The Enigma is a cipher machine which was created by a native born German, Arthur Scherbuis. Its function is based on the principle of the rotor, which is a wired codewheel. The rotor's body is about the size of a hockey puck and it is made of a nonconducting material of electricity (ie. rubber). This puck consists of two sides- the input plate and the output plate. Around the circumference of this puck, on each side-both the input plate and output plate- there are twenty-six evenly spaced electrical contacts. The twenty-six contacts on the input plate are connected by wires through the body of the rotor to the other twenty-six contacts on the output plate in a random arrangement. Then, an alphabet ring is placed around the rotor. Since each of the twenty-six contacts on both sides represents a letter, the rotor is said to embody a cipher alphabet. It is the initial random wiring of these contacts that is responsible for the "secret" of the machine.
Each contact on the input plate is connected to a key on a typewriter keyboard. However, each contact on the output plate is connected to a flashlight bulb which illuminates a letter on a glass screen. When enciphering with the Enigma, the message sender types in the plaintext and notes which letter lights up following each typed letter. These successive lit-up letters form the cipher text. The rotor is pushed forward one space, 1/26th of an evolution, with each press of a typewriter key. This usually allows each plaintext letter to have a different ciphertext letter each time it is typed in.
The Enigma is usually accompanied with eight rotors, each with a different wiring of the contacts. However, the cipher machine is only capable of utilizing three at a time. The purpose of this was to make the deciphering of the Enigma very difficult. So, those using the Enigma created a standard key list to avoid confusion of when to use certain combinations of three rotors. This key list specified which three of the eight rotors were to be used each day and in what order they should be placed in the machine. The key list also indicated what letter on each rotor's alphabetic ring should be displayed in the windows of the Enigma lid before typing in the plaintext message.
Due to the level of difficulty created to decipher the Enigma, many found this to be a valuable cipher machine, especially the Germans. The Enigma played a key role in World War II's Battle of the Atlantic in which the Germans used it to put messages radioed to U-boats in secret form. It was not until the British were able to capture some key documents from German warships, that the cipher was finally broken. Uthilizing this vital information, the Allies were allowed to intercept, solve, and read the coded radioed messages relayed between Admiral Karl Donitz, Hitler's commander of submarines, and his U-boats at sea. These deciphered messages informed the British and Americans about the locations and movements of the U-boats, thus enabling the Allies to divert their ships around the trouble areas while simultaneously destroying German subs. Hence, the Germans' attempt to stop the Allied ships from delivering supplies to Britain failed miserably. As a result, the Allies won the key battle that determined the outcome of the great war.
Bibliography
Kahn, David. Seizing the Enigma. Houghton Mifflin Company : Boston, 1991, pp. 31-40.
Kozaczuk, Wladyslaw. Enigma: How the German Machine Cipher Was Broken and How It Was Read by the Allies in World War TWo. University Publications of America, Inc., 1984, pp. 1-13, 272-277.
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