Back is a pioneer of early digital asset research similar to
Wei Dai,
David Chaum, and
Hal Finney. In 1997, Back invented
Hashcash. A similar system is used in
Bitcoin. He also implemented
credlib, a library that implements the credential systems of
Stefan Brands and
David Chaum. He was the first to describe the "non-interactive forward secrecy" security property for email and to observe that any
identity-based encryption scheme can be used to provide non-interactive forward secrecy. He is also known for promoting the use of ultra-compact code with his 2-line and 3-line
RSA in Perl
signature block and non-exportable
T-shirts to protest
cryptography export regulations. Back has promoted the use of satellites and mesh networks to broadcast and receive bitcoin transactions, as a backup for the traditional internet.
Relationship to Satoshi Nakamoto Back was one of the first two people to receive an email from
Satoshi Nakamoto, the pseudonymous inventor of bitcoin.
Craig Wright had sued Back for stating that Wright was not Nakamoto, with Wright subsequently dropping the suit. The 2024
HBO documentary
Money Electric: The Bitcoin Mystery, directed by
Cullen Hoback, examined Back as its principal Satoshi Nakamoto suspect, with Hoback stating that "the evidence pointing in Adam's direction was a lot harder to poke holes in." The film noted that Back is the only person named in the body of the
Bitcoin white paper, and that Back's writing style resembles Nakamoto's. Hoback also highlighted Back's move to
Malta, his edits to Wikipedia's Bitcoin article that restored its Nakamoto section and listed other suspects but not himself, and his joining the Bitcoin forum on April 17, 2013, the same day the size of Nakamoto's holdings first became public. In an on-camera interview for the documentary, after Hoback listed him among the suspects, Back replied: "I thought you might think I'm Satoshi. And I don't want that to be on the record, really." == Business career ==