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Zygalski sheets

April 12, 2024

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.

A Zygalski sheet

The Zygalski-sheet apparatus takes its name from Polish Cipher Bureau mathematician–cryptologist Henryk Zygalski, who invented it about October 1938.

Method edit

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.[1] 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 right 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:

When the sheets were superposed and moved in the proper sequence and the proper manner with respect to each other, in accordance with a strictly defined program, the number of visible apertures gradually decreased. And, if a sufficient quantity of data was available, there finally remained a single aperture, probably corresponding to the right case, that is, to the solution. From the position of the aperture one could calculate the order of the rotors, the setting of their rings, and, by comparing the letters of the cipher keys with the letters in the machine, likewise permutation S; in other words, the entire cipher key.[2]

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.[3]

Manufacture edit

 
Demonstration of two perforated sheets at Bletchley Park Museum

The Cipher Bureau's manual manufacture of the sheets, which for security reasons was done by the mathematician-cryptologists themselves,[4] using razor blades, was very time-consuming. By 15 December 1938 only a third of the job had been finished.

On that date, the Germans introduced rotors IV and V, thus increasing the labor of making the sheets tenfold, since ten times as many sheets were now needed (for the now 60 possible combinations of sequences, in an Enigma machine, of 3 rotors selected from among the now 5).[3]

On 25 July 1939, five weeks before the outbreak of World War II, the Polish General Staff's Cipher Bureau disclosed to their French and British allies, at Warsaw, their cryptologic achievements in breaking Enigma ciphers.[5] Part of the disclosures involved Zygalski's "perforated-sheet" method.

The British, at Bletchley Park, near London, England, undertook the production of two complete sets of perforated sheets. The work was done, with the aid of perforators, by a section headed by John R.F. Jeffreys.[6][7] The sheets were known at Bletchley as Netz (from Netzverfahren, "net method"), though they were later remembered by Gordon Welchman as "Jeffreys sheets"; the latter term, however, referred to another catalog produced by Jeffreys' section.[6]

The first set was completed in late December 1939. On 28 December part of the second set was delivered to the Polish cryptologists,[7] who had by then escaped from German-overrun Poland to PC Bruno outside Paris, France. The remaining sheets were completed on 7 January 1940,[8] and were couriered by Alan Turing to France shortly thereafter.[7] "With their help," writes Rejewski, "we continued solving Enigma daily keys."[3] The sheets were used by the Poles to make the first wartime decryption of an Enigma message, on 17 January 1940.[7][9]

In May 1940, the Germans once again completely changed the procedure for enciphering message keys (with the exception of a Norwegian network). As a result, Zygalski's sheets were of no use, though the Herivel tip could still be used.[10]

See also edit

Notes edit

  1. ^ On 15 December 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.
  2. ^ Marian Rejewski, "The Mathematical Solution of the Enigma Cipher," Appendix E to Władysław Kozaczuk, Enigma, 1984, p. 289.
  3. ^ a b c Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", Appendix C to Władysław Kozaczuk, Enigma, 1984, p. 243.
  4. ^ Marian Rejewski, "Remarks on Appendix 1 to British Intelligence in the Second World War by F.H. Hinsley," p. 82.
  5. ^ Władysław Kozaczuk, Enigma, 1984, p. 59.
  6. ^ a b Ralph Erskine, "The Poles Reveal their Secrets: Alastair Denniston's Account of the July 1939 Meeting at Pyry," Cryptologia 30 (4), December 2006, pp. 294–305.
  7. ^ a b c d Ralph Erskine, "Breaking Air Force and Army Enigma," in Action this Day, edited by Ralph Erskine and Michael Smith, 2001, p. 53.
  8. ^ Herivel 2008, p. 7
  9. ^ Władysław Kozaczuk, Enigma, 1984, pp. 84, 94 (note 8).
  10. ^ Marian Rejewski, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", Appendix C to Władysław Kozaczuk, Enigma, 1984, pp. 243, 245.

References edit

  • Herivel, John (2008), Herivelismus and the German Military Enigma, Cleobury Mortimer, Shropshire: M & M Baldwin, ISBN 978-0947712464
  • Kozaczuk, Władysław (1984), Enigma: How the German Machine Cipher was Broken, and how it was Read by the Allies in World War Two, edited and translated by Christopher Kasparek (2 ed.), Frederick, Maryland: University Publications of America, ISBN 978-0890935477 A revised and augmented translation of W kręgu enigmy, Warsaw, Książka i Wiedza, 1979, supplemented with appendices by Marian Rejewski and others.
  • Rejewski, Marian (1982), "Remarks on Appendix 1 to British Intelligence in the Second World War by F.H. Hinsley," translated by Christopher Kasparek", Cryptologia, vol. 6, no. 1 (published January 1982), pp. 75–83, doi:10.1080/0161-118291856867
  • Rejewski, Marian (1984), Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods Appendix C of Kozaczuk 1984, pp. 241–245
  • Rejewski, Marian (1984), The Mathematical Solution of the Enigma Cipher Appendix E of Kozaczuk 1984, pp. 272–291

External links edit

April 12, 2024
zygalski, sheets, method, cryptologic, technique, used, polish, cipher, bureau, before, during, world, during, also, british, cryptologists, bletchley, park, decrypt, messages, enciphered, german, enigma, machines, zygalski, sheetthe, zygalski, sheet, apparatu. 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 A Zygalski sheetThe Zygalski sheet apparatus takes its name from Polish Cipher Bureau mathematician cryptologist Henryk Zygalski who invented it about October 1938 Contents 1 Method 2 Manufacture 3 See also 4 Notes 5 References 6 External linksMethod editZygalski 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 1 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 right 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 When the sheets were superposed and moved in the proper sequence and the proper manner with respect to each other in accordance with a strictly defined program the number of visible apertures gradually decreased And if a sufficient quantity of data was available there finally remained a single aperture probably corresponding to the right case that is to the solution From the position of the aperture one could calculate the order of the rotors the setting of their rings and by comparing the letters of the cipher keys with the letters in the machine likewise permutation S in other words the entire cipher key 2 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 3 Manufacture edit nbsp Demonstration of two perforated sheets at Bletchley Park MuseumThe Cipher Bureau s manual manufacture of the sheets which for security reasons was done by the mathematician cryptologists themselves 4 using razor blades was very time consuming By 15 December 1938 only a third of the job had been finished On that date the Germans introduced rotors IV and V thus increasing the labor of making the sheets tenfold since ten times as many sheets were now needed for the now 60 possible combinations of sequences in an Enigma machine of 3 rotors selected from among the now 5 3 On 25 July 1939 five weeks before the outbreak of World War II the Polish General Staff s Cipher Bureau disclosed to their French and British allies at Warsaw their cryptologic achievements in breaking Enigma ciphers 5 Part of the disclosures involved Zygalski s perforated sheet method The British at Bletchley Park near London England undertook the production of two complete sets of perforated sheets The work was done with the aid of perforators by a section headed by John R F Jeffreys 6 7 The sheets were known at Bletchley as Netz from Netzverfahren net method though they were later remembered by Gordon Welchman as Jeffreys sheets the latter term however referred to another catalog produced by Jeffreys section 6 The first set was completed in late December 1939 On 28 December part of the second set was delivered to the Polish cryptologists 7 who had by then escaped from German overrun Poland to PC Bruno outside Paris France The remaining sheets were completed on 7 January 1940 8 and were couriered by Alan Turing to France shortly thereafter 7 With their help writes Rejewski we continued solving Enigma daily keys 3 The sheets were used by the Poles to make the first wartime decryption of an Enigma message on 17 January 1940 7 9 In May 1940 the Germans once again completely changed the procedure for enciphering message keys with the exception of a Norwegian network As a result Zygalski s sheets were of no use though the Herivel tip could still be used 10 See also editCryptanalysis of the Enigma Bomba cryptologic bomb machine designed about October 1938 by Marian Rejewski to facilitate the retrieval of Enigma keys Bombe a machine inspired by Rejewski s cryptologic bomb that was used by British and American cryptologists during World War II Grille cryptography Punched card Jacquard loomNotes edit On 15 December 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 Wladyslaw Kozaczuk Enigma 1984 pp 242 43 Marian Rejewski The Mathematical Solution of the Enigma Cipher Appendix E to Wladyslaw Kozaczuk Enigma 1984 p 289 a b c Marian Rejewski Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys Appendix C to Wladyslaw Kozaczuk Enigma 1984 p 243 Marian Rejewski Remarks on Appendix 1 to British Intelligence in the Second World War by F H Hinsley p 82 Wladyslaw Kozaczuk Enigma 1984 p 59 a b Ralph Erskine The Poles Reveal their Secrets Alastair Denniston s Account of the July 1939 Meeting at Pyry Cryptologia 30 4 December 2006 pp 294 305 a b c d Ralph Erskine Breaking Air Force and Army Enigma in Action this Day edited by Ralph Erskine and Michael Smith 2001 p 53 Herivel 2008 p 7 Wladyslaw Kozaczuk Enigma 1984 pp 84 94 note 8 Marian Rejewski Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys Appendix C to Wladyslaw Kozaczuk Enigma 1984 pp 243 245 References editHerivel John 2008 Herivelismus and the German Military Enigma Cleobury Mortimer Shropshire M amp M Baldwin ISBN 978 0947712464 Kozaczuk Wladyslaw 1984 Enigma How the German Machine Cipher was Broken and how it was Read by the Allies in World War Two edited and translated by Christopher Kasparek 2 ed Frederick Maryland University Publications of America ISBN 978 0890935477 A revised and augmented translation of W kregu enigmy Warsaw Ksiazka i Wiedza 1979 supplemented with appendices by Marian Rejewski and others Rejewski Marian 1982 Remarks on Appendix 1 to British Intelligence in the Second World War by F H Hinsley translated by Christopher Kasparek Cryptologia vol 6 no 1 published January 1982 pp 75 83 doi 10 1080 0161 118291856867 Rejewski Marian 1984 Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys and of German Efforts to Frustrate Those Methods Appendix C of Kozaczuk 1984 pp 241 245 Rejewski Marian 1984 The Mathematical Solution of the Enigma Cipher Appendix E of Kozaczuk 1984 pp 272 291External links editJavascript demonstration of Zygalski sheets Polish Enigma Double Archived 2007 03 12 at the Wayback Machine About the Enigma National Security Agency Archived 2004 04 14 at the Wayback Machine The Enigma Code Breach by Jan Bury The Enigma and the Intelligence Archived 2007 07 11 at the Wayback Machine Codebreaking and Secret Weapons in World War II By Bill Momsen A Brief History of Computing Technology 1930 to 1939 Casselman Bill Marian Rejewski and the First Break into Enigma Feature Column American Mathematical Society retrieved 2014 11 15 Casselman Bill The Polish Attack on Enigma II Zygalski sheets Feature Column American Mathematical Society retrieved 2014 11 15 The Daily Telegraph obituary of Mavis Batey https www telegraph co uk news obituaries military obituaries special forces obituaries 10447712 Mavis Batey obituary html Retrieved from https en wikipedia org w index php title Zygalski sheets amp oldid 1191039010, wikipedia, wiki, book, books, library,

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