Wednesday, September 20, 2006

Enigma lecture at the IET

Last night I went to a superb lecture at my institute on the German Enigma machine and how they went about cracking it's encrypted messages at Bletchley Park. Dr Mark Baldwin - the lecturer - had brought along his working four-rota machine and gave a demo. The quality of construction was excellent with that sixty year old example still working perfectly. Although I had a vague idea of how it worked he explained in great details the mechanical and wiring details. Having recently re-listened to Steve Gibson's excellent encryption series on Security Now! (episodes 30 to 37) I now see that the Enigma was a good example of how to do encryption. The Germans avoided security by obscurity - the allies had many working Enigmas and had figured out the wiring of all the rota sets before the war even started. The power of he system is in the size of the key-space and it was sloppy practises that allowed the allies to crack the system. Repeated use of sweetheart's names etc. as well as non-random sequences of keys allowed the size of the key-space to be radically reduced and in a symmetric stream cypher these are bad ideas!
Dr Mark Baldwin's Enigma site is here.

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