01Wallets
Hold ecash on your phone.
Independent, open source, and free. Run a Cashu wallet on iOS, Android, or in the browser, and hold bearer tokens the way you hold cash.
Open source ecash for bitcoin.
Instant, bearer, peer-to-peer.
The protocol, in four parts.
Cashu is an open protocol for Chaumian ecash on bitcoin. Mints issue bearer tokens against Lightning, wallets hold them, and blind signatures keep a mint from tying the withdrawal to the spend that follows it. Every part of it is specified in public.
02Mints
Bitcoin in, bitcoin out.
Mints bridge Lightning and ecash. A blind signature lets a mint issue a token without learning who ends up holding it. Ecash is a claim on its mint, not a deposit.
03Spec
Every byte, in the open.
Cashu is documented in version-controlled NUTs. Read them, implement them, fork them, propose your own. Nothing about the protocol is held back.
04Tokens
Send money like a message.
Tokens are bearer strings of bitcoin. Instant, final, and small enough to fit anywhere text goes: a chat, a QR, an email, an HTTP header.
Eight implementations, one spec.
Active across Python, Rust, TypeScript, and Kotlin. The cashubtc organization hosts the spec, the SDKs, and the reference wallets.
Implementations
nutshellWallet & mint (opens in a new tab)cdkDev kit (opens in a new tab)cocoWallet toolkit (opens in a new tab)+ 5 more in the cashubtc org
cashubtc/nuts/nut-00.mdv0 (CBOR encoding)
// Cashu Token v4, CBOR encoding { "t": [{ "i": h'00ad268c4d1f5826',// keyset id "p": [{ "a": 64,// sats "s": h'02ab34c1…9c7cf1',// blinded signature "d": h'0248e1b9…5b73e4'// DLEQ proof }, { "a": 128,// sats "s": h'03c9f0a7…41ae7e', "d": h'0187bd42…62d4a6' }] }], "m": "https://mint.example.com", "u": "sat", "v": 4 }
In the press
Bypassing financial gatekeepers with Bitcoin
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Jack Dorsey wants WhatsApp rival to use Bitcoin
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The censorship-resistant Cashu protocol powering Cuba's financial revolution
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Cashu: a vision for a Bitcoin-powered ecash ecosystem
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