German Enigma Device

AMoulden

The enigma device was used during World War Two to encrypt and decrypt German military messages. It was originally developed by Arthur Sherbius in 1918 for commercial purposes, but the German military adopted it in 1928. It was a pretty simple machine consisting of four rotors with all the letters of the alphabet on each, a keyboard, and wiring leading to a light panel to show the newly encoded letters. To use it, one person would type the required message on the keyboard, while a second read off and recorded the encoded letters appearing on the light panel. As each letter was typed in, the rightmost rotor would click forward one letter, 1/26 of a revolution. When that first rotor had made a complete revolution, the second rotor would click forward one letter. And the same for the third rotor, and when added later, the fourth. This made sure that no letter would ever be represented by the same symbol twice in one message. The machine worked the same way in reverse; type in the encrypted message, and read the resulting letters.*
Of course, if the machine always started from the same point, it would not be much of an encryption device, for any codesman would soon notice the pattern. To insure against this, the position of the rotors were set each day for a different codeword. However, if the Germans wanted to be able to actually read the messages, they had to make sure that the encrypting machine and the decrypting one were set to the same code. Thus, they produced a list of key words, one for each day of the year, and sent it out to the operators. At precisely noon each day, the operator would change to the next code on the list.
Another safety precaution to minimalize the damage, should a list of the codes be captured, was that each branch of the military had a different set of keys, with each branch further divided to cause even more confusion. For example, there were four different key sets for the navy alone, one each for warships in foreign waters, warships in home waters, shipyards, and U-boats. Interestingly, the navy’s codes were printed on pink paper, with special red ink so as to bleed instantly should in be exposed to water, such as when a ship was captured.
Due to these precautions and the incomprehensibility of the Enigma’s messages, the German officers generally considered their codes to be completely safe. However safe the machine itself was, there were several weak spots in the way the messages were sent, with the main one being the lack of training for the German Enigma operators. This gave Ally cryptologists quite an opening. For example, one German officer received an encoded message that he was unable to translate. He sent an unencoded message back to the sending officer, requesting that the message be sent again. Ally spies caught both the request and the resent message. Such carelessness on the part of the German operators was a large factor in the Allies’ breaking of the German codes.
As simple as the Enigma device was, the codes it produced were so difficult that during WWII, the British, American, and French military cipheranalysts could not figure it out. The code stayed unbroken until the Germans denied their peace treaty with Poland, and the Poles began attempting to decipher the Germans’ military messages in earnest. Eventually, a Polish mathematician, Marian Rejewski, with Henryk Zygalski and Jerzy Rozycki, cracked the Enigma’s code with the help of a list of captured key sheets. Later, they gave the formula to crack the Enigma to the Allies. Many war historians believe that this shortened the war on the European front by up to two years.
(Note- this explanation is extremely simplified, and completely ignores how the wiring works to complete the code. For more information, go to http://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma )

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