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Voice encryption unit
The KY-57 was a wide-band voice encryption unit that was
developed in the USA during the 1970s as a replacement
of the NESTOR cryptographic
products, such as the KY-38.
It was suitable for use with a wide range of military
radios and telehone lines. As part of the VINSON family
of devices, it was the main crypto 'workhorse' of the US
Army during the 1980s. Even today, many radios and voice
encryption devices are still backwards compatible with
the KY-57, that is also known as the TSEC/KY-57.
The airborne version of the KY-57 is called the
KY-58.
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The KY-57 uses the
NSA-developed Type-1
SAVILLE cryptographic algorithm. When used in
combination with a radio transceiver, such as the
SINCGARS non-ICOM
RT-1439/VRC, the KY-57 allows signal fades or losses
for up to 12 seconds without losing synchronization.
The KY-57 was eventually superceeded by the
KY-99 that offered newer - more advanced -
cryptographic algorithms, but still was backwards
compatible with the KY-57. Later
SINCGARS ICOM radios, such as the
RT-1523, had built-in KY-57
compatibility. |
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Both voice and data can be encrypted with the KY-57.
Voice data is digitized using Continuous Variable
Slope Delta modulation (CVSD), similar to other
voice crypto systems of the same era, such as the
Philips Spendex-10 and the
Telsy TS-500. Data from the CVSD modulator is mixed
with data from a key stream generator that is seeded by
a Traffic Encryption Key (TEK). The resulting digital
data stream of 16 kbps requires a wide-band radio
channel, making it unsuitable for use on HF radio
frequencies. Rather than the standard 5 kHz (voice only)
channel spacing, the KY-57 requires a 25 kHz channel,
which is why it is a VHF/UHF-only product. The KY-57 was
sometimes used in combination with
HAVE QUICK frequency hopping.
The KY-57 was produced until 1993, when it was replaced
by more advanced encryption units such as the
KY-99 and radios with integrated COMSEC
[1] .
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