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
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
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.
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
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 .
Although Typex was decommissioned many years ago, they are rarely found
in museums and very few, if any, are in private hands.
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 .
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.
When unused, the wheels were usually stored inside a special
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
The following Typex models are currently known:
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.
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).
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 .
The machine was in excellent condition and came with several reels
of paper tape. Unfortunately, the five cipher wheels were missing.
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 .
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).
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.
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
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
whilst Typex was merely a copy of the
More about SIGABA
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.
- Wikipedia, Typex
Retrieved April 2012.
- Kevin Coleman, Volunteer at Bletchley Park
Some photographs on this page courtesy Kevin Coleman. September 2009.
- Jerry Proc's crypto pages, TYPEX
History/development of Typex by various contributors.
- James Rusbridger and Eric Nave, Betrayal at Pearl Harbor
ISBN 1-85479-162-1. Cornwall (UK) 1992. pp. 226-232.
- National Cryptologic Museum, Photographs of CCM/Typex
Supplied by David Hamer and reproduced here with kind permission.
Retrieved November 2012.
- Wikipedia, Combined Cipher Machine
Retrieved November 2012.
- Jerry Proc's crypto pages, CCM Mk II (Combined Cipher Machine)
Retrieved November 2012.
- 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.
- Typex Maintenance Manual
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