William F. Friedman

William F. Friedman
Born
Wolf Friedman

September 24, 1891
DiedNovember 12, 1969(1969-11-12) (aged 78)
Washington, D.C., United States
NationalityRomanian, Russian, American
OccupationEngineer
SpouseElizebeth Smith Friedman
Children2
Engineering career
Significant advancecryptologist

William Frederick Friedman (September 24, 1891 – November 12, 1969) was a US Army cryptographer who ran the research division of the Army's Signal Intelligence Service (SIS) in the 1930s, and parts of its follow-on services into the 1950s. In 1940, subordinates of his led by Frank Rowlett broke Japan's PURPLE cipher, thus disclosing Japanese diplomatic secrets before America's entrance into World War II.