Enigma Machine

An Enigma machine is any of a family of related electro-mechanical rotor machines used for the encryption and decryption of secret messages. The first Enigma was invented by German engineer Arthur Scherbius at the end of World War I.^[1] This model and its variants were used commercially from the early 1920s, and adopted by military and government services of several countries — most notably by Nazi Germany before and during World War II.^[2] Several different Enigma models were produced, but the German military models, the Wehrmacht Enigmas, are the ones most commonly discussed.

In December 1932, the Polish Cipher Bureau began breaking Germany's Enigma ciphers. Five weeks before the outbreak of World War II, on 25 July 1939, in Warsaw, the Polish Cipher Bureau gave Enigma-decryption techniques and equipment to French and British military intelligence.^[3][4] During the war, allied codebreakers were able to decrypt a vast number of messages that had been enciphered using the Enigma. The intelligence gleaned from this source, codenamed "Ultra" by the British, was a substantial aid to the Allied war effort.^[5]

The exact influence of Ultra on the course of the war is debated; an oft-repeated assessment is that decryption of German ciphers hastened the end of the European war by two years.^[6][7][8] Winston Churchill told Britain's King George VI after World War II: "It was thanks to Ultra that we won the war."^[9]

Though the Enigma cipher had cryptographic weaknesses, in practice it was only in combination with other factors (procedural flaws, operator mistakes, occasional captured hardware and key tables, etc.) that those weaknesses allowed Allied cryptographers to be so successful.^{[10]http://en.wikipedia.org/wiki/Enigma_machine}