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The KG-40AR is a functional and physical drop-in replacement for the
(now obsolete) KG40 and KG-40A COMSEC devices,
developed and produced by
Ultra Electronics Ltd.
in the UK around 2004,
for the US Department of Defence (DoD)
This is the first time in history that the US Department of Defence
(DoD) has procured a
Type 1 cryptographic system
from an offshore company .
The KG-40AR is based upon Ultra's Multi Link Processor (MLP)
and the BID/2200.
The original KG-40 was a half-duplex device that provided cryptographic
data protection for the Navy Link 11 system and any other systems that met
the Tactical Data Information Link A (TADIL-A) data standards. It linked the
computer and the data terminal set. The KG-40 used a (now obsolete)
128-bit cryptographic key. 1
In 1991 the KG-40 was replaced by the KG-40A and existing KG-40s were
upgraded by installing a KG40 MOD replacement board. This improved cipher
security by implementing a new algorithm that required longer
keys. As a result, KYK-13
fill devices could no longer be used and
or CYZ-10 had to be used instead. 1
Although the KG-40A is no longer in production, the units were still
widely used in the field in 2015 .
In 2014 it was announced that they would be
succeeded by the British KG-40AR.
The image above shows a typical KG-40AR unit, which has the same
form factor as the KG-40A it replaces .
The standard U-229 fill port
is at the bottom left. It is compatible with
the DS-102 and DS-101 data transfer standards.
Just above the FILL connector is the FILL-MODE selector.
In 2004, the US Navy awarded
Ultra Electronics in the UK
a US$ 2.4 million contract for the development of the KG-40AR .
It would be based on Ultra's proved Multi Link Processor (MLP)
which incorporates Ultra's
BID/2200 cryptographic module
that has been in use with the Royal Navy since 1999.
The BID/2200 is approved by the
Communications Electronics Security Group (CESG)
and also by NATO
The KG-40AR is currently in use (2015)
and was still in production in 2014.
It is backwards compatible with the older
and (modified) KG-40.
It is sometimes erroneously suggested, even on renowned website
such as 
that the KG-40A introduced a key length of 128 bits
and that after this, the KYK-13 fill device could no longer be used.
Everyone seems to quote from the same source  however.
This can not be correct, as the KYK-13 does support a
maximum key length of 128 bits.
This means that the original KG-40 probably
used a 128-bit key, whilst the later KG-40A required a longer key.
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