TELWA

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The so-called TELWA code was a cryptography process that was used by the Allies during World War II .

Its formal name was the US War Department Telegraph Code . It was used over a long period of time and was therefore issued in various, modified editions, e.g. B. 1919 and 1942. It was used to encrypt administrative and personnel matters of no strategic importance. The code comprised several thousand groups of five letters each, arranged so that the groups could be pronounced.

The radio messages always began with the letter combination TELWA, hence the name. The TELWA code is a replacement code in which five letters each had the same meaning; the individual letters in a group of five were interdependent.

In the course of the Second World War, German cryptanalysts found that it was a replacement code ( substitution code ). By analyzing a large number of messages, a certain mathematical regularity could be determined, which was intended to detect transmission errors, but helped the Germans with the analysis. By examining repetitions, for example at the beginning and at the end of radio messages, the Germans were able to decipher the first five-letter combination , which in the course of time resulted in a large number of substitutions. Since this replacement did not offer a changeable component ( key ), a one-time assignment was sufficient to decrypt all key texts .

Towards the end of the war, the Allies learned of the successful decipherment through interrogations of German prisoner -of- war code-breakers by the Target Intelligence Committee .

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