The Enigma Machine

How it worked - and how it was cracked

Introduction to the Enigma Machine

The German military used the Enigma cipher machine during WW2 to keep their communications secret. The Enigma machine is an electro-mechanical device that relies on a series of rotating rotors to scramble plain text messages into incoherent ciphertext. The machine's variable elements can be set in many billions of combinations, and each one will generate a completely different ciphertext message. If you know how the machine has been set up, you can type the ciphertext back in and it will unscramble the message. If you don't know the Enigma setting, the message remains indecipherable. For this reason the Germans thought it to be impossible to crack

How it was cracked

With the help of Polish mathematicians who had managed to acquire a machine prior to the outbreak of WW2, British code breakers stationed at Bletchley Park managed to exploit weaknesses in the machine and how it was used and were able to crack the Enigma code. With information provided by the Poles, mathematician Alan Turing developed the Bombe machine, which was able to decipher enigma codes as long as the hardware of the Enigma was known and that a plain-text 'crib' of about 20 letters could be guessed accurately.With this the codebreakers at Bletchley could decipher many of the German messages they intercepted.