Clifford Cocks

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Clifford Cocks
Clifford Cocks in 2015, portrait via the Royal Society
Born Clifford Christopher Cocks
(1950-12-28) 28 December 1950 (age 64)[citation needed]
Prestbury, Cheshire, United Kingdom
Nationality British
Fields Cryptography
Alma mater University of Cambridge (BA)
Known for
Notable awards

Clifford Christopher Cocks CB[2] FRS[1] (born 28 December 1950[3][4]) is a British mathematician and cryptographer at Government Communications Headquarters (GCHQ). He discovered the widely used encryption algorithm now commonly known as RSA, about three years before it was independently rediscovered by Ronald Rivest, Adi Shamir, and Leonard Adleman at MIT which won them the Turing Award in 2002. He has not been generally recognised for this achievement because his work was classified information, and therefore not released to the public at the time.[5][6]


Cocks was educated at Manchester Grammar School[citation needed] and went on to study the Mathematical Tripos as an undergraduate at King's College, Cambridge. He continued as a postgraduate student[citation needed] at the University of Oxford, where he specialised in number theory.

Career and research[edit]

Cocks left Oxford to join CESG, an arm of GCHQ, in September 1973. At GCHQ, Cocks was told about James H. Ellis' "non-secret encryption",[7] an idea which had been suggested in the late 1960s but never successfully implemented. Cocks was intrigued, and in 1973 he developed what later became known as the RSA encryption algorithm.[8][9] GCHQ appears not to have been able to find a way to use the algorithm, and in any case, treated it as classified information. In 1977 the algorithm was independently rediscovered and published by Rivest, Shamir, and Adleman, who named it after their initials, but Cocks' prior achievement remained secret until 1997.[10]

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.

As of 2003, Clifford Cocks held the post of Chief Mathematician at GCHQ.

Awards and honours[edit]

In 1968, Cocks won Silver at the International Mathematical Olympiad.[11] Cocks was elected a Fellow of the Royal Society (FRS) in 2015,[12] his certificate of election reads:

Cocks was made a Companion of the Order of the Bath in 2008 (the citation describes him as "Counsellor, Foreign and Commonwealth Office"),[2] and was awarded an honorary degree from the University of Bristol in 2008.[13]


  1. ^ a b c "Certificate of election: EC/2015/07 Cocks, Clifford Christopher". London: The Royal Society. Archived from the original on 2015-09-24. 
  2. ^ a b "New Year Honours—United Kingdom" (PDF). The London Gazette. 2007-12-28. Retrieved 2008-03-07. 
  3. ^ "Clifford Cocks Oration". University of Bristol. Archived from the original on 2008-09-15. Retrieved 2008-11-04. 
  4. ^ "Dr Clifford Cocks CB". Bristol University. Retrieved 2011-08-14. 
  5. ^ Cocks, Clifford (2001). "An Identity Based Encryption Scheme Based on Quadratic Residues". Cryptography and Coding. Lecture Notes in Computer Science 2260. Springer. pp. 360–363. doi:10.1007/3-540-45325-3_32. 
  6. ^ New York Times article on GCHQ's disclosure of the work of Cocks and Williamson
  7. ^ James Ellis' account of the invention of non-secret encryption at the Wayback Machine (archived June 10, 2003)
  8. ^ Cocks' November 1973 internal GCHQ note on his discovery
  9. ^ U.S. Patent 6,731,755
  10. ^ Wired article on public key cryptography at GCHQ
  11. ^ Clifford Cocks's results at the International Mathematical Olympiad
  12. ^ "Mr Clifford Cocks CB FRS". Royal Society. Archived from the original on 2015-09-24. 
  13. ^ "Honorary degrees awarded". University of Bristol. Retrieved 2008-03-07.