James Ellis
Born in Australia on the 25th September 1924, Ellis was to become a well-respected mathematician and computer scientist who joined GCHQ in 1952. He worked on a number of important cryptographic developments, but his identification of the concept of Public Key Cryptography (PKC) was the most significant and far reaching.
Ellis came up with the idea after reading a research paper written during WWII from Bell Laboratories which explored the concepts behind the protection of voice communications. Ellis, working closely with his GCHQ colleague Clifford Cocks, developed what became known as the RSA (Rivest-Shamir-Adleman) asymmetric key encryption algorithm, which was further taken forward by GCHQ mathematician Malcolm Williamson pioneering a process of key exchanges.
The discovery in 1973 remained classified for a long time and was, at first, only made available for official governmental communications. However, PKC was thought of independently and developed commercially, and is now the basis for all secure transactions on the internet.
Ellis died on the 25th November 1997 aged 73, ironically just a month before the public announcement of the GCHQ achievement was made.