Bombe Guide, Meaning , Facts, Information and Description
In the history of cryptography, a bombe was an electromechanical machine used by British and American codebreakers to help break German Enigma machine signals during World War II. The bombe was invented by Alan Turing with an important refinement suggested by Gordon Welchman. Using the Turing-Welchman bombe, the Allies were able to read a high proportion of the German Enigma traffic, and it was the primary tool used for this purpose.The bombe was named after an earlier Enigma codebreaking device designed by Polish cryptanalysts, known as the Bomba.
The standard services Enigma contained a set of three rotors, each of which could be set in any of 26 positions. The bombe worked by trying each possible position and applying a certain test. The test would eliminate most of the 26×26×26=17576 positions of all three rotors, and the remaining possible settings could be examined by hand. To use a bombe, a cryptanalyst first had to produce a so-called crib — a section of the ciphertext where he knew (or could guess) the corresponding plaintext.
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Using Polish codebreaking techniques, British cryptanalysts at Bletchley Park were, at the beginning of World War II, able to read Enigma messages by exploiting weaknesses in the German operating procedure. There was the concern that the Germans might at any point change their procedure rendering the current methods obsolete.
To preempt this, British mathematician Alan Turing designed the bombe on a more general principle — the assumption of the presence of text that analysts could guess somewhere in the message, a cryptanalytical technique known as cribbing, also termed a known plaintext attack.
By the end of March 1941, a more advanced version of the Bombe had been developed, the "Jumbo" machine.
During 1940, 178 messages were broken on the two machines, nearly all successfully. By the end of 1941, there were 16 bombes in use. By the end of 1942, this had increased to 49 bombes; at the end of 1943, this figure had more than doubled to 99 bombes in operation. By May 1945, there were 211 operational machines, and required nearly 2,000 staff to operate.
By late 1941 the change in German Navy fortunes led Admiral Karl Dönitz to become convinced that the Allies could read Navy communications and a fourth thin rotor with unknown wiring was added to German Navy systems to produce the Triton system, with a lock-out which would allow them to remain compatible with three rotor machines when necessary. As before, the unknown wiring would prevent the reading of the messages. Fortunately for the Allies, in December 1941, before the machine went into official service, a submarine accidentally sent a message with four rotors, then sent the same message using only three, disclosing the wiring of the extra rotor. In February 1942 the change became official and the ability to read the critical messages for the submarines largely ceased until new equipment became available which could use the information about the fourth rotor wiring to decrypt messages.
That spring was known as the "Happy Time" for the submarines, with renewed success in their attacks on shipping due in part to the security of their communications and the German ability to read the convoy messages sent in Allied Naval Cipher No. 3 and find out where the convoys were. Between January and March 1942 submarines sank 216 ships off the US East Coast. In May 1942 the US switched for the first time to using a convoy system and to requiring blackouts of coastal cities so ships wouldn't be silhouetted against their lights but the improvement was small.
An urgent work plan to design bombes which could decrypt the four rotor system, with delivery scheduled for August or September of 1942, was begun at Bletchley Park. The urgent need, doubts about the British design and slow progress with it prompted the US to start investigating designs for a parallel effort, based in part wiring diagrams provided to US Navy officers during a visit to Bletchley park in July 1942. Funding for a full US development effort was requested on 3 September 1942 and approved the following day.
The last manufactured United States bombe, with four wheel sets, is on display at the National Cryptologic Museum. Jack Ingram, Curator of the museum, describes being told of the existence of a second and searching for it but not finding it whole. Whether it remains in storage in pieces, waiting to be discovered, or no longer exists, is unknown.
This is an Article on Bombe. Page Contains Information, Facts Details or Explanation Guide About Bombe The British bombe
The principle of the bombe
A description of the machine
The bombes were built by the British Tabulating Machine company at Letchworth. The machine was built under the direction of Harold 'Doc' Keen and was codenamed CANTAB.Usage
The first bombe, which was based on Turing's original design and so lacked a diagonal board, arrived at Bletchley Park in March 1940 and was named "Victory". The second bombe — "Agnus" — was equipped with Welchman's diagonal board, and was installed on 8 August 1940; bombes of this type were called "Spider" bombes. United States Navy bombes
References
External links