Zygalski was, from September 1932, a civilian cryptologist with the Polish General Staff"s Biuro Szyfrów (Cipher Bureau), housed in the Saxon Palace in Warsaw. He worked there with fellow Poznań University alumni and Cipher Bureau cryptology-course graduates Marian Rejewski and Jerzy Różycki. Together they developed methods and equipment for breaking Enigma messages.
In late 1938, in response to growing complexities in German encryption procedures, Zygalski designed the "perforated sheets," also known as "Zygalski sheets," a manual device for finding Enigma settings.
This scheme, like the earlier "card catalog," was independent of the number of connections being used in the Enigma"s plugboard, or commutator. After the war he remained in exile in the United Kingdom and worked, until his retirement, as a lecturer in mathematical statistics at the University of Surrey.
He died August 30, 1978, at Liss, was cremated and his ashes taken to London. Shortly before his death, he was honored by the Polish University in Exile with an honorary doctorate for his role in breaking Enigma.