William F. Friedman

William F. Friedman was an American cryptologist whose career ran from Riverbank Laboratories through the U.S. Army's Signal Intelligence Service. He was a prolific author, teacher, and organizer of cryptologic work.

Scientific cryptology

Friedman introduced mathematical and scientific approaches to cryptologic analysis and developed training material used by generations of practitioners. Before the United States entered the Second World War, his team made a major breakthrough against the Japanese diplomatic system known to Americans as PURPLE.

Enduring influence

His legacy includes both cryptanalysis and communications protection. That combination makes him a foundational figure for a security history that treats attacking and defending information systems as connected disciplines.

In memoriam

Friedman died in 1969. His work continues to be recognized by the U.S. cryptologic community and by historians of cryptography.

Timeline

• 1891-09-24Born in Kishinev, then in the Russian Empire.
• 1915Begins cryptologic work at Riverbank Laboratories.
• 1930Builds the Army Signal Intelligence Service's cryptanalytic staff.
• 1940His team achieves a decisive solution of Japan's PURPLE diplomatic cipher.
• 1969-11-02Dies in Washington, D.C.