Wei Dai (Chinese:戴维^[1] orChinese:戴伟^[2]) is acomputer engineer known for contributions to cryptography and cryptocurrencies. He developed theCrypto++ cryptographic library, created the b-money cryptocurrency system, and co-proposed theVMAC message authentication algorithm.

Dai graduated from theUniversity of Washington with a degree in computer science, just before creating b-money in 1998.^[3]

He is described as an "intensely private computer engineer".^[4] Wei Dai was a member of theCypherpunks,Extropians, and SL4 mailing lists in the 1990s. On SL4 he exchanged with people such asEliezer Yudkowsky,Robin Hanson,Nick Bostrom,Aubrey de Grey,Anders Sandberg,Eric Drexler,David Pearce,Hal Finney, and others in a nascentrationalist community.^[5]

Dai has contributed to the field ofcryptography and has identified criticalCipher Block Chaining (CBC) vulnerabilities affecting SSH2^[6] and the browserexploit againstSSL/TLS known asBEAST (Browser Exploit Against SSL/TLS).^[7][8]

Crypto++ is an open-sourceC++library that provides implementations of cryptographic algorithms. It was originally written by Dai and first released in 1995.^[9][10] In June 2015 Dai stepped away from the Crypto++ project to work on other projects, with the Crypto++ community continuing to maintain the project.^[11]

In 1998, Dai helped to spark interest incryptocurrencies^[12] with the publication of "b-money, an anonymous, distributed electronic cash system".^[13][14] In the paper, Dai outlines the basic properties of all modern day cryptocurrency systems: "...a scheme for a group of untraceable digital pseudonyms to pay each other with money and to enforce contracts amongst themselves without outside help".^[15][16]

VMAC is a block cipher-basedmessage authentication code (MAC) algorithm using a universal hash proposed by Ted Krovetz and Wei Dai in April 2007. The algorithm was designed for high performance backed by a formal analysis.^[17][18]

Described as "money which is impossible to regulate",^[19] Dai'sb-money described the core concepts later implemented inBitcoin^[20] and other cryptocurrencies:

• Requires a specified amount of computational work (akaProof of work).
• The work done is verified by the community who update a collective ledger book.
• The worker is awarded funds for their effort.
• Exchange of funds is accomplished by collective bookkeeping and authenticated with cryptographic hashes.
• Contracts are enforced through the broadcast and signing of transactions with digital signatures (i.e.,public key cryptography).

Wei Dai andAdam Back were the first two people contacted bySatoshi Nakamoto as he was developingBitcoin in 2008^[4] and the b-money paper was referenced in the subsequent Bitcoin whitepaper.^[21]

In a May 2011 article, noted cryptographerNick Szabo stated:

Myself, Wei Dai, andHal Finney were the only people I know of who liked the idea (or in Dai's case his related idea) enough to pursue it to any significant extent until Nakamoto (assuming Nakamoto is not really Finney or Dai).^[22]

However, Dai questions b-money's influence on Bitcoin:

...my understanding is that the creator of Bitcoin, who goes by the name Satoshi Nakamoto, didn't even read my article before reinventing the idea himself. He learned about it afterward and credited me in his paper. So my connection with the project is quite limited.^[23]

There has been much speculation as to the identity of Satoshi Nakamoto, with suspects including Wei Dai himself,Nick Szabo, andHal Finney, all of whom have denied the putative identification.^{[24][25][12][26]}

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