James H. Ellis

Ellis first proposed his scheme for "non-secret encryption" in 1970, in a (then) secret GCHQ internal report "The Possibility of Secure Non-Secret Digital Encryption".^[3] Ellis said that the idea first occurred to him after reading a paper from World War II by someone at Bell Labs describing the scheme named Project C43,^[1] a way to protect voice communications by the receiver adding (and then later subtracting) random noise.^[4]

Clifford Cocks and Malcom Williamson, two other GCHQ cryptographers, furthered Ellis' initial PKC related work. As all of this work prior to 1997 was classified, it never became part of very significant mainstream initiatives that developed into modern PKC commercial endeavors, such as the work on Diffie–Hellman key exchange, RSA and other PKC linked initiatives which have become part of the modern world of Internet security.^[5]

On 18 December 1997, Clifford Cocks delivered a public talk which contained a brief history of GCHQ's contribution to PKC.^[6] In March 2016, Robert Hannigan, the director of GCHQ made a speech at MIT re-emphasising GCHQ's early contribution to public-key cryptography and in particular the contributions of Ellis, Cocks and Williamson.^[2][7]

• James Ellis' account of the invention of non-secret encryption at the Wayback Machine (archived 10 June 2003)
• Ellis, J.H., The possibility of secure non-secret digital encryption Archived 7 March 2016 at the Wayback Machine, CSEG Report 3006, January 1970.
• Ellis, J.H., The possibility of secure non-secret analogue encryption Archived 16 March 2016 at the Wayback Machine, CSEG Report 3007, May 1970.