Bearer Tokens for Bitcoin: A Look at Cashu
summary
Cashew is a Chaumian e‑cash protocol built on Bitcoin and Lightning that issues bearer tokens by minting lightning sats into blind signatures via the Blind Diffie‑Hellman Key Exchange, then handing wallets JSON/B64 tokens (no accounts). Minting/melting is multi‑step: quote → lightning invoice → blinded outputs → unblinded signatures; tokens include mint URL, keyset ID and secrets. It supports pay‑to‑blinded‑key (ephemeral shared secrets to preserve unlinkability), a 31‑knot NUT API, and a proposed non‑interactive mint delegation for liveness; TEEs are suggested to prevent mint theft.
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chapters (15)
- 0:00Introduction
- 1:11Cashu tokens and cash analogy
- 2:35Cashu vs Bitcoin/Lightning
- 3:59Privacy guarantees
- 5:44Cashu protocol flow
- 8:33Minting with blinded signatures
- 12:23Cashu token anatomy
- 14:53Offline token transfers
- 15:38Locking to public keys
- 17:24Pay to blinded key
- 18:48Melting process and redemption
- 20:33Cashu future and delegation
- 24:19Mint failure recovery
- 25:27Learn and contribute
- 26:10Q&A
