In 1929, while studying mathematics at Poznań University, Rejewski attended a secret cryptology course conducted by the Polish General Staff's Cipher Bureau ("Biuro Szyfrów"), which he joined in September 1932. The Bureau had had no success in reading Enigma-enciphered messages and set Rejewski to work on the problem in late 1932; he deduced the machine's secret internal wiring after only a few weeks. Rejewski and his two colleagues then developed successive techniques for the regular decryption of Enigma messages. His own contributions included the cryptologic card catalog, derived using the cyclometer that he had invented, and the cryptologic bomb.