Clifford Christopher Cocks  (born 28 December 1950) is a British mathematician and cryptographer. In 1973, while working at the United Kingdom Government Communications Headquarters (GCHQ), he invented a public-key cryptography algorithm equivalent to what would become (in 1977) the RSA algorithm.
Clifford Christopher Cocks
28 December 1950
Prestbury, Cheshire, England, United Kingdom
|Education||Manchester Grammar School|
|Alma mater||University of Cambridge (BA)|
The idea was classified information and his insight remained hidden for 24 years, although it was independently invented by Ronald Rivest, Adi Shamir, and Leonard Adleman in 1977. Public-key cryptography using prime factorisation is now part of nearly every Internet transaction.
Cocks was educated at Manchester Grammar School and went on to study the Mathematical Tripos as an undergraduate at King's College, Cambridge. He continued as a PhD student at the University of Oxford, where he specialised in number theory under Bryan Birch, but left academia without finishing his doctorate.
Non-secret encryption Edit
Cocks left Oxford to join Communications-Electronics Security Group (CESG), an arm of GCHQ, in September 1973. Soon after, Nick Patterson told Cocks about James H. Ellis' non-secret encryption, an idea which had been published in 1969 but never successfully implemented. Several people had attempted creating the required one-way functions, but Cocks, with his background in number theory, decided to use prime factorization, and did not even write it down at the time. With this insight, he quickly developed what later became known as the RSA encryption algorithm.
GCHQ was not able to find a way to use the algorithm, and treated it as classified information. The scheme was also passed to the NSA. With a military focus, financial considerations, and low computing power, the power of public-key cryptography was unrealised in both organisations:
I judged it most important for military use. In a fluid military situation you may meet unforeseen threats or opportunities. ... if you can share your key rapidly and electronically, you have a major advantage over your opponent. Only at the end of the evolution from Berners-Lee [in 1989] designing an open internet architecture for CERN, its adaptation and adoption for the Arpanet ... did public key cryptography realise its full potential. -Ralph Benjamin
In 1977, the algorithm was independently invented and published by Rivest, Shamir and Adleman, who named it after their initials. There is no evidence of a hint or leak, conscious or unconscious, and Cocks has dismissed the idea. The British achievement remained secret until 1997.
Public revelation Edit
In 1987, the GCHQ had plans to release the work, but Peter Wright's Spycatcher MI5 memoir caused them to delay revealing the research by ten years. 24 years after its discovery, on 18 December 1997, Cocks revealed the GCHQ history of public-key research in a public talk. James Ellis had died on 25 November 1997, a month before the public announcement was made.
Identity-based encryption Edit
In 2001, Cocks developed one of the first secure identity-based encryption (IBE) schemes, based on assumptions about quadratic residues in composite groups. The Cocks IBE scheme is not widely used in practice due to its high degree of ciphertext expansion. However, it is currently one of the few IBE schemes which do not use bilinear pairings, and rely for security on more well-studied mathematical problems.
Awards and honours Edit
Cocks was made a Companion of the Order of the Bath in 2008 (the citation describes him as "Counsellor, Foreign and Commonwealth Office"). He was awarded an honorary degree from the University of Bristol in 2008, and an honorary Doctor of Science from the University of Birmingham in 2015.
With James Ellis and Malcolm Williamson, Cocks was honoured for his part in the development of public-key cryptography by the Institute of Electrical and Electronics Engineers (IEEE) in 2010 and by induction into the Cryptologic Hall of Honor in 2021.
Clifford Cocks is distinguished for his work in cryptography. He was the first to devise a practicable implementation of public key cryptography, and more recently a practicable scheme for identity based public key encryption. Such achievements have been fundamental in ensuring the security of the world's electronic communications, security that we now take for granted.
- Anon (2016). "Cocks, Clifford Christopher". Who's Who (online Oxford University Press ed.). Oxford: A & C Black. doi:10.1093/ww/9780199540884.013.U261614. (Subscription or UK public library membership required.)
- Anon (2015). "Mr Clifford Cocks CB FRS". London: Royal Society. Archived from the original on 17 November 2015.
- "Clifford Cocks Oration". University of Bristol. Archived from the original on 15 September 2008. Retrieved 4 November 2008.
- "Dr Clifford Cocks CB". University of Bristol. Retrieved 14 August 2011.
- New York Times article on GCHQ's disclosure of the work of Cocks and Williamson
- Cocks, Clifford (2001). "An Identity Based Encryption Scheme Based on Quadratic Residues". Cryptography and Coding. Lecture Notes in Computer Science. Vol. 2260. Springer. pp. 360–363. doi:10.1007/3-540-45325-3_32. ISBN 978-3-540-43026-1.
- In conversation with Clifford Cocks
- "James Ellis' account of the invention of non-secret encryption". Archived from the original on 10 June 2003. Retrieved 10 June 2003.
- "The Open Secret". Wired. Archived from the original on 26 March 2023.
- GCHQ pioneers on birth of public-key crypto
- Cocks, C. C. (20 November 1973). "Note on "Non-Secret Encryption"" (PDF). GCHQ. Archived from the original (PDF) on 2018-09-28.
- U.S. Patent 6,731,755
- Wired article on public-key cryptography at GCHQ
- Simon Singh (1999). The Code Book: The Secret History of Codes and Code-breaking. Fourth Estate. ISBN 1-85702-879-1.
- Clifford Cocks's results at International Mathematical Olympiad
- In conversation with Clifford Cocks
- "New Year Honours—United Kingdom" (PDF). The London Gazette. 28 December 2007. Retrieved 7 March 2008.
- "Honorary degrees awarded". University of Bristol. Retrieved 7 March 2008.
- "Honorary Graduates of the University of Birmingham since 2000" (PDF).
- IEEE honours GCHQ public-key crypto inventors
- "Mr Clifford Cocks CB FRS". Royal Society. Archived from the original on 24 September 2015.
- Anon (2015). "Certificate of election: EC/2015/07 Cocks, Clifford Christopher". London: royalsociety.org. Archived from the original on 7 May 2009. Retrieved 11 November 2019.