Zygalski sheets
（重定向自Perforated sheet）
![A Zygalski sheet](/Images/godic/202502/02/Płachta_Zygalskiego_-_decrypting_Enigma4857.jpg")
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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.