Chaumian ecash is a form of digital cash, invented by David Chaum, that uses blind signatures to issue bearer tokens redeemable at a central mint while preserving payer privacy. The mint signs blinded token requests so it cannot link issued tokens to the users who later spend them, providing strong untraceability with offline-style bearer transfer. It matters as the cryptographic foundation for privacy-preserving custodial payment systems, revived in Bitcoin through mints such as Cashu and Fedimint.
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- In operation a user obtains blindly signed tokens from a mint, then spends them with recipients who redeem or reissue them, with the mint unable to correlate issuance and redemption. The model reintroduces a trusted custodian for liquidity in exchange for strong privacy and instant, low-cost transfers layered over Bitcoin and Lightning.