Solomon Kullback

Solomon Kullback (April 3, 1907 – August 5, 1994) was an American cryptanalyst and mathematician, who was one of the first three employees hired by William F. Friedman at the US Army's Signal Intelligence Service (SIS) in the 1930s, along with Frank Rowlett and Abraham Sinkov. He went on to a long and distinguished career at SIS and its eventual successor, the National Security Agency (NSA). Kullback was the Chief Scientist at the NSA until his retirement in 1962, whereupon he took a position at the George Washington University.

The Kullback–Leibler divergence is named after Kullback and Richard Leibler.

Life and career Kullback was born to Jewish parents in Brooklyn, New York. His father Nathan had been born in Vilna, Russian Empire, (now Vilnius, Lithuania) and had immigrated to the US as a young man circa 1905, and became a naturalized American in 1911. Kullback attended Boys High School in Brooklyn. He then went to City College of New York, graduating with a BA in 1927 and an MA in math in 1929. He learned at Bletchley Park that the British were producing intelligence of high quality by exploiting the Enigma machine. He also cooperated with the British in the solution of more conventional German codebook-based systems. Shortly after his return to the States, Kullback moved into the Japanese section as its chief.

When the National Security Agency (NSA) was formed in 1952, Rowlett became chief of cryptanalysis. The primary problem facing research and development in the post-war period was development of high-speed processing equipment. Kullback supervised a team of about 60 people, including such innovative thinkers in automated data processing development as Leo Rosen and Sam Snyder. His staff pioneered new forms of input and memory, such as magnetic tape and drum memory, and compilers to make machines truly "multi-purpose". Kullback gave priority to using computers to generate communications security (COMSEC) materials.

Kullback's book Information Theory and Statistics was published by John Wiley & Sons in 1959. The book was republished, with additions and corrections, by Dover Publications in 1968.

Retirement Solomon Kullback retired from NSA in 1962, and focused on his teaching at George Washington University and publishing new papers. In 1963 he was elected as a Fellow of the American Statistical Association. He reached the rank of colonel, and was inducted into the Military Intelligence Hall of Fame.

Kullback is remembered by his colleagues at NSA as straightforward; one described him as "totally guileless, you always knew where you stood with him." One former NSA senior recalled him as a man of unlimited energy and enthusiasm and a man whose judgment was usually "sound and right."