refresh older imported text from archive

documentation/docs/src/SUMMARY.md

@@ -31,9 +31,15 @@
 - [RPC Nodes](nyx/rpc-node.md)
 - [Ledger Live Support](nyx/ledger-live.md)
 
-# Coconut
-- [Coconut](coconut.md)
-- [Bandwidth Credentials](bandwidth-credentials.md)
+# zkNyms (prev. Coconut)
+- [What are zkNyms?](ecash/what-are-zknyms.md)
+- [zkNym Generation & Useage: Overview](ecash/zknym-overview.md)
+  - [Feature: Unlinkability](ecash/unlinkability.md)
+  - [Feature: Double Spend Protection](ecash/double-spend-prot.md)
+  - [Feature: Rerandomisation & Incremental Spend](ecash/rerandomise.md)
+- [Archive](ecash/archive.md)
+  - [Coconut](ecash/coconut.md)
+  - [Bandwidth Credentials](ecash/bandwidth-credentials.md)
 
 # Tools
 - [NymCLI](tools/nym-cli.md)

documentation/docs/src/ecash/archive.md

@@ -0,0 +1,3 @@
+# Archive
+
+You can find the previous pages related to ecash - referred to then as 'Coconut' - in this archive.

documentation/docs/src/ecash/coconut.md

@@ -1,7 +1,5 @@
 # Coconut
 
-> Coconut is in active development - stay tuned for code and integration examples
-
 Coconut is a cryptographic signature scheme that produces privacy-enhanced credentials. It lets application programmers who are concerned with resource access control to think and code in a new way.
 
 Most of the time, when we build system security, we think of _who_ questions:

documentation/docs/src/ecash/double-spend-prot.md

@@ -0,0 +1,41 @@
+# Double Spend Protection
+Double spend protection in the context of zkNym is a balancing act between speed, reliability, and UX. There are two possible modes for protecting against attempted double spending of zkNyms:
+
+- Online: The online approach mandates that ingress Gateways instantly deposit zkNyms received from clients to the NymAPI Quorum for verification. Once verified by the Quroum, the ingress Gateway is paid proprtional to the amount of bandwidth 'spent' with the zkNym, and proceeds to grant the client access to the network.
+- Offline: In contrast, the offline approach involves the periodic submission of collected zkNyms by ingress Gateways to the Quorum, instead of an instant check. Subsequently, the Quorum nodes perform checks to detect any instances of double-spending and identify the public key associated with such occurrences, whereas the ingress Gateways only do a simple check to check that _that particular_ zkNym had not been spent with itself before.
+
+> The zkNym system takes the **offline** approach.
+
+## Offline Approach: Pros & Cons
+The advantages of the offline approach are manifold:
+- Immediate access to the Nym network upon zkNym submission, eliminating any delays in service provisioning until payments are deposited and verified as would occur in the online approach.
+- Alleviates performance strain on ingress Gateways and Quorum members, serving as a more efficient method compared to the online counterpart. By moving computationally intense work to the Quorum, this means that Gateway nodes are able to be run on less powerful machines, meaning more operators can more easily run them (and cover their costs) and thus increase the overall number and spread of Gateways around the globe.
+- Moreover, we can circumvent the potential issue of overwhelming the blockchain with the serial numbers of spent coins (like in the case of the Zcash DoS attack). TODO reword
+
+However, the offline approach introduces certain limitations.
+- Ingress Gateways accept zkNyms without preemptively checking for instances of double spending thus making them susceptible to unknowingly accepting double-spent credentials.
+- Any potential repercussions against double spenders can only be implemented once the user requests a new credential for their zkNym Generator (aka they have to 'top up' and buy more bandwidth allowance), assuming they haven't altered their identifier, such as the Bech32 address.
+
+An exploitable scenario arises from these limitations:
+- A malicious user purchases bandwidth and aggregates a valid credential in the standard way, worth $10 of crypto/fiat. Subsequently, the malicious user proceeds to sell the credential to 100 users for $1 each, allowing each user to generate zkNyms of 100MB from this **valid** credential. Under the offline approach, entry nodes forego double-spending checks, enabling all 100 users to access the network without obtaining a subscription. The 100 MB limit does not prevent that, as the bandwidth consumption is tracked locally between client and ingress node. This loophole highlights the need for stringent measures to counter such potential abuses within the system.
+
+We can, however, mitigate this problem.
+
+## Solution to Offline Double Spending
+To efficiently prevent the fraudulent use of tickets within the Nym network, a two-tiered solution is in place that combines (1) the immediate detection of double-spending attempts at the entry node level and (2) subsequent identification and blacklisting at the nym-API level.
+
+TODO check against https://www.figma.com/board/geUGlj4Dffddx3E08vMZxz/Ecash-Flow?node-id=0-1&node-type=CANVAS&t=yuSZkEQRna8RqzwD-0 to check you havent gone off piste
+
+### Entry Node Implementation: Real-Time Ticket Unspending Validation
+Each zkNym contains as an attribute a unique serial number, which is revealed in plaintext to the respective ingress Gateway. Each Gateway has a copy of a [Bloom Filter](https://www.geeksforgeeks.org/bloom-filters-introduction-and-python-implementation/) - on receiving a zkNym, it will check against its copy in a local database to check whether this serial number has already been seen. If so, it rejects the zkNym as being double-spent and the client's connection request is rejected. If not, it will add the serial number to its local DB cache.
+
+> Since each time a zkNym is rerandomised its serial number is changed, the serial number being shared in no way identifies a client or user.
+
+Each Gateway will periodically share their serial numbers with the Quorum and refresh their copy of the Bloom Filters from the Quorum, in order to refresh the global list shared by all ingress Gateways and the Quorum. See the step below for more on this.
+
+> Crucially, ingress Gateways refrain from extensive computations to identify the original ticket owner, and avoids broadcasting information about the double-spending attempt to other ingress Gateways. The entry node is also not involved in any global blacklisting process of the clients. The sole purpose of this check is to swiftly identify any attempts at double-spending and add the seen ticket's serial number to the local DB cache.
+
+### Nym-API Implementation: Blacklisting and Penalties for Double-Spenders
+All Gateways periodically forward the collected zkNyms to the Quorum, enabling them to pinpoint and blacklist any clients who double spend. Upon receiving the tickets, the Quorum appends all the incoming serial numbers to the global list of spend zkNym serial numbers and proceed with the identification process for any malicious users engaging in double-spending.
+
+This identification phase involves looking for instances of double spending, identifying the id of the double-spending client, and blacklisting this client by its id. Subsequently, when this client requests a new credential, their plaintext public identifier is included in the request. The Quorum then checks if this identifier is blacklisted. If it is, a new credential is not issued. Furthermore, since the PSCs are only attainable after depositing NYM as payment, the Quorum has the authority to withhold the deposited NYMs as a punitive measure for any detected instances of double-spending.

documentation/docs/src/ecash/rerandomise.md

@@ -0,0 +1,47 @@
+# Rerandomisation & Incremental Spend
+
+Each zkNym generated by the Generator will not be valid for the entire amount of data that the credential aggregated from the PSCs is; if the aggregated credential is worth (e.g.) 10GB of Mixnet data, each zkNym created by the Generator will be worth far less.
+
+```admonish info
+The functionality included in the following code block examples were added to the [nym-cli tool](../tools/nym-cli.md) for illustrative purposes only: this is not necessarily how credentials will be accessed in the future.
+
+**Furthermore, the `nym-cli` uses the words 'tickets' in place of 'zkNyms' and 'ticketbook' in place of 'aggregated credential': this was WIP internal wording that we are moving away from now.**
+
+The numbers used in this high level overview are for illustration purposes only. The figures used in production will potentially vary. Note that individual zkNym sizes will be uniform across the Network.
+```
+
+This is to account for the need for a client to change their ingress Gateway, either because the Gateway itself has gone down / is not offering the required bandwidth, or because a user might simply want to split their traffic across multiple Gateways for extra privacy.
+
+In order to accomodate this then each generated zkNym will be worth a far smaller amount than the aggregated credential fed into the zkNym Generator. A single aggregated credential worth (e.g.) 10GB of data might be split into 100MB zkNym chunks. This means that clients are not tied to particular Gateways they have 'spent' their entire subscription amount with; if the ingress Gateway goes down, or the client simply wishes to use another ingress Gateway, the user has multiple other zkNyms they can use that account for their remaining purchased bandwidth.
+
+Going back to the `nym-cli` tool to illustrate this; we can generate multiple unlinkable zkNyms ('tickets' on this command output) from a single aggregated credential ('ticketbook' below):
+
+```
+❯ ./nym-cli ecash generate-ticket --credential-storage storage.db --provider 6qidVK21zpHD298jdDa1RRpbRozP29ENVyqcSbm6hQrG --full
+TICKETBOOK DATA:
+4Ys9pzUf9MPxX4s5RASyrRoY9fPk1a1kFuPBP2jm2L5PyUy535yPEfjHAfpUTC1Lf2d155TmjukvcDycQYfBSDfhEUJM4J3qPNfG3B5aQEEkefESZp3CM5AEnAu1AEyhpepbYw6BuXokiNcmaYtq3yJQbA4KicKP8FowoRzKHmXpJoUqY8wYQughGfdtXgr3rVaZmK21X51P1NL2UW1aCE512WWfy6P1LJHByWywT3qVw28Z83
+
+generating payment information for 50 tickets. this might take a while!...
+AVAILABLE TICKETS
++-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------+
+| index | binary data                                                                                                                                                   | spend status       |
++============================================================================================================================================================================================+
+| 0     | 4kgKyJLq1zQuk9r9AbEFHPqD8mDuxsLSjgo9XW4Lf7EqGSbgfNsWSEcTbRPEMFLzpstbX5azsA3opFh851h4g5qCG2qE3Luwqua4GG2ebJhk91rvEc5JPctbVQxL62fkfQ6svdcNp…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 1     | 4kefQqViRZd5YezMHH1FTcgUGPK2E2ivfmwgf59exvsnR8tsb5aJtGVwpA7wAJT6icPeo8jtDwDZ3WMPJxL3VRLiakAQr79zh7ixM89gowg3ChHEy6ewmHcT7T6RFkZFsMCMj1CNd…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 2     | 4kxaKdBxyFzJ8gxSZCh1v3wBfN7JvnCJuoJ4MWqkkMHtt2XgRKbDmHCv5ZxtA57Qk8LC3NDMBmqjADvY34mAPdT3tLBL4uxse9ASa227Ji96dwgxvfbpvLXSSr5o4vuPRV9K7UfpJ…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 3     | 4kdYwUJwXyxZBLQXextd4GsU2MATjzArVq5Ec459fTXyrm6q3vxurWULzBMpV5UjcmjJtnw1zFqt7f8Ydu5gyxwAVXP3Nwpn83ouguv2n4YrUewZCvFAqQYXgahhhaQGp6RxK2Arh…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+...
+
+| 46    | 4kg8bfQ7kGgq5TkkqXagpAEu95gmGT4i7NKbaxJtp2gRgWRrQZM1rxaDAzAxfghoM6PFNbYgKsnLD4MF8HtXW3p92CnPBjswzJ1EbtsMGpgDER3CYFt2ivAhMAVXFziF5UjVJXhpa…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 47    | 4kipbH5Fqt5E9hFMynm9vzFh5FkxKRdHrSEiiJWDwmg3mASctR61sXoFD5u5ZMBwGdvz9sWsRfrpR4MX2NNfRhC85aUxqtkAv3hXZiCLtE1pUC54Cq7YXHyv2XTNKpvuFZs2GmwYg…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 48    | 4kxYZ26HXvxVhh4quHXeCUyQokydeF5wkwUi8fMx6P3uoMvuiPaNP1SJTbYnaQEFFtF6U4dGop6QckUYvbtwQFoGJTJesHFHTDtHbshj5Dg8DwbyaHuAR86zGwYMUPved4XKUTMLa…1057bytes remaining | NOT SPENT |
+|-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------|
+| 49    | 4kb6zmPebRxjKLVicctq2whvANjWJMoohiPBMr21cT4xj78nvXmJEK8EB4PpqQVFo6ddU9uzuer5ggQZNZgETX2VXBzymBYNzXBuXjLJi1WRdAiASqWz5Hv5im1TJh4XBE4mxKo8Q…1057bytes remaining | NOT SPENT |
++-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------+
+```

documentation/docs/src/ecash/unlinkability.md

@@ -0,0 +1,36 @@
+# zkNym Unlinkability
+Each time a credential is requested by an ingress Gateway to prove that a client has purchased data to send through the Mixnet, the zkNym Generator will provide a new, unlinkable zkNym. This is a rereandomised value that is able to be verified as being legitimate (in that it was created by feeding a valid root credential into the Generator) but **not linked to any other zkNyms**, either previously generated or to be generated in the future.
+
+```admonish info
+The functionality included in the following code block examples were added to the [nym-cli tool](../tools/nym-cli.md) for illustrative purposes only: this is not necessarily how credentials will be accessed in the future.
+
+**Furthermore, the `nym-cli` uses the words 'tickets' in place of 'zkNyms' and 'ticketbook' in place of 'aggregated credential': this was WIP internal wording that we are moving away from now.**
+
+TODO ONCE THESE DOCS ARE GOOD TO GO, CHANGE NYM-CLI ARGS IN SAME PR
+```
+
+```
+❯ ./nym-cli ecash generate-ticket --credential-storage storage.db --provider 6qidVK21zpHD298jdDa1RRpbRozP29ENVyqcSbm6hQrG --ticket-index=3
+TICKETBOOK DATA:
+4Ys9pzUf9MPxX4s5RASyrRoY9fPk1a1kFuPBP2jm2L5PyUy535yPEfjHAfpUTC1Lf2d155TmjukvcDycQYfBSDfhEUJM4J3qPNfG3B5aQEEkefESZp3CM5AEnAu1AEyhpepbYw6BuXokiNcmaYtq3yJQbA4KicKP8FowoRzKHmXpJoUqY8wYQughGfdtXgr3rVaZmK21X51P1NL2UW1aCE512WWfy6P1LJHByWywT3qVw28Z83
+
+attempting to generate payment for ticket 3...
+
+PAYMENT FOR TICKET 3:
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
+```
+
+Now lets generate another zkNym to spend either topping up once the previous one's data allowance has been used, or with another Gateway. Notice that the `ticket-index` is the same: this is generated from the same aggregated credential as the one above!
+
+```
+❯ ./nym-cli ecash generate-ticket --credential-storage storage.db --provider 6qidVK21zpHD298jdDa1RRpbRozP29ENVyqcSbm6hQrG --ticket-index=3
+TICKETBOOK DATA:
+4Ys9pzUf9MPxX4s5RASyrRoY9fPk1a1kFuPBP2jm2L5PyUy535yPEfjHAfpUTC1Lf2d155TmjukvcDycQYfBSDfhEUJM4J3qPNfG3B5aQEEkefESZp3CM5AEnAu1AEyhpepbYw6BuXokiNcmaYtq3yJQbA4KicKP8FowoRzKHmXpJoUqY8wYQughGfdtXgr3rVaZmK21X51P1NL2UW1aCE512WWfy6P1LJHByWywT3qVw28Z83
+
+attempting to generate payment for ticket 3...
+
+PAYMENT FOR TICKET 3:
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
+```
+
+These are both generated by the _same_ underlying credential fed into the zkNym Generator and verified and used in a way that they cannot be tied to each other. An ingress Gateway might (for instance) get 100 connection requests from 100 Nym clients, each validated with a zkNym. It has no way of knowing whether these are all zkNyms from the same single subscription, or 100 different ones.

documentation/docs/src/ecash/what-are-zknyms.md

@@ -0,0 +1,51 @@
+# What are zkNyms?
+
+The zkNym scheme enables the creation and use of unlinkable, rerandomisable anonymous access credentials that are 'spent' with Gateways in order to anonymously prove that someone has paid for Mixnet access. This implementation incorporates elements of both the [Coconut Credential](./coconut.md) and [Offline Ecash](https://arxiv.org/pdf/2303.08221) schemes.
+
+As outlined in the [overview](./zknym-overview.md) on the next page, zkNyms allow for users to pay for Mixnet access in a manner that is **unlinkable to their payment account**; even with pseudonymous cryptocurrencies, or fiat. This solves one of the fundamental privacy problems with the majority of VPNs and dVPNs in production today: the linkability of a user's session with their payment information, which can in the majority of cases be easily used to deanonymise them, either at the behest of an authority or by the service operators themselves.
+
+> The current zkNym scheme is non-generic in that it is only used for gating Mixnet access. A generic scheme based on zkNyms is being actively researched in order to facilitate more generic and customisable anonymous credentials for other applications and services.
+
+## Motivations
+This scheme lets application programmers who are concerned with resource access control to think and code in a new way.
+
+Most of the time, when we build system security, we think of _who_ questions:
+
+- Has Alice identified herself (authentication)?
+- Is Alice allowed to take a specific action (authorisation)?
+
+This fundamentally changes these questions. Rather than asking _who_ a user is, it allows application designers to ask different questions, mostly centered around questions of _rights_:
+
+- Does the entity taking this action have a right to do X?
+
+This allows a different kind of security. Many of the computer systems we talk to every day don't need to know _who we are_, they only need to know if we have a _right to use_ the system. The credentials are generated cooperatively by decentralised, trustless systems.
+
+Once the credentials are generated, they can be _re-randomized:_ entirely new credentials, which no one has ever seen before, can be presented to the ingress point of the Nym Network, and validated without being linkable back to the signatures produced by the Quorum of credential signers.
+
+These properties allow zkNyms to act as something like cryptographic bearer tokens generated by decentralised systems. The tokens can be mutated so that they are not traceable, but still verified with the original permissions intact.
+
+Users present cryptographic claims encoded inside the credentials to get secure access to resources despite the systems verifying credential usage not being able to know who they are.
+
+### Re-randomisation vs pseudonymity
+We stand on the shoulders of giants. Ten years ago, Bitcoin showed the way forward by allowing people to control resource access without recourse to _who_ questions. Rather, in Bitcoin and succeeding blockchains, a private key proves a _right to use_.
+
+But as we can now see, private keys in blockchain systems act only as a minor barrier to finding out _who_ is accessing resources. A Bitcoin or Ethereum private key is effectively a long-lived pseudonym which is easily traceable through successive transactions.
+
+**zkNyms allows us to build truly private systems rather than pseudonymous ones.**
+
+## Features
+Just like normal credentials, zkNyms can be signed with a secret key and later verified by anybody with the correct public key. They also have additional superpowers when compared to "normal" signature schemes like RSA or DSA.
+
+Specifically, it is an implementation of a blinded, re-randomizable, selective disclosure threshold credential signature scheme.
+
+Let's say you have a `message` with the content `This credential controls X` in hand. In addition to the normal `sign(message, secretKey)` and `verify(message, publicKey)` functions present in other signature schemes, Coconut adds the following:
+
+1. _[Blind signatures](https://en.wikipedia.org/wiki/Blind_signature)_ - disguises message content so that the signer can't see what they're signing. This defends users against signers: the entity that signed can't identify the user who created a given credential, since they've never seen the message they're signing before it's been _blinded_ (turned into seemingly random binary data). The scheme uses zero-knowledge proofs so that the signer can sign confidently without seeing the unblinded content of the message.
+
+2. _Re-randomizable signatures_ - take a signature, and generate a brand new signature that is valid for the same underlying message `This credential controls X`. The new bitstring in the re-randomized signature is equivalent to the original signature but not linkable to it. So a user can generate multiple zkNyms from a single credential source, unlinkable to any previous "shown" zkNym. But the underlying content of the re-randomized credential is the same (including for things like double-spend protection). This once again protects the user against the signer, because the signer can't trace the signed message that they gave back to the user when it is presented. It also protects the user against the relying party that accepts the signed credential. The user can generate multiple re-randomized credentials repeatedly, and although the underlying message is the same in all cases, there's no way of tracking them by watching the user present the same credential multiple times.
+
+3. _Selective disclosure of attributes_ - allows someone with the public key to verify some, but not all, parts of a message. So you could for instance selectively reveal parts of a signed message to some people, but not to others. This is a very powerful property of the scheme which is to be explored more in future work, potentially leading to diverse applications: voting systems, anonymous currency, privacy-friendly KYC systems, etc.
+
+4. _[Threshold issuance](https://en.wikipedia.org/wiki/Threshold_cryptosystem)_ - allows signature generation to be split up across multiple nodes and decentralized, so that either all signers need to sign (_n of n_ where _n_ is the number of signers) or only a threshold number of signers need to sign a message (_t of n_ where _t_ is the threshold value).
+
+Taken together, these properties provide privacy for applications when it comes to generating and using signatures for cryptographic claims. If you compare it to existing tech, you might think of it as a sort of supercharged decentralized privacy-friendly [JWT](https://jwt.io/).

documentation/docs/src/ecash/zknym-overview.md

@@ -0,0 +1,53 @@
+# zkNym Generation and Usage: High Level Overview
+
+```admonish info
+Access to the Mixnet is - at the time of publication - free for everyone. However, soon™ it will be required for each connecting client to present a valid credential - a zkNym - to their ingress Gateway to access the Mixnet. This document outlines the payment flow and zkNym generation for zkNyms.
+
+zkNym access will vary depending on use:
+- individual developers will have access to something like a faucet for credentials.
+- larger application integrations will have their own 'under the hood' credential generation and distribution scheme for importing credentials into apps automatically.
+- and NymVPN users will have a variety of payment methods avaliable to them.
+_More on this soon_.
+```
+
+Generation of zkNyms involves the following actors / pieces of infrastructure:
+- [NymAPI](https://nymtech.net/operators/nodes/nym-api.html) instances working together on Distributed Key Generation, referred to as the **NymAPI Quorum**. Members of the Quorum are a subset of the Nyx chain Validator set, and are part of a multisig used for triggering reward payouts to the Network Infrastructure Node Operators.
+- **zkNym Requester** represented by a Bech32 address on the Nyx blockchain. This Requester might be a single user using the NymVPN app, or represent a company purchasing zkNyms to distribute to their application users, in the instance of an app integrating a Mixnet client via one of the SDKs.
+- **OrderAPI**: an API creating crypto/fiat <> NYM swaps and then depositing NYM in a smart contract managed by the NymAPI Quroum for payment verification. Implementation details of the API will be released in the future.
+
+Generation happens in 3 distinct stages:
+- Key Generation & Payment
+- Deposit NYM tokens & issue credential
+- Generate unlinkable zkNyms for Nym Network access
+
+The vast majority of this - from the perspective of the Requester - happens under the hood, but results in the creation and usage of an **unlinkable, rerandomisable anonymous proof-of-payment credential** - a zkNym - with which to access the Mixnet without fear of doxxing themselves via linking app usage and payment information. The user experience is further enhanced by the fact that a single credential can be split into multiple small zkNyms, meaning that a Requester may buy a large chunk of bandwidth but 'spend' this in the form of multiple zkNyms with different ingress Gateways. Whilst this happens under the hood, what it affords the Requester is an ease of experience in that they have to 'top up' their bandwidth less and are able to chop and change ingress points to the Nym Network as they see fit, akin to the UX of most modern day VPNs and dVPNs.
+
+TODO ADD A BIG DIAGRAM FOR EACH STAGE
+
+## Key Generation & Payment
+- A Cosmos [Bech32 address](https://docs.cosmos.network/main/build/spec/addresses/bech32) is created for the Requester.
+This is used to identify themselves when interacting with the OrderAPI via signed authentication tokens. This is the only identity that the OrderAPI is able to see, and is not able to link this to generated zkNyms. This identity never leaves the Requester’s device and there is no email or any personal details needed for signup. If a Requester is simply 'topping up' their subscription, the creation of the address is skipped as it already exists.
+- The Requester can then interact with various payment backends to pay for their zkNyms with non-NYM crypto, fiat options, or natively with NYM tokens.
+- Payment options will trigger the OrderAPI. This will:
+  - Create a swap for <PAYMENT_AMOUNT> <> NYM tokens.
+  - Deposit these tokens with the NymAPI Quorum via a CosmWasm smart contract deployed on the Nyx blockchain.
+- The Requester generates an ed25519 keypair: this is used to identify and authenticate them in the case of using zkNyms across several devices as an individual user. However, this is never used in the clear: these keys are used as private attribute values within generated credentials which are verified via zero-knowledge.
+- The Requester sends a request to each member of the Quorum requesting a credential. This request is signed with their private key and includes the transaction hash of the NYM deposit into the deposit contract, performed either by themselves or the OrderAPI. _(( TODO double check which keypair and make clear ))_
+
+## Deposit NYM & Issue zkNym
+- Once NYM tokens have been deposited into the contract controlled by the Quorum's multisig and a credential is requested, each member of the Quroum performs several checks to verify the request is valid:
+  - They verify the signature sent as part of the request is valid and that the request was made in the last 48 hours.
+  - They verify that the amount requested matches the amount deposited in the transcation, the hash of which was signed and sent as part of the request.
+- Each member then creates a partial blinded signature - a 'partial signed credential' ('PSC') - from their fragment of the master key generated and split amongst them at the beginning of the Quroum in the initial DKG ceremony.
+  - The member also creates a `key:value` entry in their local cache with the transaction hash as the key, and the PSC + encrypted signature as the value. This is used later for zkNym validation and is cleaned after a predefined timeout.
+- These PSCs are given back to the Requester after setting up a secure channel via DH key ex., with each replying Quorum member also sending their public key for verification that the returned PSC was signed by them.
+
+> In other words, each member of the Quorum who responds to the Requester's request for a zkNym (since this is a threshold cryptsystem, not all members of the Quroum must respond to create a credential, only enough to pass the threshold) returns a PSC signed with part of the master key.
+
+- Once the Requester has received > threshold number of PSCs they can assemble them into a credential signed by the master key. The Requester never learns this master key (it is a private attribute) but the credential can be verified by the Quroum as being valid by checking for a proof that the credential's private attribute - the value of the master key - is valid.
+- This credential is fed into the Requester's local 'zkNym Generator'.
+
+## Access Network
+- The zkNym Generator is entirely offline and holds the credential created from the aggregated threshold PSCs returned from individual members of the Quorum. Each time an application requests an access credential, the Generator will provide an unlinkable and unique zkNym to the requesting ingress Gateway.
+- _((TODO add a point on what spend is in other terms))_
+- This zkNym is later presented to the Quorum by the Gateway that collected it, which is used to calculate reward percentages given to Nym Network infrastructure operators by the Quorum, with payouts triggered by their multisig wallet.