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Gretacoder 605
2048 kb/s serial link encryptor

Gretacoder 605 was a link encryptor, developed by Gretag in Regensdorf (Switzerland) in the mid-1990s. It was intended for the continuous encryption and decryption of serial (RS422) data at speeds up to 2048 kb/s (synchronous). It was the successor to the earlier Gretacoder 524 and is backwards compatible. It was available with a variety of interface options, such as V.35.
All controls are at the front panel, together with two security modules (SM), left and right, and a physical key. The physical key locks the right SM and prevents the case from being opened. The user interface consists of a series of buttons and an 2-row LCD display at the top left.

The image on the right shows the front panel of a typical Gretacoder 605. The case and the front panel layout is identical to that of the earlier (and slower) Gretacoder 524. It is also identical to the X.25 variant, the Gretacoder 545 [1], although the case of the latter was grey.
Gretacoder 605

The Gretacoder 605 was part of a range of encryption devices that were released over time, consisting of the 522, 524, 526 and 605 models, that are more or less (backwards) compatible with each other, differing only in speed and interface. To allow customization, the interface was generally implemented as a separate daughter card, making the unit suitable for wide range of applications and networks. The device shown here supports the V.35 standard.

Earlier versions of the Gretacoder 605 contained the AT&T logo, as Gretag was acquired by AT&T (USA) in 1991. In 1995, the company was sold to IRE (later: SafeNet) and the AT&T logo disappeared.
Gretacoder 605 Gretacoder 605 front panel without the key being present Gretacoder 605 front panel with keys present Connections at rear panel Placing the leftmost plug-in module Removing the rightmost plug-in Releasing the rightmost security plug-in Rightmost security plug-in

Please note that the Gretacoder 605 does not contain a physical MODEM. It can only encrypt serial data in a variety of formats, but needs an external modem in order to connect it to the outside world (e.g. via telephone lines). Two separate proprietary connectors are available at the back. The leftmost one connects to the device that needs to be protected (plain text), whilst the rightmost one delivers the cipher text.

The Gretacoder supports two encryption standards: (1) Gretag's own proprietary block cipher with a key length of 64 or 128 bits, or (2) industry standard DES with a key length of 56 bits [2]. The latter was supplied for customers who wanted an industry standard, despite the fact that by the early 1990s DES increasingly became critisized as being unsafe. The in-house developed 128 bit key block cipher provided much stronger security.
The Gretacoder 605 is built inside a rather neat cream metal case, that measures only 22 x 7 x 36.5 cm. The case consists of two parts: A metal frame holding the PCBs and the front panel, and a cream outer shell. The latter is held in place by just two large bolt at the rear.
The outer shell can only be removed when the two bolts are taken out and the physical key (at the right of the front panel) is released. The internal frame holds the front panel and two PCBs: the Main PCB at the bottom and a smaller interface board at the top.

Depending on the customer's requirements, a different interface board would be used. The interface connects to the main PCB by means of a 40-pin ribbon cable. The interface shown here has two proprietary rectanglular connectors, marked PLAIN and CIPHER.
Frame with main PCB

At the heart of the main PCB is the M80C154 microcontroller, which is compatible with the industry standard 8051. Several supporting chips are present (e.g. RAM and serial interfaces) and the firmware is contained in EEPROM. Encryption and decryption is implemented in two custom chips on the main PCB. The main PCB is slightly different from the one in the Gretacoder 524. Newer generation custom chips have been used, and provisions for the two DB25 connectors at the rear have been removed. Interfacing is now always done via a daughter card.

At the rear, the main PCB has a female DB9 socket marked REMOTE CONTROL. The purpose of this socket is currently unknown, but it seems to be a standard asynchronous RS-232 port, probably used for a controlling terminal.
Frame with main PCB Gretacoder 605 interior Interface board Top view of main PCB Interface board Interface board

Help required
As Gretag is no longer in business, background information about the company and its devices are very hard to find. Unfortunately, we have no further information about this device at present. If you have more, different or better information, please contact us. Your help is appreciated.
  1. Gretacoder Data Systems AG., Gretacoder 545, X.25 Data Encryption
    4-page sales brochure. April 1997.

  2. Cyberspace Policy Institute, Growing Development of Foreign Encryption Products
    10 June 1999. p. 44. Retrieved March 2012.

  3. OKI Semiconductor, M80C154 processor datasheet
    CMOS 8-bit 8051-compatible microcontroller. January 1998. Retrieved March 2012.

  4. Wikipedia, V.35 Standard
    Retrieved July 2012.

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