James H. Ellis

James Henry Ellis ( born September 25, 1924 in Prestbury, † 25 November 1997) was a British engineer and cryptographer, the beginning of the 1970s an asymmetric cryptosystem proposed, which was not initially published for reasons of confidentiality.


Ellis parents came from Australia and he was born in England. He grew up in London and studied at Imperial College London Physics. After studying Ellis was first at the Post Office Research Station in northwest London worked and went in 1952 to the GCHQ to London Borough of Hillingdon. He stayed with the company and in 1965 moved their headquarters Cheltenham.

The idea

In symmetric cryptosystems, the key distribution is complex. In the late 1960s, therefore, the GCHQ asked his employee Ellis is a proposal to reduce costs. Ellis went to work. When studying literature, he came across Shannon's work Communication in the Presence of Noise (about: " communication with noise signals occurring "). After reading the article of this pioneer of the idea of the asymmetric key cryptography was born: The receiver has the message of the sender from the beginning a superposition of noise. Thus, the message is garbled. However, since the receiver can subtract its noise component afterwards, because he knows him very well, he alone can read the message.

Ellis, who was a mathematician, was not sure how he would implement his idea. The completed 1973-1974 two young mathematicians - Clifford Cocks and Malcolm Williamson. The work of three researchers at GCHQ initially remained secret. 1976 Diffie and Hellman published a preliminary work for public-key cryptography, which was known as the RSA cryptosystem, a year later. The GCHQ had Williamson 1976 prohibits publication.


  • Simon Singh: The Code Book. The Art of encryption from the ancient times to the age of the Internet. Translated from English by Klaus Fritz. With numerous black and white illustrations pp. 338-352. German Taschenbuch Verlag, Munich 2012 ( 11th Edition ), ISBN 978-3-42333071-8