The collaborative work of Clifford Cocks, James Ellis, and Malcolm Williamson at GCHQ resulted in the discovery of public key cryptography (PKC) in the early 1970s. Even though outside researchers subsequently made similar discoveries, the UK’s GCHQ did not make public the fact that Ellis, Cocks, and Williamson had “scooped” their outside counterparts until 1997.
Mr. Ellis proposed the possibility of PKC as early as 1970, and in 1973, he devised a public key system based on the difficulty of factoring integers. In 1974, Mr. Williamson made some revisions to the system, and Mr. Cocks designed protocols for its use.
The security of the global communication infrastructure is built on public key cryptography and the importance of PKC in enabling the modern world of secure banking, e-commerce, and encrypted messaging cannot be overstated. The invention of PKC alone was a major achievement, but all three of these mathematicians made numerous additional contributions to joint NSA/GCHQ cryptologic missions, including security support to warfighters.
Their work also helped build relationships with academic mathematicians.
Mr. Ellis passed away in 1997 and Mr. Williamson in 2015. Mr. Williamson and Mr. Cocks continued in service as consultants at GCHQ until 2015.