Err(e) => return Err(ReplyKeyStorageError::DbOpenError(e)),
-            Ok(db) => db,
-        };
-
-        Ok(ReplyKeyStorage { db })
-    }
-
-    fn read_encryption_key(&self, raw_key: sled::IVec) -> SurbEncryptionKey {
-        let key_bytes_ref = raw_key.as_ref();
-        // if this fails it means we have some database corruption and we
-        // absolutely can't continue
-
-        if key_bytes_ref.len() != SurbEncryptionKeySize::USIZE {
-            error!("REPLY KEY STORAGE DATA CORRUPTION - ENCRYPTION KEY HAS INVALID LENGTH");
-            panic!("REPLY KEY STORAGE DATA CORRUPTION - ENCRYPTION KEY HAS INVALID LENGTH");
-        }
-
-        // this can only fail if the bytes have invalid length but we already asserted it
-        SurbEncryptionKey::try_from_bytes(key_bytes_ref).unwrap()
-    }
-
-    // TOOD: perhaps we could also store some part of original message here too?
-    pub fn insert_encryption_key(
-        &mut self,
-        encryption_key: SurbEncryptionKey,
-    ) -> Result<(), ReplyKeyStorageError> {
-        let digest = encryption_key.compute_digest();
-
-        let insertion_result = match self.db.insert(digest, encryption_key.to_bytes()) {
-            Err(e) => Err(ReplyKeyStorageError::DbWriteError(e)),
-            Ok(existing_key) => {
-                if existing_key.is_some() {
-                    panic!("HASH COLLISION DETECTED")
-                };
-                Ok(())
-            }
-        };
-
-        // TODO: perhaps we could implement some batching mechanism to avoid frequent flushes?
-        self.db.flush().unwrap();
-        insertion_result
-    }
-
-    // Once we use key once, we do not expect to use it again
-    pub fn get_and_remove_encryption_key(
-        &self,
-        key_digest: EncryptionKeyDigest,
-    ) -> Result<Option<SurbEncryptionKey>, ReplyKeyStorageError> {
-        let removal_result = match self.db.remove(key_digest) {
-            Err(e) => Err(ReplyKeyStorageError::DbReadError(e)),
-            Ok(existing_key) => {
-                Ok(existing_key.map(|existing_key| self.read_encryption_key(existing_key)))
-            }
-        };
-
-        // TODO: not sure how to feel about flushing it every single time here...
-        // same with insertion
-        self.db.flush().unwrap();
-        removal_result
-    }
-}
@@ -1,4 +1,4 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 use crate::spawn_future;
@@ -10,10 +10,9 @@ use rand::seq::SliceRandom;
 use rand::thread_rng;
 use std::ops::Deref;
 use std::sync::Arc;
-use std::time;
 use std::time::Duration;
 use tokio::sync::{RwLock, RwLockReadGuard};
-use topology::{nym_topology_from_detailed, NymTopology};
+use topology::{nym_topology_from_detailed, NymTopology, NymTopologyError};
 use url::Url;

 // I'm extremely curious why compiler NEVER complained about lack of Debug here before
@@ -55,18 +54,36 @@ impl<'a> TopologyReadPermit<'a> {
        &'a self,
        ack_recipient: &Recipient,
        packet_recipient: Option<&Recipient>,
-    ) -> Option<&'a NymTopology> {
-        // Note: implicit deref with Deref for TopologyReadPermit is happening here
-        let topology_ref_option = self.permit.as_ref();
-        topology_ref_option.as_ref().filter(|topology_ref| {
-            !(!topology_ref.can_construct_path_through(DEFAULT_NUM_MIX_HOPS)
-                || !topology_ref.gateway_exists(ack_recipient.gateway())
-                || if let Some(packet_recipient) = packet_recipient {
-                    !topology_ref.gateway_exists(packet_recipient.gateway())
-                } else {
-                    false
-                })
-        })
+    ) -> Result<&'a NymTopology, NymTopologyError> {
+        // 1. Have we managed to get anything from the refresher, i.e. have the nym-api queries gone through?
+        let topology = self
+            .permit
+            .as_ref()
+            .as_ref()
+            .ok_or(NymTopologyError::EmptyNetworkTopology)?;
+
+        // 2. does it have any mixnode at all?
+        // 3. does it have any gateways at all?
+        // 4. does it have a mixnode on each layer?
+        topology.ensure_can_construct_path_through(DEFAULT_NUM_MIX_HOPS)?;
+
+        // 5. does it contain OUR gateway (so that we could create an ack packet)?
+        if !topology.gateway_exists(ack_recipient.gateway()) {
+            return Err(NymTopologyError::NonExistentGatewayError {
+                identity_key: ack_recipient.gateway().to_base58_string(),
+            });
+        }
+
+        // 6. for our target recipient, does it contain THEIR gateway (so that we could create
+        if let Some(recipient) = packet_recipient {
+            if !topology.gateway_exists(recipient.gateway()) {
+                return Err(NymTopologyError::NonExistentGatewayError {
+                    identity_key: recipient.gateway().to_base58_string(),
+                });
+            }
+        }
+
+        Ok(topology)
    }
 }

@@ -104,10 +121,10 @@ impl TopologyAccessor {

    // only used by the client at startup to get a slightly more reasonable error message
    // (currently displays as unused because health checker is disabled due to required changes)
-    pub async fn is_routable(&self) -> bool {
+    pub async fn ensure_is_routable(&self) -> Result<(), NymTopologyError> {
        match &self.inner.read().await.0 {
-            None => false,
-            Some(ref topology) => topology.can_construct_path_through(DEFAULT_NUM_MIX_HOPS),
+            None => Err(NymTopologyError::EmptyNetworkTopology),
+            Some(ref topology) => topology.ensure_can_construct_path_through(DEFAULT_NUM_MIX_HOPS),
        }
    }
 }
@@ -120,14 +137,14 @@ impl Default for TopologyAccessor {

 pub struct TopologyRefresherConfig {
    validator_api_urls: Vec<Url>,
-    refresh_rate: time::Duration,
+    refresh_rate: Duration,
    client_version: String,
 }

 impl TopologyRefresherConfig {
    pub fn new(
        validator_api_urls: Vec<Url>,
-        refresh_rate: time::Duration,
+        refresh_rate: Duration,
        client_version: String,
    ) -> Self {
        TopologyRefresherConfig {
@@ -187,13 +204,10 @@ impl TopologyRefresher {
    /// # Arguments
    ///
    /// * `topology`: active topology constructed from validator api data
-    /// * `mixnodes_count`: total number of active mixnodes
-    fn check_layer_distribution(
-        &self,
-        active_topology: &NymTopology,
-        mixnodes_count: usize,
-    ) -> bool {
+    fn check_layer_distribution(&self, active_topology: &NymTopology) -> bool {
        let mixes = active_topology.mixes();
+        let mixnodes_count = active_topology.num_mixnodes();
+
        if active_topology.gateways().is_empty() {
            return false;
        }
@@ -244,7 +258,7 @@ impl TopologyRefresher {

        let mixnodes = match self.validator_client.get_cached_active_mixnodes().await {
            Err(err) => {
-                error!("failed to get network mixnodes - {}", err);
+                error!("failed to get network mixnodes - {err}");
                return None;
            }
            Ok(mixes) => mixes,
@@ -252,17 +266,16 @@ impl TopologyRefresher {

        let gateways = match self.validator_client.get_cached_gateways().await {
            Err(err) => {
-                error!("failed to get network gateways - {}", err);
+                error!("failed to get network gateways - {err}");
                return None;
            }
            Ok(gateways) => gateways,
        };

-        let mixnodes_count = mixnodes.len();
        let topology = nym_topology_from_detailed(mixnodes, gateways)
            .filter_system_version(&self.client_version);

-        if !self.check_layer_distribution(&topology, mixnodes_count) {
+        if !self.check_layer_distribution(&topology) {
            warn!("The current filtered active topology has extremely skewed layer distribution. It cannot be used.");
            None
        } else {
@@ -293,8 +306,8 @@ impl TopologyRefresher {
            .await;
    }

-    pub async fn is_topology_routable(&self) -> bool {
-        self.topology_accessor.is_routable().await
+    pub async fn ensure_topology_is_routable(&self) -> Result<(), NymTopologyError> {
+        self.topology_accessor.ensure_is_routable().await
    }

    pub fn start_with_shutdown(mut self, mut shutdown: task::ShutdownListener) {
@@ -324,21 +337,4 @@ impl TopologyRefresher {
            log::debug!("TopologyRefresher: Exiting");
        })
    }
-
-    pub fn start(mut self) {
-        spawn_future(async move {
-            #[cfg(not(target_arch = "wasm32"))]
-            let mut interval = tokio_stream::wrappers::IntervalStream::new(tokio::time::interval(
-                self.refresh_rate,
-            ));
-
-            #[cfg(target_arch = "wasm32")]
-            let mut interval =
-                gloo_timers::future::IntervalStream::new(self.refresh_rate.as_millis() as u32);
-
-            while (interval.next().await).is_some() {
-                self.refresh().await;
-            }
-        })
-    }
 }
@@ -1,7 +1,7 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use config::NymConfig;
+use config::{NymConfig, DB_FILE_NAME};
 use nymsphinx::params::PacketSize;
 use serde::{Deserialize, Serialize};
 use std::marker::PhantomData;
@@ -30,10 +30,36 @@ const DEFAULT_TOPOLOGY_RESOLUTION_TIMEOUT: Duration = Duration::from_millis(5_00
 // bandwidth bridging protocol, we can come back to a smaller timeout value
 const DEFAULT_GATEWAY_RESPONSE_TIMEOUT: Duration = Duration::from_secs(5 * 60);

+// reply-surbs related:
+
+// define when to request
+// clients/client-core/src/client/replies/reply_storage/surb_storage.rs
+const DEFAULT_MINIMUM_REPLY_SURB_STORAGE_THRESHOLD: usize = 10;
+const DEFAULT_MAXIMUM_REPLY_SURB_STORAGE_THRESHOLD: usize = 200;
+
+// define how much to request at once
+// clients/client-core/src/client/replies/reply_controller.rs
+const DEFAULT_MINIMUM_REPLY_SURB_REQUEST_SIZE: u32 = 10;
+const DEFAULT_MAXIMUM_REPLY_SURB_REQUEST_SIZE: u32 = 100;
+
+const DEFAULT_MAXIMUM_ALLOWED_SURB_REQUEST_SIZE: u32 = 500;
+
+const DEFAULT_MAXIMUM_REPLY_SURB_WAITING_PERIOD: Duration = Duration::from_secs(10);
+
+// 12 hours
+const DEFAULT_MAXIMUM_REPLY_SURB_AGE: Duration = Duration::from_secs(12 * 60 * 60);
+
+// 24 hours
+const DEFAULT_MAXIMUM_REPLY_KEY_AGE: Duration = Duration::from_secs(24 * 60 * 60);
+
 pub fn missing_string_value() -> String {
    MISSING_VALUE.to_string()
 }

+pub trait ClientCoreConfigTrait {
+    fn get_gateway_endpoint(&self) -> &GatewayEndpointConfig;
+}
+
 #[derive(Debug, Clone, Deserialize, PartialEq, Serialize)]
 #[serde(deny_unknown_fields)]
 pub struct Config<T> {
@@ -44,31 +70,46 @@ pub struct Config<T> {
    #[serde(default)]
    debug: DebugConfig,
 }
+impl<T> ClientCoreConfigTrait for Config<T> {
+    fn get_gateway_endpoint(&self) -> &GatewayEndpointConfig {
+        &self.client.gateway_endpoint
+    }
+}

 impl<T> Config<T> {
    pub fn new<S: Into<String>>(id: S) -> Self
    where
        T: NymConfig,
    {
-        let mut cfg = Config::default();
-        cfg.with_id(id);
-        cfg
+        Config::default().with_id(id)
    }

-    pub fn with_id<S: Into<String>>(&mut self, id: S)
+    pub fn with_id<S: Into<String>>(mut self, id: S) -> Self
    where
        T: NymConfig,
    {
-        let id = id.into();
+        self.client.id = id.into();
+        self.set_empty_fields_to_defaults();
+        self
+    }
+
+    pub fn set_empty_fields_to_defaults(&mut self) -> bool
+    where
+        T: NymConfig,
+    {
+        let id = &self.client.id;
+        let mut changes_made = false;

        // identity key setting
        if self.client.private_identity_key_file.as_os_str().is_empty() {
+            changes_made = true;
            self.client.private_identity_key_file =
-                self::Client::<T>::default_private_identity_key_file(&id);
+                self::Client::<T>::default_private_identity_key_file(id);
        }
        if self.client.public_identity_key_file.as_os_str().is_empty() {
+            changes_made = true;
            self.client.public_identity_key_file =
-                self::Client::<T>::default_public_identity_key_file(&id);
+                self::Client::<T>::default_public_identity_key_file(id);
        }

        // encryption key setting
@@ -78,8 +119,9 @@ impl<T> Config<T> {
            .as_os_str()
            .is_empty()
        {
+            changes_made = true;
            self.client.private_encryption_key_file =
-                self::Client::<T>::default_private_encryption_key_file(&id);
+                self::Client::<T>::default_private_encryption_key_file(id);
        }
        if self
            .client
@@ -87,36 +129,35 @@ impl<T> Config<T> {
            .as_os_str()
            .is_empty()
        {
+            changes_made = true;
            self.client.public_encryption_key_file =
-                self::Client::<T>::default_public_encryption_key_file(&id);
+                self::Client::<T>::default_public_encryption_key_file(id);
        }

        // shared gateway key setting
        if self.client.gateway_shared_key_file.as_os_str().is_empty() {
+            changes_made = true;
            self.client.gateway_shared_key_file =
-                self::Client::<T>::default_gateway_shared_key_file(&id);
+                self::Client::<T>::default_gateway_shared_key_file(id);
        }

        // ack key setting
        if self.client.ack_key_file.as_os_str().is_empty() {
-            self.client.ack_key_file = self::Client::<T>::default_ack_key_file(&id);
+            changes_made = true;
+            self.client.ack_key_file = self::Client::<T>::default_ack_key_file(id);
        }

-        if self
-            .client
-            .reply_encryption_key_store_path
-            .as_os_str()
-            .is_empty()
-        {
-            self.client.reply_encryption_key_store_path =
-                self::Client::<T>::default_reply_encryption_key_store_path(&id);
+        if self.client.reply_surb_database_path.as_os_str().is_empty() {
+            changes_made = true;
+            self.client.reply_surb_database_path =
+                self::Client::<T>::default_reply_surb_database_path(id);
        }

        if self.client.database_path.as_os_str().is_empty() {
-            self.client.database_path = self::Client::<T>::default_database_path(&id);
+            changes_made = true;
+            self.client.database_path = self::Client::<T>::default_database_path(id);
        }
-
-        self.client.id = id;
+        changes_made
    }

    pub fn with_disabled_credentials(&mut self, disabled_credentials_mode: bool) {
@@ -141,8 +182,15 @@ impl<T> Config<T> {

    pub fn set_high_default_traffic_volume(&mut self) {
        self.debug.average_packet_delay = Duration::from_millis(10);
-        self.debug.loop_cover_traffic_average_delay = Duration::from_millis(2_000_000); // basically don't really send cover messages
-        self.debug.message_sending_average_delay = Duration::from_millis(4); // 250 "real" messages / s
+        // basically don't really send cover messages
+        self.debug.loop_cover_traffic_average_delay = Duration::from_millis(2_000_000);
+        // 250 "real" messages / s
+        self.debug.message_sending_average_delay = Duration::from_millis(4);
+    }
+
+    pub fn set_no_cover_traffic(&mut self) {
+        self.debug.disable_loop_cover_traffic_stream = true;
+        self.debug.disable_main_poisson_packet_distribution = true;
    }

    pub fn set_custom_version(&mut self, version: &str) {
@@ -181,10 +229,6 @@ impl<T> Config<T> {
        self.client.gateway_shared_key_file.clone()
    }

-    pub fn get_reply_encryption_key_store_path(&self) -> PathBuf {
-        self.client.reply_encryption_key_store_path.clone()
-    }
-
    pub fn get_ack_key_file(&self) -> PathBuf {
        self.client.ack_key_file.clone()
    }
@@ -213,14 +257,18 @@ impl<T> Config<T> {
        &self.client.gateway_endpoint
    }

-    pub fn get_gateway_endpoint(&self) -> &GatewayEndpointConfig {
-        &self.client.gateway_endpoint
-    }
-
    pub fn get_database_path(&self) -> PathBuf {
        self.client.database_path.clone()
    }

+    pub fn get_reply_surb_database_path(&self) -> PathBuf {
+        self.client.reply_surb_database_path.clone()
+    }
+
+    pub fn get_version(&self) -> &str {
+        &self.client.version
+    }
+
    // Debug getters
    pub fn get_debug_config(&self) -> &DebugConfig {
        &self.debug
@@ -274,8 +322,36 @@ impl<T> Config<T> {
        self.debug.use_extended_packet_size
    }

-    pub fn get_version(&self) -> &str {
-        &self.client.version
+    pub fn get_minimum_reply_surb_storage_threshold(&self) -> usize {
+        self.debug.minimum_reply_surb_storage_threshold
+    }
+
+    pub fn get_maximum_reply_surb_storage_threshold(&self) -> usize {
+        self.debug.maximum_reply_surb_storage_threshold
+    }
+
+    pub fn get_minimum_reply_surb_request_size(&self) -> u32 {
+        self.debug.minimum_reply_surb_request_size
+    }
+
+    pub fn get_maximum_reply_surb_request_size(&self) -> u32 {
+        self.debug.maximum_reply_surb_request_size
+    }
+
+    pub fn get_maximum_allowed_reply_surb_request_size(&self) -> u32 {
+        self.debug.maximum_allowed_reply_surb_request_size
+    }
+
+    pub fn get_maximum_reply_surb_waiting_period(&self) -> Duration {
+        self.debug.maximum_reply_surb_waiting_period
+    }
+
+    pub fn get_maximum_reply_surb_age(&self) -> Duration {
+        self.debug.maximum_reply_surb_age
+    }
+
+    pub fn get_maximum_reply_key_age(&self) -> Duration {
+        self.debug.maximum_reply_key_age
    }
 }

@@ -303,6 +379,22 @@ pub struct GatewayEndpointConfig {
    pub gateway_listener: String,
 }

+#[cfg_attr(target_arch = "wasm32", wasm_bindgen)]
+impl GatewayEndpointConfig {
+    #[cfg_attr(target_arch = "wasm32", wasm_bindgen(constructor))]
+    pub fn new(
+        gateway_id: String,
+        gateway_owner: String,
+        gateway_listener: String,
+    ) -> GatewayEndpointConfig {
+        GatewayEndpointConfig {
+            gateway_id,
+            gateway_owner,
+            gateway_listener,
+        }
+    }
+}
+
 impl From<topology::gateway::Node> for GatewayEndpointConfig {
    fn from(node: topology::gateway::Node) -> GatewayEndpointConfig {
        let gateway_listener = node.clients_address();
@@ -355,16 +447,19 @@ pub struct Client<T> {
    /// acknowledgement so that nobody besides the client knows which packet it refers to.
    ack_key_file: PathBuf,

-    /// Full path to file containing reply encryption keys of all reply-SURBs we have ever
-    /// sent but not received back.
-    reply_encryption_key_store_path: PathBuf,
-
    /// Information regarding how the client should send data to gateway.
    gateway_endpoint: GatewayEndpointConfig,

    /// Path to the database containing bandwidth credentials of this client.
    database_path: PathBuf,

+    /// Path to the persistent store for received reply surbs, unused encryption keys and used sender tags.
+    // this was set to use #[serde(default)] for the purposes of compatibility for multi-surbs introduced in 1.1.4.
+    // if you're reading this message and we have already introduced some breaking changes, feel free
+    // to remove that attribute since at this point the client configs should have gotten regenerated
+    #[serde(default)]
+    reply_surb_database_path: PathBuf,
+
    /// nym_home_directory specifies absolute path to the home nym Clients directory.
    /// It is expected to use default value and hence .toml file should not redefine this field.
    nym_root_directory: PathBuf,
@@ -388,9 +483,9 @@ impl<T: NymConfig> Default for Client<T> {
            public_encryption_key_file: Default::default(),
            gateway_shared_key_file: Default::default(),
            ack_key_file: Default::default(),
-            reply_encryption_key_store_path: Default::default(),
            gateway_endpoint: Default::default(),
            database_path: Default::default(),
+            reply_surb_database_path: Default::default(),
            nym_root_directory: T::default_root_directory(),
            super_struct: Default::default(),
        }
@@ -422,11 +517,12 @@ impl<T: NymConfig> Client<T> {
        T::default_data_directory(Some(id)).join("ack_key.pem")
    }

-    fn default_reply_encryption_key_store_path(id: &str) -> PathBuf {
-        T::default_data_directory(Some(id)).join("reply_key_store")
+    fn default_reply_surb_database_path(id: &str) -> PathBuf {
+        T::default_data_directory(Some(id)).join("persistent_reply_store.sqlite")
    }
+
    fn default_database_path(id: &str) -> PathBuf {
-        T::default_data_directory(Some(id)).join("db.sqlite")
+        T::default_data_directory(Some(id)).join(DB_FILE_NAME)
    }
 }

@@ -500,6 +596,37 @@ pub struct DebugConfig {

    /// Controls whether the sent sphinx packet use a NON-DEFAULT bigger size.
    pub use_extended_packet_size: Option<ExtendedPacketSize>,
+
+    /// Defines the minimum number of reply surbs the client wants to keep in its storage at all times.
+    /// It can only allow to go below that value if its to request additional reply surbs.
+    pub minimum_reply_surb_storage_threshold: usize,
+
+    /// Defines the maximum number of reply surbs the client wants to keep in its storage at any times.
+    pub maximum_reply_surb_storage_threshold: usize,
+
+    /// Defines the minimum number of reply surbs the client would request.
+    pub minimum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs the client would request.
+    pub maximum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs a remote party is allowed to request from this client at once.
+    pub maximum_allowed_reply_surb_request_size: u32,
+
+    /// Defines maximum amount of time the client is going to wait for reply surbs before explicitly asking
+    /// for more even though in theory they wouldn't need to.
+    #[serde(with = "humantime_serde")]
+    pub maximum_reply_surb_waiting_period: Duration,
+
+    /// Defines maximum amount of time given reply surb is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    #[serde(with = "humantime_serde")]
+    pub maximum_reply_surb_age: Duration,
+
+    /// Defines maximum amount of time given reply key is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    #[serde(with = "humantime_serde")]
+    pub maximum_reply_key_age: Duration,
 }

 #[derive(Clone, Copy, Debug, Serialize, Deserialize, PartialEq, Eq)]
@@ -525,6 +652,14 @@ impl Default for DebugConfig {
            disable_loop_cover_traffic_stream: false,
            disable_main_poisson_packet_distribution: false,
            use_extended_packet_size: None,
+            minimum_reply_surb_storage_threshold: DEFAULT_MINIMUM_REPLY_SURB_STORAGE_THRESHOLD,
+            maximum_reply_surb_storage_threshold: DEFAULT_MAXIMUM_REPLY_SURB_STORAGE_THRESHOLD,
+            minimum_reply_surb_request_size: DEFAULT_MINIMUM_REPLY_SURB_REQUEST_SIZE,
+            maximum_reply_surb_request_size: DEFAULT_MAXIMUM_REPLY_SURB_REQUEST_SIZE,
+            maximum_allowed_reply_surb_request_size: DEFAULT_MAXIMUM_ALLOWED_SURB_REQUEST_SIZE,
+            maximum_reply_surb_waiting_period: DEFAULT_MAXIMUM_REPLY_SURB_WAITING_PERIOD,
+            maximum_reply_surb_age: DEFAULT_MAXIMUM_REPLY_SURB_AGE,
+            maximum_reply_key_age: DEFAULT_MAXIMUM_REPLY_KEY_AGE,
        }
    }
 }
@@ -1,38 +1,68 @@
 // Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-#[cfg(feature = "reply-surb")]
-use crate::client::reply_key_storage::ReplyKeyStorageError;
+use crate::client::replies::reply_storage::ReplyStorageBackend;
 use crypto::asymmetric::identity::Ed25519RecoveryError;
 use gateway_client::error::GatewayClientError;
+use topology::NymTopologyError;
 use validator_client::ValidatorClientError;

 #[derive(thiserror::Error, Debug)]
-pub enum ClientCoreError {
+pub enum ClientCoreError<B: ReplyStorageBackend> {
    #[error("I/O error: {0}")]
    IoError(#[from] std::io::Error),
+
    #[error("Gateway client error: {0}")]
    GatewayClientError(#[from] GatewayClientError),
+
    #[error("Ed25519 error: {0}")]
    Ed25519RecoveryError(#[from] Ed25519RecoveryError),
+
    #[error("Validator client error: {0}")]
    ValidatorClientError(#[from] ValidatorClientError),

-    #[cfg(feature = "reply-surb")]
-    #[error("Reply key storage error: {0}")]
-    ReplyKeyStorageError(#[from] ReplyKeyStorageError),
-
    #[error("No gateway with id: {0}")]
    NoGatewayWithId(String),
+
    #[error("No gateways on network")]
    NoGatewaysOnNetwork,
+
+    #[error("Failed to setup gateway")]
+    FailedToSetupGateway,
+
    #[error("List of validator apis is empty")]
    ListOfValidatorApisIsEmpty,
+
    #[error("Could not load existing gateway configuration: {0}")]
    CouldNotLoadExistingGatewayConfiguration(std::io::Error),
+
    #[error("The current network topology seem to be insufficient to route any packets through")]
-    InsufficientNetworkTopology,
+    InsufficientNetworkTopology(#[from] NymTopologyError),
+
+    #[error("experienced a failure with our reply surb persistent storage: {source}")]
+    SurbStorageError { source: B::StorageError },
+
+    #[error("The gateway id is invalid - {0}")]
+    UnableToCreatePublicKeyFromGatewayId(Ed25519RecoveryError),
+
+    #[error("The identity of the gateway is unknwown - did you run init?")]
+    GatewayIdUnknown,
+
+    #[error("The owner of the gateway is unknown - did you run init?")]
+    GatewayOwnerUnknown,
+
+    #[error("The address of the gateway is unknown - did you run init?")]
+    GatwayAddressUnknown,

    #[error("Unexpected exit")]
    UnexpectedExit,
 }
+
+/// Set of messages that the client can send to listeners via the task manager
+#[derive(thiserror::Error, Debug)]
+pub enum ClientCoreStatusMessage {
+    #[error("The connected gateway is slow, or the connection to it is slow")]
+    GatewayIsSlow,
+    #[error("The connected gateway is very slow, or the connection to it is very slow")]
+    GatewayIsVerySlow,
+}
@@ -1,33 +1,29 @@
 // Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-//! Collection of initialization steps used by client implementations
-
-use std::{sync::Arc, time::Duration};
-
-use config::NymConfig;
-use crypto::asymmetric::{encryption, identity};
-use gateway_client::GatewayClient;
-use gateway_requests::registration::handshake::SharedKeys;
-use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::addressing::nodes::NodeIdentity;
-use rand::rngs::OsRng;
-use rand::seq::SliceRandom;
-use rand::thread_rng;
-use tap::TapFallible;
-use topology::{filter::VersionFilterable, gateway};
-use url::Url;
-
+use crate::client::replies::reply_storage::ReplyStorageBackend;
 use crate::{
    client::key_manager::KeyManager,
    config::{persistence::key_pathfinder::ClientKeyPathfinder, Config},
    error::ClientCoreError,
 };
+use config::NymConfig;
+use crypto::asymmetric::identity;
+use gateway_client::GatewayClient;
+use gateway_requests::registration::handshake::SharedKeys;
+use rand::{rngs::OsRng, seq::SliceRandom, thread_rng};
+use std::{sync::Arc, time::Duration};
+use tap::TapFallible;
+use topology::{filter::VersionFilterable, gateway};
+use url::Url;

-pub async fn query_gateway_details(
+pub(super) async fn query_gateway_details<B>(
    validator_servers: Vec<Url>,
-    chosen_gateway_id: Option<&str>,
-) -> Result<gateway::Node, ClientCoreError> {
+    chosen_gateway_id: Option<String>,
+) -> Result<gateway::Node, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+{
    let validator_api = validator_servers
        .choose(&mut thread_rng())
        .ok_or(ClientCoreError::ListOfValidatorApisIsEmpty)?;
@@ -59,12 +55,39 @@ pub async fn query_gateway_details(
    }
 }

-pub async fn register_with_gateway_and_store_keys<T>(
+async fn register_with_gateway<B>(
+    gateway: &gateway::Node,
+    our_identity: Arc<identity::KeyPair>,
+) -> Result<Arc<SharedKeys>, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+{
+    let timeout = Duration::from_millis(1500);
+    let mut gateway_client = GatewayClient::new_init(
+        gateway.clients_address(),
+        gateway.identity_key,
+        gateway.owner.clone(),
+        our_identity.clone(),
+        timeout,
+    );
+    gateway_client
+        .establish_connection()
+        .await
+        .tap_err(|_| log::warn!("Failed to establish connection with gateway!"))?;
+    let shared_keys = gateway_client
+        .perform_initial_authentication()
+        .await
+        .tap_err(|_| log::warn!("Failed to register with the gateway!"))?;
+    Ok(shared_keys)
+}
+
+pub(super) async fn register_with_gateway_and_store_keys<T, B>(
    gateway_details: gateway::Node,
    config: &Config<T>,
-) -> Result<(), ClientCoreError>
+) -> Result<(), ClientCoreError<B>>
 where
    T: NymConfig,
+    B: ReplyStorageBackend,
 {
    let mut rng = OsRng;
    let mut key_manager = KeyManager::new(&mut rng);
@@ -78,71 +101,3 @@ where
        .store_keys(&pathfinder)
        .tap_err(|err| log::error!("Failed to generate keys: {err}"))?)
 }
-
-async fn register_with_gateway(
-    gateway: &gateway::Node,
-    our_identity: Arc<identity::KeyPair>,
-) -> Result<Arc<SharedKeys>, ClientCoreError> {
-    let timeout = Duration::from_millis(1500);
-    let mut gateway_client = GatewayClient::new_init(
-        gateway.clients_address(),
-        gateway.identity_key,
-        gateway.owner.clone(),
-        our_identity.clone(),
-        timeout,
-        None,
-    );
-    gateway_client
-        .establish_connection()
-        .await
-        .tap_err(|_| log::warn!("Failed to establish connection with gateway!"))?;
-    let shared_keys = gateway_client
-        .perform_initial_authentication()
-        .await
-        .tap_err(|_| log::warn!("Failed to register with the gateway!"))?;
-    Ok(shared_keys)
-}
-
-pub fn show_address<T>(config: &Config<T>) -> Result<(), ClientCoreError>
-where
-    T: config::NymConfig,
-{
-    fn load_identity_keys(
-        pathfinder: &ClientKeyPathfinder,
-    ) -> Result<identity::KeyPair, ClientCoreError> {
-        let identity_keypair: identity::KeyPair =
-            pemstore::load_keypair(&pemstore::KeyPairPath::new(
-                pathfinder.private_identity_key().to_owned(),
-                pathfinder.public_identity_key().to_owned(),
-            ))
-            .tap_err(|_| log::error!("Failed to read stored identity key files"))?;
-        Ok(identity_keypair)
-    }
-
-    fn load_sphinx_keys(
-        pathfinder: &ClientKeyPathfinder,
-    ) -> Result<encryption::KeyPair, ClientCoreError> {
-        let sphinx_keypair: encryption::KeyPair =
-            pemstore::load_keypair(&pemstore::KeyPairPath::new(
-                pathfinder.private_encryption_key().to_owned(),
-                pathfinder.public_encryption_key().to_owned(),
-            ))
-            .tap_err(|_| log::error!("Failed to read stored sphinx key files"))?;
-        Ok(sphinx_keypair)
-    }
-
-    let pathfinder = ClientKeyPathfinder::new_from_config(config);
-    let identity_keypair = load_identity_keys(&pathfinder)?;
-    let sphinx_keypair = load_sphinx_keys(&pathfinder)?;
-
-    let client_recipient = Recipient::new(
-        *identity_keypair.public_key(),
-        *sphinx_keypair.public_key(),
-        // TODO: below only works under assumption that gateway address == gateway id
-        // (which currently is true)
-        NodeIdentity::from_base58_string(config.get_gateway_id())?,
-    );
-
-    println!("\nThe address of this client is: {}", client_recipient);
-    Ok(())
-}
@@ -0,0 +1,216 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+//! Collection of initialization steps used by client implementations
+
+use std::fmt::Display;
+
+use nymsphinx::addressing::{clients::Recipient, nodes::NodeIdentity};
+use serde::Serialize;
+use tap::TapFallible;
+
+use config::NymConfig;
+use crypto::asymmetric::{encryption, identity};
+
+use crate::client::replies::reply_storage::ReplyStorageBackend;
+use crate::{
+    config::{
+        persistence::key_pathfinder::ClientKeyPathfinder, ClientCoreConfigTrait, Config,
+        GatewayEndpointConfig,
+    },
+    error::ClientCoreError,
+    init::helpers::{query_gateway_details, register_with_gateway_and_store_keys},
+};
+
+mod helpers;
+
+#[derive(Debug, Serialize)]
+pub struct InitResults {
+    version: String,
+    id: String,
+    identity_key: String,
+    encryption_key: String,
+    gateway_id: String,
+    gateway_listener: String,
+}
+
+impl InitResults {
+    pub fn new<T>(config: &Config<T>, address: &Recipient) -> Self
+    where
+        T: NymConfig,
+    {
+        Self {
+            version: config.get_version().to_string(),
+            id: config.get_id(),
+            identity_key: address.identity().to_base58_string(),
+            encryption_key: address.encryption_key().to_base58_string(),
+            gateway_id: config.get_gateway_id(),
+            gateway_listener: config.get_gateway_listener(),
+        }
+    }
+}
+
+impl Display for InitResults {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "Version: {}", self.version)?;
+        writeln!(f, "ID: {}", self.id)?;
+        writeln!(f, "Identity key: {}", self.identity_key)?;
+        writeln!(f, "Encryption: {}", self.encryption_key)?;
+        writeln!(f, "Gateway ID: {}", self.gateway_id)?;
+        write!(f, "Gateway: {}", self.gateway_listener)
+    }
+}
+
+/// Convenience function for setting up the gateway for a client. Depending on the arguments given
+/// it will do the sensible thing.
+pub async fn setup_gateway<B, C, T>(
+    register_gateway: bool,
+    user_chosen_gateway_id: Option<String>,
+    config: &Config<T>,
+) -> Result<GatewayEndpointConfig, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+    C: NymConfig + ClientCoreConfigTrait,
+    T: NymConfig,
+{
+    let id = config.get_id();
+    if register_gateway {
+        register_with_gateway(user_chosen_gateway_id, config).await
+    } else if let Some(user_chosen_gateway_id) = user_chosen_gateway_id {
+        config_gateway_with_existing_keys(user_chosen_gateway_id, config).await
+    } else {
+        reuse_existing_gateway_config::<B, C>(&id)
+    }
+}
+
+/// Get the gateway details by querying the validator-api. Either pick one at random or use
+/// the chosen one if it's among the available ones.
+/// Saves keys to disk, specified by the paths in `config`.
+pub async fn register_with_gateway<B, T>(
+    user_chosen_gateway_id: Option<String>,
+    config: &Config<T>,
+) -> Result<GatewayEndpointConfig, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+    T: NymConfig,
+{
+    println!("Configuring gateway");
+    let gateway =
+        query_gateway_details(config.get_validator_api_endpoints(), user_chosen_gateway_id).await?;
+    log::debug!("Querying gateway gives: {}", gateway);
+
+    // Registering with gateway by setting up and writing shared keys to disk
+    log::trace!("Registering gateway");
+    register_with_gateway_and_store_keys(gateway.clone(), config).await?;
+    println!("Saved all generated keys");
+
+    Ok(gateway.into())
+}
+
+/// Set the gateway using the usual procedue of querying the validator-api, but don't register or
+/// create any keys.
+/// This assumes that the user knows what they are doing, and that the existing keys are valid for
+/// the gateway being used
+pub async fn config_gateway_with_existing_keys<B, T>(
+    user_chosen_gateway_id: String,
+    config: &Config<T>,
+) -> Result<GatewayEndpointConfig, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+    T: NymConfig,
+{
+    println!("Using gateway provided by user, keeping existing keys");
+    let gateway = query_gateway_details(
+        config.get_validator_api_endpoints(),
+        Some(user_chosen_gateway_id),
+    )
+    .await?;
+    log::debug!("Querying gateway gives: {}", gateway);
+    Ok(gateway.into())
+}
+
+/// Read and reuse the existing gateway configuration from a file that was generate earlier.
+pub fn reuse_existing_gateway_config<B, T>(
+    id: &str,
+) -> Result<GatewayEndpointConfig, ClientCoreError<B>>
+where
+    B: ReplyStorageBackend,
+    T: NymConfig + ClientCoreConfigTrait,
+{
+    println!("Not registering gateway, will reuse existing config and keys");
+    T::load_from_file(Some(id))
+        .map(|existing_config| existing_config.get_gateway_endpoint().clone())
+        .map_err(|err| {
+            log::error!(
+                "Unable to configure gateway: {err}. \n
+                Seems like the client was already initialized but it was not possible to read \
+                the existing configuration file. \n
+                CAUTION: Consider backing up your gateway keys and try force gateway registration, or \
+                removing the existing configuration and starting over."
+            );
+            ClientCoreError::CouldNotLoadExistingGatewayConfiguration(err)
+        })
+}
+
+/// Get the client address by loading the keys from stored files.
+pub fn get_client_address_from_stored_keys<B, T>(
+    config: &Config<T>,
+) -> Result<Recipient, ClientCoreError<B>>
+where
+    T: config::NymConfig,
+    B: ReplyStorageBackend,
+{
+    fn load_identity_keys<B>(
+        pathfinder: &ClientKeyPathfinder,
+    ) -> Result<identity::KeyPair, ClientCoreError<B>>
+    where
+        B: ReplyStorageBackend,
+    {
+        let identity_keypair: identity::KeyPair =
+            pemstore::load_keypair(&pemstore::KeyPairPath::new(
+                pathfinder.private_identity_key().to_owned(),
+                pathfinder.public_identity_key().to_owned(),
+            ))
+            .tap_err(|_| log::error!("Failed to read stored identity key files"))?;
+        Ok(identity_keypair)
+    }
+
+    fn load_sphinx_keys<B>(
+        pathfinder: &ClientKeyPathfinder,
+    ) -> Result<encryption::KeyPair, ClientCoreError<B>>
+    where
+        B: ReplyStorageBackend,
+    {
+        let sphinx_keypair: encryption::KeyPair =
+            pemstore::load_keypair(&pemstore::KeyPairPath::new(
+                pathfinder.private_encryption_key().to_owned(),
+                pathfinder.public_encryption_key().to_owned(),
+            ))
+            .tap_err(|_| log::error!("Failed to read stored sphinx key files"))?;
+        Ok(sphinx_keypair)
+    }
+
+    let pathfinder = ClientKeyPathfinder::new_from_config(config);
+    let identity_keypair = load_identity_keys(&pathfinder)?;
+    let sphinx_keypair = load_sphinx_keys(&pathfinder)?;
+
+    let client_recipient = Recipient::new(
+        *identity_keypair.public_key(),
+        *sphinx_keypair.public_key(),
+        // TODO: below only works under assumption that gateway address == gateway id
+        // (which currently is true)
+        NodeIdentity::from_base58_string(config.get_gateway_id())?,
+    );
+
+    Ok(client_recipient)
+}
+
+pub fn output_to_json<T: Serialize>(init_results: &T, output_file: &str) {
+    match std::fs::File::create(output_file) {
+        Ok(file) => match serde_json::to_writer_pretty(file, init_results) {
+            Ok(_) => println!("Saved: {}", output_file),
+            Err(err) => eprintln!("Could not save {}: {}", output_file, err),
+        },
+        Err(err) => eprintln!("Could not save {}: {}", output_file, err),
+    }
+}
@@ -6,11 +6,9 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

 [dependencies]
-async-trait = "0.1.52"
 bip39 = "1.0.1"
 cfg-if = "0.1"
 clap = { version = "3.2", features = ["cargo", "derive"] }
-pickledb = "0.4.1"
 rand = "0.7.3"
 serde = { version = "1.0", features = ["derive"] }
 thiserror = "1.0"
@@ -1,14 +1,12 @@
 // Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use async_trait::async_trait;
 use clap::{Args, Subcommand};
 use completions::ArgShell;
-use pickledb::PickleDb;
 use rand::rngs::OsRng;
 use std::str::FromStr;

-use coconut_interface::{Attribute, Base58, BlindSignRequest, Bytable, Parameters};
+use coconut_interface::{Base58, Parameters};
 use credential_storage::storage::Storage;
 use credential_storage::PersistentStorage;
 use credentials::coconut::bandwidth::{BandwidthVoucher, TOTAL_ATTRIBUTES};
@@ -20,16 +18,12 @@ use validator_client::{CoconutApiClient, Config};

 use crate::client::Client;
 use crate::error::{CredentialClientError, Result};
-use crate::state::{KeyPair, RequestData, State};
+use crate::state::{KeyPair, State};

 #[derive(Subcommand)]
-pub(crate) enum Commands {
-    /// Deposit funds for buying coconut credential
-    Deposit(Deposit),
-    /// Lists the tx hashes of previous deposits
-    ListDeposits(ListDeposits),
-    /// Get a credential for a given deposit
-    GetCredential(GetCredential),
+pub(crate) enum Command {
+    /// Run the binary
+    Run(Run),

    /// Generate shell completions
    Completions(ArgShell),
@@ -38,169 +32,82 @@ pub(crate) enum Commands {
    GenerateFigSpec,
 }

-#[async_trait]
-pub(crate) trait Execute {
-    async fn execute(&self, db: &mut PickleDb, shared_storage: PersistentStorage) -> Result<()>;
-}
+#[derive(Args)]
+pub(crate) struct Run {
+    /// Home directory of the client that is supposed to use the credential.
+    #[clap(long)]
+    pub(crate) client_home_directory: std::path::PathBuf,

-#[derive(Args, Clone)]
-pub(crate) struct Deposit {
    /// The nymd URL that should be used
    #[clap(long)]
-    nymd_url: String,
-    /// A mnemonic for the account that does the deposit
+    pub(crate) nymd_url: String,
+
+    /// A mnemonic for the account that buys the credential
    #[clap(long)]
-    mnemonic: String,
-    /// The amount that needs to be deposited
+    pub(crate) mnemonic: String,
+
+    /// The amount of utokens the credential will hold
    #[clap(long)]
-    amount: u64,
+    pub(crate) amount: u64,
 }

-#[async_trait]
-impl Execute for Deposit {
-    async fn execute(&self, db: &mut PickleDb, _shared_storage: PersistentStorage) -> Result<()> {
-        let mut rng = OsRng;
-        let signing_keypair = KeyPair::from(identity::KeyPair::new(&mut rng));
-        let encryption_keypair = KeyPair::from(encryption::KeyPair::new(&mut rng));
+pub(crate) async fn deposit(nymd_url: &str, mnemonic: &str, amount: u64) -> Result<State> {
+    let mut rng = OsRng;
+    let signing_keypair = KeyPair::from(identity::KeyPair::new(&mut rng));
+    let encryption_keypair = KeyPair::from(encryption::KeyPair::new(&mut rng));

-        let client = Client::new(&self.nymd_url, &self.mnemonic);
-        let tx_hash = client
-            .deposit(
-                self.amount,
-                signing_keypair.public_key.clone(),
-                encryption_keypair.public_key.clone(),
-                None,
-            )
-            .await?;
-
-        let state = State {
-            amount: self.amount,
-            tx_hash: tx_hash.clone(),
-            signing_keypair,
-            encryption_keypair,
-            blind_request_data: None,
-            signature: None,
-        };
-        db.set(&tx_hash, &state).unwrap();
-
-        println!("{:?}", state);
-
-        Ok(())
-    }
-}
-
-#[derive(Args, Clone)]
-pub(crate) struct ListDeposits {}
-
-#[async_trait]
-impl Execute for ListDeposits {
-    async fn execute(&self, db: &mut PickleDb, _shared_storage: PersistentStorage) -> Result<()> {
-        for kv in db.iter() {
-            println!("{:?}", kv.get_value::<State>());
-        }
-
-        Ok(())
-    }
-}
-
-#[derive(Args, Clone)]
-pub(crate) struct GetCredential {
-    /// The hash of a successful deposit transaction
-    #[clap(long)]
-    tx_hash: String,
-    /// The nymd URL that should be used
-    #[clap(long)]
-    nymd_url: String,
-    /// If we want to get the signature without attaching a blind sign request; it is expected that
-    /// there is already a signature stored on the signer
-    #[clap(long, parse(from_flag))]
-    __no_request: bool,
-}
-
-#[async_trait]
-impl Execute for GetCredential {
-    async fn execute(&self, db: &mut PickleDb, shared_storage: PersistentStorage) -> Result<()> {
-        let mut state = db
-            .get::<State>(&self.tx_hash)
-            .ok_or(CredentialClientError::NoDeposit)?;
-
-        let network_details = NymNetworkDetails::new_from_env();
-        let config = Config::try_from_nym_network_details(&network_details)?;
-        let client = validator_client::Client::new_query(config)?;
-        let coconut_api_clients = CoconutApiClient::all_coconut_api_clients(&client).await?;
-
-        let params = Parameters::new(TOTAL_ATTRIBUTES).unwrap();
-        let bandwidth_credential_attributes = if self.__no_request {
-            if let Some(blind_request_data) = state.blind_request_data {
-                let serial_number =
-                    Attribute::try_from_byte_slice(&blind_request_data.serial_number)
-                        .map_err(|_| CredentialClientError::CorruptedBlindSignRequest)?;
-                let binding_number =
-                    Attribute::try_from_byte_slice(&blind_request_data.binding_number)
-                        .map_err(|_| CredentialClientError::CorruptedBlindSignRequest)?;
-                let pedersen_commitments_openings = vec![
-                    Attribute::try_from_byte_slice(&blind_request_data.first_attribute)
-                        .map_err(|_| CredentialClientError::CorruptedBlindSignRequest)?,
-                    Attribute::try_from_byte_slice(&blind_request_data.second_attribute)
-                        .map_err(|_| CredentialClientError::CorruptedBlindSignRequest)?,
-                ];
-                let blind_sign_request =
-                    BlindSignRequest::from_bytes(blind_request_data.blind_sign_req.as_slice())
-                        .map_err(|_| CredentialClientError::CorruptedBlindSignRequest)?;
-                BandwidthVoucher::new_with_blind_sign_req(
-                    [serial_number, binding_number],
-                    [&state.amount.to_string(), VOUCHER_INFO],
-                    Hash::from_str(&self.tx_hash)
-                        .map_err(|_| CredentialClientError::InvalidTxHash)?,
-                    identity::PrivateKey::from_base58_string(&state.signing_keypair.private_key)?,
-                    encryption::PrivateKey::from_base58_string(
-                        &state.encryption_keypair.private_key,
-                    )?,
-                    pedersen_commitments_openings,
-                    blind_sign_request,
-                )
-            } else {
-                return Err(CredentialClientError::NoLocalBlindSignRequest);
-            }
-        } else {
-            BandwidthVoucher::new(
-                &params,
-                state.amount.to_string(),
-                VOUCHER_INFO.to_string(),
-                Hash::from_str(&self.tx_hash).map_err(|_| CredentialClientError::InvalidTxHash)?,
-                identity::PrivateKey::from_base58_string(&state.signing_keypair.private_key)?,
-                encryption::PrivateKey::from_base58_string(&state.encryption_keypair.private_key)?,
-            )
-        };
-
-        // Back up the blind sign req data, in case of sporadic failures
-        state.blind_request_data = Some(RequestData::new(
-            bandwidth_credential_attributes.get_private_attributes(),
-            bandwidth_credential_attributes.pedersen_commitments_openings(),
-            bandwidth_credential_attributes.blind_sign_request(),
-        )?);
-        db.set(&self.tx_hash, &state).unwrap();
-
-        let signature = obtain_aggregate_signature(
-            &params,
-            &bandwidth_credential_attributes,
-            &coconut_api_clients,
+    let client = Client::new(nymd_url, mnemonic);
+    let tx_hash = client
+        .deposit(
+            amount,
+            signing_keypair.public_key.clone(),
+            encryption_keypair.public_key.clone(),
+            None,
        )
        .await?;
-        shared_storage
-            .insert_coconut_credential(
-                state.amount.to_string(),
-                VOUCHER_INFO.to_string(),
-                bandwidth_credential_attributes.get_private_attributes()[0].to_bs58(),
-                bandwidth_credential_attributes.get_private_attributes()[1].to_bs58(),
-                signature.to_bs58(),
-            )
-            .await?;
-        state.signature = Some(signature.to_bs58());
-        db.set(&self.tx_hash, &state).unwrap();

-        println!("Signature: {:?}", state.signature);
+    let state = State {
+        amount,
+        tx_hash,
+        signing_keypair,
+        encryption_keypair,
+    };

-        Ok(())
-    }
+    Ok(state)
+}
+
+pub(crate) async fn get_credential(state: &State, shared_storage: PersistentStorage) -> Result<()> {
+    let network_details = NymNetworkDetails::new_from_env();
+    let config = Config::try_from_nym_network_details(&network_details)?;
+    let client = validator_client::Client::new_query(config)?;
+    let coconut_api_clients = CoconutApiClient::all_coconut_api_clients(&client).await?;
+
+    let params = Parameters::new(TOTAL_ATTRIBUTES).unwrap();
+    let bandwidth_credential_attributes = BandwidthVoucher::new(
+        &params,
+        state.amount.to_string(),
+        VOUCHER_INFO.to_string(),
+        Hash::from_str(&state.tx_hash).map_err(|_| CredentialClientError::InvalidTxHash)?,
+        identity::PrivateKey::from_base58_string(&state.signing_keypair.private_key)?,
+        encryption::PrivateKey::from_base58_string(&state.encryption_keypair.private_key)?,
+    );
+
+    let signature = obtain_aggregate_signature(
+        &params,
+        &bandwidth_credential_attributes,
+        &coconut_api_clients,
+    )
+    .await?;
+    println!("Signature: {:?}", signature.to_bs58());
+    shared_storage
+        .insert_coconut_credential(
+            state.amount.to_string(),
+            VOUCHER_INFO.to_string(),
+            bandwidth_credential_attributes.get_private_attributes()[0].to_bs58(),
+            bandwidth_credential_attributes.get_private_attributes()[1].to_bs58(),
+            signature.to_bs58(),
+        )
+        .await?;
+
+    Ok(())
 }
@@ -23,18 +23,6 @@ pub enum CredentialClientError {
    #[error("Credential error: {0}")]
    Credential(#[from] CredentialError),

-    #[error("No previous deposit with that tx hash")]
-    NoDeposit,
-
-    #[error("Wrong number of attributes")]
-    WrongAttributeNumber,
-
-    #[error("Could not find any backed up blind sign request data")]
-    NoLocalBlindSignRequest,
-
-    #[error("The local blind sign request data is corrupted")]
-    CorruptedBlindSignRequest,
-
    #[error("The tx hash provided is not valid")]
    InvalidTxHash,

@@ -9,14 +9,13 @@ cfg_if::cfg_if! {
        mod error;
        mod state;

-        use commands::{Commands, Execute};
        use error::Result;
        use network_defaults::setup_env;
-        use clap::CommandFactory;
        use completions::fig_generate;
+        use commands::*;
+        use config::{DATA_DIR, DB_FILE_NAME};

-        use clap::Parser;
-        use pickledb::{PickleDb, PickleDbDumpPolicy, SerializationMethod};
+        use clap::{CommandFactory, Parser};

        #[derive(Parser)]
        #[clap(author = "Nymtech", version, about)]
@@ -25,43 +24,26 @@ cfg_if::cfg_if! {
            #[clap(short, long)]
            pub(crate) config_env_file: Option<std::path::PathBuf>,

-            /// Path where the sqlite credental database will be located.
-            /// It should point to a $HOME/$CLIENT_ID/data/db.sqlite file of
-            /// the client that is supposed to use the credential.
-            #[clap(long)]
-            pub(crate) credential_db_path: std::path::PathBuf,
-
            #[clap(subcommand)]
-            command: Commands,
+            pub(crate) command: Command,
        }

        #[tokio::main]
        async fn main() -> Result<()> {
            let args = Cli::parse();
            setup_env(args.config_env_file.clone());
-
-            let shared_storage = credential_storage::initialise_storage(args.credential_db_path.clone()).await;
-            let mut db = match PickleDb::load(
-                "credential.db",
-                PickleDbDumpPolicy::AutoDump,
-                SerializationMethod::Json,
-            ) {
-                Ok(db) => db,
-                Err(_) => PickleDb::new(
-                    "credential.db",
-                    PickleDbDumpPolicy::AutoDump,
-                    SerializationMethod::Json,
-                ),
-            };
-
            let bin_name = "nym-credential-client";

-            match &args.command {
-                Commands::Deposit(m) => m.execute(&mut db, shared_storage).await?,
-                Commands::ListDeposits(m) => m.execute(&mut db, shared_storage).await?,
-                Commands::GetCredential(m) => m.execute(&mut db, shared_storage).await?,
-                Commands::Completions(s) => s.generate(&mut crate::Cli::into_app(), bin_name),
-                Commands::GenerateFigSpec => fig_generate(&mut crate::Cli::into_app(), bin_name)
+            match args.command {
+                Command::Run(r) => {
+                    let db_path = r.client_home_directory.join(DATA_DIR).join(DB_FILE_NAME);
+                    let shared_storage = credential_storage::initialise_storage(db_path).await;
+
+                    let state = deposit(&r.nymd_url, &r.mnemonic, r.amount).await?;
+                    get_credential(&state, shared_storage).await?;
+                }
+                Command::Completions(c) => c.generate(&mut crate::Cli::into_app(), bin_name),
+                Command::GenerateFigSpec => fig_generate(&mut crate::Cli::into_app(), bin_name)
            }

            Ok(())
@@ -1,13 +1,10 @@
 // Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use coconut_interface::{Attribute, BlindSignRequest, Bytable, PrivateAttribute};
 use serde::{Deserialize, Serialize};

 use crypto::asymmetric::{encryption, identity};

-use crate::error::{CredentialClientError, Result};
-
 #[derive(Clone, Debug, Deserialize, Serialize)]
 pub(crate) struct KeyPair {
    pub public_key: String,
@@ -38,35 +35,4 @@ pub(crate) struct State {
    pub tx_hash: String,
    pub signing_keypair: KeyPair,
    pub encryption_keypair: KeyPair,
-    pub blind_request_data: Option<RequestData>,
-    pub signature: Option<String>,
-}
-
-#[derive(Clone, Debug, Deserialize, Serialize)]
-pub(crate) struct RequestData {
-    pub serial_number: Vec<u8>,
-    pub binding_number: Vec<u8>,
-    pub first_attribute: Vec<u8>,
-    pub second_attribute: Vec<u8>,
-    pub blind_sign_req: Vec<u8>,
-}
-
-impl RequestData {
-    pub fn new(
-        private_attributes: Vec<PrivateAttribute>,
-        attributes: &[Attribute],
-        blind_sign_request: &BlindSignRequest,
-    ) -> Result<Self> {
-        if private_attributes.len() != 2 || attributes.len() != 2 {
-            Err(CredentialClientError::WrongAttributeNumber)
-        } else {
-            Ok(RequestData {
-                serial_number: private_attributes[0].to_byte_vec(),
-                binding_number: private_attributes[1].to_byte_vec(),
-                first_attribute: attributes[0].to_byte_vec(),
-                second_attribute: attributes[1].to_byte_vec(),
-                blind_sign_req: blind_sign_request.to_bytes(),
-            })
-        }
-    }
 }
@@ -1,6 +1,6 @@
 [package]
 name = "nym-client"
-version = "1.1.1"
+version = "1.1.4"
 authors = ["Dave Hrycyszyn <futurechimp@users.noreply.github.com>", "Jędrzej Stuczyński <andrew@nymtech.net>"]
 description = "Implementation of the Nym Client"
 edition = "2021"
@@ -26,13 +26,14 @@ log = "0.4" # self explanatory
 pretty_env_logger = "0.4" # for formatting log messages
 rand = { version = "0.7.3", features = ["wasm-bindgen"] } # rng-related traits + some rng implementation to use
 serde = { version = "1.0.104", features = ["derive"] } # for config serialization/deserialization
-sled = "0.34" # for storage of replySURB decryption keys
+serde_json = "1.0"
 thiserror = "1.0.34"
+tap = "1.0.1"
 tokio = { version = "1.21.2", features = ["rt-multi-thread", "net", "signal"] } # async runtime
 tokio-tungstenite = "0.14" # websocket

 ## internal
-client-core = { path = "../client-core" }
+client-core = { path = "../client-core", features = ["fs-surb-storage"] }
 client-connections = { path = "../../common/client-connections" }
 coconut-interface = { path = "../../common/coconut-interface", optional = true }
 config = { path = "../../common/config" }
@@ -51,7 +52,6 @@ topology = { path = "../../common/topology" }
 validator-client = { path = "../../common/client-libs/validator-client", features = ["nymd-client"] }
 version-checker = { path = "../../common/version-checker" }
 websocket-requests = { path = "websocket-requests" }
-tap = "1.0.1"

 [features]
 coconut = ["coconut-interface", "credentials", "credentials/coconut", "gateway-requests/coconut", "gateway-client/coconut", "client-core/coconut"]
@@ -25,58 +25,59 @@ async fn get_self_address(ws_stream: &mut WebSocketStream<MaybeTlsStream<TcpStre
    let response = send_message_and_get_response(ws_stream, self_address_request).await;

    match response {
-        ServerResponse::SelfAddress(recipient) => recipient,
+        ServerResponse::SelfAddress(recipient) => *recipient,
        _ => panic!("received an unexpected response!"),
    }
 }

 async fn send_file_with_reply() {
-    let uri = "ws://localhost:1977";
-    let (mut ws_stream, _) = connect_async(uri).await.unwrap();
-
-    let recipient = get_self_address(&mut ws_stream).await;
-    println!("our full address is: {}", recipient);
-
-    let read_data = std::fs::read("examples/dummy_file").unwrap();
-
-    let send_request = ClientRequest::Send {
-        recipient,
-        message: read_data,
-        with_reply_surb: true,
-        connection_id: Some(0),
-    };
-
-    println!("sending content of 'dummy_file' over the mix network...");
-    let response = send_message_and_get_response(&mut ws_stream, send_request.serialize()).await;
-
-    let received = match response {
-        ServerResponse::Received(received) => received,
-        _ => panic!("received an unexpected response!"),
-    };
-
-    println!("writing the file back to the disk!");
-    std::fs::write("examples/received_file_withreply", received.message).unwrap();
-
-    let reply_message = b"hello from reply SURB! - thanks for sending me the file!".to_vec();
-    let reply_request = ClientRequest::Reply {
-        message: reply_message.clone(),
-        reply_surb: received.reply_surb.unwrap(),
-    };
-
-    println!(
-        "sending {:?} (using reply SURB!) over the mix network...",
-        String::from_utf8(reply_message).unwrap()
-    );
-    let response = send_message_and_get_response(&mut ws_stream, reply_request.serialize()).await;
-    let received = match response {
-        ServerResponse::Received(received) => received,
-        _ => panic!("received an unexpected response!"),
-    };
-
-    println!(
-        "received {:#?} from the mix network!",
-        String::from_utf8(received.message).unwrap()
-    );
+    todo!("reimplement surb usage here : )")
+    // let uri = "ws://localhost:1977";
+    // let (mut ws_stream, _) = connect_async(uri).await.unwrap();
+    //
+    // let recipient = get_self_address(&mut ws_stream).await;
+    // println!("our full address is: {}", recipient);
+    //
+    // let read_data = std::fs::read("examples/dummy_file").unwrap();
+    //
+    // let send_request = ClientRequest::Send {
+    //     recipient,
+    //     message: read_data,
+    //     with_reply_surb: true,
+    //     connection_id: Some(0),
+    // };
+    //
+    // println!("sending content of 'dummy_file' over the mix network...");
+    // let response = send_message_and_get_response(&mut ws_stream, send_request.serialize()).await;
+    //
+    // let received = match response {
+    //     ServerResponse::Received(received) => received,
+    //     _ => panic!("received an unexpected response!"),
+    // };
+    //
+    // println!("writing the file back to the disk!");
+    // std::fs::write("examples/received_file_withreply", received.message).unwrap();
+    //
+    // let reply_message = b"hello from reply SURB! - thanks for sending me the file!".to_vec();
+    // let reply_request = ClientRequest::Reply {
+    //     message: reply_message.clone(),
+    //     reply_surb: received.reply_surb.unwrap(),
+    // };
+    //
+    // println!(
+    //     "sending {:?} (using reply SURB!) over the mix network...",
+    //     String::from_utf8(reply_message).unwrap()
+    // );
+    // let response = send_message_and_get_response(&mut ws_stream, reply_request.serialize()).await;
+    // let received = match response {
+    //     ServerResponse::Received(received) => received,
+    //     _ => panic!("received an unexpected response!"),
+    // };
+    //
+    // println!(
+    //     "received {:#?} from the mix network!",
+    //     String::from_utf8(received.message).unwrap()
+    // );
 }

 async fn send_file_without_reply() {
@@ -91,7 +92,6 @@ async fn send_file_without_reply() {
    let send_request = ClientRequest::Send {
        recipient,
        message: read_data,
-        with_reply_surb: false,
        connection_id: Some(0),
    };

@@ -2,8 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0

 use crate::client::config::template::config_template;
-use client_core::config::Config as BaseConfig;
 pub use client_core::config::MISSING_VALUE;
+use client_core::config::{ClientCoreConfigTrait, Config as BaseConfig, DebugConfig};
 use config::defaults::DEFAULT_WEBSOCKET_LISTENING_PORT;
 use config::NymConfig;
 use serde::{Deserialize, Serialize};
@@ -73,6 +73,12 @@ impl NymConfig for Config {
    }
 }

+impl ClientCoreConfigTrait for Config {
+    fn get_gateway_endpoint(&self) -> &client_core::config::GatewayEndpointConfig {
+        self.base.get_gateway_endpoint()
+    }
+}
+
 impl Config {
    pub fn new<S: Into<String>>(id: S) -> Self {
        Config {
@@ -104,6 +110,10 @@ impl Config {
        &mut self.base
    }

+    pub fn get_debug_settings(&self) -> &DebugConfig {
+        self.get_base().get_debug_config()
+    }
+
    pub fn get_socket_type(&self) -> SocketType {
        self.socket.socket_type
    }
@@ -49,13 +49,12 @@ private_encryption_key_file = '{{ client.private_encryption_key_file }}'
 # Path to file containing public encryption key.
 public_encryption_key_file = '{{ client.public_encryption_key_file }}'

-# Full path to file containing reply encryption keys of all reply-SURBs we have ever
-# sent but not received back.
-reply_encryption_key_store_path = '{{ client.reply_encryption_key_store_path }}'
-
 # Path to the database containing bandwidth credentials
 database_path = '{{ client.database_path }}'

+# Path to the persistent store for received reply surbs, unused encryption keys and used sender tags.
+reply_surb_database_path = '{{ client.reply_surb_database_path }}'
+
 ##### additional client config options #####

 # A gateway specific, optional, base58 stringified shared key used for
@@ -1,11 +1,13 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 use crate::client::config::Config;
 use crate::error::ClientError;
 use crate::websocket;
 use client_connections::TransmissionLane;
-use client_core::client::base_client::{BaseClientBuilder, ClientInput, ClientOutput};
+use client_core::client::base_client::{
+    non_wasm_helpers, BaseClientBuilder, ClientInput, ClientOutput,
+};
 use client_core::client::inbound_messages::InputMessage;
 use client_core::client::key_manager::KeyManager;
 use client_core::client::received_buffer::{ReceivedBufferMessage, ReconstructedMessagesReceiver};
@@ -14,7 +16,7 @@ use futures::channel::mpsc;
 use gateway_client::bandwidth::BandwidthController;
 use log::*;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use nymsphinx::receiver::ReconstructedMessage;
 use task::{wait_for_signal, ShutdownNotifier};

@@ -44,8 +46,21 @@ impl SocketClient {
        #[cfg(feature = "coconut")]
        let bandwidth_controller = {
            let details = network_defaults::NymNetworkDetails::new_from_env();
-            let client_config = validator_client::Config::try_from_nym_network_details(&details)
-                .expect("failed to construct validator client config");
+            let mut client_config =
+                validator_client::Config::try_from_nym_network_details(&details)
+                    .expect("failed to construct validator client config");
+            let nymd_url = config
+                .get_base()
+                .get_validator_endpoints()
+                .pop()
+                .expect("No nymd validator endpoint provided");
+            let api_url = config
+                .get_base()
+                .get_validator_api_endpoints()
+                .pop()
+                .expect("No validator api endpoint provided");
+            // overwrite env configuration with config URLs
+            client_config = client_config.with_urls(nymd_url, api_url);
            let client = validator_client::Client::new_query(client_config)
                .expect("Could not construct query client");
            let coconut_api_clients =
@@ -94,7 +109,7 @@ impl SocketClient {

    /// blocking version of `start_socket` method. Will run forever (or until SIGINT is sent)
    pub async fn run_socket_forever(self) -> Result<(), ClientError> {
-        let shutdown = self.start_socket().await?;
+        let mut shutdown = self.start_socket().await?;
        wait_for_signal().await;

        println!(
@@ -107,8 +122,8 @@ impl SocketClient {
        // Some of these components have shutdown signalling implemented as part of socks5 work,
        // but since it's not fully implemented (yet) for all the components of the native client,
        // we don't try to wait and instead just stop immediately.
-        //log::info!("Waiting for tasks to finish... (Press ctrl-c to force)");
-        //shutdown.wait_for_shutdown().await;
+        log::info!("Waiting for tasks to finish... (Press ctrl-c to force)");
+        shutdown.wait_for_shutdown().await;

        log::info!("Stopping nym-client");
        Ok(())
@@ -123,6 +138,11 @@ impl SocketClient {
            self.config.get_base(),
            self.key_manager,
            Some(Self::create_bandwidth_controller(&self.config).await),
+            non_wasm_helpers::setup_fs_reply_surb_backend(
+                self.config.get_base().get_reply_surb_database_path(),
+                self.config.get_debug_settings(),
+            )
+            .await?,
        );

        let self_address = base_builder.as_mix_recipient();
@@ -147,6 +167,11 @@ impl SocketClient {
            self.config.get_base(),
            self.key_manager,
            Some(Self::create_bandwidth_controller(&self.config).await),
+            non_wasm_helpers::setup_fs_reply_surb_backend(
+                self.config.get_base().get_reply_surb_database_path(),
+                self.config.get_debug_settings(),
+            )
+            .await?,
        );

        let mut started_client = base_client.start_base().await?;
@@ -184,14 +209,9 @@ impl DirectClient {
    /// EXPERIMENTAL DIRECT RUST API
    /// It's untested and there are absolutely no guarantees about it (but seems to have worked
    /// well enough in local tests)
-    pub async fn send_message(
-        &mut self,
-        recipient: Recipient,
-        message: Vec<u8>,
-        with_reply_surb: bool,
-    ) {
+    pub async fn send_regular_message(&mut self, recipient: Recipient, message: Vec<u8>) {
        let lane = TransmissionLane::General;
-        let input_msg = InputMessage::new_fresh(recipient, message, with_reply_surb, lane);
+        let input_msg = InputMessage::new_regular(recipient, message, lane);

        self.client_input
            .input_sender
@@ -203,8 +223,28 @@ impl DirectClient {
    /// EXPERIMENTAL DIRECT RUST API
    /// It's untested and there are absolutely no guarantees about it (but seems to have worked
    /// well enough in local tests)
-    pub async fn send_reply(&mut self, reply_surb: ReplySurb, message: Vec<u8>) {
-        let input_msg = InputMessage::new_reply(reply_surb, message);
+    pub async fn send_anonymous_message(
+        &mut self,
+        recipient: Recipient,
+        message: Vec<u8>,
+        reply_surbs: u32,
+    ) {
+        let lane = TransmissionLane::General;
+        let input_msg = InputMessage::new_anonymous(recipient, message, reply_surbs, lane);
+
+        self.client_input
+            .input_sender
+            .send(input_msg)
+            .await
+            .expect("InputMessageReceiver has stopped receiving!");
+    }
+
+    /// EXPERIMENTAL DIRECT RUST API
+    /// It's untested and there are absolutely no guarantees about it (but seems to have worked
+    /// well enough in local tests)
+    pub async fn send_reply(&mut self, recipient_tag: AnonymousSenderTag, message: Vec<u8>) {
+        let lane = TransmissionLane::General;
+        let input_msg = InputMessage::new_reply(recipient_tag, message, lane);

        self.client_input
            .input_sender
@@ -1,14 +1,17 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use clap::Args;
-use client_core::{config::GatewayEndpointConfig, error::ClientCoreError};
-use config::NymConfig;
-
 use crate::{
    client::config::Config,
    commands::{override_config, OverrideConfig},
+    error::ClientError,
 };
+use clap::Args;
+use config::NymConfig;
+use nymsphinx::addressing::clients::Recipient;
+use serde::Serialize;
+use std::fmt::Display;
+use tap::TapFallible;

 #[derive(Args, Clone)]
 pub(crate) struct Init {
@@ -46,11 +49,19 @@ pub(crate) struct Init {
    #[clap(long, hidden = true)]
    fastmode: bool,

+    /// Disable loop cover traffic and the Poisson rate limiter (for debugging only)
+    #[clap(long, hidden = true)]
+    no_cover: bool,
+
    /// Set this client to work in a enabled credentials mode that would attempt to use gateway
    /// with bandwidth credential requirement.
    #[cfg(feature = "coconut")]
    #[clap(long)]
    enabled_credentials_mode: bool,
+
+    /// Save a summary of the initialization to a json file
+    #[clap(long)]
+    output_json: bool,
 }

 impl From<Init> for OverrideConfig {
@@ -61,6 +72,7 @@ impl From<Init> for OverrideConfig {
            disable_socket: init_config.disable_socket,
            port: init_config.port,
            fastmode: init_config.fastmode,
+            no_cover: init_config.no_cover,

            #[cfg(feature = "coconut")]
            enabled_credentials_mode: init_config.enabled_credentials_mode,
@@ -68,7 +80,30 @@ impl From<Init> for OverrideConfig {
    }
 }

-pub(crate) async fn execute(args: &Init) {
+#[derive(Debug, Serialize)]
+pub struct InitResults {
+    #[serde(flatten)]
+    client_core: client_core::init::InitResults,
+    client_listening_port: String,
+}
+
+impl InitResults {
+    fn new(config: &Config, address: &Recipient) -> Self {
+        Self {
+            client_core: client_core::init::InitResults::new(config.get_base(), address),
+            client_listening_port: config.get_listening_port().to_string(),
+        }
+    }
+}
+
+impl Display for InitResults {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "{}", self.client_core)?;
+        write!(f, "Client listening port: {}", self.client_listening_port)
+    }
+}
+
+pub(crate) async fn execute(args: &Init) -> Result<(), ClientError> {
    println!("Initialising client...");

    let id = &args.id;
@@ -92,25 +127,44 @@ pub(crate) async fn execute(args: &Init) {
    let register_gateway = !already_init || user_wants_force_register;

    // Attempt to use a user-provided gateway, if possible
-    let user_chosen_gateway_id = args.gateway.as_deref();
+    let user_chosen_gateway_id = args.gateway.clone();

-    let mut config = Config::new(id);
-    let override_config_fields = OverrideConfig::from(args.clone());
-    config = override_config(config, override_config_fields);
+    // Load and potentially override config
+    let mut config = override_config(Config::new(id), OverrideConfig::from(args.clone()));
+
+    // Setup gateway by either registering a new one, or creating a new config from the selected
+    // one but with keys kept, or reusing the gateway configuration.
+    let gateway = client_core::init::setup_gateway::<_, Config, _>(
+        register_gateway,
+        user_chosen_gateway_id,
+        config.get_base(),
+    )
+    .await
+    .tap_err(|err| eprintln!("Failed to setup gateway\nError: {err}"))?;

-    let gateway = setup_gateway(id, register_gateway, user_chosen_gateway_id, &config)
-        .await
-        .unwrap_or_else(|err| {
-            eprintln!("Failed to setup gateway\nError: {err}");
-            std::process::exit(1)
-        });
    config.get_base_mut().with_gateway_endpoint(gateway);

-    let config_save_location = config.get_config_file_save_location();
-    config
-        .save_to_file(None)
-        .expect("Failed to save the config file");
+    config.save_to_file(None).tap_err(|_| {
+        log::error!("Failed to save the config file");
+    })?;

+    print_saved_config(&config);
+
+    let address = client_core::init::get_client_address_from_stored_keys(config.get_base())?;
+    let init_results = InitResults::new(&config, &address);
+    println!("{}", init_results);
+
+    // Output summary to a json file, if specified
+    if args.output_json {
+        client_core::init::output_to_json(&init_results, "client_init_results.json");
+    }
+
+    println!("\nThe address of this client is: {}\n", address);
+    Ok(())
+}
+
+fn print_saved_config(config: &Config) {
+    let config_save_location = config.get_config_file_save_location();
    println!("Saved configuration file to {:?}", config_save_location);
    println!("Using gateway: {}", config.get_base().get_gateway_id());
    log::debug!("Gateway id: {}", config.get_base().get_gateway_id());
@@ -119,63 +173,5 @@ pub(crate) async fn execute(args: &Init) {
        "Gateway listener: {}",
        config.get_base().get_gateway_listener()
    );
-    println!("Client configuration completed.");
-
-    client_core::init::show_address(config.get_base()).unwrap_or_else(|err| {
-        eprintln!("Failed to show address\nError: {err}");
-        std::process::exit(1)
-    });
-}
-
-async fn setup_gateway(
-    id: &str,
-    register: bool,
-    user_chosen_gateway_id: Option<&str>,
-    config: &Config,
-) -> Result<GatewayEndpointConfig, ClientCoreError> {
-    if register {
-        // Get the gateway details by querying the validator-api. Either pick one at random or use
-        // the chosen one if it's among the available ones.
-        println!("Configuring gateway");
-        let gateway = client_core::init::query_gateway_details(
-            config.get_base().get_validator_api_endpoints(),
-            user_chosen_gateway_id,
-        )
-        .await?;
-        log::debug!("Querying gateway gives: {}", gateway);
-
-        // Registering with gateway by setting up and writing shared keys to disk
-        log::trace!("Registering gateway");
-        client_core::init::register_with_gateway_and_store_keys(gateway.clone(), config.get_base())
-            .await?;
-        println!("Saved all generated keys");
-
-        Ok(gateway.into())
-    } else if user_chosen_gateway_id.is_some() {
-        // Just set the config, don't register or create any keys
-        // This assumes that the user knows what they are doing, and that the existing keys are
-        // valid for the gateway being used
-        println!("Using gateway provided by user, keeping existing keys");
-        let gateway = client_core::init::query_gateway_details(
-            config.get_base().get_validator_api_endpoints(),
-            user_chosen_gateway_id,
-        )
-        .await?;
-        log::debug!("Querying gateway gives: {}", gateway);
-        Ok(gateway.into())
-    } else {
-        println!("Not registering gateway, will reuse existing config and keys");
-        let existing_config = Config::load_from_file(Some(id)).map_err(|err| {
-            log::error!(
-                "Unable to configure gateway: {err}. \n
-                Seems like the client was already initialized but it was not possible to read \
-                the existing configuration file. \n
-                CAUTION: Consider backing up your gateway keys and try force gateway registration, or \
-                removing the existing configuration and starting over."
-            );
-            ClientCoreError::CouldNotLoadExistingGatewayConfiguration(err)
-        })?;
-
-        Ok(existing_config.get_base().get_gateway_endpoint().clone())
-    }
+    println!("Client configuration completed.\n");
 }
@@ -80,6 +80,7 @@ pub(crate) struct OverrideConfig {
    disable_socket: bool,
    port: Option<u16>,
    fastmode: bool,
+    no_cover: bool,

    #[cfg(feature = "coconut")]
    enabled_credentials_mode: bool,
@@ -89,7 +90,7 @@ pub(crate) async fn execute(args: &Cli) -> Result<(), ClientError> {
    let bin_name = "nym-native-client";

    match &args.command {
-        Commands::Init(m) => init::execute(m).await,
+        Commands::Init(m) => init::execute(m).await?,
        Commands::Run(m) => run::execute(m).await?,
        Commands::Upgrade(m) => upgrade::execute(m),
        Commands::Completions(s) => s.generate(&mut Cli::into_app(), bin_name),
@@ -141,6 +142,10 @@ pub(crate) fn override_config(mut config: Config, args: OverrideConfig) -> Confi
        config.get_base_mut().set_high_default_traffic_volume();
    }

+    if args.no_cover {
+        config.get_base_mut().set_no_cover_traffic();
+    }
+
    config
 }

@@ -39,6 +39,15 @@ pub(crate) struct Run {
    #[clap(short, long)]
    port: Option<u16>,

+    /// Mostly debug-related option to increase default traffic rate so that you would not need to
+    /// modify config post init
+    #[clap(long, hidden = true)]
+    fastmode: bool,
+
+    /// Disable loop cover traffic and the Poisson rate limiter (for debugging only)
+    #[clap(long, hidden = true)]
+    no_cover: bool,
+
    /// Set this client to work in a enabled credentials mode that would attempt to use gateway
    /// with bandwidth credential requirement.
    #[cfg(feature = "coconut")]
@@ -53,7 +62,8 @@ impl From<Run> for OverrideConfig {
            api_validators: run_config.api_validators,
            disable_socket: run_config.disable_socket,
            port: run_config.port,
-            fastmode: false,
+            fastmode: run_config.fastmode,
+            no_cover: run_config.no_cover,
            #[cfg(feature = "coconut")]
            enabled_credentials_mode: run_config.enabled_credentials_mode,
        }
@@ -93,6 +103,10 @@ pub(crate) async fn execute(args: &Run) -> Result<(), ClientError> {
    let override_config_fields = OverrideConfig::from(args.clone());
    config = override_config(config, override_config_fields);

+    if config.get_base_mut().set_empty_fields_to_defaults() {
+        warn!("some of the core config options were left unset. the default values are going to get used instead.");
+    }
+
    if !version_check(&config) {
        error!("failed the local version check");
        return Err(ClientError::FailedLocalVersionCheck);
@@ -1,12 +1,17 @@
+use client_core::client::replies::reply_storage::fs_backend;
 use client_core::error::ClientCoreError;

 #[derive(thiserror::Error, Debug)]
 pub enum ClientError {
+    #[error("I/O error: {0}")]
+    IoError(#[from] std::io::Error),
+
    #[error("client-core error: {0}")]
-    ClientCoreError(#[from] ClientCoreError),
+    ClientCoreError(#[from] ClientCoreError<fs_backend::Backend>),

    #[error("Failed to load config for: {0}")]
    FailedToLoadConfig(String),
+
    #[error("Failed local version check, client and config mismatch")]
    FailedLocalVersionCheck,

@@ -14,7 +14,7 @@ use futures::channel::mpsc;
 use futures::{SinkExt, StreamExt};
 use log::*;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use nymsphinx::receiver::ReconstructedMessage;
 use tokio::net::TcpStream;
 use tokio_tungstenite::{
@@ -62,9 +62,13 @@ impl Clone for Handler {

 impl Drop for Handler {
    fn drop(&mut self) {
-        self.buffer_requester
+        if self
+            .buffer_requester
            .unbounded_send(ReceivedBufferMessage::ReceiverDisconnect)
-            .expect("the buffer request failed!")
+            .is_err()
+        {
+            error!("we failed to disconnect the receiver from the buffer! presumably the shutdown procedure has been initiated!")
+        }
    }
 }

@@ -89,18 +93,22 @@ impl Handler {

    async fn handle_send(
        &mut self,
-        recipient: &Recipient,
+        recipient: Recipient,
        message: Vec<u8>,
-        with_reply_surb: bool,
        connection_id: Option<u64>,
    ) -> Option<ServerResponse> {
+        info!(
+            "Attempting to send {:.2} kiB message to {recipient} on connection_id {connection_id:?}",
+            message.len() as f64 / 1024.0
+        );
+
        // We map the absence of a connection id as going into the general lane.
        let lane = connection_id.map_or(TransmissionLane::General, |id| {
            TransmissionLane::ConnectionId(id)
        });

        // the ack control is now responsible for chunking, etc.
-        let input_msg = InputMessage::new_fresh(*recipient, message, with_reply_surb, lane);
+        let input_msg = InputMessage::new_regular(recipient, message, lane);
        self.msg_input
            .send(input_msg)
            .await
@@ -109,53 +117,119 @@ impl Handler {
        // Only reply back with a `LaneQueueLength` if the sender providided a connection id
        let connection_id = match lane {
            TransmissionLane::General
-            | TransmissionLane::Reply
+            | TransmissionLane::ReplySurbRequest
            | TransmissionLane::Retransmission
-            | TransmissionLane::Control => return None,
+            | TransmissionLane::AdditionalReplySurbs => return None,
            TransmissionLane::ConnectionId(id) => id,
        };

        // on receiving a send, we reply back the current lane queue length for that connection id.
        // Note that this does _NOT_ take into account the packets that have been received but not
        // yet reach `OutQueueControl`, so it might be a tad low.
-        let Ok(lane_queue_lengths) = self.lane_queue_lengths.lock() else {
-            log::warn!(
-                "Failed to get the lane queue length lock, \
-                not responding back with the current queue length"
-            );
-            return None;
-        };
-
-        let queue_length = lane_queue_lengths.get(&lane).unwrap_or(0);
-        Some(ServerResponse::LaneQueueLength(connection_id, queue_length))
-    }
-
-    async fn handle_reply(
-        &mut self,
-        reply_surb: ReplySurb,
-        message: Vec<u8>,
-    ) -> Option<ServerResponse> {
-        if message.len() > ReplySurb::max_msg_len(Default::default()) {
-            return Some(
-                ServerResponse::new_error(
-                    format!(
-                        "too long message to put inside a reply SURB. Received: {} bytes and maximum is {} bytes",
-                        message.len(), ReplySurb::max_msg_len(Default::default()))
-                    )
-                );
+        if let Ok(lane_queue_lengths) = self.lane_queue_lengths.lock() {
+            let queue_length = lane_queue_lengths.get(&lane).unwrap_or(0);
+            return Some(ServerResponse::LaneQueueLength {
+                lane: connection_id,
+                queue_length,
+            });
        }

-        let input_msg = InputMessage::new_reply(reply_surb, message);
+        log::warn!("Failed to get the lane queue length lock, not responding back with the current queue length");
+        None
+    }
+
+    async fn handle_send_anonymous(
+        &mut self,
+        recipient: Recipient,
+        message: Vec<u8>,
+        reply_surbs: u32,
+        connection_id: Option<u64>,
+    ) -> Option<ServerResponse> {
+        info!(
+            "Attempting to anonymously send {:.2} kiB message to {recipient} on connection_id {connection_id:?} while attaching {reply_surbs} replySURBs.",
+            message.len() as f64 / 1024.0
+        );
+
+        // We map the absence of a connection id as going into the general lane.
+        let lane = connection_id.map_or(TransmissionLane::General, |id| {
+            TransmissionLane::ConnectionId(id)
+        });
+
+        let input_msg = InputMessage::new_anonymous(recipient, message, reply_surbs, lane);
        self.msg_input
            .send(input_msg)
            .await
            .expect("InputMessageReceiver has stopped receiving!");

+        // Only reply back with a `LaneQueueLength` if the sender providided a connection id
+        let connection_id = match lane {
+            TransmissionLane::General
+            | TransmissionLane::ReplySurbRequest
+            | TransmissionLane::Retransmission
+            | TransmissionLane::AdditionalReplySurbs => return None,
+            TransmissionLane::ConnectionId(id) => id,
+        };
+
+        // on receiving a send, we reply back the current lane queue length for that connection id.
+        // Note that this does _NOT_ take into account the packets that have been received but not
+        // yet reach `OutQueueControl`, so it might be a tad low.
+        if let Ok(lane_queue_lengths) = self.lane_queue_lengths.lock() {
+            let queue_length = lane_queue_lengths.get(&lane).unwrap_or(0);
+            return Some(ServerResponse::LaneQueueLength {
+                lane: connection_id,
+                queue_length,
+            });
+        }
+
+        log::warn!("Failed to get the lane queue length lock, not responding back with the current queue length");
+        None
+    }
+
+    async fn handle_reply(
+        &mut self,
+        recipient_tag: AnonymousSenderTag,
+        message: Vec<u8>,
+        connection_id: Option<u64>,
+    ) -> Option<ServerResponse> {
+        info!("Attempting to send {:.2} kiB reply message to {recipient_tag} on connection_id {connection_id:?}", message.len() as f64 / 1024.0);
+
+        // We map the absence of a connection id as going into the general lane.
+        let lane = connection_id.map_or(TransmissionLane::General, |id| {
+            TransmissionLane::ConnectionId(id)
+        });
+
+        let input_msg = InputMessage::new_reply(recipient_tag, message, lane);
+        self.msg_input
+            .send(input_msg)
+            .await
+            .expect("InputMessageReceiver has stopped receiving!");
+
+        // Only reply back with a `LaneQueueLength` if the sender providided a connection id
+        let connection_id = match lane {
+            TransmissionLane::General
+            | TransmissionLane::ReplySurbRequest
+            | TransmissionLane::Retransmission
+            | TransmissionLane::AdditionalReplySurbs => return None,
+            TransmissionLane::ConnectionId(id) => id,
+        };
+
+        // on receiving a send, we reply back the current lane queue length for that connection id.
+        // Note that this does _NOT_ take into account the packets that have been received but not
+        // yet reach `OutQueueControl`, so it might be a tad low.
+        if let Ok(lane_queue_lengths) = self.lane_queue_lengths.lock() {
+            let queue_length = lane_queue_lengths.get(&lane).unwrap_or(0);
+            return Some(ServerResponse::LaneQueueLength {
+                lane: connection_id,
+                queue_length,
+            });
+        }
+
+        log::warn!("Failed to get the lane queue length lock, not responding back with the current queue length");
        None
    }

    fn handle_self_address(&self) -> ServerResponse {
-        ServerResponse::SelfAddress(self.self_full_address)
+        ServerResponse::SelfAddress(Box::new(self.self_full_address))
    }

    fn handle_closed_connection(&self, connection_id: u64) -> Option<ServerResponse> {
@@ -175,7 +249,10 @@ impl Handler {

        let lane = TransmissionLane::ConnectionId(connection_id);
        let queue_length = lane_queue_lengths.get(&lane).unwrap_or(0);
-        Some(ServerResponse::LaneQueueLength(connection_id, queue_length))
+        Some(ServerResponse::LaneQueueLength {
+            lane: connection_id,
+            queue_length,
+        })
    }

    async fn handle_request(&mut self, request: ClientRequest) -> Option<ServerResponse> {
@@ -183,16 +260,25 @@ impl Handler {
            ClientRequest::Send {
                recipient,
                message,
-                with_reply_surb,
+                connection_id,
+            } => self.handle_send(recipient, message, connection_id).await,
+
+            ClientRequest::SendAnonymous {
+                recipient,
+                message,
+                reply_surbs,
                connection_id,
            } => {
-                self.handle_send(&recipient, message, with_reply_surb, connection_id)
+                self.handle_send_anonymous(recipient, message, reply_surbs, connection_id)
                    .await
            }
+
            ClientRequest::Reply {
                message,
-                reply_surb,
-            } => self.handle_reply(reply_surb, message).await,
+                sender_tag,
+                connection_id,
+            } => self.handle_reply(sender_tag, message, connection_id).await,
+
            ClientRequest::SelfAddress => Some(self.handle_self_address()),
            ClientRequest::ClosedConnection(id) => self.handle_closed_connection(id),
            ClientRequest::GetLaneQueueLength(id) => self.handle_get_lane_queue_length(id),
@@ -299,8 +385,7 @@ impl Handler {
                    if let Some(response) = self.handle_ws_request(socket_msg).await {
                        if let Err(err) = self.send_websocket_response(response).await {
                            warn!(
-                                "Failed to send message over websocket: {}. Assuming the connection is dead.",
-                                err
+                                "Failed to send message over websocket: {err}. Assuming the connection is dead.",
                            );
                            break;
                        }
@@ -308,9 +393,10 @@ impl Handler {
                }
                // or a reconstructed mix message that we need to push back to the client
                mix_messages = msg_receiver.next() => {
-                    let mix_messages = mix_messages.expect(
-                        "mix messages sender was unexpectedly closed! this shouldn't have ever happened!",
-                    );
+                    let Some(mix_messages) = mix_messages else {
+                        error!("mix messages sender was unexpectedly closed! this shouldn't have ever happened! (unless we're shutting down - TODO: implement proper graceful shutdown handler)");
+                        return
+                    };
                    if let Err(e) = self.push_websocket_received_plaintexts(mix_messages).await {
                        warn!("failed to send sphinx packets back to the client - {:?}, assuming the connection is dead", e);
                        break;
@@ -54,9 +54,8 @@ impl Listener {
                        Ok((mut socket, remote_addr)) => {
                            debug!("Received connection from {:?}", remote_addr);
                            if self.state.is_connected() {
-                                warn!("tried to duplicate!");
+                                warn!("Tried to open a duplicate websocket connection. The request came from {}", remote_addr);
                                // if we've already got a connection, don't allow another one
-                                debug!("but there was already a connection present!");
                                // while we only ever want to accept a single connection, we don't want
                                // to leave clients hanging (and also allow for reconnection if it somehow
                                // was dropped)
@@ -24,8 +24,11 @@ impl fmt::Debug for Error {
 }

 impl Error {
-    pub fn new(kind: ErrorKind, message: String) -> Self {
-        Error { kind, message }
+    pub fn new<S: Into<String>>(kind: ErrorKind, message: S) -> Self {
+        Error {
+            kind,
+            message: message.into(),
+        }
    }
 }

@@ -62,6 +65,31 @@ pub enum ErrorKind {
    Other = 0xFF,
 }

+impl TryFrom<u8> for ErrorKind {
+    type Error = Error;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            _ if value == (ErrorKind::EmptyRequest as u8) => Ok(ErrorKind::EmptyRequest),
+            _ if value == (ErrorKind::TooShortRequest as u8) => Ok(ErrorKind::TooShortRequest),
+            _ if value == (ErrorKind::UnknownRequest as u8) => Ok(ErrorKind::UnknownRequest),
+            _ if value == (ErrorKind::MalformedRequest as u8) => Ok(ErrorKind::MalformedRequest),
+
+            _ if value == (ErrorKind::EmptyResponse as u8) => Ok(ErrorKind::EmptyResponse),
+            _ if value == (ErrorKind::TooShortResponse as u8) => Ok(ErrorKind::TooShortResponse),
+            _ if value == (ErrorKind::UnknownResponse as u8) => Ok(ErrorKind::UnknownResponse),
+            _ if value == (ErrorKind::MalformedResponse as u8) => Ok(ErrorKind::MalformedResponse),
+
+            _ if value == (ErrorKind::Other as u8) => Ok(ErrorKind::Other),
+
+            n => Err(Error::new(
+                ErrorKind::MalformedResponse,
+                format!("invalid error code {}", n),
+            )),
+        }
+    }
+}
+
 impl ErrorKind {
    pub(crate) fn as_str(&self) -> &'static str {
        match *self {
@@ -1,4 +1,4 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 // all variable size data is always prefixed with u64 length
@@ -7,69 +7,115 @@
 use crate::error::{self, ErrorKind};
 use crate::text::ClientRequestText;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::{AnonymousSenderTag, SENDER_TAG_SIZE};
 use std::convert::{TryFrom, TryInto};
 use std::mem::size_of;

-/// Value tag representing [`Send`] variant of the [`ClientRequest`]
-pub const SEND_REQUEST_TAG: u8 = 0x00;
+#[repr(u8)]
+enum ClientRequestTag {
+    /// Value tag representing [`Send`] variant of the [`ClientRequest`]
+    Send = 0x00,

-/// Value tag representing [`Reply`] variant of the [`ClientRequest`]
-pub const REPLY_REQUEST_TAG: u8 = 0x01;
+    /// Value tag representing [`SendAnonymous`] variant of the [`ClientRequest`]
+    SendAnonymous = 0x01,

-/// Value tag representing [`SelfAddress`] variant of the [`ClientRequest`]
-pub const SELF_ADDRESS_REQUEST_TAG: u8 = 0x02;
+    /// Value tag representing [`Reply`] variant of the [`ClientRequest`]
+    Reply = 0x02,

-/// Value tag representing [`ClosedConnection`] variant of the [`ClientRequest`]
-pub const CLOSED_CONNECTION_REQUEST_TAG: u8 = 0x03;
+    /// Value tag representing [`SelfAddress`] variant of the [`ClientRequest`]
+    SelfAddress = 0x03,

-/// Value tag representing [`GetLaneQueueLength`] variant of the [`ClientRequest`]
-pub const GET_LANE_QUEUE_LENGHT_TAG: u8 = 0x04;
+    /// Value tag representing [`ClosedConnection`] variant of the [`ClientRequest`]
+    ClosedConnection = 0x04,
+
+    /// Value tag representing [`GetLaneQueueLength`] variant of the [`ClientRequest`]
+    GetLaneQueueLength = 0x05,
+}
+
+impl TryFrom<u8> for ClientRequestTag {
+    type Error = error::Error;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            _ if value == (Self::Send as u8) => Ok(Self::Send),
+            _ if value == (Self::SendAnonymous as u8) => Ok(Self::SendAnonymous),
+            _ if value == (Self::Reply as u8) => Ok(Self::Reply),
+            _ if value == (Self::SelfAddress as u8) => Ok(Self::SelfAddress),
+            _ if value == (Self::ClosedConnection as u8) => Ok(Self::ClosedConnection),
+            _ if value == (Self::GetLaneQueueLength as u8) => Ok(Self::GetLaneQueueLength),
+            n => Err(error::Error::new(
+                ErrorKind::UnknownRequest,
+                format!("{n} does not correspond to any valid request tag"),
+            )),
+        }
+    }
+}

 #[allow(non_snake_case)]
 #[derive(Debug)]
 pub enum ClientRequest {
+    /// The simplest message variant where no additional information is attached.
+    /// You're simply sending your `data` to specified `recipient` without any tagging.
+    ///
+    /// Ends up with `NymMessage::Plain` variant
    Send {
        recipient: Recipient,
        message: Vec<u8>,
-        // Perhaps we could change it to a number to indicate how many reply_SURBs we want to include?
-        with_reply_surb: bool,
        connection_id: Option<u64>,
    },
-    Reply {
+
+    /// Create a message used for a duplex anonymous communication where the recipient
+    /// will never learn of our true identity. This is achieved by carefully sending `reply_surbs`.
+    ///
+    /// Note that if reply_surbs is set to zero then
+    /// this variant requires the client having sent some reply_surbs in the past
+    /// (and thus the recipient also knowing our sender tag).
+    ///
+    /// Ends up with `NymMessage::Repliable` variant
+    SendAnonymous {
+        recipient: Recipient,
        message: Vec<u8>,
-        reply_surb: ReplySurb,
+        reply_surbs: u32,
+        connection_id: Option<u64>,
    },
+
+    /// Attempt to use our internally received and stored `ReplySurb` to send the message back
+    /// to specified recipient whilst not knowing its full identity (or even gateway).
+    ///
+    /// Ends up with `NymMessage::Reply` variant
+    Reply {
+        sender_tag: AnonymousSenderTag,
+        message: Vec<u8>,
+        connection_id: Option<u64>,
+    },
+
    SelfAddress,
+
    ClosedConnection(u64),
+
    GetLaneQueueLength(u64),
 }

 // we could have been parsing it directly TryFrom<WsMessage>, but we want to retain
 // information about whether it came from binary or text to send appropriate response back
 impl ClientRequest {
-    // SEND_REQUEST_TAG || with_surb || recipient || conn_id || data_len || data
-    fn serialize_send(
-        recipient: Recipient,
-        data: Vec<u8>,
-        with_reply_surb: bool,
-        connection_id: Option<u64>,
-    ) -> Vec<u8> {
+    // SEND_REQUEST_TAG || recipient || conn_id || data_len || data
+    fn serialize_send(recipient: Recipient, data: Vec<u8>, connection_id: Option<u64>) -> Vec<u8> {
        let data_len_bytes = (data.len() as u64).to_be_bytes();
        let conn_id_bytes = connection_id.unwrap_or(0).to_be_bytes();
-        std::iter::once(SEND_REQUEST_TAG)
-            .chain(std::iter::once(with_reply_surb as u8))
-            .chain(recipient.to_bytes().iter().cloned()) // will not be length prefixed because the length is constant
-            .chain(conn_id_bytes.iter().cloned())
-            .chain(data_len_bytes.iter().cloned())
+
+        std::iter::once(ClientRequestTag::Send as u8)
+            .chain(recipient.to_bytes().into_iter()) // will not be length prefixed because the length is constant
+            .chain(conn_id_bytes.into_iter())
+            .chain(data_len_bytes.into_iter())
            .chain(data.into_iter())
            .collect()
    }

-    // SEND_REQUEST_TAG || with_reply || recipient || conn_id || data_len || data
+    // SEND_REQUEST_TAG || recipient || conn_id || data_len || data
    fn deserialize_send(b: &[u8]) -> Result<Self, error::Error> {
-        // we need to have at least 1 (tag) + 1 (reply flag) + Recipient::LEN + 2*sizeof<u64> bytes
-        if b.len() < 2 + Recipient::LEN + 2 * size_of::<u64>() {
+        // we need to have at least 1 (tag) + Recipient::LEN + 2*sizeof<u64> bytes
+        if b.len() < 1 + Recipient::LEN + 2 * size_of::<u64>() {
            return Err(error::Error::new(
                ErrorKind::TooShortRequest,
                "not enough data provided to recover 'send'".to_string(),
@@ -77,21 +123,10 @@ impl ClientRequest {
        }

        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], SEND_REQUEST_TAG);
-
-        let with_reply_surb = match b[1] {
-            0 => false,
-            1 => true,
-            n => {
-                return Err(error::Error::new(
-                    ErrorKind::MalformedRequest,
-                    format!("invalid reply surb flag {}", n),
-                ))
-            }
-        };
+        debug_assert_eq!(b[0], ClientRequestTag::Send as u8);

        let mut recipient_bytes = [0u8; Recipient::LEN];
-        recipient_bytes.copy_from_slice(&b[2..2 + Recipient::LEN]);
+        recipient_bytes.copy_from_slice(&b[1..1 + Recipient::LEN]);
        let recipient = match Recipient::try_from_bytes(recipient_bytes) {
            Ok(recipient) => recipient,
            Err(err) => {
@@ -104,7 +139,7 @@ impl ClientRequest {

        let mut connection_id_bytes = [0u8; size_of::<u64>()];
        connection_id_bytes
-            .copy_from_slice(&b[2 + Recipient::LEN..2 + Recipient::LEN + size_of::<u64>()]);
+            .copy_from_slice(&b[1 + Recipient::LEN..1 + Recipient::LEN + size_of::<u64>()]);
        let connection_id = u64::from_be_bytes(connection_id_bytes);
        let connection_id = if connection_id == 0 {
            None
@@ -113,9 +148,9 @@ impl ClientRequest {
        };

        let data_len_bytes =
-            &b[2 + Recipient::LEN + size_of::<u64>()..2 + Recipient::LEN + 2 * size_of::<u64>()];
+            &b[1 + Recipient::LEN + size_of::<u64>()..1 + Recipient::LEN + 2 * size_of::<u64>()];
        let data_len = u64::from_be_bytes(data_len_bytes.try_into().unwrap());
-        let data = &b[2 + Recipient::LEN + 2 * size_of::<u64>()..];
+        let data = &b[1 + Recipient::LEN + 2 * size_of::<u64>()..];
        if data.len() as u64 != data_len {
            return Err(error::Error::new(
                ErrorKind::MalformedRequest,
@@ -128,33 +163,111 @@ impl ClientRequest {
        }

        Ok(ClientRequest::Send {
-            with_reply_surb,
            recipient,
            message: data.to_vec(),
            connection_id,
        })
    }

-    // REPLY_REQUEST_TAG || surb_len || surb || message_len || message
-    fn serialize_reply(message: Vec<u8>, reply_surb: &ReplySurb) -> Vec<u8> {
-        let reply_surb_bytes = reply_surb.to_bytes();
-        let surb_len_bytes = (reply_surb_bytes.len() as u64).to_be_bytes();
-        let message_len_bytes = (message.len() as u64).to_be_bytes();
+    // SEND_ANONYMOUS_REQUEST_TAG || reply_surbs || recipient || conn_id || data_len || data
+    fn serialize_send_anonymous(
+        recipient: Recipient,
+        data: Vec<u8>,
+        reply_surbs: u32,
+        connection_id: Option<u64>,
+    ) -> Vec<u8> {
+        let data_len_bytes = (data.len() as u64).to_be_bytes();
+        let conn_id_bytes = connection_id.unwrap_or(0).to_be_bytes();

-        std::iter::once(REPLY_REQUEST_TAG)
-            .chain(surb_len_bytes.iter().cloned())
-            .chain(reply_surb_bytes.into_iter())
-            .chain(message_len_bytes.iter().cloned())
+        std::iter::once(ClientRequestTag::SendAnonymous as u8)
+            .chain(reply_surbs.to_be_bytes().into_iter())
+            .chain(recipient.to_bytes().into_iter()) // will not be length prefixed because the length is constant
+            .chain(conn_id_bytes.into_iter())
+            .chain(data_len_bytes.into_iter())
+            .chain(data.into_iter())
+            .collect()
+    }
+
+    // SEND_ANONYMOUS_REQUEST_TAG || reply_surbs || recipient || data_len || data
+    fn deserialize_send_anonymous(b: &[u8]) -> Result<Self, error::Error> {
+        // we need to have at least 1 (tag) + sizeof<u32> (num surbs) + Recipient::LEN + 2 *sizeof<u64> bytes
+        if b.len() < 1 + size_of::<u32>() + Recipient::LEN + 2 * size_of::<u64>() {
+            return Err(error::Error::new(
+                ErrorKind::TooShortRequest,
+                "not enough data provided to recover 'send_anonymous'".to_string(),
+            ));
+        }
+
+        // this MUST match because it was called by 'deserialize'
+        debug_assert_eq!(b[0], ClientRequestTag::SendAnonymous as u8);
+
+        let reply_surbs = u32::from_be_bytes([b[1], b[2], b[3], b[4]]);
+
+        let mut recipient_bytes = [0u8; Recipient::LEN];
+        recipient_bytes.copy_from_slice(&b[5..5 + Recipient::LEN]);
+        let recipient = match Recipient::try_from_bytes(recipient_bytes) {
+            Ok(recipient) => recipient,
+            Err(err) => {
+                return Err(error::Error::new(
+                    ErrorKind::MalformedRequest,
+                    format!("malformed recipient: {:?}", err),
+                ))
+            }
+        };
+
+        let mut connection_id_bytes = [0u8; size_of::<u64>()];
+        connection_id_bytes
+            .copy_from_slice(&b[5 + Recipient::LEN..5 + Recipient::LEN + size_of::<u64>()]);
+        let connection_id = u64::from_be_bytes(connection_id_bytes);
+        let connection_id = if connection_id == 0 {
+            None
+        } else {
+            Some(connection_id)
+        };
+
+        let data_len_bytes =
+            &b[5 + Recipient::LEN + size_of::<u64>()..5 + Recipient::LEN + 2 * size_of::<u64>()];
+        let data_len = u64::from_be_bytes(data_len_bytes.try_into().unwrap());
+        let data = &b[5 + Recipient::LEN + 2 * size_of::<u64>()..];
+        if data.len() as u64 != data_len {
+            return Err(error::Error::new(
+                ErrorKind::MalformedRequest,
+                format!(
+                    "data len has inconsistent length. specified: {} got: {}",
+                    data_len,
+                    data.len()
+                ),
+            ));
+        }
+
+        Ok(ClientRequest::SendAnonymous {
+            reply_surbs,
+            recipient,
+            message: data.to_vec(),
+            connection_id,
+        })
+    }
+
+    // REPLY_REQUEST_TAG || SENDER_TAG || conn_id || message_len || message
+    fn serialize_reply(
+        message: Vec<u8>,
+        sender_tag: AnonymousSenderTag,
+        connection_id: Option<u64>,
+    ) -> Vec<u8> {
+        let message_len_bytes = (message.len() as u64).to_be_bytes();
+        let conn_id_bytes = connection_id.unwrap_or(0).to_be_bytes();
+
+        std::iter::once(ClientRequestTag::Reply as u8)
+            .chain(sender_tag.to_bytes().into_iter())
+            .chain(conn_id_bytes.into_iter())
+            .chain(message_len_bytes.into_iter())
            .chain(message.into_iter())
            .collect()
    }

-    // REPLY_REQUEST_TAG || surb_len || surb || message_len || message
+    // REPLY_REQUEST_TAG || SENDER_TAG || conn_id || message_len || message
    fn deserialize_reply(b: &[u8]) -> Result<Self, error::Error> {
-        // we need to have at the very least 2 * sizeof<u64> bytes (in case, for some peculiar reason
-        // message and reply surb were 0 len - the request would still be malformed, but would in theory
-        // be parse'able)
-        if b.len() < 1 + 2 * size_of::<u64>() {
+        if b.len() < 1 + SENDER_TAG_SIZE + 2 * size_of::<u64>() {
            return Err(error::Error::new(
                ErrorKind::TooShortRequest,
                "not enough data provided to recover 'reply'".to_string(),
@@ -162,42 +275,28 @@ impl ClientRequest {
        }

        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], REPLY_REQUEST_TAG);
+        debug_assert_eq!(b[0], ClientRequestTag::Reply as u8);

-        let reply_surb_len =
-            u64::from_be_bytes(b[1..1 + size_of::<u64>()].as_ref().try_into().unwrap());
+        // the unwrap here is fine as we're definitely using exactly SENDER_TAG_SIZE bytes
+        let sender_tag =
+            AnonymousSenderTag::from_bytes(b[1..1 + SENDER_TAG_SIZE].try_into().unwrap());

-        // make sure we won't go out of bounds here
-        if reply_surb_len > (b.len() - 1 + 2 * size_of::<u64>()) as u64 {
-            return Err(error::Error::new(
-                ErrorKind::MalformedRequest,
-                format!(
-                    "not enough data to recover reply surb with specified length {}",
-                    reply_surb_len
-                ),
-            ));
-        }
-
-        let surb_bound = 1 + size_of::<u64>() + reply_surb_len as usize;
-
-        let reply_surb_bytes = &b[1 + size_of::<u64>()..surb_bound];
-        let reply_surb = match ReplySurb::from_bytes(reply_surb_bytes) {
-            Ok(reply_surb) => reply_surb,
-            Err(err) => {
-                return Err(error::Error::new(
-                    ErrorKind::MalformedRequest,
-                    format!("malformed reply surb: {:?}", err),
-                ))
-            }
+        let mut connection_id_bytes = [0u8; size_of::<u64>()];
+        connection_id_bytes
+            .copy_from_slice(&b[1 + SENDER_TAG_SIZE..1 + SENDER_TAG_SIZE + size_of::<u64>()]);
+        let connection_id = u64::from_be_bytes(connection_id_bytes);
+        let connection_id = if connection_id == 0 {
+            None
+        } else {
+            Some(connection_id)
        };

        let message_len = u64::from_be_bytes(
-            b[surb_bound..surb_bound + size_of::<u64>()]
-                .as_ref()
+            b[1 + SENDER_TAG_SIZE + size_of::<u64>()..1 + SENDER_TAG_SIZE + 2 * size_of::<u64>()]
                .try_into()
                .unwrap(),
        );
-        let message = &b[surb_bound + size_of::<u64>()..];
+        let message = &b[1 + SENDER_TAG_SIZE + 2 * size_of::<u64>()..];
        if message.len() as u64 != message_len {
            return Err(error::Error::new(
                ErrorKind::MalformedRequest,
@@ -208,33 +307,32 @@ impl ClientRequest {
                ),
            ));
        }
-        // TODO: should this blow HERE, i.e. during deserialization that the data you're trying
-        // to send via reply is too long?

        Ok(ClientRequest::Reply {
-            reply_surb,
            message: message.to_vec(),
+            sender_tag,
+            connection_id,
        })
    }

    // SELF_ADDRESS_REQUEST_TAG
    fn serialize_self_address() -> Vec<u8> {
-        std::iter::once(SELF_ADDRESS_REQUEST_TAG).collect()
+        vec![ClientRequestTag::SelfAddress as u8]
    }

    // SELF_ADDRESS_REQUEST_TAG
-    fn deserialize_self_address(b: &[u8]) -> Self {
+    fn deserialize_self_address(b: &[u8]) -> Result<Self, error::Error> {
        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], SELF_ADDRESS_REQUEST_TAG);
+        debug_assert_eq!(b[0], ClientRequestTag::SelfAddress as u8);

-        ClientRequest::SelfAddress
+        Ok(ClientRequest::SelfAddress)
    }

    // CLOSED_CONNECTION_REQUEST_TAG
    fn serialize_closed_connection(connection_id: u64) -> Vec<u8> {
        let conn_id_bytes = connection_id.to_be_bytes();
-        std::iter::once(CLOSED_CONNECTION_REQUEST_TAG)
-            .chain(conn_id_bytes.iter().copied())
+        std::iter::once(ClientRequestTag::ClosedConnection as u8)
+            .chain(conn_id_bytes.into_iter())
            .collect()
    }

@@ -243,12 +341,12 @@ impl ClientRequest {
        if b.len() != 1 + size_of::<u64>() {
            return Err(error::Error::new(
                ErrorKind::MalformedRequest,
-                "the received closed connection has invalid length".to_string(),
+                "The received closed connection has invalid length",
            ));
        }

        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], CLOSED_CONNECTION_REQUEST_TAG);
+        debug_assert_eq!(b[0], ClientRequestTag::ClosedConnection as u8);

        let mut connection_id_bytes = [0u8; size_of::<u64>()];
        connection_id_bytes.copy_from_slice(&b[1..=size_of::<u64>()]);
@@ -260,8 +358,8 @@ impl ClientRequest {
    // GET_LANE_QUEUE_LENGHT_TAG
    fn serialize_get_lane_queue_lengths(connection_id: u64) -> Vec<u8> {
        let conn_id_bytes = connection_id.to_be_bytes();
-        std::iter::once(GET_LANE_QUEUE_LENGHT_TAG)
-            .chain(conn_id_bytes.iter().copied())
+        std::iter::once(ClientRequestTag::GetLaneQueueLength as u8)
+            .chain(conn_id_bytes.into_iter())
            .collect()
    }

@@ -270,12 +368,12 @@ impl ClientRequest {
        if b.len() != 1 + size_of::<u64>() {
            return Err(error::Error::new(
                ErrorKind::MalformedRequest,
-                "the received get lane queue length has invalid length".to_string(),
+                "The received get lane queue lengths has invalid length",
            ));
        }

        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], GET_LANE_QUEUE_LENGHT_TAG);
+        debug_assert_eq!(b[0], ClientRequestTag::GetLaneQueueLength as u8);

        let mut connection_id_bytes = [0u8; size_of::<u64>()];
        connection_id_bytes.copy_from_slice(&b[1..=size_of::<u64>()]);
@@ -289,14 +387,21 @@ impl ClientRequest {
            ClientRequest::Send {
                recipient,
                message,
-                with_reply_surb,
                connection_id,
-            } => Self::serialize_send(recipient, message, with_reply_surb, connection_id),
+            } => Self::serialize_send(recipient, message, connection_id),
+
+            ClientRequest::SendAnonymous {
+                recipient,
+                message,
+                reply_surbs,
+                connection_id,
+            } => Self::serialize_send_anonymous(recipient, message, reply_surbs, connection_id),

            ClientRequest::Reply {
                message,
-                reply_surb,
-            } => Self::serialize_reply(message, &reply_surb),
+                sender_tag,
+                connection_id,
+            } => Self::serialize_reply(message, sender_tag, connection_id),

            ClientRequest::SelfAddress => Self::serialize_self_address(),

@@ -316,28 +421,16 @@ impl ClientRequest {
            ));
        }

-        if b.len() < size_of::<u8>() {
-            return Err(error::Error::new(
-                ErrorKind::TooShortRequest,
-                format!(
-                    "not enough data provided to recover request tag. Provided only {} bytes",
-                    b.len()
-                ),
-            ));
-        }
-        let request_tag = b[0];
+        let request_tag = ClientRequestTag::try_from(b[0])?;

        // determine what kind of request that is and try to deserialize it
        match request_tag {
-            SEND_REQUEST_TAG => Self::deserialize_send(b),
-            REPLY_REQUEST_TAG => Self::deserialize_reply(b),
-            SELF_ADDRESS_REQUEST_TAG => Ok(Self::deserialize_self_address(b)),
-            CLOSED_CONNECTION_REQUEST_TAG => Self::deserialize_closed_connection(b),
-            GET_LANE_QUEUE_LENGHT_TAG => Self::deserialize_get_lane_queue_length(b),
-            n => Err(error::Error::new(
-                ErrorKind::UnknownRequest,
-                format!("type {n}"),
-            )),
+            ClientRequestTag::Send => Self::deserialize_send(b),
+            ClientRequestTag::SendAnonymous => Self::deserialize_send_anonymous(b),
+            ClientRequestTag::Reply => Self::deserialize_reply(b),
+            ClientRequestTag::SelfAddress => Self::deserialize_self_address(b),
+            ClientRequestTag::ClosedConnection => Self::deserialize_closed_connection(b),
+            ClientRequestTag::GetLaneQueueLength => Self::deserialize_get_lane_queue_length(b),
        }
    }

@@ -365,50 +458,52 @@ mod tests {
        let recipient = Recipient::try_from_base58_string("CytBseW6yFXUMzz4SGAKdNLGR7q3sJLLYxyBGvutNEQV.4QXYyEVc5fUDjmmi8PrHN9tdUFV4PCvSJE1278cHyvoe@4sBbL1ngf1vtNqykydQKTFh26sQCw888GpUqvPvyNB4f").unwrap();
        let recipient_string = recipient.to_string();

-        let send_request_no_surb = ClientRequest::Send {
+        let send_request = ClientRequest::Send {
            recipient,
            message: b"foomp".to_vec(),
-            with_reply_surb: false,
            connection_id: Some(42),
        };

-        let bytes = send_request_no_surb.serialize();
+        let bytes = send_request.serialize();
        let recovered = ClientRequest::deserialize(&bytes).unwrap();
        match recovered {
            ClientRequest::Send {
                recipient,
                message,
-                with_reply_surb,
                connection_id,
            } => {
                assert_eq!(recipient.to_string(), recipient_string);
                assert_eq!(message, b"foomp".to_vec());
-                assert!(!with_reply_surb);
                assert_eq!(connection_id, Some(42))
            }
            _ => unreachable!(),
        }
+    }

-        let send_request_surb = ClientRequest::Send {
-            recipient,
+    #[test]
+    fn send_anonymous_request_serialization_works() {
+        let original_recipient = Recipient::try_from_base58_string("CytBseW6yFXUMzz4SGAKdNLGR7q3sJLLYxyBGvutNEQV.4QXYyEVc5fUDjmmi8PrHN9tdUFV4PCvSJE1278cHyvoe@4sBbL1ngf1vtNqykydQKTFh26sQCw888GpUqvPvyNB4f").unwrap();
+
+        let send_anonymous_request = ClientRequest::SendAnonymous {
+            recipient: original_recipient,
            message: b"foomp".to_vec(),
-            with_reply_surb: true,
-            connection_id: None,
+            reply_surbs: 666,
+            connection_id: Some(42),
        };

-        let bytes = send_request_surb.serialize();
+        let bytes = send_anonymous_request.serialize();
        let recovered = ClientRequest::deserialize(&bytes).unwrap();
        match recovered {
-            ClientRequest::Send {
+            ClientRequest::SendAnonymous {
                recipient,
                message,
-                with_reply_surb,
+                reply_surbs,
                connection_id,
            } => {
-                assert_eq!(recipient.to_string(), recipient_string);
+                assert_eq!(recipient, original_recipient);
                assert_eq!(message, b"foomp".to_vec());
-                assert!(with_reply_surb);
-                assert_eq!(connection_id, None)
+                assert_eq!(connection_id, Some(42));
+                assert_eq!(reply_surbs, 666)
            }
            _ => unreachable!(),
        }
@@ -416,22 +511,23 @@ mod tests {

    #[test]
    fn reply_request_serialization_works() {
-        let reply_surb_string = "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";
-        let reply_surb = ReplySurb::from_base58_string(reply_surb_string).unwrap();
        let reply_request = ClientRequest::Reply {
+            sender_tag: [8u8; SENDER_TAG_SIZE].into(),
            message: b"foomp".to_vec(),
-            reply_surb,
+            connection_id: Some(42),
        };

        let bytes = reply_request.serialize();
        let recovered = ClientRequest::deserialize(&bytes).unwrap();
        match recovered {
            ClientRequest::Reply {
-                reply_surb,
+                sender_tag,
                message,
+                connection_id,
            } => {
-                assert_eq!(reply_surb.to_base58_string(), reply_surb_string);
+                assert_eq!(sender_tag, [8u8; SENDER_TAG_SIZE].into());
                assert_eq!(message, b"foomp".to_vec());
+                assert_eq!(connection_id, Some(42));
            }
            _ => unreachable!(),
        }
@@ -458,4 +554,15 @@ mod tests {
            _ => unreachable!(),
        }
    }
+
+    #[test]
+    fn get_lane_queue_length_request_serialization_works() {
+        let close_connection_request = ClientRequest::GetLaneQueueLength(42);
+        let bytes = close_connection_request.serialize();
+        let recovered = ClientRequest::deserialize(&bytes).unwrap();
+        match recovered {
+            ClientRequest::GetLaneQueueLength(id) => assert_eq!(id, 42),
+            _ => unreachable!(),
+        }
+    }
 }
@@ -1,36 +1,54 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 // all variable size data is always prefixed with u64 length
 // tags are u8

-#![allow(unknown_lints)] // due to using `clippy::branches_sharing_code` which does not exist on `stable` just yet
-
 use crate::error::{self, ErrorKind};
 use crate::text::ServerResponseText;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::{AnonymousSenderTag, SENDER_TAG_SIZE};
 use nymsphinx::receiver::ReconstructedMessage;
 use std::convert::TryInto;
 use std::mem::size_of;

-/// Value tag representing [`Error`] variant of the [`ServerResponse`]
-pub const ERROR_RESPONSE_TAG: u8 = 0x00;
+#[repr(u8)]
+enum ServerResponseTag {
+    /// Value tag representing [`Error`] variant of the [`ServerResponse`]
+    Error = 0x00,

-/// Value tag representing [`Received`] variant of the [`ServerResponse`]
-pub const RECEIVED_RESPONSE_TAG: u8 = 0x01;
+    /// Value tag representing [`Received`] variant of the [`ServerResponse`]
+    Received = 0x01,

-/// Value tag representing [`SelfAddress`] variant of the [`ServerResponse`]
-pub const SELF_ADDRESS_RESPONSE_TAG: u8 = 0x02;
+    /// Value tag representing [`SelfAddress`] variant of the [`ServerResponse`]
+    SelfAddress = 0x02,

-/// Value tag representing [`LaneQueueLength`] variant of the [`ServerResponse`]
-pub const LANE_QUEUE_LENGTH_RESPONSE_TAG: u8 = 0x03;
+    /// Value tag representing [`LaneQueueLength`] variant of the [`ServerResponse`]
+    LaneQueueLength = 0x03,
+}
+
+impl TryFrom<u8> for ServerResponseTag {
+    type Error = error::Error;
+
+    fn try_from(value: u8) -> Result<Self, error::Error> {
+        match value {
+            _ if value == (Self::Error as u8) => Ok(Self::Error),
+            _ if value == (Self::Received as u8) => Ok(Self::Received),
+            _ if value == (Self::SelfAddress as u8) => Ok(Self::SelfAddress),
+            _ if value == (Self::LaneQueueLength as u8) => Ok(Self::LaneQueueLength),
+            n => Err(error::Error::new(
+                ErrorKind::UnknownResponse,
+                format!("{n} does not correspond to any valid response tag"),
+            )),
+        }
+    }
+}

 #[derive(Debug)]
 pub enum ServerResponse {
    Received(ReconstructedMessage),
-    SelfAddress(Recipient),
-    LaneQueueLength(u64, usize),
+    SelfAddress(Box<Recipient>),
+    LaneQueueLength { lane: u64, queue_length: usize },
    Error(error::Error),
 }

@@ -42,24 +60,19 @@ impl ServerResponse {
        })
    }

-    // RECEIVED_RESPONSE_TAG || with_reply || (surb_len || surb) || msg_len || msg
+    // RECEIVED_RESPONSE_TAG || 1 | 0 indicating sender_tag || Option<sender_tag> || msg_len || msg
    fn serialize_received(reconstructed_message: ReconstructedMessage) -> Vec<u8> {
        let message_len_bytes = (reconstructed_message.message.len() as u64).to_be_bytes();
-        if let Some(reply_surb) = reconstructed_message.reply_surb {
-            let reply_surb_bytes = reply_surb.to_bytes();
-            let surb_len_bytes = (reply_surb_bytes.len() as u64).to_be_bytes();

-            // with_reply || surb_len || surb || msg_len || msg
-            std::iter::once(RECEIVED_RESPONSE_TAG)
+        if let Some(sender_tag) = reconstructed_message.sender_tag {
+            std::iter::once(ServerResponseTag::Received as u8)
                .chain(std::iter::once(true as u8))
-                .chain(surb_len_bytes.iter().cloned())
-                .chain(reply_surb_bytes.iter().cloned())
+                .chain(sender_tag.to_bytes().into_iter())
                .chain(message_len_bytes.iter().cloned())
                .chain(reconstructed_message.message.into_iter())
                .collect()
        } else {
-            // without_reply || msg_len || msg
-            std::iter::once(RECEIVED_RESPONSE_TAG)
+            std::iter::once(ServerResponseTag::Received as u8)
                .chain(std::iter::once(false as u8))
                .chain(message_len_bytes.iter().cloned())
                .chain(reconstructed_message.message.into_iter())
@@ -67,10 +80,9 @@ impl ServerResponse {
        }
    }

-    // RECEIVED_RESPONSE_TAG || with_reply || (surb_len || surb) || msg_len || msg
+    // RECEIVED_RESPONSE_TAG || 1 | 0 indicating sender_tag || Option<sender_tag> || msg_len || msg
    fn deserialize_received(b: &[u8]) -> Result<Self, error::Error> {
        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], RECEIVED_RESPONSE_TAG);

        // we must be able to read at the very least if it has a reply_surb and length of some field
        if b.len() < 2 + size_of::<u64>() {
@@ -79,101 +91,70 @@ impl ServerResponse {
                "not enough data provided to recover 'received'".to_string(),
            ));
        }
+        debug_assert_eq!(b[0], ServerResponseTag::Received as u8);

-        let with_reply_surb = match b[1] {
+        let has_sender_tag = match b[1] {
            0 => false,
            1 => true,
            n => {
                return Err(error::Error::new(
                    ErrorKind::MalformedResponse,
-                    format!("invalid reply flag {}", n),
+                    format!("invalid sender tag flag {n}"),
                ))
            }
        };

-        // this is a false positive as even though the code is the same, it refers to different things
-        #[allow(clippy::branches_sharing_code)]
-        if with_reply_surb {
-            let reply_surb_len =
-                u64::from_be_bytes(b[2..2 + size_of::<u64>()].as_ref().try_into().unwrap());
-
-            // make sure we won't go out of bounds here
-            if reply_surb_len > (b.len() - 2 + 2 * size_of::<u64>()) as u64 {
+        let mut i = 2;
+        let sender_tag = if has_sender_tag {
+            if b[2..].len() < SENDER_TAG_SIZE {
                return Err(error::Error::new(
-                    ErrorKind::MalformedResponse,
-                    "not enough bytes to read reply_surb bytes!".to_string(),
+                    ErrorKind::TooShortResponse,
+                    "not enough data provided to recover 'received'".to_string(),
                ));
            }
-
-            let surb_bound = 2 + size_of::<u64>() + reply_surb_len as usize;
-
-            let reply_surb_bytes = &b[2 + size_of::<u64>()..surb_bound];
-            let reply_surb = match ReplySurb::from_bytes(reply_surb_bytes) {
-                Ok(reply_surb) => reply_surb,
-                Err(err) => {
-                    return Err(error::Error::new(
-                        ErrorKind::MalformedResponse,
-                        format!("malformed reply SURB: {:?}", err),
-                    ))
-                }
-            };
-
-            let message_len = u64::from_be_bytes(
-                b[surb_bound..surb_bound + size_of::<u64>()]
-                    .as_ref()
-                    .try_into()
-                    .unwrap(),
-            );
-            let message = &b[surb_bound + size_of::<u64>()..];
-            if message.len() as u64 != message_len {
-                return Err(error::Error::new(
-                    ErrorKind::MalformedResponse,
-                    format!(
-                        "message len has inconsistent length. specified: {} got: {}",
-                        message_len,
-                        message.len()
-                    ),
-                ));
-            }
-
-            Ok(ServerResponse::Received(ReconstructedMessage {
-                message: message.to_vec(),
-                reply_surb: Some(reply_surb),
-            }))
+            i += SENDER_TAG_SIZE;
+            Some(AnonymousSenderTag::from_bytes(
+                b[2..2 + SENDER_TAG_SIZE].try_into().unwrap(),
+            ))
        } else {
-            let message_len =
-                u64::from_be_bytes(b[2..2 + size_of::<u64>()].as_ref().try_into().unwrap());
-            let message = &b[2 + size_of::<u64>()..];
-            if message.len() as u64 != message_len {
-                return Err(error::Error::new(
-                    ErrorKind::MalformedResponse,
-                    format!(
-                        "message len has inconsistent length. specified: {} got: {}",
-                        message_len,
-                        message.len()
-                    ),
-                ));
-            }
+            None
+        };

-            Ok(ServerResponse::Received(ReconstructedMessage {
-                message: message.to_vec(),
-                reply_surb: None,
-            }))
+        if b[i..].len() < size_of::<u64>() {
+            return Err(error::Error::new(
+                ErrorKind::TooShortResponse,
+                "not enough data provided to recover 'received'".to_string(),
+            ));
        }
+
+        let message_len = u64::from_be_bytes(b[i..i + size_of::<u64>()].try_into().unwrap());
+        let message = &b[i + size_of::<u64>()..];
+        if message.len() as u64 != message_len {
+            return Err(error::Error::new(
+                ErrorKind::MalformedResponse,
+                format!(
+                    "message len has inconsistent length. specified: {} got: {}",
+                    message_len,
+                    message.len()
+                ),
+            ));
+        }
+
+        Ok(ServerResponse::Received(ReconstructedMessage {
+            message: message.to_vec(),
+            sender_tag,
+        }))
    }

    // SELF_ADDRESS_RESPONSE_TAG || self_address
    fn serialize_self_address(address: Recipient) -> Vec<u8> {
-        std::iter::once(SELF_ADDRESS_RESPONSE_TAG)
-            .chain(address.to_bytes().iter().cloned())
+        std::iter::once(ServerResponseTag::SelfAddress as u8)
+            .chain(address.to_bytes().into_iter())
            .collect()
    }

    // SELF_ADDRESS_RESPONSE_TAG || self_address
    fn deserialize_self_address(b: &[u8]) -> Result<Self, error::Error> {
-        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], SELF_ADDRESS_RESPONSE_TAG);
-
        if b.len() != 1 + Recipient::LEN {
            return Err(error::Error::new(
                ErrorKind::TooShortResponse,
@@ -181,6 +162,9 @@ impl ServerResponse {
            ));
        }

+        // this MUST match because it was called by 'deserialize'
+        debug_assert_eq!(b[0], ServerResponseTag::SelfAddress as u8);
+
        let mut recipient_bytes = [0u8; Recipient::LEN];
        recipient_bytes.copy_from_slice(&b[1..1 + Recipient::LEN]);

@@ -194,12 +178,12 @@ impl ServerResponse {
            }
        };

-        Ok(ServerResponse::SelfAddress(recipient))
+        Ok(ServerResponse::SelfAddress(Box::new(recipient)))
    }

    // LANE_QUEUE_LENGTH_RESPONSE_TAG || lane || queue_length
    fn serialize_lane_queue_length(lane: u64, queue_length: usize) -> Vec<u8> {
-        std::iter::once(LANE_QUEUE_LENGTH_RESPONSE_TAG)
+        std::iter::once(ServerResponseTag::LaneQueueLength as u8)
            .chain(lane.to_be_bytes().iter().cloned())
            .chain(queue_length.to_be_bytes().iter().cloned())
            .collect()
@@ -208,7 +192,7 @@ impl ServerResponse {
    // LANE_QUEUE_LENGTH_RESPONSE_TAG || lane || queue_length
    fn deserialize_lane_queue_length(b: &[u8]) -> Result<Self, error::Error> {
        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], LANE_QUEUE_LENGTH_RESPONSE_TAG);
+        debug_assert_eq!(b[0], ServerResponseTag::LaneQueueLength as u8);

        let mut lane_bytes = [0u8; size_of::<u64>()];
        lane_bytes.copy_from_slice(&b[1..=size_of::<u64>()]);
@@ -219,15 +203,15 @@ impl ServerResponse {
            .copy_from_slice(&b[1 + size_of::<u64>()..1 + size_of::<u64>() + size_of::<usize>()]);
        let queue_length = usize::from_be_bytes(queue_length_bytes);

-        Ok(ServerResponse::LaneQueueLength(lane, queue_length))
+        Ok(ServerResponse::LaneQueueLength { lane, queue_length })
    }

    // ERROR_RESPONSE_TAG || err_code || msg_len || msg
    fn serialize_error(error: error::Error) -> Vec<u8> {
        let message_len_bytes = (error.message.len() as u64).to_be_bytes();
-        std::iter::once(ERROR_RESPONSE_TAG)
+        std::iter::once(ServerResponseTag::Error as u8)
            .chain(std::iter::once(error.kind as u8))
-            .chain(message_len_bytes.iter().cloned())
+            .chain(message_len_bytes.into_iter())
            .chain(error.message.into_bytes().into_iter())
            .collect()
    }
@@ -235,7 +219,7 @@ impl ServerResponse {
    // ERROR_RESPONSE_TAG || err_code || msg_len || msg
    fn deserialize_error(b: &[u8]) -> Result<Self, error::Error> {
        // this MUST match because it was called by 'deserialize'
-        debug_assert_eq!(b[0], ERROR_RESPONSE_TAG);
+        debug_assert_eq!(b[0], ServerResponseTag::Error as u8);

        if b.len() < size_of::<u8>() + size_of::<u64>() {
            return Err(error::Error::new(
@@ -244,26 +228,7 @@ impl ServerResponse {
            ));
        }

-        let error_kind = match b[1] {
-            _ if b[1] == (ErrorKind::EmptyRequest as u8) => ErrorKind::EmptyRequest,
-            _ if b[1] == (ErrorKind::TooShortRequest as u8) => ErrorKind::TooShortRequest,
-            _ if b[1] == (ErrorKind::UnknownRequest as u8) => ErrorKind::UnknownRequest,
-            _ if b[1] == (ErrorKind::MalformedRequest as u8) => ErrorKind::MalformedRequest,
-
-            _ if b[1] == (ErrorKind::EmptyResponse as u8) => ErrorKind::EmptyResponse,
-            _ if b[1] == (ErrorKind::TooShortResponse as u8) => ErrorKind::TooShortResponse,
-            _ if b[1] == (ErrorKind::UnknownResponse as u8) => ErrorKind::UnknownResponse,
-            _ if b[1] == (ErrorKind::MalformedResponse as u8) => ErrorKind::MalformedResponse,
-
-            _ if b[1] == (ErrorKind::Other as u8) => ErrorKind::Other,
-
-            n => {
-                return Err(error::Error::new(
-                    ErrorKind::MalformedResponse,
-                    format!("invalid error code {}", n),
-                ))
-            }
-        };
+        let error_kind = ErrorKind::try_from(b[1])?;

        let message_len =
            u64::from_be_bytes(b[2..2 + size_of::<u64>()].as_ref().try_into().unwrap());
@@ -300,8 +265,8 @@ impl ServerResponse {
            ServerResponse::Received(reconstructed_message) => {
                Self::serialize_received(reconstructed_message)
            }
-            ServerResponse::SelfAddress(address) => Self::serialize_self_address(address),
-            ServerResponse::LaneQueueLength(lane, queue_length) => {
+            ServerResponse::SelfAddress(address) => Self::serialize_self_address(*address),
+            ServerResponse::LaneQueueLength { lane, queue_length } => {
                Self::serialize_lane_queue_length(lane, queue_length)
            }
            ServerResponse::Error(err) => Self::serialize_error(err),
@@ -328,18 +293,14 @@ impl ServerResponse {
            ));
        }

-        let response_tag = b[0];
+        let response_tag = ServerResponseTag::try_from(b[0])?;

        // determine what kind of response that is and try to deserialize it
        match response_tag {
-            RECEIVED_RESPONSE_TAG => Self::deserialize_received(b),
-            SELF_ADDRESS_RESPONSE_TAG => Self::deserialize_self_address(b),
-            LANE_QUEUE_LENGTH_RESPONSE_TAG => Self::deserialize_lane_queue_length(b),
-            ERROR_RESPONSE_TAG => Self::deserialize_error(b),
-            n => Err(error::Error::new(
-                ErrorKind::UnknownResponse,
-                format!("type {}", n),
-            )),
+            ServerResponseTag::Received => Self::deserialize_received(b),
+            ServerResponseTag::SelfAddress => Self::deserialize_self_address(b),
+            ServerResponseTag::LaneQueueLength => Self::deserialize_lane_queue_length(b),
+            ServerResponseTag::Error => Self::deserialize_error(b),
        }
    }

@@ -361,35 +322,33 @@ mod tests {

    #[test]
    fn received_response_serialization_works() {
-        let reply_surb_string = "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";
-
-        let received_with_surb = ServerResponse::Received(ReconstructedMessage {
+        let received_with_sender_tag = ServerResponse::Received(ReconstructedMessage {
            message: b"foomp".to_vec(),
-            reply_surb: Some(ReplySurb::from_base58_string(reply_surb_string).unwrap()),
+            sender_tag: Some([42u8; SENDER_TAG_SIZE].into()),
        });
-        let bytes = received_with_surb.serialize();
+        let bytes = received_with_sender_tag.serialize();
        let recovered = ServerResponse::deserialize(&bytes).unwrap();
        match recovered {
            ServerResponse::Received(reconstructed) => {
                assert_eq!(reconstructed.message, b"foomp".to_vec());
                assert_eq!(
-                    reconstructed.reply_surb.unwrap().to_base58_string(),
-                    reply_surb_string
+                    reconstructed.sender_tag,
+                    Some([42u8; SENDER_TAG_SIZE].into())
                )
            }
            _ => unreachable!(),
        }

-        let received_without_surb = ServerResponse::Received(ReconstructedMessage {
+        let received_without_sender_tag = ServerResponse::Received(ReconstructedMessage {
            message: b"foomp".to_vec(),
-            reply_surb: None,
+            sender_tag: None,
        });
-        let bytes = received_without_surb.serialize();
+        let bytes = received_without_sender_tag.serialize();
        let recovered = ServerResponse::deserialize(&bytes).unwrap();
        match recovered {
            ServerResponse::Received(reconstructed) => {
                assert_eq!(reconstructed.message, b"foomp".to_vec());
-                assert!(reconstructed.reply_surb.is_none())
+                assert!(reconstructed.sender_tag.is_none())
            }
            _ => unreachable!(),
        }
@@ -400,7 +359,7 @@ mod tests {
        let recipient = Recipient::try_from_base58_string("CytBseW6yFXUMzz4SGAKdNLGR7q3sJLLYxyBGvutNEQV.4QXYyEVc5fUDjmmi8PrHN9tdUFV4PCvSJE1278cHyvoe@4sBbL1ngf1vtNqykydQKTFh26sQCw888GpUqvPvyNB4f").unwrap();
        let recipient_string = recipient.to_string();

-        let self_address_response = ServerResponse::SelfAddress(recipient);
+        let self_address_response = ServerResponse::SelfAddress(Box::new(recipient));
        let bytes = self_address_response.serialize();
        let recovered = ServerResponse::deserialize(&bytes).unwrap();
        match recovered {
@@ -413,11 +372,14 @@ mod tests {

    #[test]
    fn lane_queue_length_response_serialization_works() {
-        let lane_queue_length_response = ServerResponse::LaneQueueLength(13, 42);
+        let lane_queue_length_response = ServerResponse::LaneQueueLength {
+            lane: 13,
+            queue_length: 42,
+        };
        let bytes = lane_queue_length_response.serialize();
        let recovered = ServerResponse::deserialize(&bytes).unwrap();
        match recovered {
-            ServerResponse::LaneQueueLength(lane, queue_length) => {
+            ServerResponse::LaneQueueLength { lane, queue_length } => {
                assert_eq!(lane, 13);
                assert_eq!(queue_length, 42)
            }
@@ -1,11 +1,11 @@
-// Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
+// Copyright 2021-2022 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

 use crate::error::ErrorKind;
 use crate::requests::ClientRequest;
 use crate::responses::ServerResponse;
 use nymsphinx::addressing::clients::Recipient;
-use nymsphinx::anonymous_replies::ReplySurb;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use serde::{Deserialize, Serialize};
 use std::convert::{TryFrom, TryInto};

@@ -19,15 +19,22 @@ pub(super) enum ClientRequestText {
    Send {
        message: String,
        recipient: String,
-        with_reply_surb: bool,
+        connection_id: Option<u64>,
+    },
+    #[serde(rename_all = "camelCase")]
+    SendAnonymous {
+        recipient: String,
+        message: String,
+        reply_surbs: u32,
+        connection_id: Option<u64>,
+    },
+    #[serde(rename_all = "camelCase")]
+    Reply {
+        sender_tag: String,
+        message: String,
        connection_id: Option<u64>,
    },
    SelfAddress,
-    #[serde(rename_all = "camelCase")]
-    Reply {
-        message: String,
-        reply_surb: String,
-    },
 }

 impl TryFrom<String> for ClientRequestText {
@@ -46,7 +53,6 @@ impl TryInto<ClientRequest> for ClientRequestText {
            ClientRequestText::Send {
                message,
                recipient,
-                with_reply_surb,
                connection_id,
            } => {
                let message_bytes = message.into_bytes();
@@ -57,23 +63,42 @@ impl TryInto<ClientRequest> for ClientRequestText {
                Ok(ClientRequest::Send {
                    message: message_bytes,
                    recipient,
-                    with_reply_surb,
+                    connection_id,
+                })
+            }
+            ClientRequestText::SendAnonymous {
+                recipient,
+                message,
+                reply_surbs,
+                connection_id,
+            } => {
+                let message_bytes = message.into_bytes();
+                let recipient = Recipient::try_from_base58_string(recipient).map_err(|err| {
+                    Self::Error::new(ErrorKind::MalformedRequest, err.to_string())
+                })?;
+                Ok(ClientRequest::SendAnonymous {
+                    recipient,
+                    message: message_bytes,
+                    reply_surbs,
                    connection_id,
                })
            }
            ClientRequestText::SelfAddress => Ok(ClientRequest::SelfAddress),
            ClientRequestText::Reply {
+                sender_tag,
                message,
-                reply_surb,
+                connection_id,
            } => {
                let message_bytes = message.into_bytes();
-                let reply_surb = ReplySurb::from_base58_string(reply_surb).map_err(|err| {
-                    Self::Error::new(ErrorKind::MalformedRequest, err.to_string())
-                })?;
+                let sender_tag =
+                    AnonymousSenderTag::try_from_base58_string(sender_tag).map_err(|err| {
+                        Self::Error::new(ErrorKind::MalformedRequest, err.to_string())
+                    })?;

                Ok(ClientRequest::Reply {
+                    sender_tag,
                    message: message_bytes,
-                    reply_surb,
+                    connection_id,
                })
            }
        }
@@ -89,7 +114,7 @@ pub(super) enum ServerResponseText {
    #[serde(rename_all = "camelCase")]
    Received {
        message: String,
-        reply_surb: Option<String>,
+        sender_tag: Option<String>,
    },
    SelfAddress {
        address: String,
@@ -131,15 +156,13 @@ impl From<ServerResponse> for ServerResponseText {
                    // TODO: ask DH what is more appropriate, lossy utf8 conversion or returning error and then
                    // pure binary later
                    message: String::from_utf8_lossy(&reconstructed.message).into_owned(),
-                    reply_surb: reconstructed
-                        .reply_surb
-                        .map(|reply_surb| reply_surb.to_base58_string()),
+                    sender_tag: reconstructed.sender_tag.map(|tag| tag.to_base58_string()),
                }
            }
            ServerResponse::SelfAddress(recipient) => ServerResponseText::SelfAddress {
                address: recipient.to_string(),
            },
-            ServerResponse::LaneQueueLength(lane, queue_length) => {
+            ServerResponse::LaneQueueLength { lane, queue_length } => {
                ServerResponseText::LaneQueueLength { lane, queue_length }
            }
            ServerResponse::Error(err) => ServerResponseText::Error {
@@ -1,6 +1,6 @@
 [package]
 name = "nym-socks5-client"
-version = "1.1.1"
+version = "1.1.4"
 authors = ["Dave Hrycyszyn <futurechimp@users.noreply.github.com>"]
 description = "A SOCKS5 localhost proxy that converts incoming messages to Sphinx and sends them to a Nym address"
 edition = "2021"
@@ -19,13 +19,14 @@ pin-project = "1.0"
 pretty_env_logger = "0.4"
 rand = { version = "0.7.3", features = ["wasm-bindgen"] }
 serde = { version = "1.0", features = ["derive"] } # for config serialization/deserialization
-snafu = "0.6"
+serde_json = "1.0.89"
+tap = "1.0.1"
 thiserror = "1.0.34"
 tokio = { version = "1.21.2", features = ["rt-multi-thread", "net", "signal"] }
 url = "2.2"

 # internal
-client-core = { path = "../client-core" }
+client-core = { path = "../client-core", features = ["fs-surb-storage"] }
 client-connections = { path = "../../common/client-connections" }
 coconut-interface = { path = "../../common/coconut-interface", optional = true }
 config = { path = "../../common/config" }
@@ -46,7 +47,6 @@ task = { path = "../../common/task" }
 topology = { path = "../../common/topology" }
 validator-client = { path = "../../common/client-libs/validator-client", features = ["nymd-client"] }
 version-checker = { path = "../../common/version-checker" }
-tap = "1.0.1"

 [features]
 coconut = ["coconut-interface", "credentials", "gateway-requests/coconut", "gateway-client/coconut", "credentials/coconut", "client-core/coconut"]
@@ -2,8 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0

 use crate::client::config::template::config_template;
-use client_core::config::Config as BaseConfig;
 pub use client_core::config::MISSING_VALUE;
+use client_core::config::{ClientCoreConfigTrait, Config as BaseConfig, DebugConfig};
 use config::defaults::DEFAULT_SOCKS5_LISTENING_PORT;
 use config::NymConfig;
 use nymsphinx::addressing::clients::Recipient;
@@ -12,6 +12,9 @@ use std::path::PathBuf;

 mod template;

+const DEFAULT_CONNECTION_START_SURBS: u32 = 20;
+const DEFAULT_PER_REQUEST_SURBS: u32 = 3;
+
 #[derive(Debug, Default, Deserialize, PartialEq, Serialize)]
 #[serde(deny_unknown_fields)]
 pub struct Config {
@@ -19,6 +22,9 @@ pub struct Config {
    base: BaseConfig<Config>,

    socks5: Socks5,
+
+    #[serde(default)]
+    socks5_debug: Socks5Debug,
 }

 impl NymConfig for Config {
@@ -52,25 +58,51 @@ impl NymConfig for Config {
    }
 }

+impl ClientCoreConfigTrait for Config {
+    fn get_gateway_endpoint(&self) -> &client_core::config::GatewayEndpointConfig {
+        self.base.get_gateway_endpoint()
+    }
+}
+
 impl Config {
    pub fn new<S: Into<String>>(id: S, provider_mix_address: S) -> Self {
        Config {
            base: BaseConfig::new(id),
            socks5: Socks5::new(provider_mix_address),
+            socks5_debug: Socks5Debug::default(),
        }
    }

+    #[must_use]
    pub fn with_port(mut self, port: u16) -> Self {
        self.socks5.listening_port = port;
        self
    }

+    #[must_use]
    pub fn with_provider_mix_address(mut self, address: String) -> Self {
        self.socks5.provider_mix_address = address;
        self
    }

+    pub fn with_anonymous_replies(mut self, anonymous_replies: bool) -> Self {
+        self.socks5.send_anonymously = anonymous_replies;
+        self
+    }
+
    // getters
+    pub fn get_base(&self) -> &BaseConfig<Self> {
+        &self.base
+    }
+
+    pub fn get_base_mut(&mut self) -> &mut BaseConfig<Self> {
+        &mut self.base
+    }
+
+    pub fn get_debug_settings(&self) -> &DebugConfig {
+        self.get_base().get_debug_config()
+    }
+
    pub fn get_config_file_save_location(&self) -> PathBuf {
        self.config_directory().join(Self::config_file_name())
    }
@@ -80,17 +112,21 @@ impl Config {
            .expect("malformed provider address")
    }

-    pub fn get_base(&self) -> &BaseConfig<Self> {
-        &self.base
-    }
-
-    pub fn get_base_mut(&mut self) -> &mut BaseConfig<Self> {
-        &mut self.base
+    pub fn get_send_anonymously(&self) -> bool {
+        self.socks5.send_anonymously
    }

    pub fn get_listening_port(&self) -> u16 {
        self.socks5.listening_port
    }
+
+    pub fn get_connection_start_surbs(&self) -> u32 {
+        self.socks5_debug.connection_start_surbs
+    }
+
+    pub fn get_per_request_surbs(&self) -> u32 {
+        self.socks5_debug.per_request_surbs
+    }
 }

 #[derive(Debug, Deserialize, PartialEq, Eq, Serialize)]
@@ -101,6 +137,14 @@ pub struct Socks5 {

    /// The mix address of the provider to which all requests are going to be sent.
    provider_mix_address: String,
+
+    /// Specifies whether this client is going to use an anonymous sender tag for communication with the service provider.
+    /// While this is going to hide its actual address information, it will make the actual communication
+    /// slower and consume nearly double the bandwidth as it will require sending reply SURBs.
+    ///
+    /// Note that some service providers might not support this.
+    #[serde(default)]
+    send_anonymously: bool,
 }

 impl Socks5 {
@@ -108,6 +152,7 @@ impl Socks5 {
        Socks5 {
            listening_port: DEFAULT_SOCKS5_LISTENING_PORT,
            provider_mix_address: provider_mix_address.into(),
+            send_anonymously: false,
        }
    }
 }
@@ -117,6 +162,26 @@ impl Default for Socks5 {
        Socks5 {
            listening_port: DEFAULT_SOCKS5_LISTENING_PORT,
            provider_mix_address: "".into(),
+            send_anonymously: false,
+        }
+    }
+}
+
+#[derive(Debug, Deserialize, PartialEq, Eq, Serialize)]
+#[serde(deny_unknown_fields)]
+pub struct Socks5Debug {
+    /// Number of reply SURBs attached to each `Request::Connect` message.
+    connection_start_surbs: u32,
+
+    /// Number of reply SURBs attached to each `Request::Send` message.
+    per_request_surbs: u32,
+}
+
+impl Default for Socks5Debug {
+    fn default() -> Self {
+        Socks5Debug {
+            connection_start_surbs: DEFAULT_CONNECTION_START_SURBS,
+            per_request_surbs: DEFAULT_PER_REQUEST_SURBS,
        }
    }
 }
@@ -49,13 +49,12 @@ private_encryption_key_file = '{{ client.private_encryption_key_file }}'
 # Path to file containing public encryption key.
 public_encryption_key_file = '{{ client.public_encryption_key_file }}'

-# Full path to file containing reply encryption keys of all reply-SURBs we have ever
-# sent but not received back.
-reply_encryption_key_store_path = '{{ client.reply_encryption_key_store_path }}'
-
 # Path to the database containing bandwidth credentials
 database_path = '{{ client.database_path }}'

+# Path to the persistent store for received reply surbs, unused encryption keys and used sender tags.
+reply_surb_database_path = '{{ client.reply_surb_database_path }}'
+
 ##### additional client config options #####

 # A gateway specific, optional, base58 stringified shared key used for
@@ -92,6 +91,12 @@ provider_mix_address = '{{ socks5.provider_mix_address }}'
 # The port on which the client will be listening for incoming requests
 listening_port = {{ socks5.listening_port }}

+# Specifies whether this client is going to use an anonymous sender tag for communication with the service provider.
+# While this is going to hide its actual address information, it will make the actual communication
+# slower and consume nearly double the bandwidth as it will require sending reply SURBs.
+#
+# Note that some service providers might not support this.
+send_anonymously = {{ socks5.send_anonymously }}

 ##### logging configuration options #####

@@ -104,6 +109,9 @@ listening_port = {{ socks5.listening_port }}
 # The following options should not be modified unless you know EXACTLY what you are doing
 # as if set incorrectly, they may impact your anonymity.

+# [socks5_debug]
+
+
 [debug]

 average_packet_delay = '{{ debug.average_packet_delay }}'
@@ -3,11 +3,14 @@

 use crate::client::config::Config;
 use crate::error::Socks5ClientError;
+use crate::socks;
 use crate::socks::{
    authentication::{AuthenticationMethods, Authenticator, User},
    server::SphinxSocksServer,
 };
-use client_core::client::base_client::{BaseClientBuilder, ClientInput, ClientOutput};
+use client_core::client::base_client::{
+    non_wasm_helpers, BaseClientBuilder, ClientInput, ClientOutput,
+};
 use client_core::client::key_manager::KeyManager;
 use client_core::config::persistence::key_pathfinder::ClientKeyPathfinder;
 use futures::channel::mpsc;
@@ -54,8 +57,21 @@ impl NymClient {
        #[cfg(feature = "coconut")]
        let bandwidth_controller = {
            let details = network_defaults::NymNetworkDetails::new_from_env();
-            let client_config = validator_client::Config::try_from_nym_network_details(&details)
-                .expect("failed to construct validator client config");
+            let mut client_config =
+                validator_client::Config::try_from_nym_network_details(&details)
+                    .expect("failed to construct validator client config");
+            let nymd_url = config
+                .get_base()
+                .get_validator_endpoints()
+                .pop()
+                .expect("No nymd validator endpoint provided");
+            let api_url = config
+                .get_base()
+                .get_validator_api_endpoints()
+                .pop()
+                .expect("No validator api endpoint provided");
+            // overwrite env configuration with config URLs
+            client_config = client_config.with_urls(nymd_url, api_url);
            let client = validator_client::Client::new_query(client_config)
                .expect("Could not construct query client");
            let coconut_api_clients =
@@ -80,7 +96,7 @@ impl NymClient {
        client_input: ClientInput,
        client_output: ClientOutput,
        self_address: Recipient,
-        mut shutdown: ShutdownListener,
+        shutdown: ShutdownListener,
    ) {
        info!("Starting socks5 listener...");
        let auth_methods = vec![AuthenticationMethods::NoAuth as u8];
@@ -101,35 +117,30 @@ impl NymClient {
            config.get_provider_mix_address(),
            self_address,
            shared_lane_queue_lengths,
+            socks::client::Config::new(
+                config.get_send_anonymously(),
+                config.get_connection_start_surbs(),
+                config.get_per_request_surbs(),
+            ),
            shutdown.clone(),
        );
-        tokio::spawn(async move {
-            // Ideally we should have a fully fledged task manager to check for errors in all
-            // tasks.
-            // However, pragmatically, we start out by at least reporting errors for some of the
-            // tasks that interact with the outside world and can fail in normal operation, such as
-            // network issues.
-            // TODO: replace this by a generic solution, such as a task manager that stores all
-            // JoinHandles of all spawned tasks.
-            if let Err(res) = sphinx_socks
-                .serve(
-                    input_sender,
-                    received_buffer_request_sender,
-                    connection_command_sender,
-                )
-                .await
-            {
-                shutdown.send_we_stopped(Box::new(res));
-            }
-        });
+        task::spawn_with_report_error(
+            async move {
+                sphinx_socks
+                    .serve(
+                        input_sender,
+                        received_buffer_request_sender,
+                        connection_command_sender,
+                    )
+                    .await
+            },
+            shutdown,
+        );
    }

    /// blocking version of `start` method. Will run forever (or until SIGINT is sent)
-    pub async fn run_forever(self) -> Result<(), Box<dyn Error + Send>> {
-        let mut shutdown = self
-            .start()
-            .await
-            .map_err(|err| Box::new(err) as Box<dyn Error + Send>)?;
+    pub async fn run_forever(self) -> Result<(), Box<dyn Error + Send + Sync>> {
+        let mut shutdown = self.start().await?;

        let res = wait_for_signal_and_error(&mut shutdown).await;

@@ -147,12 +158,13 @@ impl NymClient {
    pub async fn run_and_listen(
        self,
        mut receiver: Socks5ControlMessageReceiver,
-    ) -> Result<(), Box<dyn Error + Send>> {
+        sender: task::StatusSender,
+    ) -> Result<(), Box<dyn Error + Send + Sync>> {
        // Start the main task
-        let mut shutdown = self
-            .start()
-            .await
-            .map_err(|err| Box::new(err) as Box<dyn Error + Send>)?;
+        let mut shutdown = self.start().await?;
+
+        // Listen to status messages from task, that we forward back to the caller
+        shutdown.start_status_listener(sender);

        let res = tokio::select! {
            biased;
@@ -193,6 +205,11 @@ impl NymClient {
            self.config.get_base(),
            self.key_manager,
            Some(Self::create_bandwidth_controller(&self.config).await),
+            non_wasm_helpers::setup_fs_reply_surb_backend(
+                self.config.get_base().get_reply_surb_database_path(),
+                self.config.get_debug_settings(),
+            )
+            .await?,
        );

        let self_address = base_builder.as_mix_recipient();
@@ -1,14 +1,17 @@
 // Copyright 2021 - Nym Technologies SA <contact@nymtech.net>
 // SPDX-License-Identifier: Apache-2.0

-use clap::Args;
-use client_core::{config::GatewayEndpointConfig, error::ClientCoreError};
-use config::NymConfig;
-
 use crate::{
    client::config::Config,
    commands::{override_config, OverrideConfig},
+    error::Socks5ClientError,
 };
+use clap::Args;
+use config::NymConfig;
+use nymsphinx::addressing::clients::Recipient;
+use serde::Serialize;
+use std::fmt::Display;
+use tap::TapFallible;

 #[derive(Args, Clone)]
 pub(crate) struct Init {
@@ -20,6 +23,14 @@ pub(crate) struct Init {
    #[clap(long)]
    provider: String,

+    /// Specifies whether this client is going to use an anonymous sender tag for communication with the service provider.
+    /// While this is going to hide its actual address information, it will make the actual communication
+    /// slower and consume nearly double the bandwidth as it will require sending reply SURBs.
+    ///
+    /// Note that some service providers might not support this.
+    #[clap(long)]
+    use_anonymous_sender_tag: bool,
+
    /// Id of the gateway we are going to connect to.
    #[clap(long)]
    gateway: Option<String>,
@@ -46,11 +57,19 @@ pub(crate) struct Init {
    #[clap(long, hidden = true)]
    fastmode: bool,

+    /// Disable loop cover traffic and the Poisson rate limiter (for debugging only)
+    #[clap(long, hidden = true)]
+    no_cover: bool,
+
    /// Set this client to work in a enabled credentials mode that would attempt to use gateway
    /// with bandwidth credential requirement.
    #[cfg(feature = "coconut")]
    #[clap(long)]
    enabled_credentials_mode: bool,
+
+    /// Save a summary of the initialization to a json file
+    #[clap(long)]
+    output_json: bool,
 }

 impl From<Init> for OverrideConfig {
@@ -59,14 +78,39 @@ impl From<Init> for OverrideConfig {
            nymd_validators: init_config.nymd_validators,
            api_validators: init_config.api_validators,
            port: init_config.port,
+            use_anonymous_sender_tag: init_config.use_anonymous_sender_tag,
            fastmode: init_config.fastmode,
+            no_cover: init_config.no_cover,
            #[cfg(feature = "coconut")]
            enabled_credentials_mode: init_config.enabled_credentials_mode,
        }
    }
 }

-pub(crate) async fn execute(args: &Init) {
+#[derive(Debug, Serialize)]
+pub struct InitResults {
+    #[serde(flatten)]
+    client_core: client_core::init::InitResults,
+    socks5_listening_port: String,
+}
+
+impl InitResults {
+    fn new(config: &Config, address: &Recipient) -> Self {
+        Self {
+            client_core: client_core::init::InitResults::new(config.get_base(), address),
+            socks5_listening_port: config.get_listening_port().to_string(),
+        }
+    }
+}
+
+impl Display for InitResults {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "{}", self.client_core)?;
+        write!(f, "SOCKS5 listening port: {}", self.socks5_listening_port)
+    }
+}
+
+pub(crate) async fn execute(args: &Init) -> Result<(), Socks5ClientError> {
    println!("Initialising client...");

    let id = &args.id;
@@ -91,25 +135,47 @@ pub(crate) async fn execute(args: &Init) {
    let register_gateway = !already_init || user_wants_force_register;

    // Attempt to use a user-provided gateway, if possible
-    let user_chosen_gateway_id = args.gateway.as_deref();
+    let user_chosen_gateway_id = args.gateway.clone();

-    let mut config = Config::new(id, provider_address);
-    let override_config_fields = OverrideConfig::from(args.clone());
-    config = override_config(config, override_config_fields);
+    // Load and potentially override config
+    let mut config = override_config(
+        Config::new(id, provider_address),
+        OverrideConfig::from(args.clone()),
+    );
+
+    // Setup gateway by either registering a new one, or creating a new config from the selected
+    // one but with keys kept, or reusing the gateway configuration.
+    let gateway = client_core::init::setup_gateway::<_, Config, _>(
+        register_gateway,
+        user_chosen_gateway_id,
+        config.get_base(),
+    )
+    .await
+    .tap_err(|err| eprintln!("Failed to setup gateway\nError: {err}"))?;

-    let gateway = setup_gateway(id, register_gateway, user_chosen_gateway_id, &config)
-        .await
-        .unwrap_or_else(|err| {
-            eprintln!("Failed to setup gateway\nError: {err}");
-            std::process::exit(1)
-        });
    config.get_base_mut().with_gateway_endpoint(gateway);

-    let config_save_location = config.get_config_file_save_location();
-    config
-        .save_to_file(None)
-        .expect("Failed to save the config file");
+    config.save_to_file(None).tap_err(|_| {
+        log::error!("Failed to save the config file");
+    })?;

+    print_saved_config(&config);
+
+    let address = client_core::init::get_client_address_from_stored_keys(config.get_base())?;
+    let init_results = InitResults::new(&config, &address);
+    println!("{}", init_results);
+
+    // Output summary to a json file, if specified
+    if args.output_json {
+        client_core::init::output_to_json(&init_results, "socks5_client_init_results.json");
+    }
+
+    println!("\nThe address of this client is: {}\n", address);
+    Ok(())
+}
+
+fn print_saved_config(config: &Config) {
+    let config_save_location = config.get_config_file_save_location();
    println!("Saved configuration file to {:?}", config_save_location);
    println!("Using gateway: {}", config.get_base().get_gateway_id());
    log::debug!("Gateway id: {}", config.get_base().get_gateway_id());
@@ -118,62 +184,5 @@ pub(crate) async fn execute(args: &Init) {
        "Gateway listener: {}",
        config.get_base().get_gateway_listener()
    );
-    println!("Client configuration completed.");
-
-    client_core::init::show_address(config.get_base()).unwrap_or_else(|err| {
-        eprintln!("Failed to show address\nError: {err}");
-        std::process::exit(1)
-    });
-}
-
-async fn setup_gateway(
-    id: &str,
-    register: bool,
-    user_chosen_gateway_id: Option<&str>,
-    config: &Config,
-) -> Result<GatewayEndpointConfig, ClientCoreError> {
-    if register {
-        // Get the gateway details by querying the validator-api. Either pick one at random or use
-        // the chosen one if it's among the available ones.
-        println!("Configuring gateway");
-        let gateway = client_core::init::query_gateway_details(
-            config.get_base().get_validator_api_endpoints(),
-            user_chosen_gateway_id,
-        )
-        .await?;
-        log::debug!("Querying gateway gives: {}", gateway);
-
-        // Registering with gateway by setting up and writing shared keys to disk
-        log::trace!("Registering gateway");
-        client_core::init::register_with_gateway_and_store_keys(gateway.clone(), config.get_base())
-            .await?;
-        println!("Saved all generated keys");
-
-        Ok(gateway.into())
-    } else if user_chosen_gateway_id.is_some() {
-        // Just set the config, don't register or create any keys
-        // This assumes that the user knows what they are doing, and that the existing keys are
-        // valid for the gateway being used
-        println!("Using gateway provided by user, keeping existing keys");
-        let gateway = client_core::init::query_gateway_details(
-            config.get_base().get_validator_api_endpoints(),
-            user_chosen_gateway_id,
-        )
-        .await?;
-        log::debug!("Querying gateway gives: {}", gateway);
-        Ok(gateway.into())
-    } else {
-        println!("Not registering gateway, will reuse existing config and keys");
-        let existing_config = Config::load_from_file(Some(id)).map_err(|err| {
-            log::error!(
-                "Unable to configure gateway: {err}. \n
-                Seems like the client was already initialized but it was not possible to read \
-                the existing configuration file. \n
-                CAUTION: Consider backing up your gateway keys and try force gateway registration, or \
-                removing the existing configuration and starting over."
-            );
-            ClientCoreError::CouldNotLoadExistingGatewayConfiguration(err)
-        })?;
-        Ok(existing_config.get_base().get_gateway_endpoint().clone())
-    }
+    println!("Client configuration completed.\n");
 }
@@ -82,17 +82,19 @@ pub(crate) struct OverrideConfig {
    nymd_validators: Option<String>,
    api_validators: Option<String>,
    port: Option<u16>,
+    use_anonymous_sender_tag: bool,
    fastmode: bool,
+    no_cover: bool,

    #[cfg(feature = "coconut")]
    enabled_credentials_mode: bool,
 }

-pub(crate) async fn execute(args: &Cli) -> Result<(), Box<dyn Error + Send>> {
+pub(crate) async fn execute(args: &Cli) -> Result<(), Box<dyn Error + Send + Sync>> {
    let bin_name = "nym-socks5-client";

    match &args.command {
-        Commands::Init(m) => init::execute(m).await,
+        Commands::Init(m) => init::execute(m).await?,
        Commands::Run(m) => run::execute(m).await?,
        Commands::Upgrade(m) => upgrade::execute(m),
        Commands::Completions(s) => s.generate(&mut Cli::into_app(), bin_name),
@@ -121,6 +123,10 @@ pub(crate) fn override_config(mut config: Config, args: OverrideConfig) -> Confi
            .set_custom_validator_apis(parse_validators(&raw_validators));
    }

+    if args.use_anonymous_sender_tag {
+        config = config.with_anonymous_replies(true)
+    }
+
    if let Some(port) = args.port {
        config = config.with_port(port);
    }
@@ -136,6 +142,10 @@ pub(crate) fn override_config(mut config: Config, args: OverrideConfig) -> Confi
        config.get_base_mut().set_high_default_traffic_volume();
    }

+    if args.no_cover {
+        config.get_base_mut().set_no_cover_traffic();
+    }
+
    config
 }

@@ -22,6 +22,14 @@ pub(crate) struct Run {
    #[clap(long)]
    config: Option<String>,

+    /// Specifies whether this client is going to use an anonymous sender tag for communication with the service provider.
+    /// While this is going to hide its actual address information, it will make the actual communication
+    /// slower and consume nearly double the bandwidth as it will require sending reply SURBs.
+    ///
+    /// Note that some service providers might not support this.
+    #[clap(long)]
+    use_anonymous_sender_tag: bool,
+
    /// Address of the socks5 provider to send messages to.
    #[clap(long)]
    provider: Option<String>,
@@ -43,6 +51,15 @@ pub(crate) struct Run {
    #[clap(short, long)]
    port: Option<u16>,

+    /// Mostly debug-related option to increase default traffic rate so that you would not need to
+    /// modify config post init
+    #[clap(long, hidden = true)]
+    fastmode: bool,
+
+    /// Disable loop cover traffic and the Poisson rate limiter (for debugging only)
+    #[clap(long, hidden = true)]
+    no_cover: bool,
+
    /// Set this client to work in a enabled credentials mode that would attempt to use gateway
    /// with bandwidth credential requirement.
    #[cfg(feature = "coconut")]
@@ -56,8 +73,9 @@ impl From<Run> for OverrideConfig {
            nymd_validators: run_config.nymd_validators,
            api_validators: run_config.api_validators,
            port: run_config.port,
-            fastmode: false,
-
+            use_anonymous_sender_tag: run_config.use_anonymous_sender_tag,
+            fastmode: run_config.fastmode,
+            no_cover: run_config.no_cover,
            #[cfg(feature = "coconut")]
            enabled_credentials_mode: run_config.enabled_credentials_mode,
        }
@@ -86,7 +104,7 @@ fn version_check(cfg: &Config) -> bool {
    }
 }

-pub(crate) async fn execute(args: &Run) -> Result<(), Box<dyn std::error::Error + Send>> {
+pub(crate) async fn execute(args: &Run) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let id = &args.id;

    let mut config = match Config::load_from_file(Some(id)) {
@@ -102,6 +120,10 @@ pub(crate) async fn execute(args: &Run) -> Result<(), Box<dyn std::error::Error
    let override_config_fields = OverrideConfig::from(args.clone());
    config = override_config(config, override_config_fields);

+    if config.get_base_mut().set_empty_fields_to_defaults() {
+        warn!("some of the core config options were left unset. the default values are going to get used instead.");
+    }
+
    if !version_check(&config) {
        error!("failed the local version check");
        return Err(Box::new(Socks5ClientError::FailedLocalVersionCheck));
@@ -1,21 +1,24 @@
-use client_core::error::ClientCoreError;
-
 use crate::socks::types::SocksProxyError;
+use client_core::client::replies::reply_storage::fs_backend;
+use client_core::error::ClientCoreError;

 #[derive(thiserror::Error, Debug)]
 pub enum Socks5ClientError {
    #[error("I/O error: {0}")]
    IoError(#[from] std::io::Error),
+
    #[error("client-core error: {0}")]
-    ClientCoreError(#[from] ClientCoreError),
+    ClientCoreError(#[from] ClientCoreError<fs_backend::Backend>),

    #[error("SOCKS proxy error")]
    SocksProxyError(SocksProxyError),

    #[error("Failed to load config for: {0}")]
    FailedToLoadConfig(String),
+
    #[error("Failed local version check, client and config mismatch")]
    FailedLocalVersionCheck,
+
    #[error("Fail to bind address")]
    FailToBindAddress,
 }
@@ -13,7 +13,7 @@ pub mod error;
 pub mod socks;

 #[tokio::main]
-async fn main() -> Result<(), Box<dyn Error + Send>> {
+async fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
    setup_logging();
    println!("{}", banner());

@@ -126,11 +126,33 @@ impl AsyncWrite for StreamState {
    }
 }

+#[derive(Debug, Copy, Clone)]
+pub(crate) struct Config {
+    use_surbs_for_responses: bool,
+    connection_start_surbs: u32,
+    per_request_surbs: u32,
+}
+
+impl Config {
+    pub(crate) fn new(
+        use_surbs_for_responses: bool,
+        connection_start_surbs: u32,
+        per_request_surbs: u32,
+    ) -> Self {
+        Self {
+            use_surbs_for_responses,
+            connection_start_surbs,
+            per_request_surbs,
+        }
+    }
+}
+
 /// A client connecting to the Socks proxy server, because
 /// it wants to make a Nym-protected outbound request. Typically, this is
 /// something like e.g. a wallet app running on your laptop connecting to
 /// `SphinxSocksServer`.
 pub(crate) struct SocksClient {
+    config: Config,
    controller_sender: ControllerSender,
    stream: StreamState,
    auth_nmethods: u8,
@@ -160,6 +182,7 @@ impl Drop for SocksClient {
 impl SocksClient {
    #[allow(clippy::too_many_arguments)]
    pub fn new(
+        config: Config,
        stream: TcpStream,
        authenticator: Authenticator,
        input_sender: InputMessageSender,
@@ -175,6 +198,7 @@ impl SocksClient {
        let connection_id = Self::generate_random();

        SocksClient {
+            config,
            controller_sender,
            connection_id,
            stream: StreamState::Available(stream),
@@ -268,14 +292,14 @@ impl SocksClient {
        self.handle_request().await
    }

-    async fn send_connect_to_mixnet(&mut self, remote_address: RemoteAddress) {
-        let req = Request::new_connect(self.connection_id, remote_address, self.self_address);
+    async fn send_anonymous_connect_to_mixnet(&mut self, remote_address: RemoteAddress) {
+        let req = Request::new_connect(self.connection_id, remote_address, None);
        let msg = Message::Request(req);

-        let input_message = InputMessage::new_fresh(
+        let input_message = InputMessage::new_anonymous(
            self.service_provider,
            msg.into_bytes(),
-            false,
+            self.config.connection_start_surbs,
            TransmissionLane::ConnectionId(self.connection_id),
        );
        self.input_sender
@@ -284,6 +308,30 @@ impl SocksClient {
            .expect("InputMessageReceiver has stopped receiving!");
    }

+    async fn send_connect_to_mixnet_with_return_address(&mut self, remote_address: RemoteAddress) {
+        let req = Request::new_connect(self.connection_id, remote_address, Some(self.self_address));
+        let msg = Message::Request(req);
+
+        let input_message = InputMessage::new_regular(
+            self.service_provider,
+            msg.into_bytes(),
+            TransmissionLane::ConnectionId(self.connection_id),
+        );
+        self.input_sender
+            .send(input_message)
+            .await
+            .expect("InputMessageReceiver has stopped receiving!");
+    }
+
+    async fn send_connect_to_mixnet(&mut self, remote_address: RemoteAddress) {
+        if self.config.use_surbs_for_responses {
+            self.send_anonymous_connect_to_mixnet(remote_address).await
+        } else {
+            self.send_connect_to_mixnet_with_return_address(remote_address)
+                .await
+        }
+    }
+
    async fn run_proxy(&mut self, conn_receiver: ConnectionReceiver, remote_proxy_target: String) {
        self.send_connect_to_mixnet(remote_proxy_target.clone())
            .await;
@@ -300,6 +348,8 @@ impl SocksClient {

        let connection_id = self.connection_id;
        let input_sender = self.input_sender.clone();
+        let anonymous = self.config.use_surbs_for_responses;
+        let per_request_surbs = self.config.per_request_surbs;

        let recipient = self.service_provider;
        let (stream, _) = ProxyRunner::new(
@@ -316,7 +366,16 @@ impl SocksClient {
            let provider_request = Request::new_send(conn_id, read_data, socket_closed);
            let provider_message = Message::Request(provider_request);
            let lane = TransmissionLane::ConnectionId(conn_id);
-            InputMessage::new_fresh(recipient, provider_message.into_bytes(), false, lane)
+            if anonymous {
+                InputMessage::new_anonymous(
+                    recipient,
+                    provider_message.into_bytes(),
+                    per_request_surbs,
+                    lane,
+                )
+            } else {
+                InputMessage::new_regular(recipient, provider_message.into_bytes(), lane)
+            }
        })
        .await
        .into_inner();
@@ -54,8 +54,8 @@ impl MixnetResponseListener {

    async fn on_message(&self, reconstructed_message: ReconstructedMessage) {
        let raw_message = reconstructed_message.message;
-        if reconstructed_message.reply_surb.is_some() {
-            warn!("this message had a surb - we didn't do anything with it");
+        if reconstructed_message.sender_tag.is_some() {
+            warn!("this message was sent anonymously - it couldn't have come from the service provider");
        }

        let response = match Message::try_from_bytes(&raw_message) {
@@ -5,7 +5,7 @@ use std::convert::TryFrom;
 use self::types::SocksProxyError;

 pub mod authentication;
-mod client;
+pub(crate) mod client;
 pub(crate) mod mixnet_responses;
 mod request;
 pub mod server;
@@ -3,6 +3,7 @@ use crate::error::Socks5ClientError;
 use super::{
    authentication::Authenticator, client::SocksClient, mixnet_responses::MixnetResponseListener,
 };
+use crate::socks::client;
 use client_connections::{ConnectionCommandSender, LaneQueueLengths};
 use client_core::client::{
    inbound_messages::InputMessageSender, received_buffer::ReceivedBufferRequestSender,
@@ -21,6 +22,7 @@ pub struct SphinxSocksServer {
    listening_address: SocketAddr,
    service_provider: Recipient,
    self_address: Recipient,
+    client_config: client::Config,
    lane_queue_lengths: LaneQueueLengths,
    shutdown: ShutdownListener,
 }
@@ -33,6 +35,7 @@ impl SphinxSocksServer {
        service_provider: Recipient,
        self_address: Recipient,
        lane_queue_lengths: LaneQueueLengths,
+        client_config: client::Config,
        shutdown: ShutdownListener,
    ) -> Self {
        // hardcode ip as we (presumably) ONLY want to listen locally. If we change it, we can
@@ -44,6 +47,7 @@ impl SphinxSocksServer {
            listening_address: format!("{}:{}", ip, port).parse().unwrap(),
            service_provider,
            self_address,
+            client_config,
            lane_queue_lengths,
            shutdown,
        }
@@ -86,6 +90,7 @@ impl SphinxSocksServer {
            tokio::select! {
                Ok((stream, _remote)) = listener.accept() => {
                    let mut client = SocksClient::new(
+                        self.client_config,
                        stream,
                        self.authenticator.clone(),
                        input_sender.clone(),
@@ -1,5 +1,3 @@
-use snafu::Snafu;
-
 /// SOCKS4 Response codes
 #[allow(dead_code)]
 pub(crate) enum ResponseCodeV4 {
@@ -10,24 +8,26 @@ pub(crate) enum ResponseCodeV4 {
 }

 /// Possible SOCKS5 Response Codes
-#[derive(Debug, Snafu)]
+#[allow(dead_code)]
+#[derive(Debug, thiserror::Error)]
 pub(crate) enum ResponseCodeV5 {
+    #[error("SOCKS5 Server Success")]
    Success = 0x00,
-    #[snafu(display("SOCKS5 Server Failure"))]
+    #[error("SOCKS5 Server Failure")]
    Failure = 0x01,
-    #[snafu(display("SOCKS5 Rule failure"))]
+    #[error("SOCKS5 Rule failure")]
    RuleFailure = 0x02,
-    #[snafu(display("network unreachable"))]
+    #[error("network unreachable")]
    NetworkUnreachable = 0x03,
-    #[snafu(display("host unreachable"))]
+    #[error("host unreachable")]
    HostUnreachable = 0x04,
-    #[snafu(display("connection refused"))]
+    #[error("connection refused")]
    ConnectionRefused = 0x05,
-    #[snafu(display("TTL expired"))]
+    #[error("TTL expired")]
    TtlExpired = 0x06,
-    #[snafu(display("Command not supported"))]
+    #[error("Command not supported")]
    CommandNotSupported = 0x07,
-    #[snafu(display("Addr Type not supported"))]
+    #[error("Addr Type not supported")]
    AddrTypeNotSupported = 0x08,
 }

@@ -65,7 +65,6 @@ async function main() {
 *
 * Message and recipient are taken from the values in the user interface.
 *
- * @param {Client} nymClient the nym client to use for message sending
 */
 async function sendMessageTo() {
  const message = document.getElementById('message').value;
@@ -96,10 +95,13 @@ function displaySend(message) {
 /**
 * Display received text messages in the browser. Colour them green.
 *
- * @param {string} message
+ * @param {Uint8Array} raw
 */
-function displayReceived(message) {
-  const content = message;
+function displayReceived(raw, sender_tag) {
+  const content = new TextDecoder().decode(raw);
+  if (sender_tag !== undefined) {
+    console.log("this message also contained some surbs from", sender_tag)
+  }

  let timestamp = new Date().toISOString().substr(11, 12);
  let receivedDiv = document.createElement('div');
@@ -116,7 +118,7 @@ function displayReceived(message) {
 /**
 * Display the nymClient's sender address in the user interface
 *
- * @param {Client} nymClient
+ * @param {String} address
 */
 function displaySenderAddress(address) {
  document.getElementById('sender').value = address;
@@ -17,38 +17,7 @@ importScripts('nym_client_wasm.js');
 console.log('Initializing worker');

 // wasm_bindgen creates a global variable (with the exports attached) that is in scope after `importScripts`
-const { default_debug, get_gateway, NymClient, set_panic_hook, Config } = wasm_bindgen;
-
-class ClientWrapper {
-  constructor(config, onMessageHandler) {
-    this.rustClient = new NymClient(config);
-    this.rustClient.set_on_message(onMessageHandler);
-    this.rustClient.set_on_gateway_connect(this.onConnect);
-  }
-
-  selfAddress = () => {
-    return this.rustClient.self_address();
-  };
-
-  onConnect = () => {
-    console.log('Established (and authenticated) gateway connection!');
-  };
-
-  start = async () => {
-    // this is current limitation of wasm in rust - for async methods you can't take self by reference...
-    // I'm trying to figure out if I can somehow hack my way around it, but for time being you have to re-assign
-    // the object (it's the same one)
-    this.rustClient = await this.rustClient.start();
-  };
-
-  sendMessage = async (recipient, message) => {
-    this.rustClient = await this.rustClient.send_message(recipient, message);
-  };
-
-  sendBinaryMessage = async (recipient, message) => {
-    this.rustClient = await this.rustClient.send_binary_message(recipient, message);
-  };
-}
+const { default_debug, NymClientBuilder, set_panic_hook, Config, GatewayEndpointConfig } = wasm_bindgen;

 let client = null;

@@ -62,11 +31,12 @@ async function main() {
  set_panic_hook();

  // validator server we will use to get topology from
-  const validator = 'https://validator.nymtech.net/api'; //"http://localhost:8081";
-  const preferredGateway = 'E3mvZTHQCdBvhfr178Swx9g4QG3kkRUun7YnToLMcMbM';
-
-  const gatewayEndpoint = await get_gateway(validator, preferredGateway);
-  gatewayEndpoint.gateway_listener = "wss://gateway1.nymtech.net:443"; // this is needed if we want it to work on the web. However this gateway is a v1 gateway, we will need to change for v2 once we get there
+  const validator = 'https://qwerty-validator-api.qa.nymte.ch/api';
+  
+  const gatewayId = 'EVupP2tRUeZo5Y6RpBHAbm8kSntpgNyZNL6yCr7BDEoG';
+  const gatewayOwner = 'n1rmlew3euapuq7rs4s4j9apv00whrsazr764kl7';
+  const gatewayListener = 'ws://176.58.120.72:9000';
+  const gatewayEndpoint = new GatewayEndpointConfig(gatewayId, gatewayOwner, gatewayListener)

  // only really useful if you want to adjust some settings like traffic rate
  // (if not needed you can just pass a null)
@@ -94,12 +64,17 @@ async function main() {
  };

  console.log('Instantiating WASM client...');
-  client = new ClientWrapper(config, onMessageHandler);
+  
+  let clientBuilder = new NymClientBuilder(config, onMessageHandler)
  console.log('Web worker creating WASM client...');
-  await client.start();
+  let local_client = await clientBuilder.start_client();
  console.log('WASM client running!');
-
-  const selfAddress = client.rustClient.self_address();
+  
+  const selfAddress = local_client.self_address();
+  
+  // set the global (I guess we don't have to anymore?)
+  client = local_client;
+  
  console.log(`Client address is ${selfAddress}`);
  self.postMessage({
    kind: 'Ready',
@@ -114,7 +89,8 @@ async function main() {
      switch (event.data.kind) {
        case 'SendMessage': {
          const { message, recipient } = event.data.args;
-          await client.sendMessage(message, recipient);
+          let uint8Array = new TextEncoder().encode(message);
+          await client.send_regular_message(uint8Array, recipient);
        }
      }
    }
@@ -106,6 +106,34 @@ pub struct Debug {

    /// Controls whether the sent sphinx packet use the NON-DEFAULT bigger size.
    pub use_extended_packet_size: bool,
+
+    /// Defines the minimum number of reply surbs the client wants to keep in its storage at all times.
+    /// It can only allow to go below that value if its to request additional reply surbs.
+    pub minimum_reply_surb_storage_threshold: usize,
+
+    /// Defines the maximum number of reply surbs the client wants to keep in its storage at any times.
+    pub maximum_reply_surb_storage_threshold: usize,
+
+    /// Defines the minimum number of reply surbs the client would request.
+    pub minimum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs the client would request.
+    pub maximum_reply_surb_request_size: u32,
+
+    /// Defines the maximum number of reply surbs a remote party is allowed to request from this client at once.
+    pub maximum_allowed_reply_surb_request_size: u32,
+
+    /// Defines maximum amount of time the client is going to wait for reply surbs before explicitly asking
+    /// for more even though in theory they wouldn't need to.
+    pub maximum_reply_surb_waiting_period_ms: u64,
+
+    /// Defines maximum amount of time given reply surb is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    pub maximum_reply_surb_age_ms: u64,
+
+    /// Defines maximum amount of time given reply key is going to be valid for.
+    /// This is going to be superseded by key rotation once implemented.
+    pub maximum_reply_key_age_ms: u64,
 }

 impl From<Debug> for ConfigDebug {
@@ -135,6 +163,16 @@ impl From<Debug> for ConfigDebug {
            disable_main_poisson_packet_distribution: debug
                .disable_main_poisson_packet_distribution,
            use_extended_packet_size,
+            minimum_reply_surb_storage_threshold: debug.minimum_reply_surb_storage_threshold,
+            maximum_reply_surb_storage_threshold: debug.maximum_reply_surb_storage_threshold,
+            minimum_reply_surb_request_size: debug.minimum_reply_surb_request_size,
+            maximum_reply_surb_request_size: debug.maximum_reply_surb_request_size,
+            maximum_allowed_reply_surb_request_size: debug.maximum_allowed_reply_surb_request_size,
+            maximum_reply_surb_waiting_period: Duration::from_millis(
+                debug.maximum_reply_surb_waiting_period_ms,
+            ),
+            maximum_reply_surb_age: Duration::from_millis(debug.maximum_reply_surb_age_ms),
+            maximum_reply_key_age: Duration::from_millis(debug.maximum_reply_key_age_ms),
        }
    }
 }
@@ -157,6 +195,16 @@ impl From<ConfigDebug> for Debug {
            disable_main_poisson_packet_distribution: debug
                .disable_main_poisson_packet_distribution,
            use_extended_packet_size: debug.use_extended_packet_size.is_some(),
+            minimum_reply_surb_storage_threshold: debug.minimum_reply_surb_storage_threshold,
+            maximum_reply_surb_storage_threshold: debug.maximum_reply_surb_storage_threshold,
+            minimum_reply_surb_request_size: debug.minimum_reply_surb_request_size,
+            maximum_reply_surb_request_size: debug.maximum_reply_surb_request_size,
+            maximum_allowed_reply_surb_request_size: debug.maximum_allowed_reply_surb_request_size,
+            maximum_reply_surb_waiting_period_ms: debug
+                .maximum_reply_surb_waiting_period
+                .as_millis() as u64,
+            maximum_reply_surb_age_ms: debug.maximum_reply_surb_age.as_millis() as u64,
+            maximum_reply_key_age_ms: debug.maximum_reply_key_age.as_millis() as u64,
        }
    }
 }
@@ -0,0 +1,30 @@
+// Copyright 2022 - Nym Technologies SA <contact@nymtech.net>
+// SPDX-License-Identifier: Apache-2.0
+
+use client_core::client::base_client::ClientInput;
+use client_core::client::inbound_messages::InputMessage;
+use js_sys::Promise;
+use std::sync::Arc;
+use wasm_bindgen::JsValue;
+use wasm_bindgen_futures::future_to_promise;
+
+// defining helper trait as we could directly call the method on the wrapper
+pub(crate) trait InputSender {
+    fn send_message(&self, message: InputMessage) -> Promise;
+}
+
+impl InputSender for Arc<ClientInput> {
+    fn send_message(&self, message: InputMessage) -> Promise {
+        let this = Arc::clone(self);
+        future_to_promise(async move {
+            match this.input_sender.send(message).await {
+                Ok(_) => Ok(JsValue::null()),
+                Err(_) => {
+                    let js_error =
+                        js_sys::Error::new("InputMessageReceiver has stopped receiving!");
+                    Err(JsValue::from(js_error))
+                }
+            }
+        })
+    }
+}
@@ -2,59 +2,65 @@
 // SPDX-License-Identifier: Apache-2.0

 use self::config::Config;
+use crate::client::helpers::InputSender;
 use crate::client::response_pusher::ResponsePusher;
 use client_connections::TransmissionLane;
 use client_core::client::base_client::{BaseClientBuilder, ClientInput, ClientOutput};
+use client_core::client::replies::reply_storage::browser_backend;
 use client_core::client::{inbound_messages::InputMessage, key_manager::KeyManager};
-use crypto::asymmetric::identity;
+use gateway_client::bandwidth::BandwidthController;
+use js_sys::Promise;
 use nymsphinx::addressing::clients::Recipient;
+use nymsphinx::anonymous_replies::requests::AnonymousSenderTag;
 use rand::rngs::OsRng;
+use std::sync::Arc;
 use task::ShutdownNotifier;
 use wasm_bindgen::prelude::*;
+use wasm_bindgen_futures::future_to_promise;
 use wasm_utils::{console_error, console_log};

 pub mod config;
+mod helpers;
 mod response_pusher;

 #[wasm_bindgen]
 pub struct NymClient {
-    config: Config,
-
-    /// KeyManager object containing smart pointers to all relevant keys used by the client.
-    // due to disgusting workaround I had to wrap the key_manager in an Option
-    // so that the interface wouldn't change (i.e. both `start` and `new` would still return a `NymClient`)
-    key_manager: Option<KeyManager>,
-    self_address: Option<String>,
-
-    // TODO: this should be stored somewhere persistently
-    // received_keys: HashSet<SURBEncryptionKey>,
-    /// Channel used for transforming 'raw' messages into sphinx packets and sending them
-    /// through the mix network.
-    client_input: Option<ClientInput>,
-
-    // callbacks
-    on_message: Option<js_sys::Function>,
-    on_binary_message: Option<js_sys::Function>,
-    on_gateway_connect: Option<js_sys::Function>,
+    self_address: String,
+    client_input: Arc<ClientInput>,

    // even though we don't use graceful shutdowns, other components rely on existence of this struct
    // and if it's dropped, everything will start going offline
-    _shutdown: Option<ShutdownNotifier>,
+    _shutdown: ShutdownNotifier,
 }

 #[wasm_bindgen]
-impl NymClient {
+pub struct NymClientBuilder {
+    config: Config,
+
+    /// KeyManager object containing smart pointers to all relevant keys used by the client.
+    key_manager: KeyManager,
+
+    reply_surb_storage_backend: browser_backend::Backend,
+
+    on_message: js_sys::Function,
+
+    // unimplemented:
+    bandwidth_controller: Option<BandwidthController>,
+    disabled_credentials: bool,
+}
+
+#[wasm_bindgen]
+impl NymClientBuilder {
    #[wasm_bindgen(constructor)]
-    pub fn new(config: Config) -> Self {
-        Self {
+    pub fn new(config: Config, on_message: js_sys::Function) -> Self {
+        //, key_manager: Option<KeyManager>) {
+        NymClientBuilder {
+            reply_surb_storage_backend: Self::setup_reply_surb_storage_backend(&config),
            config,
-            key_manager: Some(Self::setup_key_manager()),
-            on_message: None,
-            on_binary_message: None,
-            on_gateway_connect: None,
-            client_input: None,
-            self_address: None,
-            _shutdown: None,
+            key_manager: Self::setup_key_manager(),
+            on_message,
+            bandwidth_controller: None,
+            disabled_credentials: true,
        }
    }

@@ -69,117 +75,154 @@ impl NymClient {
        KeyManager::new(&mut rng)
    }

-    pub fn set_on_message(&mut self, on_message: js_sys::Function) {
-        self.on_message = Some(on_message);
-    }
-
-    pub fn set_on_binary_message(&mut self, on_binary_message: js_sys::Function) {
-        self.on_binary_message = Some(on_binary_message);
-    }
-
-    pub fn set_on_gateway_connect(&mut self, on_connect: js_sys::Function) {
-        self.on_gateway_connect = Some(on_connect)
-    }
-
-    fn as_mix_recipient(&self) -> Recipient {
-        // another disgusting (and hopefully temporary) workaround
-        let key_manager_ref = self
-            .key_manager
-            .as_ref()
-            .expect("attempting to call 'as_mix_recipient' after 'start'");
-
-        Recipient::new(
-            *key_manager_ref.identity_keypair().public_key(),
-            *key_manager_ref.encryption_keypair().public_key(),
-            identity::PublicKey::from_base58_string(&self.config.gateway_endpoint.gateway_id)
-                .expect("no gateway has been selected"),
+    // don't get too excited about the name, under the hood it's just a big fat placeholder
+    // with no persistence
+    fn setup_reply_surb_storage_backend(config: &Config) -> browser_backend::Backend {
+        browser_backend::Backend::new(
+            config.debug.minimum_reply_surb_storage_threshold,
+            config.debug.maximum_reply_surb_storage_threshold,
        )
    }

+    fn start_reconstructed_pusher(client_output: ClientOutput, on_message: js_sys::Function) {
+        ResponsePusher::new(client_output, on_message).start()
+    }
+
+    pub async fn start_client(self) -> Promise {
+        future_to_promise(async move {
+            console_log!("Starting the wasm client");
+
+            let base_builder = BaseClientBuilder::new(
+                &self.config.gateway_endpoint,
+                &self.config.debug,
+                self.key_manager,
+                self.bandwidth_controller,
+                self.reply_surb_storage_backend,
+                self.disabled_credentials,
+                vec![self.config.validator_api_url.clone()],
+            );
+
+            let self_address = base_builder.as_mix_recipient().to_string();
+            let mut started_client = match base_builder.start_base().await {
+                Ok(base_client) => base_client,
+                Err(err) => {
+                    let error_msg = format!("failed to start the base client components - {err}");
+                    console_error!("{}", error_msg);
+                    let js_error = js_sys::Error::new(&error_msg);
+                    return Err(JsValue::from(js_error));
+                }
+            };
+
+            let client_input = started_client.client_input.register_producer();
+            let client_output = started_client.client_output.register_consumer();
+
+            Self::start_reconstructed_pusher(client_output, self.on_message);
+
+            Ok(JsValue::from(NymClient {
+                self_address,
+                client_input: Arc::new(client_input),
+                _shutdown: started_client.shutdown_notifier,
+            }))
+        })
+    }
+}
+
+#[wasm_bindgen]
+impl NymClient {
    pub fn self_address(&self) -> String {
-        if let Some(address) = &self.self_address {
-            address.clone()
-        } else {
-            self.as_mix_recipient().to_string()
+        self.self_address.clone()
+    }
+
+    fn parse_recipient(recipient: &str) -> Result<Recipient, JsValue> {
+        match Recipient::try_from_base58_string(recipient) {
+            Ok(recipient) => Ok(recipient),
+            Err(err) => {
+                let error_msg = format!("{recipient} is not a valid Nym network recipient - {err}");
+                console_error!("{}", error_msg);
+                let js_error = js_sys::Error::new(&error_msg);
+                Err(JsValue::from(js_error))
+            }
        }
    }

-    // Right now it's impossible to have async exported functions to take `&mut self` rather than mut self
-    // TODO: try Rc<RefCell<Self>> approach?
-    pub async fn send_message(self, message: String, recipient: String) -> Self {
-        console_log!("Sending {} to {}", message, recipient);
-
-        let message_bytes = message.into_bytes();
-        self.send_binary_message(message_bytes, recipient).await
+    fn parse_sender_tag(tag: &str) -> Result<AnonymousSenderTag, JsValue> {
+        match AnonymousSenderTag::try_from_base58_string(tag) {
+            Ok(tag) => Ok(tag),
+            Err(err) => {
+                let error_msg = format!("{tag} is not a valid Nym AnonymousSenderTag - {err}");
+                console_error!("{}", error_msg);
+                let js_error = js_sys::Error::new(&error_msg);
+                Err(JsValue::from(js_error))
+            }
+        }
    }

-    pub async fn send_binary_message(self, message: Vec<u8>, recipient: String) -> Self {
-        console_log!("Sending {} bytes to {}", message.len(), recipient);
-
-        let recipient = Recipient::try_from_base58_string(recipient).unwrap();
-        let lane = TransmissionLane::General;
-
-        let input_msg = InputMessage::new_fresh(recipient, message, false, lane);
-
-        self.client_input
-            .as_ref()
-            .expect("start method was not called before!")
-            .input_sender
-            .send(input_msg)
-            .await
-            .expect("InputMessageReceiver has stopped receiving!");
-
-        self
-    }
-
-    fn start_reconstructed_pusher(
-        client_output: ClientOutput,
-        on_message: Option<js_sys::Function>,
-        on_binary_message: Option<js_sys::Function>,
-    ) {
-        ResponsePusher::new(client_output, on_message, on_binary_message).start()
-    }
-
-    pub async fn start(mut self) -> NymClient {
-        console_log!("Starting the wasm client");
-
-        let base_builder = BaseClientBuilder::new(
-            &self.config.gateway_endpoint,
-            &self.config.debug,
-            self.key_manager.take().unwrap(),
-            None,
-            true,
-            vec![self.config.validator_api_url.clone()],
+    /// The simplest message variant where no additional information is attached.
+    /// You're simply sending your `data` to specified `recipient` without any tagging.
+    ///
+    /// Ends up with `NymMessage::Plain` variant
+    pub fn send_regular_message(&self, message: Vec<u8>, recipient: String) -> Promise {
+        console_log!(
+            "Attempting to send {:.2} kiB message to {recipient}",
+            message.len() as f64 / 1024.0
        );

-        self.self_address = Some(base_builder.as_mix_recipient().to_string());
-        let mut started_client = match base_builder.start_base().await {
-            Ok(base_client) => base_client,
-            Err(err) => {
-                console_error!("failed to start base client components - {}", err);
-                // proper error handling is left here as an exercise for the reader (hi Mark : ))
-                panic!("failed to start base client components - {err}")
-            }
+        let recipient = match Self::parse_recipient(&recipient) {
+            Ok(recipient) => recipient,
+            Err(err) => return Promise::reject(&err),
        };
-        match self.on_gateway_connect.as_ref() {
-            Some(callback) => {
-                callback
-                    .call0(&JsValue::null())
-                    .expect("on connect callback failed!");
-            }
-            None => console_log!("Gateway connection established - no callback specified"),
+        let lane = TransmissionLane::General;
+
+        let input_msg = InputMessage::new_regular(recipient, message, lane);
+        self.client_input.send_message(input_msg)
+    }
+
+    /// Creates a message used for a duplex anonymous communication where the recipient
+    /// will never learn of our true identity. This is achieved by carefully sending `reply_surbs`.
+    ///
+    /// Note that if reply_surbs is set to zero then
+    /// this variant requires the client having sent some reply_surbs in the past
+    /// (and thus the recipient also knowing our sender tag).
+    ///
+    /// Ends up with `NymMessage::Repliable` variant
+    pub fn send_anonymous_message(
+        &self,
+        message: Vec<u8>,
+        recipient: String,
+        reply_surbs: u32,
+    ) -> Promise {
+        console_log!(
+            "Attempting to anonymously send {:.2} kiB message to {recipient} while attaching {reply_surbs} replySURBs.",
+            message.len() as f64 / 1024.0
+        );
+
+        let recipient = match Self::parse_recipient(&recipient) {
+            Ok(recipient) => recipient,
+            Err(err) => return Promise::reject(&err),
        };
+        let lane = TransmissionLane::General;

-        // those should be moved to a completely different struct, but I don't want to break compatibility for now
-        let client_input = started_client.client_input.register_producer();
-        let client_output = started_client.client_output.register_consumer();
+        let input_msg = InputMessage::new_anonymous(recipient, message, reply_surbs, lane);
+        self.client_input.send_message(input_msg)
+    }

-        let on_message = self.on_message.take();
-        let on_binary_message = self.on_binary_message.take();
-        Self::start_reconstructed_pusher(client_output, on_message, on_binary_message);
-        self.client_input = Some(client_input);
-        self._shutdown = Some(started_client.shutdown_notifier);
+    /// Attempt to use our internally received and stored `ReplySurb` to send the message back
+    /// to specified recipient whilst not knowing its full identity (or even gateway).
+    ///
+    /// Ends up with `NymMessage::Reply` variant
+    pub fn send_reply(&self, message: Vec<u8>, recipient_tag: String) -> Promise {
+        console_log!(
+            "Attempting to send {:.2} kiB reply message to {recipient_tag}",
+            message.len() as f64 / 1024.0
+        );

-        self
+        let sender_tag = match Self::parse_sender_tag(&recipient_tag) {
+            Ok(recipient) => recipient,
+            Err(err) => return Promise::reject(&err),
+        };
+        let lane = TransmissionLane::General;
+
+        let input_msg = InputMessage::new_reply(sender_tag, message, lane);
+        self.client_input.send_message(input_msg)
    }
 }
@@ -5,27 +5,18 @@ use client_core::client::base_client::ClientOutput;
 use client_core::client::received_buffer::{ReceivedBufferMessage, ReconstructedMessagesReceiver};
 use futures::channel::mpsc;
 use futures::StreamExt;
+use js_sys::Uint8Array;
 use wasm_bindgen::JsValue;
 use wasm_bindgen_futures::spawn_local;
-use wasm_utils::console_log;
+use wasm_utils::console_error;

 pub(crate) struct ResponsePusher {
    reconstructed_receiver: ReconstructedMessagesReceiver,
-    on_message: Option<js_sys::Function>,
-    on_binary_message: Option<js_sys::Function>,
+    on_message: js_sys::Function,
 }

 impl ResponsePusher {
-    pub(crate) fn new(
-        client_output: ClientOutput,
-        on_message: Option<js_sys::Function>,
-        on_binary_message: Option<js_sys::Function>,
-    ) -> Self {
-        if on_message.is_none() && on_binary_message.is_none() {
-            // exercise for the reader : )
-            panic!("neither 'on_message' nor 'on_binary_message' was set!")
-        }
-
+    pub(crate) fn new(client_output: ClientOutput, on_message: js_sys::Function) -> Self {
        // register our output
        let (reconstructed_sender, reconstructed_receiver) = mpsc::unbounded();

@@ -40,7 +31,6 @@ impl ResponsePusher {
        ResponsePusher {
            reconstructed_receiver,
            on_message,
-            on_binary_message,
        }
    }

@@ -49,23 +39,20 @@ impl ResponsePusher {
            let this = JsValue::null();

            while let Some(reconstructed) = self.reconstructed_receiver.next().await {
-                for msg in reconstructed {
-                    if let Some(ref callback_binary) = self.on_binary_message {
-                        let arg1 = serde_wasm_bindgen::to_value(&msg.message).unwrap();
-                        callback_binary
-                            .call1(&this, &arg1)
-                            .expect("on binary message failed!");
-                    }
-                    if let Some(ref callback) = self.on_message {
-                        if msg.reply_surb.is_some() {
-                            console_log!("the received message contained a reply-surb that we do not know how to handle (yet)")
-                        }
-                        let stringified = String::from_utf8_lossy(&msg.message).into_owned();
-                        let arg1 = serde_wasm_bindgen::to_value(&stringified).unwrap();
-                        callback.call1(&this, &arg1).expect("on message failed!");
-                    }
+                for reconstructed_msg in reconstructed {
+                    let (msg, tag) = reconstructed_msg.into_inner();
+
+                    let msg_slice: &[u8] = &msg;
+                    let array = Uint8Array::from(msg_slice);
+                    let arg1 = JsValue::from(array);
+                    let arg2 = JsValue::from(tag);
+                    self.on_message
+                        .call2(&this, &arg1, &arg2)
+                        .expect("on binary message failed!");
                }
            }
+
+            console_error!("we stopped receiving reconstructed messages!")
        })
    }
 }
--- a/Show More
+++ b/Show More