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Typex (BID/08)
UK Wheel-based cipher machine - wanted item

Typex was a British wheel-based electro-mechanical cipher machine. It was developed in 1934 by Wing Commander OGW Lywood and was the UK adaption of the commercial Enigma machine [1]. After the first prototype in 1935, the first production batch of 30 Typex Mark I machines was delivered to the RAF in early 1937. Typex is sometimes written as Type X or TypeX.
 
Some nice examples of Typex machines can be found in the Bletchley Park musem (UK). The image on the right was taken during the Enigma Reunion in 2009 at BP, during which occasion the protective plexiglass covers were removed and demonstrations were given by John Harper.

The image on the right shows a WWII Typex machine that was modified to mimic the operation of the German Enigma machine. Once the German messages were broken with help of the Bombe machines, the intercepted messages were decrypted manually using these machines.
  
Typex modified to mimic the operation of an Enigma machine

The Typex shown in the image is a Mark 22 (BID/08/2), which appeared relatively late in the war. It offered additional security by the addition of a plugboard at either side of the keyboard. This extension also helped when simulating Enigma operation. Compared to Enigma, the plugboard was more versatile as it allowed each letter to be swapped with every other letter, rather than swapping them in pairs like the Enigma did. Some Typex machines were modified to CCM/Typex; a machine that allowed the British to exchange secure messages with the Americans during WWII.

In the UK, Typex remained in service until the mid-1950s, when they were replaced by more modern encryption systems, but in other countries they were used well into the 1960s. The Royal Canadian Navy replaced their Typex and CCM machines by KL-7 in 1962, whilst the Canadian Embassies used them until 1968 [3]. Although Typex was decommissioned many years ago, they are rarely found in museums and very few, if any, are in private hands.
 
Typex modified to mimic the operation of an Enigma machine The actual Typex machine Close-up of the wheel windows of the Typex Close-up of the leftmost plugboard Close-up of the rightmost plugboard Another view of the Typex Mark 22 Interior of the Typex Mark 22 The complex mechanics inside the Typex

 
Wheels
The wheels of the Typex closely resemble those of the German Enigma machine. Each wheel has 26 letters around its circumference and has 26 contacts at either side. Each wheel has a thumbwheel that is used to alter the start position, and is driven by a saw-tooth ring at the right.
 
The image on the right shows a full set of 5 Typex rotors as they were shown by David White at the Enigma Reunion 2009. In order to improve reliability, each contact was doubled [1].

Typex is a 5-wheel machine, of which the first two rotors from the right remain static during encipherment (although they could be altered manually). In order to cause more frequent wheel-turnovers (irregular stepping), multiple notches were present on the wheels (e.g. 5, 7 and 9). This feature was also present on the Zählwerk Enigma, but not on the Service Enigma.
  
A full set of 4 Typex wheels

When unused, the wheels were usually stored inside a special wooden box. Some types of Typex wheels had a removable wire-core. It allowed easy changing, swapping and testing of the wheel wiring in the field. The rightmost image below shows various stages of the wire-cores.
 
A full set of 4 Typex wheels Another view of the 5 Typex wheels Typex entry wheel (static) Spring-loaded contacts Wooden box with 5 Typex wheels Typex wheel cores displayed by CGHQ in 2009. Photograph courtsey Kevin Coleman [2].

 
Models
The following Typex models are currently known:
 
Operation
The image below shows a simplified diagram that explains how the scrambler of the Typex machine actually works. At first glance, the machine is quite similar to the commercial Enigma machine. At the right is the entry disc and a the far left the reflector, each with 26 contacts.

Typex scrambler as shown in the Maintenance Manual [9]

In between the entry disc and the reflector, are five cipher wheels of which the rightmost two are static (i.e. they can be set, but they don't move during encipherment). The leftmost three wheels are controlled by a stepping mechanism that is similar (but not identical) to the stepping mechanism of the Enigma. Another difference is the addition of a plugboard (bottom) that allows the reflector to be rewired in the field, similar to the Enigma's Umkehrwalze D (UKW-D or Dora).
 
Typex Mark VI
The Typex Mark VI (Mk.6) was a rather small version of the Typex machine, that printed straight to a small paper strip.

The image on the right shows a rare example of the Typex Mark VI that was sold in an auction at Bonhams in London in November 2012 [8]. The machine was in excellent condition and came with several reels of paper tape. Unfortunately, the five cipher wheels were missing.
  
Pictures of Typex Mark VI courtesy Bonhams London [8]

 
Typex Mark VI in front of its storage box. Photo courtesy Bonhams [8] Close-up of the keyboard and the reflector. Photo courtesy Bonhams [8] Typex Mark VI inside its storage box. Photo courtesy Bonhams [8]

 
Combined Cipher Machine (CCM/Typex)
In 1943, the Americans and the British agreed upon a common standard for the secure exchange of cipher messages. The British would convert their Typex machine, and the Americans their SIGABA (ECM, Electronic Cipher machine), in order to obtain a mutually compatible machine. Although the Americans knew the Typex machine, SIGABA was never shown to the British.
 
The common machine was called the Combined Cipher Machine (CCM), but it should be noted that there were two versions of this machine: an American one and a British one. Although the machines were compatible in operation, they were actually quite different in appearance.

The image on the right shows the British variant: CCM/Typex, which is in fact a standard Typex machine, with a CCM rotor basket installed. The machine shown here is part of the collection of the NCM. Many thanks to historian David Hamer for supplying these photographs [5].

In order to support the CCM rotor set, the Typex machine had to be modified somewhat. The most obvious modification is the presence of two vertical mounting posts that were used to keep the CCM rotor basket in place (1).
  
Copyright NCM (via David Hamer). Reproduced here with kind permission [5].

The new rotor basket (2) was mounted above the normal drum and connected to the Typex via a large plug that was inserted into the socket at the right side of the keyboard (3). The plug that was previously connected to this socket, was inserted into a socket on the CCM basket (4).
 
The image on the right shows the CCM unit for Typex in a wooden transit case, just as it was delivered by the factory. It consists of a sturdy metal base plate, with a 5-rotor drum at the front, similar to the one used in CCM/SIGABA.

The actual cipher wheels are not present in the photograph. They would be inserted in between the contact plates of the drum. Towards the rear is a large switch (5) that was used to select the mode of operation: ENCIPHER or DECIPHER.

The base plate was mounted on top of a Typex and bolted in place by means of four rigged screw terminals at the corners. The entire mechanism is driven by a metal lever (6) at the center that was attached to the main shaft of the Typex. According to the serial number plate at the front, the unit is called C.C.M. Mark III.
  
Copyright NCM (via David Hamer). Reproduced here with kind permission [5].

Although there are some similarities, the CCM/Typex rotor basket shown here is different from the one used in the CCM/SIGABA. The presence of the ENCYPHER/DECYPHER switch (4) suggests that encryption was not reciproke (i.e. not reversable). On the SIGABA, such a switch was already present at the front right. Furthermore the mounting screws are at different positions.

As noted before, there are two versions of the CCM: the British CCM/Typex and the American CCM/SIGABA. It is likely that the CCM modification for both machines was manufactured by the Americans. Whilst the Typex machine was known to the Americans, the Americans never showed the original SIGABA (ECM) to the British. SIGABA was far more complex than Typex and was considered cryptographically superior, whilst Typex was merely a copy of the German Enigma.

 More about SIGABA
 
Typex machine with supporting posts for CCM modification Close-up of the main shaft of a modified Typex CCM/Typex machine CCM/Typex rotor basket CCM/Typex rotor basket in transit box

 
Wanted
Although a long time has passed since the last Typex machine was decommissioned, these machines are hardly found in museums. Crypto Museum is still looking for a genuine Typex machine for its collection, and for additional information and documentation about this machine. If you think you can help, please contact us.
 
References
  1. Wikipedia, Typex
    Retrieved April 2012.

  2. Kevin Coleman, Volunteer at Bletchley Park
    Some photographs on this page courtesy Kevin Coleman. September 2009.

  3. Jerry Proc's crypto pages, TYPEX
    History/development of Typex by various contributors.

  4. James Rusbridger and Eric Nave, Betrayal at Pearl Harbor
    ISBN 1-85479-162-1. Cornwall (UK) 1992. pp. 226-232.

  5. National Cryptologic Museum, Photographs of CCM/Typex
    Supplied by David Hamer and reproduced here with kind permission.
    Retrieved November 2012.

  6. Wikipedia, Combined Cipher Machine
    Retrieved November 2012.

  7. Jerry Proc's crypto pages, CCM Mk II (Combined Cipher Machine)
    Retrieved November 2012.

  8. Bonhams (London), Auction of Typex Mark VI (S/N: 6077)
    Images of Typex Mark VI reproduced here with kind permission.
    19799, lot 79, 14 November 2012, sold for GBP 13,750.

  9. Typex Maintenance Manual
    Date unknown.

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