View source for Genevieve Grotjan Feinstein (nonfiction)

[[File:Genevieve Grotjan Feinstein.jpg|thumb|Genevieve Marie Grotjan Feinstein.]]'''Genevieve Marie Grotjan Feinstein''' (April 30, 1913 – August 10, 2006) was an American [[Mathematician (nonfiction)|mathematician]] and cryptanalyst. She worked for the Signals Intelligence Service throughout World War II, during which time she played an important role in deciphering the Japanese cryptography machine Purple, and later worked on the Cold War-era [[Venona project (nonfiction)|Venona project]].

== Career ==

Feinstein discovered a passion for mathematics at a young age and aspired to become a math teacher. She graduated from the University at Buffalo ''summa cum laude'' in February 1936 with a mathematics degree. At the beginning of World War II, U.S. President [[Franklin D. Roosevelt (nonfiction)|Franklin D. Roosevelt]] made it possible for women to fulfill non-combat roles in the military. She passed the necessary tests to become a government mathematician in 1939, and was hired by [[William F. Friedman (nonfiction)|William F. Friedman]] to work as a cryptanalyst for the Army's Signals Intelligence Service (SIS). For eighteen months, she worked with other SIS codebreakers to decipher the code used by Purple, a Japanese cryptography machine, and ultimately played a key role in cracking the cipher in September 1940, by finding cyclical behavior in the code. This enabled the construction of an equivalent machine by the SIS which in turn enabled the interception of almost all messages exchanged between the Japanese government and its embassies in foreign countries. Purple-encoded reports from [[Hiroshi Oshima (nonfiction)|Hiroshi Oshima]], the Japanese ambassador in Berlin, were a main source of intelligence about Axis plans.

After the conclusion of World War II, Feinstein continued to work at the SIS, as the Cold War began, trying to decode encrypted messages sent by the Soviet KGB and Main Intelligence Directorate (GRU). She made a significant breakthrough in the early stages of the [[Venona project (nonfiction)|Venona project]], which allowed American cryptographers to recognize when an individual cipher key was reused, but resigned from the SIS in 1947. After resigning from government cryptanalysis, she began working in the faculty of George Mason University, where she served as a professor of mathematics.

== Personal life == 

Genevieve Grotjan married the chemist [[Hyman Feinstein (nonfiction)|Hyman Feinstein]] in 1943.  They had a son named [[Ellis Feinstein (nonfiction)|Ellis Feinstein]]. 

Genevieve Grotjan died in 2006.

== Legacy ==

Feinstein's breakthrough in deciphering the Purple machine has been called, in the Encyclopedia of American Women at War, "one of the greatest achievements in the history of U.S. codebreaking". She was posthumously inducted into the NSA Hall of Honor in 2010, and an award in cryptology was established at George Mason University in her honor.

== References ==

* U.S., Social Security Death Index, 1935-2014
* [[William F. Friedman (nonfiction)|Friedman, William F.]] (October 14, 1940). "Preliminary Historical Report on the Solution of the Type "B" Machine" (PDF).
* [[Megan Findling (nonfiction)|Findling, Megan]] (2013). "Feinstein, Genevieve Grotjan (1912–2006)". In Tendrich Frank, Lisa (ed.). Encyclopedia of American Women at War: From the Home Front to the Battlefields. ABC-CLIO. pp. 215–217. ISBN 978-1-59884-443-6.
* [[Lisa Mundy (nonfiction)|Mundy, Liza]] (2017). ''Code Girls: The Untold Story of the American Women Code Breakers of World War II''. New York, Boston: Hachette Books. ISBN 978-0-316-35253-6.
* "Genevieve Grotjan Feinstein". National Security Agency. January 15, 2009. Retrieved March 14, 2015.
* "Genevieve Grotjan Feinstein: 2010 Inductee". National Security Agency. April 6, 2011. Retrieved March 14, 2015.

* [[Venona project (nonfiction)]]