Wednesday, October 22, 2014

The Enigma Machine

The enigma machine was an electro-mechanical encryption device used around World War II. The main parts are the keyboard, which moves the rotors, then applies a current through the rotors. This current is sent back through the rotors by a reflector and then it lights up a lamp in the lamp field representing the encrypted letter. The lamp stayed lit for as long as the key was pressed, once the key was released, pressing the same key again would move the rotors and another lamp would light. The reflector was its principal weakness, it made encrypting and decrypting easy, for the same wheel position, if A was encrypted to G, pressing G decrypted it back to A. This had the side effect that a letter would never encrypt to itself, a property exploited by the people who broke the enigma code.

Enhancements were made to the machine, such as a plug board that exchanged letters before sending them through the rotors.

Other enhancement were the rewirable reflector, UKW D, another was the UHR box.

The following two pages contain all the technical information needed to understand or replicate the Enigma machine

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