claude-dev-suite Cashu
Open-source Chaumian e-cash protocol for Bitcoin Lightning. Single mint operator (vs Fedimint's federated). Specs evolve via NUTs (github.com/cashubtc/nuts).
Mint reference: cashubtc/nutshell (Python).
Architecture
- Mint: one entity issuing Cashu notes.
- Wallet: holds notes, transacts.
- Lightning bridge: mint accepts/sends LN payments.
Lifecycle
Mint (deposit BTC → notes)
- Wallet asks mint for an LN invoice (specifying amount).
- Wallet pays invoice via LN.
- Mint signs blinded note(s) for the wallet (blind signing).
- Wallet now holds notes, has anonymity within mint.
Spend (intra-mint payment)
- Wallet A sends notes to Wallet B (any transport: NFC, QR, Nostr, email).
- Wallet B presents notes to mint, receives fresh notes (swap).
- Note serial numbers added to spent set; can't be spent again.
Melt (notes → LN)
- Wallet asks mint to pay an LN invoice using its notes.
- Mint pays invoice; consumes notes.
NUTs (specs)
Modular spec evolution:
- NUT-00 to NUT-04 — baseline mint, melt, swap, mint info.
- NUT-05 — melting (pay LN with notes).
- NUT-06 — mint info endpoint.
- NUT-07 — token state check.
- NUT-09 — restoring tokens from seed.
- NUT-10 — spending conditions (P2PK, htlc).
- NUT-11 — P2PK locked tokens.
- NUT-12 — DLEQ proofs.
- NUT-13 — MPP.
- ... (active development).
Privacy
- Within-mint: blind signatures hide deposit-to-withdrawal mapping.
- Across mints: no privacy gain (each mint sees its own ledger).
- LN gateway sees source/destination of LN payments.
Trust model
Single-mint trust:
- Mint operator can refuse to redeem (rugpull).
- Mint operator can refuse to honor melts.
- Users mitigate by keeping balances small / transient.
Compare to Fedimint's threshold trust — Cashu is simpler but more custodial-feeling.
Implementations
- nutshell (Python) — reference mint.
- cashu-ts — TypeScript wallet/mint.
- cashu-rs — Rust impl.
- cashu.me — web wallet.
- Minibits — mobile wallet.
- eNuts — mobile wallet (cross-platform).
- Macadamia — iOS-focused.
Use cases
- Spam-resistance for Nostr (zaps via Cashu).
- Micro-payments with no LN-channel overhead.
- Privacy-mode for service users.
- Streaming sats for content.
Lightning Address integration
Cashu mints often expose Lightning Addresses:
user@minturl.com → LNURL-pay → mint generates note for user
Compared to Fedimint
| Aspect | Cashu | Fedimint |
|---|---|---|
| Trust | Single mint | Federated multisig |
| Setup | Trivial (run one mint) | Multi-guardian setup |
| Privacy within mint | Yes (blind sigs) | Yes |
| Cross-mint atomic swaps | Possible | Possible (by design) |
| Mobile wallets | Many | Fedi (primary) |
Status
Beta production. Active development; new NUTs added regularly. Multiple mints in use globally (some open, some private).