William F. Friedman

William Frederick Friedman was a United States Army cryptographer who ran the research division of the Army's Signal Intelligence Service in the 1930s and parts of its follow-on services into the 1950s. Born Wolf Friedman in Kishinev in 1891, he grew up in Pittsburgh and joined George Fabyan's Riverbank Laboratories in 1915, first as head of genetics and then in cryptology, where he trained Army officers and wrote technical monographs. He served as General Pershing's personal cryptographer in France and published a monograph on the index of coincidence. He coined the term cryptanalysis, wrote the work that became the Army's main cryptographic textbook, and developed rotor machines, the best of which became SIGABA. In 1940 subordinates led by Frank Rowlett broke the Japanese PURPLE cipher. He received the Medal for Merit in 1946 and the National Security Medal in 1955, and died in 1969.