Richard A. Leibler (March 18, 1914,

Chicago, Illinois (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = Country , subdivision_name ...

– October 25, 2003,

Reston, Virginia Reston is a census-designated place in Fairfax County, Virginia and a principal city of the Washington metropolitan area. As of the 2020 U.S. Census, Reston's population was 63,226. Founded in 1964, Reston was influenced by the Garden City movem ...

) was an American

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

and

cryptanalyst Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...

. Richard Leibler was born in March 1914. He received his A.M. in mathematics from

Northwestern University Northwestern University is a private research university in Evanston, Illinois. Founded in 1851, Northwestern is the oldest chartered university in Illinois and is ranked among the most prestigious academic institutions in the world. Charte ...

and his Ph.D. from the

University of Illinois The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the University ...

in 1939. While working at the

National Security Agency The National Security Agency (NSA) is a national-level intelligence agency of the United States Department of Defense, under the authority of the Director of National Intelligence (DNI). The NSA is responsible for global monitoring, collecti ...

, he and

Solomon Kullback Solomon Kullback (April 3, 1907August 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 ...

formulated the

Kullback–Leibler divergence In mathematical statistics, the Kullback–Leibler divergence (also called relative entropy and I-divergence), denoted D_\text(P \parallel Q), is a type of statistical distance: a measure of how one probability distribution ''P'' is different fro ...

, a measure of similarity between probability distributions which has found important applications in

information theory Information theory is the scientific study of the quantification (science), quantification, computer data storage, storage, and telecommunication, communication of information. The field was originally established by the works of Harry Nyquist a ...

and

cryptology Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adve ...

. Leibler is also credited by the NSA as having opened up "new methods of attack" in the celebrated

VENONA The Venona project was a United States counterintelligence program initiated during World War II by the United States Army's Signal Intelligence Service (later absorbed by the National Security Agency), which ran from February 1, 1943, until Octob ...

code-breaking project during 1949-1950; this may be a reference to his joint paper with Kullback, which was published in the open literature in 1951 and was immediately noted by Soviet cryptologists. He was director of the Communications Research Division at the Institute for Defense Analyses from 1962 to 1977. He was inducted into the

NSA Hall of Honor The Hall of Honor is a memorial at the National Security Agency headquarters in Fort Meade, Maryland. It honors individuals who rendered distinguished service to American cryptology. The Hall of Honor The Hall of Honor is located on the grounds ...

for his efforts against the VENONA code.

References

External links

Biography in NSA's Cryptologic Hall of Honor
1914 births 2003 deaths 20th-century American mathematicians American cryptographers Modern cryptographers Northwestern University alumni University of Illinois alumni {{crypto-bio-stub