Thursday, March 02, 2006

Enigma codes

The project to crack the remaining three enigma codes has completed

A while ago Whit Diffie gave a talk on the Vennona decrypts to Ron Rivest's reading group at MIT and tried to get me and others interested in analyzing the problem from the point of view of the complexity of the effort.

The Vennona codes demonstrate the problem of using a one time pad in practice. Used correctly one time pads provide perfect confidentiality. There is not even a theoretical possibility of breaking the code. Used incorrectly they reduce to one of the simplest forms of cryptographic problem: an alphabetic substitution cipher where one text is used as the 'key' to encrypt another.

Breaking the Vennona codes led to the discovery of the Cambridge spy ring, the exposure of Fusch and the execution of the Rosenbergs. The M4 group might be interested in taking on this challenge as a followup.

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