Adam Back
BornJuly 1970 (age 52)
London, England, UK
EducationUniversity of Exeter
Scientific career
FieldsCryptographic protocols
Electronic cash
Privacy-enhancing technologies
Distributed systems
InstitutionsZero-Knowledge Systems
Pi Corporation
ThesisParallelization of general purpose programs using optimistic techniques from parallel discrete event simulation (1995)
Doctoral advisorStephen Turner

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.


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.

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, Adam spent his career as a consultant in start ups and larger companies in applied cryptography, writing cryptographic libraries, designing, reviewing and breaking other people's cryptographic protocols.[3]

Cryptography software

Back's "Munitions" T-shirt featured computer code that was considered to be a weapon in the United States.
Back's "Munitions" T-shirt featured computer code that was considered to be a weapon in the United States.

Back is a pioneer of early digital asset research similarly as 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 file and non-exportable T-shirts[19][20] to protest cryptography export regulations.[21]

Back was one of the first two people to receive an email from Satoshi Nakamoto.[22][2] In 2016, the Financial Times cited Back as a potential Nakamoto candidate, along with Nick Szabo and Hal Finney.[23] Craig Wright had sued Back for stating that Wright was not Nakamoto, with Wright subsequently dropping the suit.[2]

Back has promoted the use of satellites and mesh networks to broadcast and receive bitcoin transactions, as a backup for the traditional internet.[24]

Business career

On 3 October 2016, Back was appointed as CEO of Blockstream.[25]


  1. ^ Singh, Rachna (2019). The Bitcoin Saga: A Mixed Montage. Bloomsbury Publishing. ISBN 978-9388271837.
  2. ^ a b c Kharif, Olga (2 June 2020). "Latest Satoshi Nakamoto Candidate Buying Bitcoin No Matter What". Bloomberg. Retrieved 3 June 2020.
  3. ^ "Proof of Work - An interview with Adam Back (Blockstream)". Archived from the original on 15 December 2021.
  4. ^ Leising, Matthew (30 June 2018). "Is Bitcoin Creator Writing a Book? Cryptic Note Indicates Yes". Bloomberg. Retrieved 13 May 2020.
  5. ^ Bustillos, Maria (25 August 2015). "Inside the Fight Over Bitcoin's Future". New Yorker. Retrieved 13 May 2020.
  6. ^ Narayanan, Arvind; Bonneau, Joseph; Felten, Edward; Miller, Andrew; Goldfeder, Steven (2016). Bitcoin and Cryptocurrency Technologies: A Comprehensive Introduction. Princeton and Oxford: Princeton University Press. ISBN 978-0-691-17169-2.
  7. ^ Shaw, Jessica Marmor (8 January 2018). "Bitcoin and cryptocurrency on Twitter: The most important people to follow". Marketwatch. Retrieved 14 May 2020.
  8. ^ "Bitcoin: A Peer-to-Peer Electronic Cash System" (PDF).
  9. ^ Casey, Michael J. (22 October 2020). "BitBeat: Bitcoin Coding Allstars Launch Sidechains Project to Boost Innovation". WSJBlogs. Retrieved 14 May 2020.
  10. ^ Frisby, Dominic (2015). "Footnotes". Bitcoin: The future of money?. Unbound. ISBN 978-1783521029.
  11. ^ "credlib - Credential Library".
  12. ^ Boyd, Colin. "A Modern View on Forward Security" (PDF). IACR. Retrieved 14 May 2020.
  13. ^ Anderson, Ross (2002). "Two remarks on public key cryptology" (PDF). Cambridge University. Retrieved 14 May 2020.
  14. ^ "Non-Interactive Forward Secrecy".
  15. ^ Salomon, David (2003). "Secure Programming with Perl". Data Privacy and Security. Springer. p. 200. ISBN 9781441918161.
  16. ^ Judmayer, Aljosha; Stifter, Nicholas (2017). "Before bitcoin". Blocks and Chains: Introduction to Bitcoin, Cryptocurrencies, and Their Consensus Mechanisms (Synthesis Lectures on Information Security, Privacy, and Tru). Morgan & Claypool Publishers. p. 17. ISBN 9781627057165.
  17. ^ "export-a-crypto-system sig".
  18. ^ Sinn, Richard (2007). "Secure Programming with Perl". Software Security Technologies. Cengage Learning. p. 366. ISBN 9781428319455.
  19. ^ Blanchette, Jean-François (2012). "On the brink of revolution". Burdens of Proof: Cryptographic Culture and Evidence Law in the Age of Electronic Documents. MIT Press. p. 50. ISBN 978-0262017510.
  20. ^ "Munitions T-shirt".
  21. ^ Brunton, Finn (2019). "On the brink of revolution". Digital Cash: The Unknown History of the Anarchists, Utopians, and Technologists Who Created Cryptocurrency. Princeton Press. p. 97. ISBN 9780691179490.
  22. ^ RATLIFF, EVAN (16 July 2019). "Was Bitcoin Created by This International Drug Dealer? Maybe!". Wired. Retrieved 13 May 2020.
  23. ^ Kaminska, Izabella (7 May 2016). "Bitcoin: Identity crisis". Financial Times. Retrieved 4 June 2020.
  24. ^ del Castillo, Michael (17 December 2018). "Who Needs Verizon? Blockstream Broadcasts Entire Bitcoin Blockchain From Space". Forbes. Retrieved 13 May 2020.
  25. ^ Blockstream (3 October 2016). "Blockstream Appoints Hashcash Inventor Dr. Adam Back as CEO". PR News Wire. Retrieved 2020-12-05.