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Breaking German Navy Ciphers

U-534 was a German type IXC/40 submarine (U-boat) of the German Navy (Kriegsmarine) that serviced during WWII. The ship was built in 1942 by Deutsche Werft AG in Hamburg-Finkenwerder (Germany) and was designated 'werk 352'. It was launched on 23 September 1942 and commissioned on 23 December 1942. It was commanded by Oberleutnant Herbert Nollau [1].

Initially, the ship was assigned to the 4th U-boat Flotilla, but in April 1944, after some changes, it was transferred to the 2nd flotilla. On 1 May 1945 the boat went on its last patrol as part of the 33rd flotilla. Only five days later it was sunk by an attacking British Liberator aircraft. 49 of the 52 crew members survived the fatal blast.

The ship was discovered in 1986 on the sea bed of the Kattegat, off the coast of Denmark, by Danish wreckhunter Aage Jensen, nearly 41 years after it was sunk. In 1996, the recovered U-boat was transported to Birkenhead (England).
Photograph put into the public domain by 'Paul Adams' (via Wikipedia)

There it has been on public display at the Warship Preservation Trust until the museum closed down in 2006. The U-boat has since been aqcuired by the Merseytravel transit authority and is now on public display again at the Woodside Ferry Terminal in Liverpool (England) [1].

Enigma messages
Many artefacts were recovered from the U-354 by Danish wreck diver Aage Jensen, such as weapons, equipment, bottles, name plates, stamps, breathing masks, clocks, binoculars, tools, etc. Amoung the recovered documents was also a large number of ciphertext Enigma messages.

As the contents of these messages was hitherto unknown German researcher Michael Hörenberg set out in 2012 to break the messages again by using distributed computing power.

Starting in July 2012 by combining 112 Intel CPU cores, using a modified software Turing Bombe and brute force attacks, he achieved his first break on 31 July 2012, based on a ciphertext-only attack. By 20 October, 46 of the 50 messages had already been broken again. One message, of 1 May 1945, is of particular historical importance, as it was sent by Dönitz.
Authentic Naval Enigma M4 message. Copyright Michael Hörenberg 2012.

Breaking the messages again is still very difficult, even with todays computing power. One of the main problems is the fact that most documents are damaged and are only partly complete and sometimes the start of the message is missing completely. Furthermore, the handwriting of the German operators is a challenge in itself. More information from Michael Hörenberg's website [3].

Message from Dönitz
This message was sent on 1 May 1945. It is of historical importance as it was sent by Admiral Dönitz to announce his apportment as Hitler's successor after the latter committed suicide.

The message was originated on an Enigma M4 machine and was broken again on 20 October by Michael Hörenberg and is reproduced here by his kind permission.

 Full message text


A number of letters and letter-combinations that are not frequently used in German, were used as puntuation marks in the text. The following markup codes were used by the German Navy:

X   Period
End of line or abbreviation (German: Punkt).
XX   Colon
(German: Doppelpunkt)
Y   Comma
YY   Dash, hyphen, slash
KK   Brackets, used as KK–KK
Text can be placed between parenthesis (brackets) by placing the letter combination 'KK' before and after it (Klammern). E.g. KKTULPEKK should be printed as (Tulpe).
J   Stress mark (or quote), used as J–J
It was possible to stress a certain part of the text by placing the letter 'J' before and after the text, e.g. REICHSLEITER J BOHRMAN J, could be printed as: Reichsleiter 'Bohrman'.
UD   Question mark (?)
  1. Wikipedia, German submarine U-534
    Retrieved October 2012.

  2. Diveship Ternen, Items found inside the U-534
    Website. Retrieved October 2012.

  3. Michael Hörgenberg, Breaking German Navy Ciphers
    The U-534 breaking project. July 2012.

  4. Oberkommando der Kriegsmarine, Der Schlüssel M, Verfahren M Allgemein
    Operating procedure for Naval Enigma. Berlin 1940.
    Crypto Museum #300359. 1

  5. Doppelbuchstabentauschtafeln für Kenngruppen
    Bigram substitution table for Message Indicators. Crypto Museum #300356. 1
  1. Document kindly supplied by Arthur Bauer.

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© Crypto Museum. Created: Friday 15 May 2015. Last changed: Friday, 23 February 2018 - 22:28 CET.
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