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Military grade portable cipher machine (wanted item)
Picoflex was cipher machine
developed by Philips Usfa between
1976 and 1982 in co-operation with the German manufacturer
AEG Telefunken.
It was a small portable cryptographic machine that was crypto-compatible with
NATO CEROFF equipment, such as RACE
(KL-51)
and Aroflex.
A cut-down version of it,
called Miniflex
was produced for civil applications.
In all, over 300 units were produced.
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Picoflex is a compact light-weight field-grade off-line encryption/decryption
device for written messages. The crypto text is formatted into 5-letter groups
containing only the 26 characters of the Latin alphabet.
The 2000 character memory can hold 1 crypto message for transmission and
an unlimited number of crypto messages for decryption at the same time, subject,
of course, to the available memory.
Text, produced by Picoflex, can be written down or transmitted by voice,
morse or telegraphy over standard telephone or radio connections.
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The image above shows a typical Picoflex unit seated on a desk with the
acoustic coupler in use for transmission of a message via a standard telephone
line (PSTN). To the left of the Picoflex, the standard thermal printer is
attached. In practice however, this printer produced a lot of unwanted
emissions (EMC) and would not pass NATO standards. It was later placed in
a Telefunken designed case, which had much better TEMPEST
shielding.
The keyboard in the image has a transparent rubber cover, protecting it
agains dust and moist. This rubber cover would become white and brittle
over the years and was subsequently removed from most units.
The radio interface is not shown in this image.
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The basic crypto unit can be used as a stand-alone device for manual input and
read-only output. The speed of operation can be enhanced by the addition of one
or more installable options:
- A thermal strip printer,
- An acoustic telephone coupler,
- A radio modem.
These options allowed the machine to be be used over the available communication
channels and allowed messages to be printed out as plain text.
As Picoflex was a military device, it was painted green and was housed in
a robust green carrying case. The accessories (i.e. the printer, the
acoustic coupler and the radio modem) were also painted green.
Please refer to the
Miniflex Operating Instructions
for an overview of the three modules.
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Like Miniflex, Picoflex was a co-production between
Philips Usfa and AEG Telefunken.
Telefunken produced the die-cast aluminium case, the keyboard, the display
and the power adapter, whilst Philips designed and built the CPU
and the crypto module.
In the Netherlands, Picoflex was sold under the Philips brand, whilst Telefunken
took care of the German market. Telefunken later moved their sales to
ANT (Later: ANT Bosch GmbH). It is entire possible to find
Picoflex units with either the Philips, Telefunken or ANT logo on it.
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Although the physical dimensions and case of the Picoflex are identical
to the Miniflex, the contents, and hence the crypto,
of the Picoflex are entirely different.
Whilst Miniflex uses a crypto algorithm that is purely software-based,
Picoflex uses advanced crypto software in combination with a sealed hardware-based
crypto module.
The crypto module contains a complex ASIC-based hardware circuit,
with the embedded NATO-approved crypto algorithm,
making it crypto-compatible with similar systems like Aroflex
and RACE (KL-51).
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In order to protect the Picoflex against enemy eavesdroppers, great care was
taken to ensure that the unit was TEMPEST proof.
This means that the case is well protected against unwanted emission of
power and signals that could otherwise be exploited to recover the original
clear text of a message. The transparent parts of the display and the printer,
contain a metal grid that helps shielding these signals.
In practice, the thermal printer caused some problems as it produces
high-energy sparks. Although the level of shielding was sufficient for civil
applications, the enclosure of the printer was later replaced by a better
shielded one by Telefunken.
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