Typex (also named “Standard X” or “TypeX”) was a British machine of Chiffrement brought into service in 1937. It was about a commercial alternative of Enigma with modifications intended to increase safety. This machine was initially called “RAF Enigma with Type X attachments”.

History and evolution

In the years 1920, the British government sought a replacement solution for their system of coding of the type dictionary which was made safe little and which, with the Surchiffrement, appeared slow and difficult to use in practice. In 1926, an inter-departmental committee studied the question of using machines of coding. During several years the committee studied many options, including a suggestion of the chief of squadron O.G.W.G. Lywood to adapt the commercial apparatus Enigma, but no decision was made. In August 1934 Lywood started to work on a machine without awaiting the authorization of RAF. Lywood worked with J.C. Coulson, A.P. Lemmon, and W.E. Smith with Kidbrooke in the Comté of Oxford, on a print unit provided by the Creed & Company. The first prototype was delivered to the ministry for the Air the April 30th 1935. Beginning 1937, approximately 30 Typex Mk I were provided to the RAF.

The design of the following models began in February 1937. In June 1938, a demonstration of the model Typex Mk II was made at the committee of the figure, which placed order of 350 apparatuses. After some tests, the machine was quickly adopted by the army and other governmental departments.

Operation

Typex arrived in several versions and comprised five rotors with reflectors statics. In the majority of the versions, the first two rotors remained stationary during coding, although they could be positioned with the hand. These stationary rotors provided a kind of protection similar to the static table of mixture of the letters of the Enigma machine (named English plugboard or German Steckerverbindung), of which Typex was deprived.

Another improvement of Typex compared to the commercial release of Enigma was that each rotor contained several notches which made turn the close rotor. Whereas Enigma changed configuration with each 26e touches in a hurry, Typex could change after 5,11,13 and 21 pressures.

The rotors of Typex were composed of two parts, a ingot containing the electric sheath was inserted in a metal casing. Various casings contained numbers different of notches to their periphery, such as 5,7 or 9 notches. Each ingot could be inserted in two different directions in a casing while turning over it. With use, all the rotors of the machine used casings of the same number of notches. Normally five ingots were selected in a batch of ten.

In production, the operators could treat twenty words with the minute and the quantified or clear text was printed on a paper roller. For certain portable versions like Typex Mark III, a message was typed with a hand while the other hand turned a crank to actuate the apparatus (Devours and Kruh, 1985).

Safety and use

Typex was used by the British army and the RAF. These apparatuses were also used in the Commonwealth Countries like the Canada and the New Zealand. A great difference between Enigma and Typex was that the latter was to be useful as parsimoniously as possible whereas the Germans quantified many messages of various services with Enigma. Typex was used regularly only with the high command of the British army and the RAF. The others weapons or services continued to code with their system with dictionary. The supply machines of Typex coding was very restricted and no unit of ground was authorized to have some.

Since 1943 the Americans and the British had signed the Holden Agreement and BRUSA to develop a combined machine of coding (in English Combined Cipher Machine or CCM ). The American machine SIGABA (M-134-C) was also a machine of coding to rotor, although the Americans never allowed their allies to see it. Accessories were worked out for these two models enabling them to read the messages created by the other models.

It is said that, neither Typex, neither SIGABA, nor CCM “were broken” by the Axis. Although the tests of cryptanalytic attacks had made enormous progress, the results were less convincing than against Enigma, because of the evolutions of the complexity of the system and the limited flood of the transmissions made via these means. A Typex machine was recovered by the German forces but without the rotors. Their inaptitude to use this machine to decipher the allied messages Typex could convince them of the safety of Enigma.

The Typex machines remained in service until in the Années 1970 (the New Zealand government on sale put its last machines in 1973). It is one of the reasons of the maintenance of the secrecy also a long time; another was that the British continued to read the transmissions of the foreign countries made with Enigma and Typex, as long as their users thought that they were sure.

External bonds

• a series of photographs of Typex Mark III
• a page of Jerry Proc on Typex
• Photographs of Typex to the museum Bletchley Park: .

References

• Cipher A. Deavours and Louis Kruh, Machine Cryptography and Modern Cryptanalysis , Artech House, 1985, pp144-145; 148-150.
• Ralph Erskine, The Admiralty and Cipher Machines During the Second World War: Not So Stupid after All. Newspaper off Intelligence History 2 (2) (Winter 2002).
• Ralph Erskine, The Development off Typex , The Enigma Bulletin 2 (1997): pp69-86
• Kruh and Deavours, The Typex Cryptograph Cryptologia 7 (2), pp145-167, 1983

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