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KG-40 AR
KG-40A Replenishment - this page is a stub

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) and NATO. 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 [2]. 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 and KYX-15 fill devices could no longer be used and KOI-18 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 [3]. 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 [2]. 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 [6]. 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) of GCHQ, 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 KG-40A and (modified) KG-40.

  1. It is sometimes erroneously suggested, even on renowned website such as [4] and [5], 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 [4] 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.

  1. FBO, KG-40A Replenishment (KG-40AR) COMSEC devices
    10 April 2012. Retrieved March 2015.

  2. Ultra Electronics, Information Assured, Cryptographic Solutions
    Brochure. August 2013. Retrieved February 2015.

  3. NATO Information Assurance, KG-40A
    Retrieved March 2013.

  4. Federation of American Scientists (FAS), KG-40/KG-40A
    Website. Retrieved March 2015.

  5. Jerry Proc, KG-40/40A
    Rerieved March 2015.

  6. Ultra Electronics, Ultra to supply cryptographic equipment to US Navy
    Press release. 18 May 2004. Retrieved March 2015.
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