Chaum's blind signature makes the first usable blueprint for anonymous money

AUG 22 1983 · 12:00

Video: Blind signature | Untraceable Payments Date: 1983-01-01 · Type: precursor · Tags: david-chaum, blind-signatures, digital-cash, cryptography, crypto-82, anonymous-payments, 1983 A bank can sign a token without seeing its serial number — the moment the math becomes specific enough to build. A year after he had taught the network how to forget, Chaum returned with a way for it to forget money. The blind signature is a cryptographic sleight: a bank can sign a token without seeing its serial number, so the depositor can later spend it as proof of value while the bank is structurally unable to link withdrawal to payment. The four-page Crypto '82 paper — presented at the second annual Crypto conference in Santa Barbara in August 1982, published in the Springer-Verlag proceedings in 1983 — is not the first piece of digital-cash thinking, but it is the first usable one. The mechanism works by the depositor blinding a token before submitting it for signature: the bank signs the blinded version, the depositor unblinds it, and the resulting signed token is valid but unlinkable. Payment without surveillance. The properties Chaum claimed were precise: untraceability of payee, time, and amount; the ability to prove payment when disputed; the ability to revoke tokens reported stolen. The four pages contain the seed of the entire anonymous-payment literature that follows. Every later electronic-cash scheme sits on top of it — DigiCash's ecash, Hashcash as a collateral implementation of proof-of-work value, and, by genealogy, the Bitcoin whitepaper, which cited Chaum in Satoshi's early forum posts even as the final text acknowledged him more obliquely. The boldest thing about the blind signature paper wasn't the cryptographic trick; it was the decision to treat untraceability as a design requirement rather than a regrettable side effect. Facts • Presented at Crypto '82, UC Santa Barbara, August 1982; proceedings published 1983 by Plenum/Springer-Verlag, pp. 199–203 • Co-editors of proceedings: Chaum, Ronald L. Rivest (RSA), and Alan T. Sherman • Properties claimed: untraceability of payee/time/amount, provable payment, stolen-token revocation • US Patent 4,759,063 (1988), assigned to Chaum • Satoshi Nakamoto cited Chaum as a named precedent in early Bitcoin forum posts Primary Documents • Blind Signatures for Untraceable Payments — Springer — https://link.springer.com/chapter/10.1007/978-1-4757-0602-4_18 • Full text — Satoshi Nakamoto Institute — https://nakamotoinstitute.org/library/blind-signatures/