Computer scientist and cryptographer who created b-money (1998), one of the earliest digital currency proposals, and the Crypto++ cryptographic library. Satoshi Nakamoto emailed Dai on August 22, 2008, before publishing the Bitcoin white paper, which cites b-money as a foundational reference.
Wei Dai is a computer scientist and cryptographer known for two major contributions to the field: the b-money proposal for digital currency and the Crypto++ cryptographic library. He studied computer science at the University of Washington and worked at Microsoft.
b-money (1998): In November 1998, Dai published “b-money,” a proposal for an anonymous, distributed electronic cash system, on the cypherpunks mailing list. The b-money proposal described a system where participants could create money by broadcasting the solution to a computational puzzle — a concept conceptually similar to Bitcoin’s proof-of-work mining. The paper outlined two protocols: one requiring a synchronous broadcast channel, and another using a set of servers to keep track of balances. B-money was never implemented, but it became one of the key intellectual precursors to Bitcoin.
Crypto++: Dai created and maintained Crypto++, a free, open-source C++ library providing a comprehensive collection of cryptographic algorithms and schemes. The library is widely used in academic and commercial projects and remains one of the most respected cryptographic libraries available.
Satoshi’s First Contact: On August 22, 2008, Satoshi Nakamoto emailed Dai directly, writing that he was preparing to publish a paper expanding on Dai’s b-money ideas. Satoshi asked Dai for the year of b-money’s publication to properly cite it. This email, along with a similar one sent to Adam Back two days earlier, represents the earliest known evidence of Satoshi reaching out to existing cryptographers before publishing the Bitcoin white paper. The white paper, published on October 31, 2008, cites b-money as its first reference.
Later Correspondence: In January 2009, following Bitcoin’s launch, Dai and Satoshi exchanged further emails. Dai offered thoughts on Bitcoin’s design, noting both its similarities to and differences from b-money. Dai also made philosophical observations about the nature of money and cryptocurrency that demonstrated a deep understanding of the challenges involved.
Significance: Dai’s b-money proposal is one of the most direct intellectual predecessors to Bitcoin. Satoshi’s decision to contact Dai before publication, and the prominent citation of b-money in the white paper, underscores the degree to which Bitcoin built upon Dai’s earlier work. The unit “wei” in the Ethereum cryptocurrency was named in honor of Wei Dai.
10 entries
Wei Dai's announcement of Disperse/Collect version 1.0 on the Cypherpunks mailing list. This post explicitly references 'my own Crypto++ library,' confirming that Dai was not only a theorist but an active, prolific coder who built and shipped software. This context is essential for understanding why he later chose not to implement b-money.
Wei Dai's original announcement of b-money on the Cypherpunks mailing list. Notably, b-money was mentioned as a secondary item alongside PipeNet 1.1 — an anonymous routing protocol that was Dai's primary focus. The b-money proposal that would later inspire Bitcoin was introduced in a single sentence at the end of this post.
Wei Dai's reply to Adam Back on the Cypherpunks mailing list, discussing b-money's practical limitations. Dai acknowledged that 'b-money will at most be a niche currency/contract enforcement mechanism' and revealed a shift in his political views, stating 'I now tend to think that the government monopoly of force is a net benefit.'
Satoshi emails Wei Dai asking about the correct citation for b-money, revealing that he learned of b-money from Adam Back's reference. The email included a link to the pre-release draft 'Electronic Cash Without a Trusted Third Party' (ecash.pdf) hosted at upload.ae.
Wei Dai's comments on the LessWrong 'Making money with Bitcoin?' thread. He clarified that he did not create Bitcoin but 'only described a similar idea more than a decade ago' and that Satoshi independently reinvented the concept. He revealed purchasing a Radeon 5870 GPU for mining after this thread, and warned that 'not many other cryptographers have analyzed its security.'
Nick Szabo discusses why Bitcoin took so long to be invented, the similarities and differences between bit gold and Bitcoin, and why 'nearly everybody who heard the general idea thought it was a very bad idea.'
Wei Dai's comments on the LessWrong post 'Bitcoins are not digital greenbacks,' in which he argued that Bitcoin has 'failed with regard to its monetary policy' due to price volatility, and revealed that he never responded to Satoshi's 2008 email asking for comments — regretting that he 'could have dissuaded him (or them) from the fixed supply of money idea.'
Wei Dai's reflections on Satoshi Nakamoto and on why b-money was never implemented, from a LessWrong Q&A thread. Dai stated that Satoshi 'didn't even read my article before reinventing the idea himself,' and later explained that b-money 'wasn't a complete practical design yet' and that he had 'grown somewhat disillusioned with cryptoanarchy' by the time he finished writing it up.
Wei Dai's LessWrong post revealing that Satoshi Nakamoto emailed him personally in early 2009 announcing Bitcoin v0.1, but he ignored it because he 'was more interested in Less Wrong than Cypherpunks at that point.' He later started mining in 2011 after seeing a LW article, turning ~$300 into six figures.
Adam Back reflects on his August 2008 email exchange with Satoshi Nakamoto, his regret at not reading the Bitcoin whitepaper carefully, and his testimony during the COPA v. Wright trial where the complete email chain was made public.