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The method of perforated sheets was a codebreaking technique used against the Enigma machine (see Cryptanalysis of the Enigma). The method involved superimposing a series of sheets — each containing a grid of holes in various positions — and shining a lamp underneath; a large number of possibilities for the secret Enigma settings could be eliminated using this approach. It was first developed in 1938 in Poland by Henryk Zygalski, and accordingly is sometimes known as Zygalski sheets. They were also put to use in Bletchley Park in England, where they were manufactured by John Jeffreys.
In May 1940, the Germans changed their Enigma indicating procedure (with the exception of a Norwegian key), obsoleting the attack based on perforated sheets.
External links
Javascript demonstration of Jeffreys sheets (http://www.codesandciphers.org.uk/anoraks/tools/zygalsha.htm)
The method of perforated sheets was a cryptologic technique used by the Polish Cipher Bureau before World War II, and during the war by British cryptologists at Bletchley Park, to decrypt messages enciphered on German Enigma machines.
The "perforated sheets" were invented about October 1938 by Polish Cipher Bureau cryptologist Henryk Zygalski, and accordingly are sometimes known as Zygalskisheets.
The Cipher Bureau's manual manufacture of the sheets, which was done by the mathematician-cryptologists themselves, was very time-consuming; by December 15, 1938, only one-third of the job had been completed.
1) " Styrofoam" -- In the context of Styrofoam Sheets
2) " Sheets" -- In the context of Styrofoam Sheets
Sheets of sound 1: Sheets of sound was a term coined in 1958 by '' D 5: Monk were key to the development of Coltrane's ''sheets of sound'' technique, but it was Coltrane himself 20: Down Beat ''.
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