Keying the German Navy’s Enigma

The German navy prepared keys for the Enigma cipher machine that was the Wehrmacht’s standard cryptographic system in a manner different from the army and the air force. They permitted the encipherers to select “random” starting positions of the rotors. The navy, on the other hand, prescribed these positions in keys when, in 1926, it adopted the Enigma. The motive for this is not known, but it proved superior to the other method, which was often compro- mised by the encipherers’ using as settings three-letter sequences from the type- writer keyboard (QWE and RFV, for example) or from girlfriends’ names or from obscene words. The consequence was that while Luftwaffe cryptograms in par- ticular were read by the enemy early on, the Kriegsmarine Enigma defended its messages far better. Only when the British captured important keying docu- ments could they begin to crack German naval messages.