Enigma was the German encryption device used in World War II to encode sensitive military information. Enigma gave the Nazis and Axis powers a material advantage over the Allies until it was subdued by counter-encryption activities. These included, most notably, the Allied forces’ development of the Bombe, a British decryption device.
Invented in 1918 by the German engineer Arthur Scherbius and used commercially, Enigma (albeit improved and iterated upon) made its way into the German Navy in 1926 and into other branches of the German military, which were subsequently controlled by the Nazis. The device used several rotors that corresponded with light combinations, and used keys that were changed every day as part of the encryption scheme.
Marian Rejewski, a cryptanalyst working for the Polish Biuro Szyfrów (Cipher Bureau) broke Enigma’s message keys in December 1932 using advanced mathematics and flaws he uncovered in the Germans’ processes. Rejewski passed on his work to the French and British, who invested in cryptanalysis, namely production of the Bombe. The device’s story and that of the project lead, British multidisciplinary scientist Alan Turing, were popularized in the 2014 film The Imitation Game.
“The German military’s use of the Enigma encryption device created setbacks and major disadvantages for the Allied forces, who suffered surprise attacks. Once Alan Turing and others in the British intelligence service developed the Enigma-cracking Bombe, however, it leveled the playing field and indeed shortened the war.”