A cryptographic system for untraceable payments was first described by David Chaum in 1982.[6] In 1990 Chaum extended this system to create the first cryptographic anonymous electronic cash system.,[7] which became known as ecash. [8] In 1998 Wei Dai published a description of an anonymous, distributed electronic cash system which he called "b-money".[9] Around the same time, Nick Szabo created bit gold.[10][11] Like Bitcoin, Bit gold was a currency system where users would compete to solve a proof of work function, with solutions being cryptographically chained together and published via a distributed property title registry. A variant of Bit gold, called Reusable Proofs of Work, was implemented by Hal Finney.[11]
In 2008, Satoshi Nakamoto published a paper[12][13] on The Cryptography Mailing list at metzdowd.com[14] describing the Bitcoin protocol.