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As the name suggests, the T-1000/CA is based on the
Siemens T-1000 electronic teletypewriter,
that is modified and improved for
Cryptographic Application (CA).
The actual Crypto Module was made by Philips and was bolted to the
bottom of the machine, as shown in the image on the right.
Although the Crypto Module is largely identical to that of the
Philips Aroflex
– with the Crypto Heart in a potted confidential package –
it uses a different – less secure – cryptographic algorithm.
As a result, Siemens was allowed to sell the machine to countries outside
the NATO sphere.
➤ Philips Aroflex
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In order to allow Siemens
to sell the civil version of th
Aroflex,
Philips supplied the bare Crypto Module to Siemens. In this case, the
combination was called T-1000/CA, in which the extension CA
stands for Cryptographical Application.
This variant was not sold to NATO customers.
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In Jane's Military Communication, edition 1986,
Siemens offers the machine as the T-1000/CA,
with a black (rather than cream) body stowed in a matching flight-case [1].
According to an internal Philips memo [2], just one batch of
1500 crypto add-on modules was made for Siemens.
Note that the Siemens T-1000/CA is electrically identical to the
standard Philips Aroflex,
but that the actual cryptoheart is different.
The one in the T-1000/CA is built around
OQ4407 custom chips, whereas the
Philips variant (that was used by NATO) contains the
pin-compatible OQ4406.
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The image above shows the interior of the Siemens crypto heart
that was based on the OQ4407.
The algorithm of the OQ4407 (and hence the Siemens T-1000CA)
is substantially weaker than that of the OQ4406 and could be broken
with the right means, exploiting the redundancy in the encyphered
message preamble. This would typically involve solving a set of
binary equations, an exponentially large number of times, a task that was
not trivial at the time.
Rumour has it that Philips designed and developed a special chip to speed up the
analysis of OQ4407-based crypto-logics upon request of the Dutch authorities.
The cryptograms produced by the T-1000CA machines,
typically exhibit bias in the enciphered message preamble, an unnecessary
shortcoming by design. This was certainly known by the agencies of other countries.
Also note that the crypto-logic with the OQ4407 had two 16-pin connectors
by which it was connected to the mixer board, whereas the real Aroflex
crypto-logic with the OQ4406 had only one such connector.
The same is true for the mixer board. It is therefore possible to identify
the chips inside the crypto-logic without opening them.
One cable: OQ4406, two cables: OQ4407.
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- Jane's Military Communication 1986
ISBN: 0-7106-0824-1
- Philips Usfa, Internal Memo L/5636/AvdP/JG
23 August 1982, page 5.
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© Crypto Museum. Created: Monday 19 August 2019. Last changed: Saturday, 04 January 2020 - 13:32 CET.
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