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Interesting conjecture at the end; GCHQ retained two Colossus machines until the 1970's. The Russians knew that Colossus existed and GCHQ knew that the Russians
by sgt101 8y ago
Interesting conjecture at the end; GCHQ retained two Colossus machines until the 1970'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'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?
- rleigh 8y agoMaybe because the Russians didn't know that GCHQ knew that the Russians knew that GCHQ had Colossus!
- sgt101 8y agoCould be...
- bcaa7f3a8bbc 8y agoSounds like the plot from Cryptonomicon.
- qubex 8y agoColossus was used to break Tunny (encrypted teleprinter traffic) and, as far as I can deduce (despite that machine also using rotors of an entirely different kind) was useless in analysing Enigma-type traffic. The desire to hide the achievements of Colossus at Bletchley Park was an (apparently successful) attempt to goad the Soviet Union into adopting similar cipher systems after the war so that the same techniques could be applied by the Western powers to read Soviet signals. The ruse largely worked.
- tialaramex 8y agoYes! This is so important and yet so often not understood even by people who've supposedly been to Bletchley where they spell it out pretty clearly in their museum. Tunny (the German thought of this as "Lorenz" because that was the manufacturer name) is an actual stream cipher, more or less. It's making pseudo-random bits and XORing them with plaintext to produce a ciperhtext. The plaintext is Baudot code rather than, say, ASCII, but it's definitely bits. Lorenz is doing this in (by modern standards) a ludicrously mechanical steampunk-looking way, but that's what it's doing. Even though to our modern eyes it looks not so different from Enigma in terms of the principle of operation it's entirely different and radically more like how things would be done decades later. Salsa20 and ChaCha are modern stream ciphers, they're designed for modern binary computers rather than a mechanical contraption, but the core underlying principles are the same as Lorenz. If you can make a lot of "random-looking" bits from a small key you can XOR them with your plain input to produce a ciphertext, nobody can decipher it without knowing the key in order to generate the same "random" bits. Most cryptosystems you use today have block ciphers inside them, which work quite differently, but some will have a stream cipher, a descendent of Lorenz inside them - spiting out "random-looking" bits.
- crishoj 8y agoThank you for this excellent explanation of stream ciphers.
- Moodles 8y agoYeah, the efforts of Bill Tutte and Tommy Flowers to break the Lorenz were amazing. People only remember Turing, but there are plenty of forgotten heroes in Bletchley who never got the recognition they deserve.
- theluketaylor 8y agoBill Tutte is a local hero here in Waterloo. He was already an extremly respected professor of the math faculty, but since the moratorium on secrets at Bletchley has been lifted he has been inducted into the Order of Canada and had a street named after him, among other honours. It is sad the revelation of his involvement came so close to the end of his life. He certainly deserved much more recognition.