On 12 September 1999, Ralph Erskine posted the following German Naval Message
on the Bletchley Park Mailing List:

Few authentic examples of plain text and cipher text for Naval Enigma exist. One is set out below, mainly for any person who would like to try his or her Enigma breaking skills with a bombe simulator, or to test an Enigma simulator.

This particular message is an alpha signal (E bar to the British and Americans), even though it was sent in early 1944, on Dolphin (then called Hydra by the Germans).

E bar signals were a form of short signal (but not all that short, as you can see), which were first encoded using the Signalbuch (M. Dv. Nr. 150). The Signalbuch had been designed as a visual (flag, etc.) signal book. Because of fears about Allied shore HFDF, E bar signals were very seldom used by the Atlantic U-boats after early 1943. Instead, they sent beta signals (B bar to the Allies) using the Kurzsignalheft (M. Dv. Nr. 96). That book would have given a much shorter signal here (about 27 letters or so). One reason for the continued use of E bar signals in the Arctic was because of poor radio conditions there.

Interestingly, this E bar signal was sent by the shore control. I do not recall seeing any E bar signals from the equivalent control for the Atlantic U-boats (Befehlshaber der U-Boote – BdU). Ordinary naval Enigma signals on Triton (Shark) or Hydra took a completely different form. The first two groups contained indicators with a coded message setting, in particular. They were repeated as the last two groups.

It has been suggested that references to articles dealing with Kriegsmarine short signals and the main naval Enigma indicating system may be of interest in this context, so here they are-

Ralph Erskine, Kriegsmarine Signal Indicators,
Cryptologia, 20(4), (1996), 330‐340.

Ralph Erskine, Kriegsmarine Short Signal Systems –
and How Bletchley Park Exploited Them
Cryptologia, 23(1), (1999), 65‐92.

Ralph Erskine, Naval Enigma: A Missing Link,
International Journal of Intelligence and Counterintelligence,
3(4), (1989), 493‐509.

There is one misprint in the cipher text (BP received plenty of garbles). Solution is still possible, but if you use that letter, you will of course have problems. Several people have already solved the key, despite the mistake (but missing the letter in question), and without any further information from me about it.

Dolphin still used three-rotor naval Enigma (M3) in April 1944, with reflector B.

If you do solve the key, please do not give the answer here!

But it would probably interest list members (unless the list is being swamped) to learn how long your successful bombe run took (together with some processor information, and the name of the author of the bombe simulator used).

German Naval Short signal message in the Enigma key Hydra (Dolphin):

(1) 2308 KCS (2) 2023B/11 Apr. 1944 (12) (6) (5) (3) (4) E'E' 1 2 9 IWS 0125/11/773 O U K (7) (8) B O I E F R L D X T P H C T P G U B H I E G O Q B O (9) L U C I E/D E L T A/Y G U S T A V/G E L B/Y/Q U A T (10) L D , G , Q (8) P Q G D G E R V L E O F C W N V X H V V O H Z O A R (9) S C H/A C H T/Z W O/D R E I/S I E B E N/P I/C A E S (10) 8 2 3 7 P' C (8) T J P I B B C F G I R O (9) A R/Z W O/N E U N/L B S (10) 2 9 Dummies (11) LD' A/C Report G Gelb Enemy convoy in sight Q, 8237 Square 8237 [Lat. 71.27 N Long. 07.10 E] Pi Signed C29 ComSubs Arctic [Captain, Northern U-Boats] 1) Frequency. 2) Time of Interception. 3) Time-date group. 4) Serial number. 5) Key-Type discriminant (here Dolphin). 6) Setting Indicator. 7) Plain setting of Slow, Medium and Fast Wheels. Reflector always at Z, Reflector Wheel at A. 8) Cipher text. 9) Plain text. 10) Figure-letter equivalents of 9). 11) Translation. 12) Type-of-traffic discriminant.

Copyright © 1999, Ralph Erskine

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