Turingery

from Wikipedia, the free encyclopedia

The Turingery (also called: Turingismus or Turing's Method ) was one of the British cryptanalyst Alan Turing in July 1942 in the research department of Bletchley Park devised (BP) and named after him cryptanalytic way to break that of the German Wehrmacht in World War II to encrypt their Lorenz key machine used in highly secret strategic radio telex connections (own name: key addition 40; short: SZ 40; English code name Tunny ; German " tuna " ).  

prehistory

The British Codebreakers succeeded in determining the key-dependent cam setting of the individual wheels of the SZ 40, called wheel breaking .

After a successful first break-in into two German radio messages intercepted by the British on August 30, 1941 from the radio teletype line from Athens to Vienna by the British cryptanalyst John Tiltman and subsequent clarification of the basic functioning of the German rotor key machine by the British codebreaker Bill Tutte , this was the point to be able to continue breaking Tunny messages with other keys . For this purpose, it was necessary, the keys depending selected by the Germans setting the total of 501 (= 43 + 47 + 51 + 53 + 59 + 37 + 61 + 41 + 31 + 29 + 26 + 23) freely adjustable cam ( English cams ) to tap . This important step was as a wheel breaking ( German  "roll crushing" hereinafter).

method

Key wheels of the machine with clearly visible switch cams

On July 1, 1942, Testery took over this task under the leadership of Ralph Tester and continued it successfully in Europe until the end of the war . To do this, she initially used the method developed by Turing. This is based on the formation of the difference between two intercepted radio messages that were suspected of being depth . This means two ciphertexts that were encrypted with the same, or at least “almost” the same, possibly slightly “out of phase” key. (The German technical term for this case is “Klartext-Klartext-Kompromittierung” .) The British recognized an important indication of this in the twelve-digit indicator ( key to the phrase ), which the Germans still used too carelessly at that time , such as HQIBPEXEZMUG, which started the specified twelve wheels ("wheels" as the Germans called it).

By calculating the difference between two intercepted and correctly phased depths , the British were able to unlock the key and then examine its characteristics. As Turing had suggested, they used statistical methods that exploited the weakness of the mechanical " pseudo-random " rotation of the five jumping wheels of the German machine.

“Turingery introduced the principle that the key differenced at one, now called ΔΚ, could yield information unobtainable from ordinary key. This Δ principle was to be the fundamental basis of nearly all statistical methods of wheel-breaking and setting. "

“The Turingery introduced the principle that a key difference, now called ΔΚ, could produce information that could not be derived from an ordinary key. This Δ principle became the fundamental basis for almost all statistical methods for roll breaking and for determining the position of the rolls. "

literature

Web links

Individual evidence

  1. ^ Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 11. ISBN 0-947712-34-8
  2. ↑ Donald Michie : Colossus and the Breaking of the Wartime "Fish" Codes. Cryptologia , 26: 1, pp. 17-58, 2002. doi: 10.1080 / 0161-110291890740 . DOC; 220 kB .
  3. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 388.
  4. ↑ James A. Reeds, Whitfield Diffie , JV Field: Breaking Teleprinter Ciphers at Bletchley Park: An edition of IJ Good , D. Michie and G. Timms: General Report on Tunny with Emphasis on Statistical Methods (1945). Wiley - IEEE Press, 2015, p. 396 (English). ISBN 978-0-470-46589-9 .
  5. ↑ James A. Reeds, Whitfield Diffie , JV Field: Breaking Teleprinter Ciphers at Bletchley Park: An edition of IJ Good , D. Michie and G. Timms: General Report on Tunny with Emphasis on Statistical Methods (1945). Wiley - IEEE Press, 2015, p. 330 (English). ISBN 978-0-470-46589-9 .