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A three rotor prewar Enigma machine in operation. The man using the machine is a Waffen-SS NCO.

(Photo courtesy of Synder's Treasures, Bowie, Maryland).

The Enigma Cipher Machine

The Enigma was one of the best of the new electromechanical cipher machines produced for the commercial market in the 1920s. Hugo Koch, a Dutchman, conceived of the machine in 1919. Arthur Scherbius first produced it commercially in 1923. Impressed by its security, which was based on statistical analysis, the German government acquired all rights to the machine and adapted it to the needs of its new, modern military forces. It became the standard cipher machine of the military services, of German agents, and of the secret police. It was also used at all echelons from high command to front-line tactical units including individual airplanes, tanks, and ships. An ordinary three-wheel Enigma with reflector and six plug connections generated the following number of coding positions:

3,283,883,513,796,974,198,700,882,069,882,752,878,379,955,261,095,623,685,444,055,315,226,006,
433,616,627,409,666,933,182,371,154,802,769,920,000, 000,000

Given this statistical capability, proper communications procedures and practices, and the fact that solving the Enigma on a timely basis would require rapid analytic machinery which did not exist, the Germans regarded the Enigma as impenetrable even if captured. The Germans, however, did not always practice proper communications security, and, more importantly, the Allies, even in 1938-39, were on the verge of creating the necessary cryptanalytic machinery which would unlock the Enigma's secrets. The evolution of this technology and its application were major contributing factors to the ultimate Allied victory in World War II.

The Enigma machine was not a commercial success but it was taken over and improved upon to become the cryptographic workhorse of Nazi Germany. [It was broken by the Polish mathematician, Marian Rejewski, based only on captured cipher text and one list of three months worth of daily keys obtained through a spy. Continued breaks were based on developments during the war by Alan Turing, Gordon Welchman and others at Bletchley Park in England.]

Source: Kahn p.422 (and many others)