The Kriegsmarine did not literally end every message with the same phrase, but many signalmen used a familiar two-word sign-off. Dönitz was especially fond of it. Repetition supplied codebreakers with probable plaintext, making the daily rotor settings easier to attack. The example shows that even a mathematically formidable cipher can be weakened by routine communications habits.
Notable Point · 2:41:03-2:41:35
Predictable sign-offs weakened naval Enigma
Repeated formulaic endings gave codebreakers known text that helped them attack daily naval Enigma settings.