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NSA Historical Figures

Genevieve Grotjan Feinstein

2010 Hall of Honor Inductee

Women in American Cryptology Honoree

Genevieve Grotjan Feinstein was a skilled cryptanalyst whose discovery in September 1940 changed the course of history. Her successful breakthrough enabled the Army Signal Intelligence Service (SIS) to build an analog machine that solved the Japanese diplomatic system known as "Purple." Exploitation of this system provided crucial intelligence in the Atlantic and Pacific theaters during World War II.

Ms. Grotjan Feinstein was hired by William Friedman for the SIS in 1939. By 1940 she made her discovery that led to breaking the "Purple" code, and by October 1943 she was assigned to the Soviet problem and worked on the project later known as "Venona." She devised a process for recognizing the re-use of key, which, in turn, permitted the decryption of Russian KGB messages. The discovery was labeled "… the most important single cryptanalytic break in the whole history of Venona."

Ms. Grotjan Feinstein's brilliant findings in two instances enabled exploitation of communications that provided invaluable intelligence information to policymakers. This information was used by the most senior government officials for decisions in World War II and the Cold War.

In 1943, Ms. Grotjan married Hyman Feinstein, a chemist at the National Bureau of Standards. After serving as a cryptanalyst and as a research analyst for over seven years, on May 4, 1947, Genevieve Grotjan Feinstein resigned from the government and later became a professor of mathematics at George Mason University.

Genevieve Grotjan Feinstein died in 2006 at the age of 93. Before his death in 1995, Hyman Feinstein established an award in cryptology within the Department of Mathematical Sciences at George Mason in honor of his wife.