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The method of Zygalski sheets was a cryptologic technique used by the Polish Cipher Bureau before and during World War II, and during the war also by British cryptologists at Bletchley Park, to decrypt messages enciphered on German Enigma machines. The Zygalski-sheet apparatus takes its name from Polish Cipher Bureau mathematician–cryptologist Henryk Zygalski, who invented it about October 1938. ==Method== Zygalski's device comprised a set of 26 perforated sheets for each of the, initially, six possible sequences for inserting the three rotors into the Enigma machine's scrambler.〔On December 15, 1938, the Germans increased the number of rotors from three to five. Only three were still used in the machine at a time, but the number of possible rotor arrangements now jumped from 6 to 60. As a result, 60 sets of perforated sheets would now be needed. Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", Appendix C to Władysław Kozaczuk, ''Enigma'', 1984, pp. 242–43.〕 Each sheet related to the starting position of the left (slowest-moving) rotor. The 26 × 26 matrix represented the 676 possible starting positions of the middle and left rotors and was duplicated horizontally and vertically: ''a–z, a–y''. The sheets were punched with holes in the positions that would allow a "female" to occur. Polish mathematician–cryptologist Marian Rejewski writes about how the perforated-sheets device was operated: Like Rejewski's "card-catalog" method, developed using his "cyclometer," the Zygalski-sheet procedure was independent of the number of plugboard plug connections in the Enigma machine.〔Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", Appendix C to Władysław Kozaczuk, ''Enigma'', 1984, p. 243.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Zygalski sheets」の詳細全文を読む スポンサード リンク
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