Kriegsmarine M4 · 1 May 1945
Sent at 06:55
At 06:55 on 1 May 1945, Grand Admiral Dönitz sent a radio message addressed to all, enciphered on a four-rotor naval Enigma. It announced that he had been appointed Hitler's successor. Hitler had died the afternoon before, and his death had not yet been announced. A copy of the message form was later found aboard the sunken U-boat U-534. The Crypto Museum publishes the message's key, and Wikipedia shows its first sentence going through the machine letter by letter. This is a working M4 set to that key. Press Play the message and it types the plaintext, and the lamps light up the cipher the operator would have copied down.
typed
lamps
Proof that this machine is right
An Enigma never encrypts a letter as itself, because of the reflector, and the same settings decrypt what they encrypt. Type the cipher back in after a reset and the plaintext comes out. Both properties are easy to check with the keyboard. The rotors step before each letter. Rotor VIII has two notches, at M and Z, so at the fourth letter of the message the right rotor passes M and carries its neighbour along: CDTM becomes CDUN. The middle rotor can also step twice in a row, the double step, which the third test above checks.
Sources: Crypto Museum, “Message from Dönitz — 1 May 1945”, for the time, the content, U-534 and the key (M4, reflector C, Greek wheel Beta, wheel order 5-6-8, rings EPEL, plugs AE BF CM DQ HU JN LX PR SZ VW); Wikipedia, “Enigma machine”, example enciphering process, for the 32-letter test and the window letters at each step; Wikipedia, “Enigma rotor details”, for the wirings, notches and the double-step sequence ADU ADV AEW BFX BFY, which this machine also reproduces. The M4's reflector here is the thin C, as in Wikipedia's worked example. The keyboard and lamps are in alphabetical order for clarity; the military machines used a QWERTZ-like order. The plaintext is in German, as sent: “Folgendes ist sofort bekanntzugeben”, “the following is to be announced at once”. Made by Claude, 3 October 2026.