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Re:The first chosen-prefix collision for SHA-1 by tialaramex on Wednesday January 08, 2020 @11:50AM (#21993123)
There's a quantum leap in cryptography in WWII and it's a real shame that's so rarely explained even at Bletchley where they'd be well-placed to do it.

Engima (like most systems in use in the 1930s) is thinking about cryptography as being some sort of art in which the idea is to sort of stir letter symbols. Everything else often can't even be encrypted or must be elaborately transformed into letter symbols first. Bletchley has replica "Bombes" which would be used to attack this mechanically, replicating the function of the Enigma machine to defeat it.

Lorenz, which was also attacked at Bletchley using the Colossus, is a modern stream cipher. It XORs a pseudo-random stream against your plaintext bits (albeit in the 1940s these were in 5-bit ITA telegraph code) and so it isn't different in core principles from say RC4 or at a greater distance in time indeed Salsa20 - Lorenz just has about 56-bit keys where these modern ciphers have more and are better designed. Attacking this mechanically was impractical, and that's why a computer like Colossus was needed.

As a result it really isn't fair to compare 100 years ago. If we look back 50 years instead the difference is stark.

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