Whitfield Whit Diffie, born on June 5, 1944, is an American cryptographer and mathematician. He is one of the key people who helped create public-key cryptography, along with Martin Hellman and Ralph Merkle. In 1976, Diffie and Hellman wrote a paper titled New Directions in Cryptography. This paper introduced a new way to share cryptographic keys, solving a major problem in cryptography called key distribution. Their method became known as the Diffie–Hellman key exchange. This work led to the quick development of a new type of encryption called asymmetric key algorithms.
After working at Sun Microsystems, where he became a Sun Fellow, Diffie worked as Vice President for Information Security and Cryptography at the Internet Corporation for Assigned Names and Numbers from 2010 to 2012. He also worked as a visiting scholar at Stanford University’s Freeman Spogli Institute from 2009 to 2010 and as an affiliate there until 2012. He is currently a consulting scholar at the same institute.
Early life and education
Diffie was born in Washington, D.C. His mother is Justine Louise (Whitfield), a writer and scholar. His father is Bailey Wallys Diffie, who taught Iberian history and culture at the City College of New York. His interest in cryptography began at age 10 when his father, a professor, brought home books about cryptography from the library in New York.
At Jamaica High School in Queens, New York, Diffie performed well but did not work as hard as his father hoped. He graduated with a local diploma but did not take the statewide Regents exams, which would have given him an academic diploma. This was because he had already been admitted to the Massachusetts Institute of Technology based on very high scores on standardized tests. During his first two years at MIT, he felt uninterested and seriously considered moving to the University of California, Berkeley, where he believed the academic environment would be more welcoming. At MIT, he started learning to program computers to develop practical skills, even though he still thought of himself as a pure mathematician and was interested in topics like partial differential equations and topology.
Diffie earned a Bachelor of Science degree in mathematics from MIT in 1965.
Career and research
From 1965 to 1969, he worked in Greater Boston as a research assistant for the MITRE Corporation in Bedford, Massachusetts. Since MITRE was a company that worked with the government on military projects, this job helped Diffie avoid being drafted into the Vietnam War. During this time, he helped create MATHLAB, an early system for solving math problems that became the foundation for Macsyma. He also worked on other projects not related to military use.
In November 1969, Diffie became a research programmer at the Stanford Artificial Intelligence Laboratory. There, he worked on LISP 1.6, a program widely used on PDP-10 computers running the TOPS-10 operating system. He also studied problems related to making computer programs correct. During this time, he developed an interest in cryptography and computer security, guided by John McCarthy.
Diffie left the Stanford Artificial Intelligence Laboratory in May 1973 to focus on independent research in cryptography. At that time, the most recent research in the field was kept secret by the National Security Agency. Diffie said he spent time searching for rare documents in libraries and visiting friends at universities. His new girlfriend and future wife, Mary Fischer, helped him with this work.
In the summer of 1974, Diffie and Fischer met with a friend at the Thomas J. Watson Research Center in Yorktown Heights, New York. This location was home to one of the few non-government groups in the United States studying cryptography. The group’s director, Alan Konheim, could not share much information due to secrecy rules but suggested Diffie meet Martin Hellman, an electrical engineering professor at Stanford who was also studying cryptography. Their planned meeting lasted much longer than expected as they shared ideas.
Hellman hired Diffie as a part-time research programmer for the spring term of 1975. With Hellman’s support, Diffie also began studying for a doctorate in electrical engineering at Stanford in June 1975. However, he struggled with homework and the structure of classes and eventually left the program after failing a required physical exam. Although it is unclear when he left, Diffie continued working in Hellman’s lab as a research assistant until June 1978.
Between 1975 and 1976, Diffie and Hellman criticized the proposed Data Encryption Standard (DES) by the National Bureau of Standards (NBS) because its 56-bit key length was too short to prevent attacks. An audio recording exists of their review of DES at Stanford in 1976 with NBS and National Security Agency representatives. Their concerns were valid: later events showed that the National Security Agency influenced the design of DES, and the short key length made it vulnerable to attacks. When these attacks were later built outside of classified settings (such as the EFF DES cracker), it became clear that DES was no longer secure.
From 1978 to 1991, Diffie worked as Manager of Secure Systems Research for Northern Telecom in Mountain View, California. There, he designed the key management system for the PDSO security system used in X.25 networks. In 2025, he was named an IEEE Fellow for his work on public key cryptography.
In 1991, Diffie joined Sun Microsystems Laboratories in Menlo Park, California, as a distinguished engineer. He focused on public policy issues related to cryptography. He remained with Sun until November 2009, serving as chief security officer and vice president. He was also a Sun Fellow.
As of 2008, Diffie was a visiting professor at the Information Security Group at Royal Holloway, University of London.
In May 2010, Diffie joined the Internet Corporation for Assigned Names and Numbers (ICANN) as vice president for information security and cryptography. He left this position in October 2012.
Diffie is a member of the technical advisory boards of BlackRidge Technology and Cryptomathic. At these organizations, he works with researchers such as Vincent Rijmen, Ivan Damgård, and Peter Landrock.
In 2018, Diffie became a visiting professor at Zhejiang University in China. Cryptic Labs created a two-month course at the university.
In the early 1970s, Diffie worked with Martin Hellman to develop the ideas behind public key cryptography. They published their findings in 1976, solving a major problem in cryptography: how to share secret keys securely. Their work ended the government’s control over cryptographic technology, allowing companies and individuals to use it freely. This method is now known as the Diffie-Hellman key exchange.
Books:
– Privacy on the Line with Susan Landau (1998; updated edition 2007).
– New Directions in Cryptography with Martin Hellman (1976).
Diffie and Hellman won the 2015 Turing Award, considered the highest honor in computer science. The award recognized their 1976 paper, which introduced public-key cryptography and digital signatures, the basis for many internet security protocols.
Honors and awards:
– Honorary doctorate from the Swiss Federal Institute of Technology (1992).
– Fellow of the Marconi Foundation and visiting fellow of the Isaac Newton Institute.
– Doctor of Science (Honoris Causa) from Royal Holloway, University of London (2008).
– IEEE Donald G. Fink Prize Paper Award (1981, with Martin E. Hellman).
– Louis E. Levy Medal (1997).
– Golden Jubilee Award for Technological Innovation (1998).
– IEEE Richard W. Hamming Medal (2010).
– Inducted into the National Inventors Hall of Fame (2011) and named a Fellow of the Computer History Museum.
– Foreign Member of the Royal Society (2017).
– Member of the National Academy of Engineering (2017).
Personal life
Diffie calls himself an iconoclast. He has said that he was always worried about protecting people's privacy instead of focusing on government secrets.