Adam Back

Adam Back
Back in 2025
Born	July 1970 (age 55) London, England, UK
Alma mater	University of Exeter (PhD)
Scientific career
Fields	Cryptographic protocols Electronic cash Privacy-enhancing technologies Distributed systems
Institutions	Zero-Knowledge Systems Pi Corporation Blockstream
Thesis	Parallelization of general purpose programs using optimistic techniques from parallel discrete event simulation (1995)
Doctoral advisor	Stephen Turner
Website	cypherspace.org/adam

Adam Back (born July 1970) is a British cryptographer and cypherpunk. He is the CEO of Blockstream, which he co-founded in 2014. He invented Hashcash, which is used in the bitcoin mining process. Investigations by the Financial Times and The New York Times have suggested that he may be Satoshi Nakamoto, the pseudonymous inventor of bitcoin, though Back has repeatedly denied these allegations.

Back was born in London, England, in July 1970.^[1] His first computer was a Sinclair ZX81. He taught himself Basic, and spent his time reverse engineering video games, finding decryption keys in software packages. He completed his A levels in advanced mathematics, physics, and economics.^{[citation needed]}

He has a computer science PhD in distributed systems from the University of Exeter.^[2] During his PhD, Back worked with compilers to make use of parallel computers in a semi automated way. He became interested in PGP encryption, electronic cash and remailers. He spent two thirds of his time working with encryption. After graduation, Back spent his career as a consultant in startups and larger companies in applied cryptography, writing cryptographic libraries, designing, reviewing and breaking other people's cryptographic protocols.^[3]

Back is a pioneer of early digital asset research similar to Wei Dai, David Chaum, and Hal Finney.^[4][5] In 1997, Back invented Hashcash.^[6] A similar system is used in Bitcoin.^[7][8][9]

He also implemented credlib,^{[10][better source needed][11][better source needed]} a library that implements the credential systems of Stefan Brands and David Chaum.

He was the first to describe the "non-interactive forward secrecy"^[12][13][14] 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^[15] and 3-line RSA in Perl^[16][17][18] signature block and non-exportable T-shirts^[19][20] to protest cryptography export regulations.^[21]

Back has promoted the use of satellites and mesh networks to broadcast and receive bitcoin transactions, as a backup for the traditional internet.^[22]

Back was one of the first two people to receive an email from Satoshi Nakamoto, the pseudonymous inventor of bitcoin.^[23][2] In 2016, the Financial Times cited Back as a potential Nakamoto candidate, along with Nick Szabo and Hal Finney.^[24] Craig Wright had sued Back for stating that Wright was not Nakamoto, with Wright subsequently dropping the suit.^[2] In 2020, the YouTube channel Barely Sociable claimed that Back is Nakamoto. Back subsequently denied this.^[25]

In 2026, an investigation in The New York Times asserted that Back is Nakamoto, citing his use of certain less common phrases, shared niche interests, and the timing of Nakamoto’s final known communication and Back’s first public comment on Bitcoin, among other things. Back once again denied the allegation. Carreyrou concluded the article by demonstrating that while Back denied being Satoshi, he was unable to adequately explain a substantial amount of circumstantial evidence beyond categorical denial, and refused to provide the metadata attached to the e-mails he exchanged with Nakamoto. During an in-person interview, Back's body language at times appeared to contradict his denials, with his face reddening as he shifted uncomfortably when confronted with specific points. In one notable exchange, when Carreyrou raised a Satoshi quote stating "I'm better with code than with words," Back interrupted and responded as though speaking for himself, a slip that Carreyrou interpreted as Back accidentally responding as Satoshi.^[26][27]

On 3 October 2016, Back was appointed as CEO of Blockstream.^[28]

• Official website