William Friedman

From genetics to ciphers

He was born Wolfe Frederick Friedman on 24 September 1891 in Kishinev. His father, an interpreter for the Tsar’s postal service, left for the United States the following year to escape increasing anti-Semitic regulations, and in 1893 the family joined him in Pittsburgh. When his father became a US citizen, the boy’s name was changed to William.¹

He studied genetics at Cornell University and then joined Riverbank Laboratories outside Chicago, George Fabyan’s private research centre. There he became interested in ciphers – and in Elizebeth Smith, who was doing cryptanalytic research at Riverbank.^1,2

During the First World War he left Riverbank to become a cryptologic officer.¹

In the service of the US Army

On 1 January 1921 he began a six-month contract with the US Army Signal Corps, and from 1922 to 1947 he was a cryptanalyst at the War Department. In 1922 he wrote a paper on the index of coincidence and its applications in cryptography, regarded as the pioneering work in cryptomathematics.³

In 1929 he was chosen to head the newly organised Signal Intelligence Service (SIS). In the first week of April 1930 he brought in three young mathematics teachers: Solomon Kullback, Frank Rowlett and Abraham Sinkov.^2,3

A team of Army cryptanalysts under his direction reconstructed the PURPLE machine after about 18 months of intensive work – PURPLE being the American codename for a Japanese diplomatic cryptosystem.^2,3

After the war and legacy

His awards included the War Department Medal for Exceptional Civilian Service (1944), the Presidential Medal for Merit (1946) and the Presidential National Security Medal (1955). In 1955 he retired from the NSA after more than 35 years of service, and until 1969 he was its special consultant.^2,3

He died on 2 November 1969 at his home in Washington and was buried with full military honours at Arlington Cemetery.³

The NSA counts among his greatest achievements the introduction of mathematical and scientific methods into cryptology and the training materials used by several generations of students. In 1999 he was inducted into the Cryptologic Hall of Honor, and in 2002 the OPS1 building at the NSA complex was named after William and Elizebeth Friedman.¹