James H. Ellis

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

Life

Elli's parents were from Australia and he was born in England . He grew up in London and studied physics at Imperial College London . After graduating, Ellis initially worked at the Post Office Research Station in north-west London and in 1952 went to the GCHQ in the London Borough of Hillingdon . He stayed with the agency and moved to its headquarters in Cheltenham in 1965 .

Idea for an asymmetric cryptosystem

In symmetrical cryptosystems , key distribution is complex. At the end of the 1960s, the GCHQ therefore asked its colleague Ellis to propose ways to reduce costs. While studying literature, he came across Shannon's work Communication in the Presence of Noise (for example: "Message transmission when noise signals occur "). After reading the article by this pioneer of cryptography, the idea of ​​the asymmetric key was born: the recipient must superpose a noise on the sender's message from the start. Thus the message is made unrecognizable. Since the receiver can calculate the noise component afterwards because the receiver knows the noise component, he can read the message alone.

Ellis, who was not a mathematician, was unsure how to implement his idea. That was done by two young mathematicians in 1973–1974 - Clifford Cocks and Malcolm Williamson . The work of the three researchers at GCHQ initially remained a secret. In 1976 Diffie and Hellman published a preliminary work on public key cryptography , which solved the key transmission problem and was used in the RSA cryptosystem a year later . The GCHQ had banned Williamson publication in 1976.

source

• Simon Singh: Secret Messages. The art of encryption from ancient times to the Internet. Translated from the English by Klaus Fritz. With numerous black and white illustrations, pp. 338–352. Deutscher Taschenbuch Verlag, Munich 2012 (11th edition), ISBN 978-3-42333071-8

Web links

In English

• Steven Levy: The Open Secret: Public Key Cryptography at GCHQ (1999)
• James Ellis: The Story of Non-Secret Encryption ( Memento June 10, 2003 in the Internet Archive )
• Aaron D. Wyner: Introduction to Shannon's "Communication in the Presence of Noise" (PDF; 72 kB)

Individual evidence

1. ↑ Shannon: Communication in the Presence of Noise ( Memento of the original of February 8, 2010 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 301 kB)