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The Enigma rotor-type ciphering machine
of the German Armed Forces in the Computers department |
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Among the special machines that were invented and further developed over several decades to simplify the routine enciphering and deciphering of code, the Enigma machine is probably the most well known example around the world. It was used during the Second World War to encipher most of the radio messages of the German Armed Forces (Wehrmacht) before these commands were transmitted, and to decipher them after they had been received. It is possible that between 100,000 and 200,000 Enigma machines were built during World War II. From the time of Enigma onwards, the history of computer technology was strongly influenced by enciphering techniques and the efforts expended in breaking unknown codes. Today, as computers and digital telecommunications are increasingly connected together, enciphering plays a bigger role than ever before. And the Enigma story leads one to suspect that everything in the history of the world might have been changed by the systematic alteration of letters. As our knowledge grows concerning the specific events that make up the historical entity of World War II, our assessment of the role of enciphering and code breaking becomes better balanced and more discriminating. We must remember that the initial plan was to drop the atomic bomb on Germany, and that it was Japan's cities that were decimated only because the war had ended earlier in Europe. It soon becomes clear how many alternatives were possible. Thus, Enigma's role as hero is rather a negative one as far as its technical superiority and importance to the German final victory are concerned. To continue the metaphor: it became the pedestal on which the heroes of code breaking still stand today. The radio messages enciphered by Enigma machines were deciphered during the war at the British Cipher Bureau, Bletchley Park, despite the new technical refinements that the device gained on so many occasions. Finally, the Allies were able to intercept this strand of German military radio messages, with only a very few exceptions. The inventor and the operators The invention of the working principle used in Enigma dates back to the first years of World War I, when Edward Hugh Hebern (1869-1952), an American building contractor, invented in 1917 a rotating device for poly-alphabetic substitution using independent alphabets. He offered his ciphering machines to the American military. In 1918 the engineer Arthur Scherbius (1878-1929) filed the rotor principle with the patent office. He built a machine that he designated "Enigma" - the Greek word for riddle - in his "Chiffriermaschinen AG" in Berlin before demonstrating it to the public in Bern in 1923, and then in 1924 at the World Postal Congress in Stockholm. The Enigma was not much of a secret in those days. In 1927 Scherbius bought the patents of the Dutchman Hugo Alexander Koch, who had reinvented the rotor principle in 1919. After the death of Scherbius in 1929, Willi Korn was in charge of further technical development of Enigma. In 1919 the rotor principle had also been invented independently in Sweden. In all these countries, government agencies initially showed little interest in the machines. In Germany, the Enigma was taken over by the Reichswehr (German Army of the Reich), and when the massive military build-up began under Adolf Hitler in 1933, the Enigma machine remained part of the programme. Although the Enigma was the encoding machine most often used by German agencies during World War II, it was not the only one. Some strategic messages were enciphered with a number of devices that were even more complex.
The code breakers The message can only be deciphered if the recipient knows all settings of the Enigma machine that is sending. He can then use the 'same' Enigma machine to reverse the ciphering and read the fully deciphered text. The enemy's code breakers had to ascertain the physical design of the machine and its working principle. Using the analysis of the radio messages intercepted, they were forced to calculate the setting configuration anew. This had to be done within a certain period of time in which a military reaction to the deciphered information was still possible.
The collection of the Deutsches Museum includes three Enigma machines: one naval Enigma with four rotors, and two machines from the army, which employ three rotors. Together with other ciphering devices, two of these machines are held by the Computer department (sorry, these informations are only in German). Fairly often, visitors to the museum start conversations purely by chance and identify themselves as users of Enigma during the war. A few years ago, a museum was opened in Bletchley Park, near Milton-Keynes, a city not very far from London. There, the Enigma story is presented. On display are the machines used for breaking its code. The methods used are also explained. A growing circle of historians and expert cryptologists have been dealing with the historic role of Enigma for years. It is not known how many computer simulations of Enigma there are already, but it is certain that this machine will continue to challenge both dilettante and professional programmers in the future.
Recommendations for further reading
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