History of Cryptography
In the history of cryptography, the Enigma was a portable cipher machine used to encrypt and decrypt secret messages. More precisely, Enigma was a family of related electro-mechanical rotor machines comprising a variety of different models.
The Enigma was used commercially from the early 1920s on, and was also adopted by the military and governmental services of a number of nations most famously by Nazi Germany before and during World War II.
The German military model, the Wehrmacht Enigma, is the version most commonly discussed. The machine has gained notoriety because Allied cryptologists were able to decrypt a large number of messages that had been enciphered on the machine. The intelligence gained through this source codenamed ULTRA was a significant aid to the Allied war effort. The exact influence of ULTRA is debated, but a typical assessment is that the end of the European war was hastened by two years because of the decryption of German ciphers.
Although the Enigma cipher has cryptographic weaknesses, it was, in practice, only their combination with other significant factors which allowed codebreakers to read messages: mistakes by operators, procedural flaws, and the occasional captured machine or codebook.
Enigma wiring diagram showing the current flow when pressing the 'A' key is encoded to the 'D' lamp, also D yields A, but A never A
The scrambling action of the Enigma rotors shown for two consecutive letters current is passed into set of rotors, around the reflector, and back out through the rotors again. Note: The greyed-out lines represent other possible circuits within each rotor, which are hard-wired to contacts on each rotor. Letter A encrypts differently with consecutive key presses, first to G, and then to C. This is because the right hand rotor has stepped, sending the signal on a completely different route.
Enlarge
The scrambling action of the Enigma rotors shown for two consecutive letters current is passed into set
The Enigma was used commercially from the early 1920s on, and was also adopted by the military and governmental services of a number of nations most famously by Nazi Germany before and during World War II.
The German military model, the Wehrmacht Enigma, is the version most commonly discussed. The machine has gained notoriety because Allied cryptologists were able to decrypt a large number of messages that had been enciphered on the machine. The intelligence gained through this source codenamed ULTRA was a significant aid to the Allied war effort. The exact influence of ULTRA is debated, but a typical assessment is that the end of the European war was hastened by two years because of the decryption of German ciphers.
Although the Enigma cipher has cryptographic weaknesses, it was, in practice, only their combination with other significant factors which allowed codebreakers to read messages: mistakes by operators, procedural flaws, and the occasional captured machine or codebook.
Enigma wiring diagram showing the current flow when pressing the 'A' key is encoded to the 'D' lamp, also D yields A, but A never A
The scrambling action of the Enigma rotors shown for two consecutive letters current is passed into set of rotors, around the reflector, and back out through the rotors again. Note: The greyed-out lines represent other possible circuits within each rotor, which are hard-wired to contacts on each rotor. Letter A encrypts differently with consecutive key presses, first to G, and then to C. This is because the right hand rotor has stepped, sending the signal on a completely different route.
Enlarge
The scrambling action of the Enigma rotors shown for two consecutive letters current is passed into set
References: * Bauer, 2000, p. 108, Bauer, 2000, p. 112 . * Hamer, David H.; Sullivan, Geoff; Weierud, Frode; Enigma Variations: an Extended Family of Machines; Cryptologia 22(3), July 1998. Online version (PDF). * (German)Ulbricht, Heinz; Die Chiffriermaschine Enigma — Trügerische Sicherheit: Ein Beitrag zur Geschichte der Nachrichtendienste, PhD Thesis, 2005 (in German). Online version (PDF). * Hinsley and Stripp, Alan; (eds.); Codebreakers: The Inside Story of Bletchley Park; 1993; pp. 83–88. Section by Alan; Stripp The Enigma Machine: Its Mechanism and Use * Kahn, David; Seizing the Enigma: The Race to Break the German U-Boats Codes, 1939-194; (1991) * Kruh, Louis; Deavours,Cipher; The Commercial Enigma: Beginnings of Machine Cryptography; Cryptologia, 26(1), pp. 1–16, 2002. Online version (PDF). * Kozaczuk, Wladyslaw; The origins of the Enigma/ULTRA * Marks, Philip; Weierud Frode; Recovering the Wiring of Enigma 's Umkehrwalz A; Cryptologia 24(1), January 2000, pp55–66. * Smith, Michael Station X; 4 books (macmillan) 1998; Paperback 2000; ISBN 0-7522-7148-2