Adam Back

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Adam Back
Born Adam Back
July 1970 (age 46)
London, England, UK
Residence Sliema, Malta
Nationality British
Occupation Cryptographer
Known for hashcash

Adam Back (born July 1970) is a British cryptographer and crypto-hacker.

He is the inventor of hashcash, the proof-of-work system used by several anti-spam systems which inspired a similar system in bitcoin. Hashcash has also been used in a number of other protocols such as combating blog spam,[1] and defending against user namespace pollution.[2]

He implemented credlib,[3] a library that implements the credential systems of Stefan Brands and David Chaum.

He was the first to formalize the Non-Interactive Forward-Secrecy[4] 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 pioneering the use of ultra-compact code with his 3-line RSA in Perl[5] signature file and non-exportable T-shirts[6] to protest the (now relaxed) United States cryptography export regulations.

Today he is President of Blockstream, a company that seeks to further the development of bitcoin and blockchain technology.[7]

He has a computer science Ph.D. from University of Exeter.

See also[edit]


  1. ^ " - blog plugins". 
  2. ^ "I2P's Threat Model". 
  3. ^ "credlib - Credential Library". 
  4. ^ "Non-Interactive Forward Secrecy". 
  5. ^ "export-a-crypto-system sig". 
  6. ^ "Munitions T-shirt". 
  7. ^ "Blockstream". 

External links[edit]