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Dedicated Loop Encryption Device · DLED

KG-84 is a dedicated loop encryption device for digital data, developed in the early 1980s by the US National Security Agency (NSA), for use by the American Department of Defense (DoD) and by NATO. The device uses the SAVILLE encryption algorithm [1] – jointly developed by GCHQ and the NSA – and was approved for all levels of classification. When unkeyed, the KG-84 is unclassified, but remains a Controlled Cryptographic Item (CCI). It was succeeded in the mid-1990s by KIV-7.

The KG-84 measures 38 x 19.5 x 19 cm and weights approx. 10 kg. Its form factor allows two units to be installed side-by-side in a single 19" rack space. All controls are at the front, with the configuration settings hidden behind a hinged lid. All connections – with the exception of the U-229 key FILL socket – are located at the rear.

The KG-84 was manufactuered in the United States by Bendix Communications Division, Pulse Engineering and E-Systems (now: Raytheon). The image on the right shows a typical KG-84A that has been in service at NATO until at least 1992.
KG-84A bulk encryptor

The KG-84 (A/C) has a wide range of configuration options, most of which are hidden behind the hinged lid that covers the upper half of the front panel. In asynchronous mode, it can handle data rates between 50 and 9600 baud. In synchronous mode – using the internal clock – it can handle data up to 32,000 baud, and with an external clock connected it can even go up to 64,000 baud. Furthermore, the KG-84 is suitable for full-duplex, half-duplex and simplex communication.

The KG-84 was developed in 1983 and was first introduced with the US Army and the US Navy in early 1984. Following the John Walker Incident — in which the KW-7 cipher machine had been compromised for many years — the US Central Intelligence Agency (CIA) also introduced the KG-84 on its main communications circuits [6].

In 1988, the improved KG-84C was introduced, which offered several advantages over the KG-84 and KG-84A, including an improved handling of synchronisation on unstable HF radio links and the ability to handle the European telex protocol.
KG-84 with open lid

The device replaced earlier and ageing encryption systems, like the KW-7, KG-13, KG-30, KG-33 and the KG-34. The KG-84 was also used by NATO and, from 6 November 1989 onwards, by the Government of Australia [8]. The price for a single KG-84A unit in 1988, was US$ 5000. From the mid-1990s onwards, KG-84 was gruadually replaced by the smaller and more versatile KIV-7 — announced as an embeddable KG-84 module — which has the form factor of a CD-ROM player.

KG-84A bulk encryptor KG-84A with open lid Front view with lid closed Front view with open lid Settings behind lid FILL socket Rear panel with sockets uncovered KG-84A encryptor with KYK-13 key loader
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KG-84A bulk encryptor
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KG-84A with open lid
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Front view with lid closed
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Front view with open lid
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Settings behind lid
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FILL socket
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Rear panel with sockets uncovered
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KG-84A encryptor with KYK-13 key loader

The diagram below provides a quick overview of the controls at the front panel of the KG-84A. The upper half is covered by a hinged lid, behind which the configuration of the device can be set. Below the lid is the ON/OFF switch, the INITIATE switch and a compartment for the backup battery, which is needed for retaining the keys when the device is not powered externally.

To the right of the battery compartment is the ZEROIZE switch. Activating this switch — pull out and push it down — purges the cryptographic keys instantly. As the KG-84 uses the highly secret SAVILLE cryptographic algorithm, its keys are 128 bits long (120 key bits plus 8-bit checksum).

This means that a regular DS-102 compatible FILL device – such as the KYK-13 – can be used to transfer the keys. The KG-84 can hold up to four such Traffic Encryption Keys, or TEKs, selectable with a rotary switch at the bottom left.

The image on the right shows a regular KYK-13 fill device connected to the U-229 FILL socket at the bottom right of the front panel of the KG-84. To transfer a key, the MODE selector of the KG-84 should be set to FILL-V and the desired key compartment should be selected with the rotary switch at the bottom left of the front panel.
KYK-13 key loader connected to FILL socket

Next, the corrsponding key compartment on the KYK-13 should be selected, after which the INITIATE button is pressed to start the transfer. Up to four keys can be loaded this way. Once all keys are installed, the MODE selector is set to the desired mode of operation, and the KYK-13 is removed again. The FILL socket is normally covered by a rubber cap, to keep its contacts clean.

  1. KG-84
    Initial version of the KG-84 Dedicated Loop Encryption Device (DLED), introduced in 1984. RS-232 serial interface. Single-ended data signals.

  2. KG-84A
    Improved version of the KG-84. Suitable for use over landlines, microwave links and satellite. Supports TRI-TAC switched networks. RS-232 or RS-449 serial interface (strap selectable). Single-ended or balanced control signals. Addition of X-VAR mode. Improved remote keying. The device feature on this page, is of this type.

  3. KG-84C
    Same as KG-84A, but with improved HF capability, out-of-sync detection, asynchronous ciphertext, plaintext bypass and European Telex protocol.
Suitable key loaders
AN/KYK-13 Key Transfer Device
AN/CYZ-10 Data Transfer Device Philips DS-102 compatible key loader ANT/Siemens/R&S DS-102 key tape reader

The KG-84 is housed in a die-cast aluminium enclosure that mesasures 38 × 19.5 × 19 cm and weights just over 10 kg. The interior is accessible from the top and from the bottom, by removing the bolted panels. The case has several shielded compartments for full RED/BLACK separation.

At the bottom are two backplanes: one for the BLACK side and one for the RED side. Printed circuit boards (PCBs) are inserted into this back­plane from the top of the device. The diagram above gives a clear overview of the PCBs and the compartments into which they are installed.

The compartments at the rear hold the PSU and the physical line interface. The compartments at the front hold the controls and their wiring to the backplane. At the centre are three further compartments: one for the black side, one for red and one for the interface between them.
E-EQU - CCI board

With the exception of the Power Supply Unit (PSU), all board are removable and have a metal tag with their ID and serial number at the upper edge. They can be extracted by folding out the two plastic levers and lifting the board upwards. Only two boards are marked CCI (in earlier versions they were marked: CONFIDENTIAL). These boards contain the custom-made chips that hold the SAVILLE encryption algorithm. They are identical to the ones found in the KY-68 crypto phone.

KG-84A with top cover removed Top view with top cover removed Bottom side Bottom view Right side panel with configuration marks
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KG-84A with top cover removed
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Top view with top cover removed
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Bottom side
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Bottom view
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Right side panel with configuration marks

Block diagram
The simplified block diagram below shows the working principle of the KG-84.At the left is the black side, which is connected to the outside world. This is usually an (insecure) telephone line or (microwave) radio link. At the right is the red side, to which the (secure) equipment is connected.

Each side (black and red) has its own power supply unit (PSU), input/output circuitry (I/O) and control (CTL). At the centre (the grey area) is the bridge that connects the red and black sides. The bridge is also responsible for distributing the clock signals (CLK) to both sides without loosing the red/black isolation. The (full-duplex) crypto-logic is located at the red side (CCI).

Circuit boards
Below is an overview of the various plug-in cards of the KG-84a, complete with a description of their function. Note that two boards are marked CCI, which means that help hold classified parts. The individual chips (custom-made by RCA) on these boards are also marked CCI (confidential).

ID 1 Part No CCI 2 Description
Z-AMW ? - Main Power Supply Unit (PSU)
E-EQA ON315904 - Line interface
E-FNP ON278616 - RED I/O board
E-EQU ? CCI board
E-FNJ/1 ? - RED timing board
E-FNO ? - Control No. 1 board
E-FNN/1 ON278620 - Control No. 2 board
E-EQQ ? CCI board
E-FNM ON278624 - RED/BLACK interface (bridge)
E-FNL ON278628 - BLACK timing board
E-FNK ? - BLACK I/O board
E-EQY ON278480 - Central X-tal oscillator at 6.144000 MHz
  1. This is the ID number printed on the label at the edge of the PCB.
  2. When ticked, this board is marked as Controlled Cryptographic Item (CCI).

E-EWA - power circuit PSU seen from the bottom E-EQA - Line interface E-EQB/1 E-FNP E-EQU - CCI board E-FNJ/1 E-FNO
E-FNN E-EQQ - CCI board E-FNM board with die-cast cover E-FNM - solder side E-FNM - contents of the die-cast enclosure E-FNL E-FNK E-EQY - X-tal clock at 6.144 MHz
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E-EWA - power circuit
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PSU seen from the bottom
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E-EQA - Line interface
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E-EQU - CCI board
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E-EQQ - CCI board
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E-FNM board with die-cast cover
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E-FNM - solder side
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E-FNM - contents of the die-cast enclosure
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E-EQY - X-tal clock at 6.144 MHz

  • Algorithm
  • Key
    128 bits (120 bits with 8-bit checksum)
  • Keys
  • Speed
    50 — 9600 baud (async), 32,000 baud (sync), 64,000 (ext sync)
  • Power
    24V DC, 110V AC, 220V AC
  • Temperature
    0°C — +55°C
  • MTBF
    69,000 hours
  • Dimensions
    38 x 19.5 x 19 cm
  • Weight
    10.4 kg
  • Cost
    US$ 3600 per unit (1988) (no longer in production)
  • Manufacturer
    Pulse Engineering, Bendix Communications Division, E-Systems
Known accessories
  • C-11828/U
    Remote Control Unit (RCU), P/N OM363501-501
  • ?
    Remote Indicator Unit (RIU)
    FSK Modem (internal for KG-84A only) - 1990
    Type 1 modem (internal for KG-84A only) - 1990
  • FPA
    Fixed Plant Adapter (19" rack for fitting two KG-84A units)
  • UC
    Update counter (to be added to the FPA)
  • CAU
    Crypto Ancillary Unit (out-f-sync detection, resync, verification)
NSN numbers
  • 5810-01-146-3260
  • 5995-01-097-7556
    24V DC power cable
  • 5995-01-097-7555
    220V AC power cable
  • 5995-01-097-7554
    110V AC power cable
  • 5995-01-247-5734
    UGC-74/KG-84A interface cable
  • 5995-01-213-9648
    UXC-74/KG-84A interface cable
Technical publications
  • TM 11-5810-309-10
    Operator's Manual TSEC-KG-84A
  • TM 11-5810-309-23
    Organizational and Direct Support Maintenance DLED KG-84A
  • TM 11-5810-308-24P
    Organizational, Direct Support and General Support Repair Parts
    and Special Tool List, DLED, TSEC/KG-84A
  • TM 11-5810-377-10
    Operator's Manual TSEC/KG-84C
  • TM 11-5810-377-23
    Unit and Intermetiate Direct Support Maintenance KG-84C
  • KAO-184/TSEC
    Operating instructions for TSEC/KG84/KG-84A
  • KAO-210/TSEC
    Operating instructions for TSEC/KG-84C
  • KAM-410/TSEC
    Limited Maintenance Manual for TSEC/KG-84/KG-84A
  • KAM-411/TSEC
    Theory Textbook, TSEC/KG-84/KG-84A
  • KAM-412/TSEC
    Maintenance Troubleshooting Manual, TSEC/KG-84/KG-84A
  • KAM-504/TSEC
    Limited Maintenance Manual for TSEC/KG-84C
  • KAM-505/TSEC
    Maintenance Troubleshooting Manua, TSEC/KG-84C
  • MI-07115B/2
    Modification of AN/TYC-5A(V) to accept TSEC/KG-84 equipment
CCI   Controlled Cryptographic Item
Expression, introduced by the US National Security Agency (NSA), for equipment that handles information, secure communications, or otherwise contains a cryptographic component which performs a critcal communications security (COMSEC) function. CCI items are subject to special accounting controls and required markings.  Wikipedia
DLED   Dedicated Loop Encryption Device
General purpose encryption device for the protection of data streams between two fixed points (point-to-point). The KG-84 is such a DLED.
  1. NSA, Field Generation and Over-the-Air Distribution of COMSEC key... support of Tactical Operations and Excercises. Handling Instructions.
    NAG-16F. May 2001. Unclassified (U) — For Official Use Only (FOUO).

  2. Radio Terminal Set AN/TRC-170(V)3
    NSN 5820-01-148-3976. Raytheon, 1 August 1985 — 30 April 1990.
    Strapping of the KG-84 and KG-84A. pp. 4-83 — 4-86. 1
  1. DOcument obtained from Google.

  1. Antonio Anselmi, KG-84 evidences
    Blogspot Diario SWL I5-56578 Antonio. 30 January 2016.

  2. Comandant of the Marine Corps, USMC TSEC/KG-84 Encryption Equipment
    Marine Corps Order 2040.8. C2CT-dt. 7 November 1988. 1

  3. Cryptome, DOE Crypto Equipment Guide
    28 October 1997. KG-84A General Purpose Encryption Equipment. 1

  4. Cryptome, Manual for Employing Joint Tactical Communications
    Washington, 2 November 1998. 1

  5. Cryptome, Detailed COMSEC Procedures
    Appendix B of [4]. FOUO. 42 pages. 1

  6. Cryptome, Letter from CIA officer with a gripe
    5 October 1998. Retrieved May 2019. 1

  7. Department of the Navy, OPNAV Instruction 2221.3C
    14 May 1984. 1

  8. USA/Australia, Austrialian Treaty Series 1989 No 29
    Agreement between the Government of Australia and the Government of the USA,
    concerning Defense Communications Services. Canberra, 6 November 1989. 1
  1. Document obtained from Cryptome website.

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Crypto Museum. Created: Tuesday 24 August 2010. Last changed: Thursday, 09 May 2019 - 20:44 CET.
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