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One Time Pad Encryption : Historical uses

Updated: Jun 14, 2020

One-time pads have been used in special circumstances since the early 1900s. The Weimar Republic Diplomatic Service began using the method in about 1920. The breaking of poor Soviet cryptography by the British, with messages made public for political reasons in two instances in the 1920s, appears to have induced the U.S.S.R. to adopt one-time pads for some purposes by around 1930. KGB spies are also known to have used pencil and paper one-time pads more recently. Examples include Colonel Rudolf Abel, who was arrested and convicted in New York City in the 1950s, and the 'Krogers' (i.e., Morris and Lona Cohen), who were arrested and convicted of espionage in the United Kingdom in the early 1960s. Both were found with physical one-time pads in their possession.

A number of nations have used one-time pad systems for their sensitive traffic. Leo Marks reports that the British Special Operations Executive used one-time pads in World War II to encode traffic between its offices. One-time pads for use with its overseas agents were introduced late in the war. Other one-time tape cipher machines include the British machines Rockex and Noreen.

The World War II voice scrambler SIGSALY was also a form of a one-time system. It added analog noise to the signal at one end and removed it at the other end. The noise was distributed to the channel ends in the form of large shellac records of which only two were made. There were both starting synchronization and longer-term phase drift problems that arose and were solved before the system could be used.

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The NSA describes one-time tape systems like SIGTOT and 5-UCO as being used for intelligence traffic until the introduction of the electronic cipher based KW-26 in 1957.

The hotline between Moscow and Washington D.C., established in 1963 after the Cuban missile crisis, used teleprinters protected by a commercial one-time tape system. Each country prepared the keying tapes used to encode its messages and delivered them via their embassy in the other country. A unique advantage of the OTP, in this case, was that neither country had to reveal more sensitive encryption methods to the other.

During the 1983 Invasion of Grenada, U.S. forces found a supply of pairs of one-time pad books in a Cuban warehouse.

The British Army's BATCO tactical communication code is a pencil-and-paper one-time-pad system. Key material is provided on paper sheets that are kept in a special plastic wallet with a sliding pointer that indicates the last key used. New sheets are provided daily (though a small series of "training BATCO" is usually recycled on exercise) and the old ones destroyed. BATCO is used on battlefield voice nets; the most sensitive portions of a message (typically grid references) are encoded and the ciphertext is read out a letter by letter.

A related notion is the one-time code—a signal, used only once, e.g. "Alpha" for "mission completed" and "Bravo" for "mission failed" cannot be "decrypted" in any reasonable sense of the word. Understanding the message will require additional information, often 'depth' of repetition, or some traffic analysis. However, such strategies (though often used by real operatives, and baseball coaches) are not a cryptographic one-time pad in any significant sense.

While one-time pads provide perfect secrecy if generated and used properly, small mistakes can lead to successful cryptanalysis:

In 1944–1945, the U.S. Army's Signals Intelligence Service was able to solve a one-time pad system used by the German Foreign Office for its high-level traffic, codenamed GEE (Erskine, 2001). GEE was insecure because the pads were not completely random — the machine used to generate the pads produced predictable output.

In 1945 the U.S. discovered that Canberra-Moscow messages were being encrypted first using a code-book and then using a one-time pad. However, the one-time pad used was the same one used by Moscow for Washington, DC-Moscow messages. Combined with the fact that some of the Canberra-Moscow messages included known British government documents, this allowed some of the encrypted messages to be broken.

One-time pads were employed by Soviet espionage agencies for covert communications with agents and agent controllers. Analysis has shown that these pads were generated by typists using actual typewriters. This method is of course not "truly" random, as it makes certain convenient key sequences more likely than others, yet it proved to be generally effective. Without copies of the key material used, only some defects in the generation method or reuse of keys offered much hope of cryptanalysis. Beginning in the late 1940s, U.S. and U.K. intelligence agencies were able to break some of the Soviet one-time pad traffic to Moscow during WWII as a result of errors made in generating and distributing the key material.

One suggestion is that Moscow Centre personnel were somewhat rushed by the presence of German troops just outside Moscow in late 1941 and early 1942, and they produced more than one copy of the same key material during that period. This decades-long effort was finally codenamed VENONA (BRIDE had been an earlier name); it produced a considerable amount of information, including more than a little about some of the Soviet atom spies. Even so, only a small percentage of the intercepted messages were either fully or partially decrypted (a few thousand out of several hundred thousand).

Who to have been carried out by the FBI during WWII against Soviet offices in the U.S. which yielded copies of some key material. There are some claims that the material copied was helpful cryptanalytically

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