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Military digital line encryptor
- wanted item
The KG-84 is an electronic encryption device developed by the
National Security Agency (NSA) in the USA. It was used for ensuring
secure transmission of digital data over a variety of networks,
such as landlines, satellites, microwave links and Telex lines.
The KG-84 was built by Pulse Engineering, Inc. and Bendix.
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Two versions of the KG-84 are known. The KG-84A that was mainly used
for point-to-point encryption via telephone lines, microwave links
and satellites, and the KG-84C that was a Dedicated Loop Encryption
Device (DLED).
Both are able to operate in simplex, half-duplex and full-duplex
synchronous and asynchronous modes. This NSA Level 1 crypto device
is suitable for secret messages upto the level of TOP SECRET,
depending on the key-set that is loaded. It is fully complient with
NSA TEMPEST standards.
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Compared to the KG-84A, the KG-84C had some interesting extras.
It has a variable update counter, improved HF performance,
out-of-sync detection (when in synchronous mode), asynchronous
ciphertext, plaintext bypass, and the European Telex protocol.
When used with a suitable digital telephone unit, the
KG-84 could also be used for secure voice transmissions.
Data could be handled by the KG-84 in asynchronous mode at rates
between 50 and 9600 baud. In synchronous mode, it could even go up to
32,000 baud (or even 64,000 baud when used in combination with an
external clock). A later version of the KG-84, the commercial
KIV-7, was suitable for even higher data rates.
The KG-84 was a Controlled Cryptographic Item (CCI) but was UNCLASSIFIED
when unkeyed. Although most of the military KG-84 units have now been
replaced by commercial-off-the-shelf equipment (COTS), such as the
KIV-7, or were superceeded by modern IP-Crypto
equipment, they are not commonly found in museums.
The image on this page was taken from a surplus KG-84 front panel.
The rest of the machine is, unfortunately, missing.
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Before operation, the KG-84 had to be loaded with a suitable Traffix Encryption Key (TEK). To allow the unit to be used on different radio nets, up to four
TEKs could be stored in separate slots that could be selected with a rotary
switch at the bottom left on the front panel.
It also has provisions for remote rekeying.
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The keys (TEK) were loaded into the KG-84 by means of a DS-102 compatible
key fill device, such as the KYK-13,
the KYX-15 or the
KOI-18.
The fill device was connected to the fill-connector at the bottom right
of the KY-84 and the MODE selector had to be set to FILL V. The user then
has to toggle the INITIATE switch in order to start the transfer.
Whenever the key was compromised, e.g. when being captured by the enemy,
the user could wipe the stored keys by pulling the ZEROIZE-key and then
briefly pushing it down.
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In order to retain the stored keys when the KG-84 is powered down, a
standard military 6V lithium battery is used, such as the BA-5372/U
or equivalent. The battery compartment is accessable from the font
panel and is visible in the image above.
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The KG-84 can be configured for a variety of different communication
protocols and standards. Data rate, word format, synchronisation, etc.
can all be set by means of a series of selector switches that are hidden
behind a metal lid that covers about half the front panel.
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The lid is actually a 'door' with hinges at its lower side. It can be opened
by unscrewing two bolts at the top. After loosening the bolts, the door swings
open. The image on the right shows the configuration controls after the lid has
been opened.
The possible settings are partly explained on text plates inside the lid.
In a later replacement of the KG-84 (the KIV-7) the physical controls were
replaced by software-driven menu settings.
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Thursday, 04 April 2013 - 18:52 CET
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