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Tarolex was a key stream generator for a
modified Ecolex-IV cipher machine,
developed by Philips Usfa in 1966 at the request of the
Dutch Army. It was introduced in 1967, and allowed an Ecolex-IV machine
to be used with a pseudo-random key stream,
rather than with an OTT.
The machine is also known as UA 8084 (Philips)
and KL/TGA-3128 (Royal Dutch Army).
The image on the right shows a complete Tarolex setup .
The Tarolex itself is at the bottom right. On top of the Tarolex is a
standard Siemens T-100 teletype machine.
The modified Ecolex-IV is at the left.
The rear tape reader (that was used for the key tape) is replaced by
an interface with a connector. A cable runs from the connector on the
Ecolex-IV to the front of the Tarolex.
This way, the key stream, generated by Tarolex,
is fed to the Ecolex-IV instead of the usual key-tape.
Tarolex is housed in a heavy TEMPEST proof case as is clearly visible
in the photographs below. The actual key settings
are behind a door on the right half of the unit (see below).
Tarolex was developed at the request of the Royal Dutch Army, who wanted
a solution for the key-tape distribution problem of the existing
mixer machines, such
as the Ecolex-IV and,
to a lesser extent, the Ecolex-II.
In order to be able to connect Tarolex in place of the existing
key-tape reader, a suitable interface was developed as well .
Tarolex was based on the design of TROL,
that was developed between 1962 and 1965 for a NATO evaluation.
TROL was never built however,
as Philips lost the evaluation to ALVIS (BID 610) .
Tarolex is in fact a combination of the separate items
that TROL consisted of.
The name TAROLEX was also derived from TROL and stands for
Tapeless Rotorless Online Encryption.
The suffix 19" to the name was used to distinguise the machine
from the earlier TROL development.
In total, 151 Tarolex 19" units were built.
Although development of the Ecolex-X
had already started in 1965,
it would not be ready before 1972. Tarolex was therefore used as a
gap-fill solution until Ecolex-X was ready.
Nevertheless, many Tarolex units remained in service after the
Ecolex-X was rolled out in 1972.
The principle behind the Tarolex is that a short key is used to generate
a longer key. Inside the machine is a complex Pseudo-Random Number Generator
(PRNG) that generates an evenly spread, difficult to predict, stream of
characters with a very long period. The latter means that it does not repeat
itself for quite a long time. The key tape is used as the so-called seed.
Behind the door
on the right half of the front panel are the
controls and, more importantly, the key tape reader. Although the unit was
fed with a standard 5-level piece of punched tape, it is not a tape reader
in the usual sense. Rather than running through the reader and reading the
characters one-by-one, Tarolex reads all characters from the key tape
The tape reader
itself, consists of yet another 'door' behind
which 110 pins are located. These pins are used to read the key tape
that is 22 characters long (22 x 5 bits = 110 bits).
As a result, there are 2110 possible combinations,
which is approx. 1033.
The image on the right shows the opened tape reader of the Tarolex.
The 110 pins of the reader are clearly visible in the bottom half of
the image. The pins are arranged in the same pattern as on a standard
punched paper tape.
Once the tape was in place and all doors were closed again,
Tarolex was ready for use.
The advantage of the combination Ecolex-IV
and Tarolex was that, in
synchronous mode, the system kept sending a cipher stream, even when no
new information was typed on the teletype unit. This way, it was impossible
for an interceptor to determine the start or end (and hence the length) of
a message. Furthermore, it was impossible to recognize the operator from
his or her typing speed.
The image on the right was taken at the Royal Dutch Signals Museum
in 2009. They used to have a Tarolex machine on public display.
Unfortunately, the door of the machine was closed and no further
information was available at that time.
➤ More about the Signals Museum
- Photographs from Philips Usfa
Crypto Museum Archive.
- Philips Usfa, Internal Memo L/5636/AvdP/JG
23 August 1982, page 3.
- Koninklijke Landmacht, Sleutelgenerator KL-TGA-3128, Bediening
Tarolex User Manual and Technical Description (Dutch).
Royal Dutch Army. 11 July 1968. Updated 24 January 1980.
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© Crypto Museum. Created: Friday 14 June 2013. Last changed: Saturday, 24 February 2018 - 16:23 CET.