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A Goblin payment locks the sender's outputs until the recipient replies (S2) and we finalize+post. If the recipient never connects to nostr, the funds stay locked until the 24h auto-expiry. This adds a manual Cancel that reclaims them on demand (after a 10-min grace, or immediately if the send never reached a relay), marks the payment Cancelled, and best-effort voids it to the recipient. - WalletTask::NostrCancelSend: authoritative tx lookup; refuses if already finalized/confirmed (race); marks meta Cancelled BEFORE cancelling the grin tx; serialized with nostr_finalize_post via a per-service lock so a cancel and a concurrent S2 finalize can't both commit. - nostr_finalize_post returns Ok(false) (skip, no retry/re-post) when the tx is cancelled or the meta is Cancelled — covers the tx-list cancel path too. - decide() already drops a late S2 on a Cancelled meta (new unit tests assert it); recipient-side void marks a received payment Cancelled for display WITHOUT deleting the output (a malicious sender could void-then-post otherwise). - Void-before-S1 ordering handled via a (slate,sender)-bound marker. - Receipt: tap-twice 'Cancel payment' with caveat + outcome notice; honest 'Waiting for X to receive…' label; first-class Cancelled status. 6 locales. - cancel_grace_secs config (default 600).
Goblin
Goblin is a private, Cash App-style wallet for GRIN ツ — confidential digital cash on Mimblewimble, with no amounts or addresses on the chain.
Instead of passing slatepack files back and forth, you pay a username (or an npub) and the payment is delivered for you as an end-to-end encrypted message over nostr, routed through the Nym mixnet. Relays only ever see ciphertext — never the amount, the sender, or the recipient — and the mixnet hides who is talking to whom at the network layer.
Goblin is a fork of the Grim egui GRIN wallet: it keeps Grim's full GRIN node/wallet engine and layers a Nostr-native, mobile-first payments experience on top.
What it does
- Send to people — pay a
usernameornpub; the GRIN slatepack travels as a NIP-17 gift-wrapped DM (kind 1059) over the Nym mixnet and is applied automatically by the recipient's wallet. No files to swap, no need to both be online at once. - Manual slatepacks too — when you need to pay or get paid without a handle, Settings → Wallet → Slatepacks exposes the classic by-hand flow: create a slatepack to send, or paste one to receive, finalize, or pay.
- In-app identity — a nostr payment key that is deliberately not part of your seed, so you can rotate it any time to stay unlinkable without touching your funds. An optional human-readable
name(and hosted avatar) comes from the goblin.st identity service. - Private by construction — GRIN's address-less, confidential chain; your payments and identity (nostr relays, NIP-05 lookups, price, avatars) are routed through the Nym mixnet, so who-pays-whom never touches the clear net. The GRIN node connection — block sync and broadcasting your transaction — is direct: public chain data, the same for everyone, and not tied to your identity. Keys, names and history stay on your device.
- Configurable amount pairing — show balances against a world currency, Bitcoin, or sats (rates fetched over the mixnet), or turn the preview off.
- Cross-platform — Linux, macOS, Windows, Android, built in pure Rust on egui.
How a payment travels
you ──slatepack──▶ NIP-17 gift wrap (kind 1059, NIP-44 encrypted)
│
Nym mixnet (5-hop)
│
┌─────────────┴─────────────┐
your relays recipient's DM relays (kind 10050)
└─────────────┬─────────────┘
▼
recipient ◀──unwrap, verify seal author, apply slatepack
The wrap is NIP-44-encrypted, and delivery uses the recipient's DM relay list (kind 10050).
Both parties only need one relay in common. The default set is the Goblin relay plus large public relays (relay.damus.io, nos.lol), and the set is editable in Settings → Relays.
Build
Desktop (Linux / macOS / Windows)
Goblin links the Nym mixnet SDK in-process — the wallet is a single self-contained binary, no sidecar. The SDK builds from a sibling ../nym checkout (a pinned nym tree with a small Android TLS patch):
git clone --branch goblin https://git.us-ea.st/GRIN/nym ../nym
git submodule update --init --recursive
cargo build --release
./target/release/goblin
Goblin's identity and payment traffic — nostr relays, NIP-05 lookups, price and avatar fetches — is routed over the mixnet through a network requester (the default is baked into NETWORK_REQUESTER in src/nym/sidecar.rs); the SDK's SOCKS5 listener is run in-process on 127.0.0.1:1080. If something is already listening there, Goblin reuses it. The GRIN node connection (block sync and transaction broadcast) is not mixed — it connects directly, as it carries only public chain data that isn't linked to your wallet.
Android
Install the Android SDK / NDK, then from the repo root:
./scripts/android.sh build|release v7|v8|x86
v7/v8/x86 is the device CPU architecture for build; for release pass a version in major.minor.patch form.
Identity service (goblin-nip05d)
The optional name + avatar service lives in goblin-nip05d/ (axum + SQLite) and is deployed at goblin.st. It implements NIP-05 resolution, NIP-98-authenticated registration/transfer/release, and a hardened avatar pipeline (magic-byte sniffing, bounded decode, full re-encode to a clean 256×256 PNG). The wallet is fully usable — and fully anonymous — without it.
License
Apache License v2.0.
Credits
🤖 Built with AI pair-programming assistance (Claude)
The underlying cross-platform GRIN wallet engine is the upstream Grim project.