VENONA, a code word with no intrinsic meaning, identified a long-term U.S. communications intelligence project directed against Soviet diplomatic espionage messages. While such traffic was normally immune from cryptanalysis because it used the one-time pad system, Soviet resource constraints apparently caused them to copy or reuse some one-time pads. The existence of more than one message encrypted with the same key (i.e., pad) created a difficult to exploit, but substantial, cryptographic vulnerability.
VENONA was run between 1943 and 1980. There have been several releases of fully or partially decrypted messages, which still presented problems, for example, by using code names for Soviet agents and sensitive concepts. It was a further exercise to try to identify the referents of the code names, and some of the decoding remains uncertain.
Nevertheless, the released documents gave significant insight into Soviet espionage activities, as well as intelligence, diplomatic and trade operations.
The cryptanalytic approach
During the Second World War, the United States did not have a unified communications intelligence organization. VENONA was started under the Army COMINT organization, the Signal Intelligence Service. The first person to work on the material was Gene Grabeel, beginning on 1 February 1943. Initially, she was only able to do traffic analysis on the material.
In October 1943, Richard Hallock, a reserve officer, who, in civilian life, was an archeologist at the University of Chicago, gained the first, limited insight into the cryptographic error that could be exploited. More cryptanalysts joined the project in 1944, and the first true break, still limited, was made by Cecil Phillips. The break did not, at first, reveal content; it was not known that the messages related to espionage rather than diplomacy. It was well into 1946 before the first KGB traffic was read with anything approaching system.
In 1945, three discrete counterintelligence events, close in time, provided a good deal of context that helped understand the role of the traffic.
Whittaker Chambers, a Soviet agent who had tried to report his involvement with the KGB, finally gained serious attention from the Federal Bureau of Investigation (FBI). He did not give any specific information on VENONA, but raised FBI awareness of Soviet espionage and caused counterintelligence to become more active.
Shortly afterwards, Elizabeth Bentley, a KGB courier and auxiliary agent handler, also went to the FBI and named names of government employees passing documents to the Soviets. VENONA analysis, probably still through traffic analysis, confirmed her accounts.
Next, Igor Gouzenko, a GRU code clerk in Ottawa, defected in Ottawa and gave additional general information about Soviet cryptograpic practices.
According to the NSA historical overview,
In the summer of 1946, Meredith Gardner began to read portions of KGB messages that had been sent between the KGB residency (station) in New York and Moscow Center. On 31 July 1946 he extracted a phrase from a KGB New York message that had been sent to Moscow on 10 August 1944. This message, on later analysis, proved to be a discussion of clandestine KGB activity in Latin America. On 13 December Gardner was able to read a KGB message that discussed the U.S. presidential election campaign of 1944. A week later, on 20 December 1946, he broke into another KGB message that had been sent to Moscow Center two years earlier which contained a list of names of the leading scientists working on the Manhattan Project - the atomic bomb.
Britain's Government Communications Headquarters, NSA's counterpart, also participated in VENONA analysis. Under the code word MASK, they concentrated on different traffic than did NSA, working on British Government Communications Headquarters (GCHQ), working COMINTERN messages between various capital cities and Moscow from 1934 to 1937, which give a wealth of detail about Moscow's control of the various national Communist parties (including the American Communist Party). Under the code word ISCOT, they also worked on clandestine radio messages between Moscow and COMINTERN (Communist International) outstations in German-occupied Europe and in China from 1943 to 1945.
- Benson, Robert L., The Venona Story, National Security Agency
- , Memorandum for the Director from Mr. Ladd, Subject: Espionage, FBI Venona documents, 28 February 1951, at 19-37