German Cryptanalytic Attacks on the British World War II “TYPEX” Machine
Interesting conjecture at the end; GCHQ retained two Colossus machines until the 1970&#x27;s. The Russians knew that Colossus existed and GCHQ knew that the Russians knew. Why retain Colossus - people tend to say that it was because there were networks of rotor machines in use in less sophisticated countries, but given the us or them nature of the cold war it seems unlikely that there was sufficient value in retaining them through the 50&#x27;s. My guess is that there was some sort of elaborate counter bluff played out with the Soviets; that they believed that the Brits thought that they were unaware of Colossus and so would be duped by traffic sent over rotor networks... but what was in it for the Brits?