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Shortly after WWII, in the early 1950s, the US National Security Agency (NSA)
developed a rotor encryption machine, based on the same principle as the
the German Enigma machine. Unlike the Enigma however,
the KL-7 has eight rotors, seven of which were moved in a complex irregular
pattern. The KL-7 was used by the US Army and Navy, and also by some of their
NATO partners. It was designed to replace the SIGABA
machine, that was used during WWII.
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Unfortunately, the precise operation of the KL-7 is largely unknown, as the
machine still hasn't been officially declassified. Only few of them can be
spotted in museums around the world, but in most cases the machines have
been 'sanitized' or have their rotors missing.
Originally, the official name for the KL-7 was AFSAM-7.
In the early 1960s, the name was changed to TSEC/KL-7.
The machine was also known by its codename ADONIS.
The KL-7 was withdrawn from service in 1983.
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The protographs on this page were all taken at
the Royal Dutch Signals Museum in 2009 shortly before they
closed their doors prior to their planned move to a new premises.
As becomes clear from these pictures, the machine is in beautiful
condition. Unfortunately, however, this KL-7 has been de-militarised
and the rotors are empty. The full wiring is missing from the rotors
and even the spring-loaded contacts have been removed.
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The KL-7 was introduced in the 1950s and remained in serice well into
the 1970s, when it was gradually replaced by electronic machines such as
the KW-26 and the KW-37. In some countries, KL-7 machines were kept for
special purposes and as backups for many years, until finally it was
officially withdrawn from service in 1983. The last (unclassified)
message was sent on 30 June 1983 by the Canadian Navy.
The successor to the KL-7 was the KL-51, a electronic
cipher machine that was also known as RACE.
It complied with the NATO CEROFF standard and was crypto compatible with
similar systems, such as Aroflex
and Picoflex.
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During its lifetime, the KL-7 has been compromised several times.
The most famous story is that of John Anthony Walker who worked
for the US Navy and successfully spied for the Russians for 17 years.
From day one, he passed on the key lists and other cipher material
of the KL-47 (a variant of the KL-7) used by the US Navy's Command
Center for Atlantic submarine forces. The Russians even supplied him
with a rotor scanner, so that he could easily trace the internal
wiring of each rotor
[1]
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In operation, the KL-7 was not one of the most reliable machines.
It fact, it was known for its many contact problems, some of which
were, no doubt, related to bad or improper maintenance. Many former
users recall their struggles with the KL-7 in order to properly
(de)code a message.
The German Bundeswehr even developed an assembly known as the KLX-7,
that allowed two machines to be used in tandem (i.e. in parallel)
so that errors could be detected.
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- Kl-7 Simulator for Windows
In 2009, Dirk Rijmenants finally managed to crack the KL-7 mystery.
Download this beautiful KL-7 simulator for Windows and discover
how the machine works.
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- H. Keith Melton, Ultimate spy.
ISBN: 0-7513-4791-4, 1996-2002
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