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Switzerland Gretag Omnisec
Portable off-line electronic cipher machine
- wanted item
Gretacoder 906, also known as GC-906, is a portable electronic
cipher machine,
introduced in 1980 by Gretag AG in Regensdorf (Switzerland)
as the successor to the GC-905.
Contrary to the GC-905, it features a full keyboard and an LCD
display.
It is compatible with the earlier GC-805.
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The predecessor of the device, Gretacoder 905, had been introduced in
1977, and was one of the first electronic pocket cipher machines in the world.
It came at a time when competitor Crypto AG (Hagelin) had just
released its first electronic cipher machine, the H-460.
A few years earlier, Crypto AG
had secretly been taken over by the American intelligence service CIA
and its German counterpart, the BND. Although the Gretacoder 905
was less user-friendly than Hagelin's H-460, it was
smaller and could be carried in a pocket.
Unknown to the public however, the Hagelin H-460
contained an NSA-created backdoor, which allowed CIA and
BND to read the diplomatic traffic
of a number of countries [1]. Losing customers to Gretag meant that they
would no longer be able to do that, so it was decided to let Hagelin
also introduce a pocket cipher machine, but one that was more user-friendly
than the Gretacoder 905 and would be preferred by customers.
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Hagelin's answer to the Gretacoder 905 was the HC-520.
It had the size of a pocket calculator of the era and had an alphanumeric
keyboard and and a Liquid Crystal Display (LCD). In reality, the
HC-520 had been developed by
Siemens and contained an NSA-developed
backdoor. As it made the Gretacoder 905 less popular,
Gretag decided to develop a new pocket cipher machine as
its successor: the Gretacoder 906.
It was approximately the same size and was introduced in 1980.
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The Gretacoder 906 was not compatible with its predecessor,
Gretacoder 905, but with Gretacoder 805
— a family of modular electronic cipher machines that had been introduced in 1978.
It allowed Gretag's users to choose between compatible desktop, briefcase
and pocket devices.
To make Gretacoder 906 even more attractive, Gretag introduced the
PE-906 peripheral expansion unit
shown in the image on the right. It contains a
thermal printer, a punched paper tape reader and an acoustic modem. At the front
of the PE-906 is a cradle for the Gretacoder 906.
The image on the right shows how the PE-906 combination could
be used in a hotel room. The Gretacoder 906 is installed in the cradle
at the front.
The acoustic coupler allows encrypted text
to be sent and received via any regular analog telephone line (POTS),
using any telephone set.
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Gretacoder 906 was introduced in 1980 and was in production for many years.
In 1987, as part of a reorganisation, the production rights
were transferred to Omnisec, another Swiss crypto manufacturer,
founded that same year by former Gretag employee Dr. Pierre Schmid.
It has since come to light however, that
Omnisec was owned by the CIA, just like
competitor Crypto AG [2].
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The central piece is the Gretacoder 906 (GC906) device itself. It is similar in
size to its precessor, Gretacoder 905, but has a full keyboard and an
11-character Liquid Crystal Display (LCD).
The device is built around the efficient low-power
CDP1802 microprocessor,
developed by RCA in the mid-1970s. It is powered by internal batteries,
by an external AC power adapter or by the
PE-906 peripheral expansion unit.
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Although it is possible to use the Gretacoder 906 as a stand-alone device,
it could be expanded with several interfaces, by placing it in the PE-906
peripheral adapter shown on the right. The GC-906 connects to it via
25-pin connector.
The PE-906 provides power, additional memory for 4000 characters, a hand-operated
punched paper tape reader, a thermal printer and an acoustic modem that allows
encrypted messages to be transmitted and received via any standard
analogue telephone set.
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At present we are unable to show the interior of the Gretacoder 906, as we
don't have one of these in our collection. If you know of a
Gretacoder 906 that is available, please contact us.
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The PE-906 peripheral expander is housed in a metal enclosure that measures
315 × 210 × 70 mm and weight 2675 grams. It consists of a base panel that
holds the main printed circuit board (PCB),
and a molded case shell that
covers the base panel and holds the
manual optical paper tape reader.
The interior can be accessed by loosening 4 bolts in the corners of the
bottom panel.
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The CDP1802 processor itself is not present.
It is possible that it was removed from the empty socket on the PCB,
or that the PE-906 is connected directly to the databus of the
CDP1802 processor inside the Gretacoder 906 itself.
Any further information on this topic is most welcome.
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Device Pocket cipher machine Purpose Text encryption Manufacturer Gretag, Omnisec Type Gretacoder 906 Model GC-906 Year 1980 Algorithm Prioprietary nonlinear cipher generator Keys see below Compatibility see below Key space ~ 1060 Key period 1054 Keyboard 28 keys (9 control keys) Formatting 5-letter groups (A-P) Editing Character shift/insert/delete, Block shift Cipher text 5-letter groups (consisting of A-P) Memory 719 characters Display 11-character LCD 5 × 7 matrix plus 7 control indicators Power 6V (4 × NCC50CF 1.2V/0.5Ah NiCd battery) Temperature 0°C to +50°C Storage -15°C to +70°C Dimensions 185 × 130 × 26 mm Weight 550 g
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Combiner Secret customer-specific key in pluggable EPROM: 1038 Elementary Secret daily key consisting of 16 letters: 1022 Auxiliary Non-secret message key, 10 letters generated automatically: 1014
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GC-505 Online/offline telex encryptor - Briefcase version
- Desktop version
GC-521 SP-300 GCA (cipher teleprinter))
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40.79.21 Battery charger 40.79.29 Bag for charger 40.79.00 Key plug-in module (EPROM) 40.79.20 Leather bag for GC-906 98.10.39 Operating manual 13.09.03 NiCd battery (4 needed) 40.79.23 Military metal case 40.73.61 Gretag Key Generator GKC1 (for programming plug-in EPROM)
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Device Peripheral expander for Gretacoder 906 Manufactuers Gretag, Omnisec Model PE-906 Peripherals Thermal printer
Acoustic modem
Extended memory
Manual paper tape reader
Mains PSU Memory 4000 characters Dimensions 315 × 210 × 70 mm Weight 2675 g
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The acoustic coupler is connected to the
8-pin 270° DIN socket
at the left side of the PE-906. The image below shows the pinput of this
connector, when showing into the socket.
The wiring is currently unknown.
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Inside the cradle of the PE-906 — in which the Gretacoder 906 can be
installed — is a 25-pin male receptacle that mates with the 25-pin female
connector at the rear of the Gretacoder 906.
The diagram below shows the pinout of the PE-906 receptacle
when looking into the cradle.
The wiring is currently unknown.
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Kindly provided by Andreas Obermeier [4]
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© Crypto Museum. Created: Saturday 13 January 2024. Last changed: Tuesday, 05 March 2024 - 16:48 CET.
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![Gretacoder 906. Image extracted from brochure [A].](img/gc906_full.jpg)
