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High-speed Trunk Encryption Device - wanted item

KG-81 was a high-speed Trunk Encryption Device (TED), also known as a Bulk Encryption Device, developed by the American National Security Agency (NSA), probably in the late 1970s. It uses the WALBURN cryptographic algorithm, and is primarily intended for the encryption of microwave trunks, high-speed landline circuits, video teleconferencing, T-1 satellite channels, etc. [1].

Like the other members of the WALBURN family, the KG-81 was certified to encrypt and decrypt messages up to the level of TOP SECRET. The device itself is an UNCLASSIFIED controlled cryptographic item (CCI) as long as it is unkeyed. When keyed, it assumes the classification level of the key in use. All members of the WALBURN family are suitable for simplex and full-duplex traffic, and are fully interoperable.

The image on the right shows the front panel of a KG-81 [2]. The front panel measures 145 x 155 mm and the unit is 470 mm deep. Typically, two KG-81 units were mounted side-by-side in a special 19" rackmount adapter unit.
Font view of the KG-81. Photograph by Ralph Simpson.

Cryptographic keys, or crypto variables as they are called in NSA language, are loaded into the device by means of a standard key transfer device, or key-filler, such as the KYK-13. The key-filler is connected to the 5-pin U-229 connector at the font panel, marked FILL. Once connected, the MODE-switch at the top left is set to LOAD and the ACTIVATE button is pressed.

The KG-81 was capable of encrypting and decrypting data at a maximum speed of 20 Mbps, which was extremely fast at the time. In the late 1980s, the KG-81 was replaced by the much faster KG-95 that ran at 50 Mbps [1]. None of the WALBURN family members are in production anymore and they have all been replaced by the backwards compatible and interoperable KIV-19.

Co-production by Philips
In Europe, KG-81 units were built by Philips Usfa, under licence of the NSA, from 1982 onwards. Over the years, Philips produced hundreds of KG-81 units, suitable 19" racks and interfaces for NATO. This was the result of a NATO evaluation, codenamed HISPEED, a few years earlier, in which Philips dropped its SATCOLEX product in return for co-production of the KG-81.

The image on the right shows an original black & white photograph that was made at Philips Usfa in the early 1980s [3]. It shows part of a 19" rack, with two KG-81 units mounted in a single frame. Below the encryption units is a Philips-designed line interface for connection to the teleprinter network (telex).

 More about Philips HISPEED
Close-up of a 19'' rack with KG-81 units

  1. Federation of American Scientists (FAS), WALBURN Family and KIV-19
    FAS website. 5 May 1998. Retrieved December 2012.

  2. Ralph Simpson, Photograph of KG-81 front panel
    Retrieved December 2012.

  3. Crypto Museum, Photographs of KG-81 units in the HISPEED project
    Crypto Museum Photo Archive #301324.
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Crypto Museum. Created: Tuesday 04 December 2012. Last changed: Sunday, 25 February 2018 - 15:12 CET.
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