Dr Clifford Cocks CB

Doctor of Science

19 February 2008 – Orator: Professor Nigel Smart

Mr Vice-Chancellor,Clifford Cocks

Our world depends on an invisible glue which allows us to keep our data secure and to prove who we are to organisations. This glue is called ‘public key cryptography’. We all use it to buy items securely on the Internet and in our chip-and-pin cards, mobile phones and pay television sets. Clifford Cocks, who stands before us today, is one of the great, unsung heroes in the development of this technology. His work is a shining example of the long tradition of mutually beneficial interactions between mathematicians and computer scientists in government communications, which famously includes Alan Turing's development of fundamentally new mathematical and computational techniques to break codes in the Second World War.

The concept of public key cryptography is truly amazing. The official history is that the idea occurred in 1976 to two Stanford academics called Whit Diffie and Marty Hellman. But while Diffie and Hellman explained how the idea could be applied, they could not create a system that was fully usable. In the following year, three MIT academics, Rivest, Shamir and Adleman, invented an algorithm, now called the RSA algorithm, which allowed Diffie and Hellman’s ideas to be put into practice. The RSA algorithm and the Diffie-Hellman protocol now form the backbone of the security of our electronic age. These five pioneers formed companies and became relatively well known as the IT industry grew in the ensuing years. However, alongside this official history there is a secret one, in which Clifford Cocks is the key player.

Clifford was born on 28 December 1950 at Prestbury in Cheshire. He went to Manchester Grammer School between 1961 and 1968. It was at The Manchester Grammar School that he met Malcolm Williamson, who will be another important player in our secret history. Malcolm tells me that after being forced to learn Latin one year, and with the threat of Greek in a future year, Clifford claimed a deep interest in science in order to be transferred into a science-based stream. It was there, under the guidance of some excellent teachers, that his lifelong love of mathematics was born. His parents were delighted by his enthusiasm but a little disturbed when he decided that the book he would take to read on the beach one summer holiday was “Teach Yourself Calculus”.

In 1968, Clifford and Malcolm formed part of the British Mathematical Olympiad team. The Mathematical Olympiad is an annual event in which teams of the most able pre-university mathematicians from around the world compete in solving mathematical problems. The British team of 1968 was particularly talented, and in the competition held in Moscow Clifford won a Silver Medal.

On returning from the Olympiad, Clifford went to King’s College Cambridge to study mathematics. His former college tutor tells me that Clifford was one of a group of undergraduate mathematicians in the late sixties and early seventies who really helped put King’s on the mathematical map. On leaving Cambridge, Clifford spent a short time at Oxford studying an esoteric part of number theory before deciding to apply his mathematics by joining the Government Communications Headquarters (GCHQ) at Cheltenham in 1973. In 1940, the famous mathematician G.H. Hardy had remarked that Relativity and Number Theory were the truly great parts of mathematics as they had not been tainted by finding application. Hardy was soon proved wrong about relativity by the advent of the nuclear age, but in 1973 he was still correct about number theory. Clifford was about to alter that position for good by finding the most compelling application of Number Theory.

Three years before Clifford joined GCHQ, another employee called James Ellis had had a novel idea, which he called “non-secret encryption”. This idea looked as if it would solve a number of key problems in cryptography. What Ellis called “non-secret encryption” we now call public key cryptography – which I referred to a moment ago, so Ellis had discovered a concept akin to the one that Diffie and Hellman were to discover, but like Diffie and Hellman he was unable to come up with a way of creating a practical system.

The story is that on arriving at GCHQ, Clifford was given Ellis’s internal report so that he had something to do. He started working on it using his number theory background and within a very short time had invented the algorithm (now known as the RSA algorithm) that was to be identified four years later by Rivest, Shamir and Adleman.

Clifford’s school friend, Williamson, had also joined GCHQ around this time, and he managed, after reading Ellis’s report, to come up with what we now know as the Diffie-Hellman protocol. So by 1973, Ellis, Cocks and Williamson had invented all of the key components that the five American academics were to put together four years later.

The story of this discovery was kept secret for a further 24 years. In 1997, Clifford announced to a conference the true history of the development of public key cryptography, and various internal reports were declassified to support the story. Alas, Ellis, whose original idea it had all stemmed from, died a few months before the announcement.

Many people would be content with one such achievement in a lifetime. However, Clifford was also involved in another cryptographic revolution, namely the invention of a technique called identity-based cryptography. The creation of such a system had been the holy grail of cryptography since the early 1980s. In 2000 a team at Stanford announced that they had found one, but it was soon revealed that Clifford had done so a few years earlier. In 2001, Clifford became the Chief Mathematician at GCHQ. He considers that his main administrative achievement since then is the setting up of the Heilbronn Institute for Mathematical Research – a joint partnership between GCHQ and the University of Bristol. This institute has not only provided a focus for the growth of pure mathematics at Bristol; it has also acted as a catalyst for the subject’s sustainability across the United Kingdom. A few years ago, the American Mathematical Society stated that “Pure Mathematics will be the Applied Mathematics of the 21st Century”, and the Heilbronn Institute will help the United Kingdom to be at the forefront of this work. It is fitting that Clifford helped set this institute up, since he is one of the people who showed that the most pure and esoteric areas of mathematics can actually have immense and profound applications.

Clifford received no shareholdings in large, successful companies as a result of his invention; nor has he received many academic prizes or honours. Clifford’s work was done out of love for the subject, and as a duty to his country; he has not sought publicity. It became apparent to me, from my enquiries in preparing this oration, that his main characteristic is one of overwhelming modesty; all who come in contact with him mention this as his most important characteristic. In January 2008 he was made a Companion of the Order of the Bath in the New Year's Honours list.

Clifford Cocks has been a leading figure in the development of our electronic world. He has not sought recognition and accolades and his motivations, like his mathematics, have been of the purest kind. He epitomises the scientist who works for the benefit of his country, and as such provides a role model for a large cohort of cryptographers who follow in his footsteps.

Mr Vice-Chancellor, I present to you Clifford Cocks as eminently worthy of the degree of Doctor of Science honoris causa.