Marian Rejewski was responsible for the initial analysis that enabled exploitation of the German ENIGMA cryptographic machine. Without his breakthroughs, which he provided to the French and British in 1939, the U.K. and U.S. may have never been able to exploit ENIGMA.
Mr. Rejewski was selected by the Polish Defense Ministry for their Cipher Bureau, and began work against the ENIGMA in October 1932. For security reasons he was only able to work part-time on the machine, after other employees had gone home. Working alone, he applied unconventional statistical analysis to uncover ENIGMA's cryptographic techniques allowing the machine to be solved.
His breakthrough came when he and two colleagues who joined him devised a method of recovering the daily settings for the ENIGMA. Their work led to development of the bomba, a machine that was further developed by the British and used throughout World War II to read ENIGMA messages.
Just before the Germany conquered Poland, Mr. Rejewski and his colleagues escaped to Great Britain. After the war, he returned home, but was marginalized by the new communist government for having lived in a capitalist country. However, he lived to see himself hailed as a Polish national hero whose cryptologic achievement played a key role in defeating Nazi Germany.
Mr. Rejewski's genius was that he recognized traditional attacks as useless against ENIGMA. He became the first to employ a higher-algebraic attack against any cryptographic system. His insight produced a solution that had evaded his French and British peers for a decade, and thanks to his contributions, ENIGMA-derived intelligence enabled U.S. and British efforts to defeat Germany.