B-Dienst
[2] B-Dienst worked on cryptanalysis and deciphering (decrypting) of enemy and neutral states' message traffic and security control of Kriegsmarine key processes and machinery.
B-Dienst was instrumental in moulding Wehrmacht operations during the Battles of Norway and France in spring 1940, primarily due to the cryptanalysis successes it had achieved against early and less secure British Naval ciphers.
[10] During World War II, B-Dienst was located in 72–76 Tirpitzufer in Berlin, which was later renamed Bendlerblock, until it was bombed in December 1943, when they re-located to a bunker outside the city, which was code-named BISMARCK.
Kurt Fricke ran the major enquiry which investigated the sinking of the German auxiliary cruiser, colloquially known as an armed raider, the Atlantis in the context of Enigma security.
Konteradmiral Ludwig Stummel (5 August 1898 in Kevelaer – 30 November 1983 in Kronberg im Taunus) had succeeded Theodor Arps as Group Director of Naval Warfare department: Communications (4/SKL) from 1 January 1940 to 15 June 1941.
As well as running the B-Dienst cipher bureau, one of the responsibilities of group heads was to investigate situations in which the Naval Enigma and keying procedures could be compromised and take appropriate action.
[18] The most important individual at B-Dienst was former radio man[19] and energetic cryptologist Oberregierungsrat (Senior Civil Service Councillor) Captain Wilhelm Tranow, head of the English language cryptanalysts.
The distribution list:[26] Two grades of intelligence were produced according to their source: The captured bulletin contained both B and X-B with XB information being framed in black boxes on the page.
[37] During 1943, when U-boat operations moved to a defensive Battle of the Atlantic Campaign Climax, a distinct type of message began to be exchanged, which eventually became commonplace, i.e. Allied contact and attack reports.
Particular concerns included Allied location devices, the positions of U.S. Navy Escort carrier groups (in an attempt to ensure that U-boats surface safely).
On 11 September 1939, they read a message that informed them of a convoy assembling off the coast of the Bristol Channel, and dispatched U-boat U-31 which sank SS Aviemore about 220 miles (350 km) southwest of Cape Clear.
Perhaps B-Dienst's biggest success was in mid-March–April 1940, when a version of Naval Cypher No.1 was penetrated[43] and messages revealed plans for an Anglo-French expedition against Norway under the cover name Operation Stratford.
Exact data on British counter-measures such as landing fields, and the arrival of transports at Harstad were known in advance, enabling German Armed Forces to take appropriate action.
Naval Code, Brown edition, could still be read at the end of 1943, but a heavy air raid in Berlin in November 1943 destroyed large numbers of their records, reducing their operational effectiveness drastically.
[49] By October 1941, sufficient traffic was being generated for B-Dienst to start to notice the vital importance of the cypher giving it the moniker Convoy Cipher and gave it the code name Frankfurt.
B-Dienst were able to quickly break this code with some success, until the Stencil Subtractor system was introduced on 1 December 1943, enabling the changing of recyphering tables on a daily basis.
B-Dienst set about trying to determine how the new recyphering worked and by January 1944, displaying an astonishing high degree of skill managed to establish the principles of the Stencil Subtractor single conversion indicator procedure which was effective at that time.
By January 1944, B-Dienst was able to break the December 1943 traffic in the Auxiliary table, but only due to the fact that they were working with an edition of Naval Code which was almost at end of life.
Also Taunus The compact British Syko Device, a manual strip cipher system, gave the wireless operator on an aircraft a way of converting message text into code.
In 1942 HMS Renown used Nyko whilst carrying out wireless telegraphy calibration and testing at Gibraltar, and B-Dienst were able to locate the ship as her name was spelt out on a number of messages.
B-Dienst exceeded in reading a number of messages, which consisted mainly of time of arrivals and sailings of convoys and other merchant ship traffic between England and the invasion coats.
For example, during the Norwegian Campaign, the Büffel, boat NS25, a converted whaler used as an auxiliary patrol ship, made a mistake, when it requested a weather report with the service abbreviation QOB.
Early in the war, most of these probes were undertaken by Ludwig Stummel and when a combination of events raised suspicion that the security of the Naval Enigma had been compromised, he would launch an investigation.
He presumed that even with a Naval Enigma, and all the rotors, a solution was not possible without the daily keys and indicators, believing that the system was so extraordinarily difficult, that it was unthinkable.
Believing both document types would both have to be seized and that a British vessel would have to come alongside the German ship with a boarding party and search her (which was exactly what happened on a number of occasions).
[89] As the grid was used by all the German Navy, senior personnel in the Third Reich hierarchy, who held the Home Waters U-boat Enigma Key, could follow submarine movements.
[90] To paraphrase David Kahn These instructions were enciphered using Naval Enigma with Officers keys and transmitted to all U-boats in six parts totaling 504 four-letter groups on 10 September 1941, and went into effect immediately.
[76][93] The investigators found this striking (German:Besonders Auffällig), as according to Dönitz reports, the U-boats in the southern sector had not signaled their position after departure, and Kriegsmarine Command had not received any information regarding their attacks since heading south.
[96] The shift in the Battle of the Atlantic in 1943 against the Kriegsmarine and the U-boats showed up in monthly statistics reports and triggered a series of security investigations, which continued through the first half of 1943, and each one cleared Naval Enigma.
Dr Timothy Mulligan, a naval historian and expert on U-boat commanders, has concluded that the captains' increasing reluctance to signal HQ except in emergencies indicated that they believed the Key M infrastructure was compromised.
