The Laureates

Copyright © Klaus Tschira Stiftung / Peter Badge

Whitfield Diffie

Born 5 June 1944, Washington, D.C., USA

ACM A.M. Turing Award (2015 — Together with Martin Hellman) – For inventing and promulgating both asymmetric public-key cryptography, including its application to digital signatures, and a practical cryptographic key-exchange method.

Whitfield Diffie was born on 5 June 1944 in Washington, D.C. to Bailey Wallys Diffie, an Iberian historian at the City College of New York, who is was first to champion a multi-cultural understanding of Latin-American civilization, and Justine Louise Whitfield, a writer and scholar who was perhaps the foremost scholar of Madame de Sévigné (whose letters are the major source of social history of the courts of Louis the XIIIth and XIVth) in the English-speaking world.

Though Diffie learned to read late, already 10 years old, there was never any doubting his high intellect and he progressed rapidly. Prior to that, he had simply preferred that his parents read to him. He was introduced to cryptography by his teacher that same year and expressed an immediate interest, studying books his father brought from the City College Library. This interest was short-lived — being replaced in youth by a broader interest in mathematics — but returned some twenty-five years later to become the basis of his career.

Good scores on standardized tests won out over mediocre grades, and led to Diffie’s admission to MIT to pursue a degree in pure mathematics. In 1965, he received his bachelor degree in mathematics from MIT and began working under Roland Silver at the Mitre Corporation. From Silver, Diffie learned an approach to programming understood by very few people at the time. He worked on Mathlab, a symbolic mathematical manipulation which received the hospitality of Marvin Minsky’s Artificial Intelligence Laboratory at MIT. The AI lab was in the same building with the Multics Project (the root Unix) and Diffie began thinking about the value and limitations of Multics’s security techniques.

In a casual conversation in 1965, Bill Mann, whom Diffie met as a freshman at MIT, mistakenly told Diffie that NSA encrypted the telephone conversations within its own buildings. Diffie understood how this might be done but did not see how it could achieve his concept of security. This misunderstanding planted the first of the seeds that would lead to Diffie’s most important discovery.

In the process of his Mathlab work, Diffie became convinced that proving correctness of programs was the most important problem in contemporary engineering. In 1969, he moved to the Artificial Intelligence Laboratory at Stanford University, whose director, John McCarthy, was the foremost champion of the provable correctness approach.

Shortly after Diffie’s arrival, McCarthy gave a lecture in Bordeaux about what we would now call Internet commerce, though his approach was more like the Minitel system that would be developed in France a decade later. When McCarthy recounted this presentation, Diffie began to think about office automation, particularly wondering what could be done to replace signatures — written signatures lean heavily on being hard to duplicate, whereas digital data can always be duplicated exactly. This was the second seed of his discovery.

In August 1972, a chance event led Diffie to a lasting interest in cryptography. Larry Roberts, who was developing the ARPAnet, prepotent sire of the Internet, approached Howard Rosenblum of NSA to work jointly on ARPAnet security. Roberts, however, did not want to support secret work and Rosenblum did not want to do anything else. Having become interested in network security, Roberts discussed the subject with his many visitors, one of whom was John McCarthy. John in turn became excited and, when he returned to California, he transmitted his enthusiasm to the researchers of his AI Lab. At the time, everyone took network security to be synonymous with cryptography; several of the staff and students worked briefly on cryptography but for Diffie it became a lasting passion.

In early 1973, Diffie left on an indefinite leave to travel and work on the problem full time. Perhaps unconsciously following his family’s historical orientation, Diffie made a methodical reading of David Kahn’s The Codebreakers the centerpiece of his work. This led Diffie to an understanding of the requirements that a cryptographic system would need to satisfy.
An early benefit of this journey was Diffie’s union with his wife, Mary Lynn Fischer. He describes her as his first discovery, without which he would not have made any of the others.

In the summer of 1974, Diffie was advised to look up Martin Hellman when he returned to Stanford. The meeting quickly extended over dinner to their wives Mary and Dorothy. The harmony between the two families nourished a collaboration between Diffie and Hellman which was intense for the next four years and led to their discovery and implementation of public-key cryptography. Public-key cryptography solved both of the problems that had been nagging Diffie for years. It allowed negotiation of secret cryptographic keys between people who did not previously know any common secret and it provided a “digital signature” that could enable authentication of online communication.

Diffie and Hellman’s work was published in their November 1976 paper, “New Directions in Cryptography.” This work transformed cryptography and laid the foundation for secure information exchange on the Internet.

Diffie spent the 1980’s working as the manager of secure systems research at Northern Telecom and moved to Sun Microsystems in 1991, where he remained as the chief security officer until 2009. He continued to adamantly work to protect the individual and business right to use encryption, leading to the book he co-authored with Susan Landau, “Privacy on the Line, the Politics of Wiretapping and Encryption.”

Diffie is a fellow of the Marconi Society, the Franklin Institute, and the National Inventors Hall of Fame. Most recently, he has been elected to the National Academy of Engineering and the Royal Society of London.

Additional accolades attributed to Diffie are the IEEE Donald G. Fink Prize Paper Award in 1981, the Paris Kanellakis Theory and Practice Award in 1996 (with Martin Hellman, Ralph Merkle, Ronald Rivest and Adi Shamir), the Golden Jubilee Award for Technological Innovation from the IEEE Information Theory Society in 1998, and the IEEE Richard W. Hamming Medal in 2010.