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The VENONA project was a long-running and highly secret collaboration between United States intelligence agencies and the United Kingdom's MI5 that involved the cryptanalysis of messages sent by several Soviet intelligence agencies. The British codename for VENONA was Bride.

In the early years of the Cold War, it was one of the West's most important sources on Soviet intelligence activity, and although unknown to the public, it was important in many famous events of the early Cold War, such as the case of Elizabeth Bentley, and the Rosenberg case.

Background

U.S. Army Signal Security Agency (commonly called Arlington Hall) codebreakers had intercepted large volumes of encrypted high-level Soviet diplomatic and intelligence traffic during and immediately after World War II. The British had stopped intercepting Soviet traffic, at Winston Churchill's orders, shortly after Germany invaded the Soviet Union in 1941, and had no traffic to contribute to the project after that time.

This traffic, some of which was thought to be encrypted with a one-time pad system, was stored and analyzed in relative secrecy by hundreds of cryptanalysts over a 40-year period starting in the early 1940s. Due to what turned out to be a serious blunder on the part of the Soviets - re-using pages of some of the one-time pads in other pads, which were then used for other messages - this traffic was vulnerable to crypanalysis.

The Venona Project was initiated under orders from the Chief of Military Intelligence, Carter Clarke, who mistrusted Joseph Stalin. He feared that Stalin and Hitler would sign a peace treaty in order to focus Germany's military forces on the destruction of Great Britain and the U.S.

The breakin

The Soviet systems in general used a code to convert words and letters into numbers, to which an additive key (from one-time pads) were added, further disguising the content. Some brilliant cryptanalysis by American and British codebreakers 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.

It was Arlington Hall's Lt. Richard Hallock, working on Soviet "Trade" traffic, who first discovered that the Soviets were re-using pages. Hallock and his colleagues (including Genevieve Feinstein, Cecil Phillips, 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.

A very young Meredith Gardner (of what would become the National Security Agency) then used this material to break in to what turned out to be NKVD (and later GRU) traffic, by reconstructing the code used to convert text to numbers. Samuel Chew and Cecil Phillips also made valuable contributions. 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 physical theft of code books (a partially burned one was recovered by the Finns) to bugging embassy rooms in which text was entered into encrypting devices (analyzing the keystrokes by listening to them being punched in), contributed to achieving as much plaintext as was recovered. 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 co-operation between the Japanese and Finnish cryptanalytic organizations; when the Americans broke into Japanese codes during WWII, they gained access to this information.

There has been speculation that the reason for the key material duplication was the increase in work (including key pad generation) in the period after the German attack in June of 1941. Other suggestions have it that it was Guderian's tanks just outside Moscow in early December that year which forced Moscow Centre to make such a fundamental error.

Results

The NSA reported that, according to the serial numbers of the Venona cables, thousands were sent, but only a fraction were available to the cryptanalysts. Approximately 2,200 of the messages were decrypted and translated; some 50 percent of the 1943 GRU-Naval Washington to Moscow messages were broken, but none for any other year, although several thousand were sent between 1941 and 1945. The decryption rate of the NKVD cables was:

• 1942 1.8%
• 1943 15.0%
• 1944 49.0%
• 1945 1.5%

Out of some hundreds of thousands of intercepted cyphertexts, it is claimed that under 3000 have been partially or wholly decrypted.

The Soviets eventually stopped reusing key pad material, possibly after learning of the US / British work from several of their agents, after which their one-time pad traffic reverted to completely unreadable.

Significance

Main articles: Significance of Venona

The NSA followed Soviet intelligence traffic for only a few years in World War II, and decrypted only a small portion of that traffic. The Venona project was a thirty-eight year investigation conducted by the NSA and FBI counterintelligence, and held classified for an additional fifteen years after the program ended. Researchers, historians, and the public, struggle to understand its significance and meaning.

Senator Daniel Patrick Moynihan, Chairman of the bipartisan Commission on Government Secrecy was responsible for securing the release of Venona project materials. He wrote "The Venona intercepts contained overwhelming proof of the activities of Soviet spy networks in America, complete with names, dates, places, and deeds." (*).

• Espionage
• Venona
• Historical events in cryptography
• World War II espionage
• U.S. history of anti-Communism
• Nuclear secrecy