James Henry Ellis (25 September 1924 – 25 November 1997) was a British engineer and

cryptographer Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

. In 1970, while working at the

Government Communications Headquarters Government Communications Headquarters, commonly known as GCHQ, is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the Uni ...

(GCHQ) in Cheltenham, he conceived of the possibility of "non-secret encryption", more commonly termed

public-key cryptography Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key. Key pairs are generated with cryptographic alg ...

Early life, education and career

Ellis was born in Britain, although he was conceived in Australia, and grew up in Britain. He almost died at birth, and it was thought that he might be learning disabled. He became an orphan who lived with his grandparents in London's East End.The Open Secret
/ref> He showed a gift for mathematics and physics at a

grammar school A grammar school is one of several different types of school in the history of education in the United Kingdom and other English-speaking countries, originally a school teaching Latin, but more recently an academically oriented secondary school ...

Leyton Leyton () is a town in east London, England, within the London Borough of Waltham Forest. It borders Walthamstow to the north, Leytonstone to the east, and Stratford to the south, with Clapton, Hackney Wick and Homerton, across the River L ...

, and gained a degree in physics. He then worked at the

Post Office Research Station The Post Office Research Station was first established as a separate section of the General Post Office in 1909. In 1921, the Research Station moved to Dollis Hill, north west London, initially in ex-army huts. The main permanent buildings at ...

Dollis Hill Dollis Hill is an area in northwest London, which consists of the streets surrounding the 35 hectares (86 acres) Gladstone Park. It is served by a London Underground station, Dollis Hill, on the Jubilee line, providing good links to central Lo ...

. In 1952, Ellis joined the

(GCHQ) in

Eastcote Eastcote is a suburban area in the London Borough of Hillingdon, in northwest London. In the Middle Ages, Eastcote was one of the three areas that made up the parish of Ruislip, under the name of Ascot. The name came from its position to the e ...

, west London. In 1965, he moved to Cheltenham to join the newly formed Communications-Electronics Security Group (CESG), an arm of GCHQ. In 1949, Ellis married Brenda, an artist and designer, and they had four children but she never knew anything about his work.

Invention of non-secret encryption

Ellis first proposed his scheme for "non-secret encryption" in 1970, in a (then) secret

GCHQ Government Communications Headquarters, commonly known as GCHQ, is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the Uni ...

internal report "The Possibility of Secure Non-Secret Digital Encryption". Ellis said that the idea first occurred to him after reading a paper from

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

by someone at

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial Research and development, research and scientific developm ...

describing the scheme named Project C43, a way to protect voice communications by the receiver adding (and then later subtracting) random noise (possibly this 1944 paper or the 1945 paper co-authored by

Claude Shannon Claude Elwood Shannon (April 30, 1916 – February 24, 2001) was an American mathematician, electrical engineer, and cryptographer known as a "father of information theory". As a 21-year-old master's degree student at the Massachusetts Inst ...

). 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 Christopher Cocks (born 28 December 1950) is a British mathematician and cryptographer. In 1973, while working at the United Kingdom Government Communications Headquarters (GCHQ), he invented a public-key cryptography algorithm equiv ...

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 is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to kn ...

, the discovery was kept secret. Not long thereafter, Cocks' friend and fellow mathematician,

Malcolm Williamson Malcolm Benjamin Graham Christopher Williamson, (21 November 19312 March 2003) was an Australian composer. He was the Master of the Queen's Music from 1975 until his death. Biography Williamson was born in Sydney in 1931; his father was an A ...

, 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 Hellman is a surname. Notable people with the surname include: * Åke Hellman (1915–2017), Finnish centenarian, painter, and art professor *Bonnie Hellman (born 1950), American actress *C. Doris Hellman (1910–1973), American historian of scienc ...

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 The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collect ...

(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. In March 2016, the director of GCHQ made a speech at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

re-emphasising GCHQ's early contribution to public-key cryptography and in particular the contributions of Ellis, Cocks and Williamson.Director Robert Hannigan dispels some myths about encryption in MIT speech
GCHQ, 7 March 2016, retrieved 14 March 2016

References

External links

* * Ellis, J.H.
The possibility of secure non-secret digital encryption
CSEG Report 3006, January 1970. * Ellis, J.H.
The possibility of secure non-secret analogue encryption
CSEG Report 3007, May 1970. {{DEFAULTSORT:Ellis, James H. Alumni of Imperial College London GCHQ cryptographers History of computing in the United Kingdom Modern cryptographers People from Leytonstone Public-key cryptographers 1924 births 1997 deaths Engineers from London