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Subtraction device for decrypting encrypted numerical codes

c. 1944

Museum for Communication Frankfurt, Museum Foundation Post and Telecommunication

Museum for Communication Frankfurt, Museum Foundation Post and Telecommunication

German counterintelligence services used a machine called a subtraction device to decrypt intercepted radio messages. British agents used a 5-character code, to which the same digit was added to each group of 5 digits. The intercepted groups of 5 characters were entered in the subtraction device and the digits from 0–9 were removed from them. The result was printed out on paper. The Germans knew groups of 5 that were not possible, meaning they could quickly identify the right combinations.

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  • Title: Subtraction device for decrypting encrypted numerical codes
  • Date Created: c. 1944
  • Location Created: Deutschland
  • Rights: © Museumsstiftung Post und Telekommunikation
  • Material: Metalle

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