Henryk Zygalski (1906-1978) was a Polish mathematician who joined the Polish General Staff's Biuro Szyfrów (Cipher Bureau) in Warsaw as a civilian cryptologist on September 1, 1932. He worked with fellow Poznań University alumni and Cipher Bureau cryptology-course graduates Marian Rejewski and Jerzy Różycki at developing methods and equipment for breaking messages enciphered on various German models of the Enigma machine.

In late 1938, in response to growing complexities in German encryption procedures, he designed the Zygalski sheets ("perforated sheets"), a manual method that, like the earlier "card catalog" method, was independent of the number of plug connections being used in the Enigma's commutator.

More information about Zygalski may be found in the article on Marian Rejewski.

Reference

Władysław Kozaczuk , Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War II, edited and translated by Christopher Kasparek, Frederick, MD, University Publications of America, 1984.