Typex (also spelled Type X or TypeX) was the primary cipher machine used by the British military during World War II by and into the early Cold War. Based on the commercial Enigma, it was significantly enhanced to increase its security, providing robust encrypted military and government communications from 1937 throughout the late 1950s. New Zealand and other Commonwealth countries continued to use Typex well until early 1970s.
Description Like Enigma, Typex was a rotor machine. Typex came in a number of variations, but all contained five rotors, as opposed to three or four in the Enigma. Like the Enigma, the signal was sent through the rotors twice, using a "reflector" at the end of the rotor stack. On a Typex rotor, each electrical contact was doubled to improve reliability. Of the five rotors, typically the first two were stationary. These provided additional enciphering without adding complexity to the rotor turning mechanisms. Their purpose was similar to the plugboard in the Enigmas, offering additional randomization that could be easily changed. Unlike Enigma's plugboard, however, the wiring of those two rotors could not be easily changed day-to-day. Plugboards were added to later versions of Typex. The major improvement the Typex had over the standard Enigma was that the rotors in the machine contained multiple notches that would turn the neighbouring rotor. This eliminated an entire class of attacks on the system, whereas Enigma's fixed notches resulted in certain patterns appearing in the cyphertext that could be seen under certain circumstances.
Some Typex rotors came in two parts, where a slug containing the wiring was inserted into a metal casing. Different casings contained different numbers of notches around the rim, such as 5, 7 or 9 notches. Each slug could be inserted into a casing in two different ways by turning it over. In use, all the rotors of the machine would use casings with the same number of notches. Normally five slugs were chosen from a set of ten. On some models, operators could achieve a speed of 20 words a minute, and the output ciphertext or plaintext was printed on paper tape. For some portable versions, such as the Mark III, a message was typed with the left hand while the right hand turned a handle. Several Internet Typex articles say that only Vaseline was used to lubricate Typex machines and that no other lubricant was used. Vaseline was used to lubricate the rotor disc contacts. Without this there was a risk of arcing which would burn the insulation between the contacts. For the rest of the machine two grades of oil (Spindle Oils 1 and 2) were used. Regular cleaning and maintenance was essential. In particular, the letters/figures cam-cluster balata discs had to be kept lubricated.
History and development By the 1920s, the British Government was seeking a replacement for its book cipher systems, which had been shown to be insecure and which proved to be slow and awkward to use. In 1926, an inter-departmental committee was formed to consider whether they could be replaced with cipher machines. Over a period of several years and at large expense, the committee investigated a number of options but no proposal was decided upon. One suggestion was put forward by Wing Commander Oswyn G. W. G. Lywood to adapt the commercial Enigma by adding a printing unit but the committee decided against pursuing Lywood's proposal.
In August 1934, Lywood began work on a machine authorised by the RAF. Lywood worked with J. C. Coulson, Albert P. Lemmon, and Ernest W. Smith at Kidbrooke in Greenwich, with the printing unit provided by Creed & Company. The first prototype was delivered to the Air Ministry on 30 April 1935. In early 1937, around 30 Typex Mark I machines were supplied to the RAF. The machine was initially termed the "RAF Enigma with Type X attachments". The Typex Mark II and the more compact Mark III and VI are the most widely described but several distinct Typex models were developed over its operational lifespan. The development of Typex Mark II, the successor to the original Typex cipher machine, began in February 1937. By June 1938, the Typex Mark II was demonstrated to the cipher-machine committee, who approved an order for 350 units. The Mark II was significantly larger than the Enigma, weighing approximately 120 lb (54 kg) and measuring 30 in (760 mm) × 22 in (560 mm) × 14 in (360 mm) due to the incorporation of two printers: one for plaintext and one for ciphertext. Following successful trials, After trials, the machine was adopted by the RAF, Army and other government departments. During World War II, a large number of Typex machines were manufactured by the tabulating machine manufacturer Powers-Samas. Typex Mark III was a more portable variant, using the same drums as the Mark II machines powered by turning a handle (it was also possible to attach a motor drive). The maximum operating speed is around 60 letters a minute, significantly slower than the 300 achievable with the Mark II. Typex Mark VI was another handle-operated variant, measuring 20 in (510 mm) × 12 in (300 mm) × 9 in (230 mm), weighing 30 lb (14 kg) and consisting of over 700 components. Plugboards for the reflector were added to the machine from November 1941. For inter-Allied communications during World War II, the Combined Cipher Machine (CCM) was developed, used in the Royal Navy from November 1943. The CCM was implemented by making modifications to Typex and the United States ECM Mark II machine so that they would be compatible. Typex Mark VIII was a Mark II fitted with a morse perforator. Typex 22 (BID/08/2) and Typex 23 (BID/08/3) were late models, that incorporated plugboards for improved security. Mark 23 was a Mark 22 modified for use with the CCM. In New Zealand, Typex Mark II and Mark III were superseded by Mark 22 and Mark 23 on 1 January 1950. The Royal Air Force used a combination of the Creed Teleprinter and Typex until 1960. This amalgamation allowed a single operator to use punch tape and printouts for both sending and receiving encrypted material. Typex machines were modified to have the same inner wirings as the Enigma machine to routinely decipher Enigma messages at Bletchey Park. Ralph Erskine estimates that around 12,000 Typex machines were built by the end of World War II.
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