James H. Ellis
Encyclopedia
James Henry Ellis was a British engineer
and mathematician
. In 1970, while working at the Government Communications Headquarters
(GCHQ) in Cheltenham
he conceived of the possibility of "non-secret encryption", more commonly termed public-key cryptography
.
, and subsequently worked at the Post Office Research Station
at Dollis Hill
. In 1952, Ellis joined GCHQ in Eastcote
, west London
. In 1965, Ellis moved to Cheltenham to join the newly-formed Communications-Electronics Security Department (CESD), an arm of GCHQ.
by someone at Bell Labs
describing a way to protect voice communications by the receiver adding (and then later subtracting) random noise (probably the 1945 paper co-authored by Claude Shannon). He realised that 'noise' could be applied mathematically but was unable to devise a way to implement the idea.
Shortly after joining GCHQ in September 1973, after studying Mathematics at Cambridge University, Clifford Cocks
was told of Ellis' proof and that no one had been able to figure out a way to implement it. He went home, thought about it, and returned with the basic idea for what has become known as the RSA asymmetric key encryption algorithm. Because any new and potentially beneficial/harmful technique developed by GCHQ is by definition classified information
, the discovery was kept secret.
Not long thereafter, Cocks' friend and fellow mathematician, Malcolm Williamson, now also working at GCHQ, after being told of Cocks' and Ellis' work, thought about the problem of key distribution and developed what has since become known as Diffie-Hellman key exchange
. Again, this discovery was classified information and it was therefore kept secret.
When, a few years later, Diffie
and Hellman
published their 1976 paper, and shortly after that Rivest
, Shamir
, and Adleman
announced their algorithm, Cocks, Ellis, and Williamson suggested that GCHQ announce that they had previously developed both. GCHQ decided against publication at the time.
At this point, only GCHQ and the National Security Agency
(NSA) in the USA knew about the work of Ellis, Cocks and Williamson. Whitfield Diffie heard a rumour, probably from the NSA, and travelled to see James Ellis. The two men talked about a range of subjects until, at the end, Diffie asked Ellis "Tell me how you invented public-key cryptography". After a long pause, Ellis replied "Well, I don't know how much I should say. Let me just say that you people made much more of it than we did."
On 18 December 1997, Clifford Cocks delivered a public talk which contained a brief history of GCHQ's contribution so that Ellis, Cocks and Williamson received some acknowledgment after nearly three decades of secrecy. James Ellis died on 25 November 1997, a month before the public announcement was made.
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
and mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
. In 1970, while working at the Government Communications Headquarters
Government Communications Headquarters
The Government Communications Headquarters is a British intelligence agency responsible for providing signals intelligence and information assurance to the UK government and armed forces...
(GCHQ) in Cheltenham
Cheltenham
Cheltenham , also known as Cheltenham Spa, is a large spa town and borough in Gloucestershire, on the edge of the Cotswolds in the South-West region of England. It is the home of the flagship race of British steeplechase horse racing, the Gold Cup, the main event of the Cheltenham Festival held...
he conceived of the possibility of "non-secret encryption", more commonly termed public-key cryptography
Public-key cryptography
Public-key cryptography refers to a cryptographic system requiring two separate keys, one to lock or encrypt the plaintext, and one to unlock or decrypt the cyphertext. Neither key will do both functions. One of these keys is published or public and the other is kept private...
.
Early life, education and career
Ellis was born in Australia, although he was conceived in Britain and grew up in London. He studied physics at Imperial College LondonImperial College London
Imperial College London is a public research university located in London, United Kingdom, specialising in science, engineering, business and medicine...
, and subsequently worked at the Post Office Research Station
Post Office Research Station
The Post Office Research Station at Dollis Hill, London, was first established in 1921 and opened by Prime Minister Ramsay MacDonald in 1933.In 1943 the world's first programmable electronic computer, Colossus Mark 1 was built by Tommy Flowers and his team, followed in 1944 and 1945 by nine...
at Dollis Hill
Dollis Hill
Dollis Hill is an area of north-west London. It lies close to Willesden, in the London Borough of Brent. As a result, Dollis Hill is sometimes referred as being part of Willesden, especially by the national press...
. In 1952, Ellis joined GCHQ in Eastcote
Eastcote
Eastcote is a suburban area established around an old village in Greater London, and is part of the London Borough of Hillingdon.In the Middle Ages, Eastcote was one of the three areas that made up the parish of Ruislip, under the name of Ascot...
, west London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
. In 1965, Ellis moved to Cheltenham to join the newly-formed Communications-Electronics Security Department (CESD), an arm of GCHQ.
Invention of non-secret encryption
Ellis said that the idea first occurred to him after reading a paper from World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
by someone at Bell Labs
Bell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
describing a way to protect voice communications by the receiver adding (and then later subtracting) random noise (probably the 1945 paper co-authored by Claude Shannon). He realised that 'noise' could be applied mathematically but was unable to devise a way to implement the idea.
Shortly after joining GCHQ in September 1973, after studying Mathematics at Cambridge University, Clifford Cocks
Clifford Cocks
Clifford Christopher Cocks, CB, is a British mathematician and cryptographer at GCHQ.He invented the widely-used encryption algorithm now commonly known as RSA, about three years before it was independently developed by Rivest, Shamir, and Adleman at MIT...
was told of Ellis' proof and that no one had been able to figure out a way to implement it. He went home, thought about it, and returned with the basic idea for what has become known as the RSA asymmetric key encryption algorithm. Because any new and potentially beneficial/harmful technique developed by GCHQ is by definition classified information
Classified information
Classified information is sensitive information to which access is restricted by law or regulation to particular groups of persons. A formal security clearance is required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation...
, the discovery was kept secret.
Not long thereafter, Cocks' friend and fellow mathematician, Malcolm Williamson, now also working at GCHQ, after being told of Cocks' and Ellis' work, thought about the problem of key distribution and developed what has since become known as Diffie-Hellman key exchange
Diffie-Hellman key exchange
Diffie–Hellman key exchange Synonyms of Diffie–Hellman key exchange include:*Diffie–Hellman key agreement*Diffie–Hellman key establishment*Diffie–Hellman key negotiation...
. Again, this discovery was classified information and it was therefore kept secret.
When, a few years later, Diffie
Whitfield Diffie
Bailey Whitfield 'Whit' Diffie is an American cryptographer and one of the pioneers of public-key cryptography.Diffie and Martin Hellman's paper New Directions in Cryptography was published in 1976...
and Hellman
Martin Hellman
Martin Edward Hellman is an American cryptologist, and is best known for his invention of public key cryptography in cooperation with Whitfield Diffie and Ralph Merkle...
published their 1976 paper, and shortly after that Rivest
Ron Rivest
Ronald Linn Rivest is a cryptographer. He is the Andrew and Erna Viterbi Professor of Computer Science at MIT's Department of Electrical Engineering and Computer Science and a member of MIT's Computer Science and Artificial Intelligence Laboratory...
, Shamir
Adi Shamir
Adi Shamir is an Israeli cryptographer. He is a co-inventor of the RSA algorithm , a co-inventor of the Feige–Fiat–Shamir identification scheme , one of the inventors of differential cryptanalysis and has made numerous contributions to the fields of cryptography and computer...
, and Adleman
Leonard Adleman
Leonard Max Adleman is an American theoretical computer scientist and professor of computer science and molecular biology at the University of Southern California. He is known for being a co-inventor of the RSA cryptosystem in 1977, and of DNA computing...
announced their algorithm, Cocks, Ellis, and Williamson suggested that GCHQ announce that they had previously developed both. GCHQ decided against publication at the time.
At this point, only GCHQ and the National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
(NSA) in the USA knew about the work of Ellis, Cocks and Williamson. Whitfield Diffie heard a rumour, probably from the NSA, and travelled to see James Ellis. The two men talked about a range of subjects until, at the end, Diffie asked Ellis "Tell me how you invented public-key cryptography". After a long pause, Ellis replied "Well, I don't know how much I should say. Let me just say that you people made much more of it than we did."
On 18 December 1997, Clifford Cocks delivered a public talk which contained a brief history of GCHQ's contribution so that Ellis, Cocks and Williamson received some acknowledgment after nearly three decades of secrecy. James Ellis died on 25 November 1997, a month before the public announcement was made.