IN 1939, WHEN THE SOVIET UNION was an ally of Nazi Germany, the U.S. Army began collecting copies of encrypted cables sent commercially to Moscow by the Soviet diplomatic missions in the United States. No effort to decrypt the cables, thought to be diplomatic in nature, was made until 1943, when reports were received that Stalin, by then an ally of the United States, was negotiating a separate peace treaty with Germany. At that time, the Army Signals Security Agency (SSA), an early predecessor of the National Security Agency (NSA), was ordered to establish a program—eventually called VENONA—to decipher the cables. The Soviet codes did not yield readily to cryptanalysis, because, as it was soon discovered, a two-part ciphering system had been employed; the second step used a one-time pad—theoretically unbreakable. As it happened, none of the messages was deciphered before the end of the war.
Once progress began to be made, however, the SSA cryptanalysts made a startling discovery. Only slightly more than half of the 750,000 intercepted cables concerned foreign ministry and trade matters; the balance involved Soviet intelligence organizations. By 1946, when the first message was decrypted, KGB, GRU (military intelligence), and naval GRU–user systems had been identified. When the VENONA program ended in October 1980, portions of nearly three thousand of the cables intercepted between 1939 and 1948 had been decrypted. The results revealed that Soviet agents had penetrated every important organization in the American government, including the Manhattan Project. The Allies were not immune; VENONA revealed Soviet penetrations in Britain, Canada, and Australia. In 1995 the VENONA decrypts were declassified. Hard copies were made available to scholars, while digital versions were posted on the NSA Website, together with several monographs providing historical details.
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