Editing Venona project (section)

===Breakthrough===
[[File:Genevieve Grotjan Feinstein.jpg|thumb|[[Genevieve Feinstein]]<ref>{{cite web|url=http://www.nsa.gov/about/cryptologic_heritage/women/honorees/feinstein.shtml |title=Women in Cryptologic History – Genevieve Feinstein – NSA/CSS |publisher=Nsa.gov |date=2009-01-15 |access-date=2014-02-15}}</ref>]]
The Soviet systems in general used a [[code]] to convert words and letters into numbers, to which additive [[key (cryptography)|key]]s (from one-time pads) were added, encrypting the content. When used correctly so that the [[plaintext]] is of a length equal to or less than that of a random key, one-time pad encryption is unbreakable.<ref>{{cite web |url=http://www.world.std.com/~franl/crypto/one-time-pad.html |archive-url=https://web.archive.org/web/20080516225512/http://www.world.std.com/~franl/crypto/one-time-pad.html |archive-date=2008-05-16 |title=Why Are One-Time Pads Perfectly Secure? |author=Francis Litterio}}</ref> However, cryptanalysis by American code-breakers revealed that some of the one-time pad material had incorrectly been reused by the Soviets (specifically, entire pages, although not complete books), which allowed decryption (sometimes only partial) of a small part of the traffic.

Generating the one-time pads was a slow and labor-intensive process, and the outbreak of war with Germany in June 1941 caused a sudden increase in the need for coded messages. It is probable that the Soviet code generators started duplicating cipher pages in order to keep up with demand.

It was Arlington Hall's Lieutenant [[Richard Hallock (Venona Project)|Richard Hallock]], working on Soviet "Trade" traffic (so called because these messages dealt with Soviet trade issues), who first discovered that the Soviets were reusing pages. Hallock and his colleagues, amongst whom were [[Genevieve Feinstein]], [[Cecil Phillips]], [[Frank W. Lewis|Frank Lewis]], [[Frank Wanat]], and [[Lucille Campbell]], went on to break into a significant amount of Trade traffic, recovering many one-time pad additive key tables in the process.
[[File:Meredith Gardner, at far left, working with cryptanalysts.jpg|thumb|[[Meredith Gardner]] (far left); most of the other code breakers were young women.]] <!-- yes, Meredith's a man -->
A young [[Meredith Gardner]] then used this material to break into what turned out to be NKVD (and later [[GRU (Soviet Union)|GRU]]) traffic by reconstructing the code used to convert text to numbers. Gardner credits [[Marie Meyer (linguist)|Marie Meyer]], a linguist with the [[Signal Intelligence Service]] with making some of the initial recoveries of the Venona codebook.<ref>{{Cite web|url=https://www.nsa.gov/About-Us/Current-Leadership/Article-View/Article/1620935/marie-meyer/|title=Marie Meyer > National Security Agency {{!}} Central Security Service > Article View|website=www.nsa.gov|access-date=2019-11-21}}</ref> [[Samuel P. Chew|Samuel Chew]] and Cecil Phillips also made valuable contributions. On December 20, 1946, Gardner made the first break into the code, revealing the existence of Soviet espionage in the [[Manhattan Project]].<ref>
{{cite web
| author = Daniel Patrick Moynihan
| author-link = Daniel Patrick Moynihan
| year = 1997
| url = https://fas.org/sgp/library/moynihan/appa6.html
| title = Report of the Commission On Protecting And Reducing Government Secrecy; Appendix A: The Experience of The Bomb
| publisher = United States Government Printing Office
| access-date = 2006-06-18
}}</ref> Venona messages also indicated that Soviet spies worked in Washington in the [[United States Department of State|State Department]], [[United States Department of the Treasury|Treasury]], [[Office of Strategic Services]] (OSS), and even the [[White House]]. Very slowly, using assorted techniques ranging from [[traffic analysis]] to [[defector]] information, more of the messages were decrypted.

Claims have been made that information from the physical recovery of code books (a partially burned one was obtained by the Finns) to [[Covert listening device|bugging]] embassy rooms in which text was entered into encrypting devices (analyzing the keystrokes by listening to them being punched in) contributed to recovering much of the plaintext. These latter claims are less than fully supported in the open literature.

One significant aid (mentioned by the NSA) in the early stages may have been work done in cooperation between the [[Japan]]ese and [[Finland|Finnish]] cryptanalysis organizations; when the Americans broke into Japanese codes during World War II, they gained access to this information.<ref>{{Cite book |last=Mundy |first=Liza |title=Code girls: the untold story of the American women code breakers of World War II |publisher=Hachette Books |year=2017 |isbn=978-0-316-35253-6 |edition=1st |location=Boston |page=38}}</ref> There are also reports that copies of signals purloined from Soviet offices by the [[Federal Bureau of Investigation]] (FBI) were helpful in the cryptanalysis. The Finnish radio intelligence sold much of its material concerning Soviet codes to the OSS in 1944 during [[Operation Stella Polaris]], including the partially burned code book.<ref>{{ cite book
| last = West
| first = Nigel
| title = Venona: the greatest secret of the Cold War
| publisher = HarperCollins
| year = 2000
| location = London
| pages = 3–10
| isbn = 978-0-00-653071-8
}}</ref>