Rotor-based cipher machine
- wanted item
HX-63 was an electromechanical
rotor-based cipher machine,
introduced in 1964 by Crypto AG in Zug (Switzerland).
It features nine electrically
wired permutations wheels, or rotors, that have more contacts than the 26
letters of the alphabet. It was patented by
Boris Hagelin, and
uses an operating principle that is very similar to that of the
– also patented –
American AFSAM-7 (KL-7).
The image on the right shows the HX-63, which is housed in a molded
plastic enclosure. At the front right is the keyboard. The 9 cipher
wheels are visible through a narrow window at the top.
The machine was developed during the 1950s, and is mentioned in reports
filed by NSA cryptographer William Friedman in 1955 and again in 1957 .
It is likely though, that it was not finished before 1963, and that it was
first sold in 1964 [A].
The first and only customer was the French Army,
who ordered 12 units .
It is very likely that no more than 15 init were ever made.
Apart from the TKG-35,
a joint development of
and Dr. Edgar Gretener,
the HX-63 was first and only
rotor-based cipher machine that was ever
built by Crypto AG.
Around 1964, Crypto AG made the transition to electronic shift-register-based
designs, and moved away from (electro)mechanical cipher machines.
In 1970, the HX-63 was succeeded by the electronic
At present, no further information about this machine is available.
During the 1950s, the US
National Security Agency (NSA)
had a secret deal with
the owner of Crypto AG,
that controlled to which countries he could sell
unreadable 1 equipment. It was known as the
During the 1950s, NSA's chief cryptologist
visited Hagelin a number of times to negotiate and alter the terms
of the agreement. One of these visits was on 22 September 1957
at Hagelin's home in Zug (Switzerland) .
The first thing to be discussed between Hagelin and Friedman,
was patent 2,802,047
that Hagelin had filed in the US in October 1953
and that had been granted a month earlier.
Although it was granted in the US, the patent was declined in Japan,
and Hagelin was clearly wondering why.
The patent describes a cipher machine in which more
contacts are used on the cipher wheels than are actually needed
and where the extra contacts of the output of the drum are looped back
to the input. This method can be described as re-entry or
re-injection and would be used in Hagelin's new HX-machine
that was underway.
Friedman was shocked when he saw the patent, but didn't say that
to Hagelin. The principle of re-injection was registered by the US
in 1944 in a secret patent,
so Hagelin's attempt should have
raised a declaration of interference.
The re-entry principle was conceived during WWII by Albert Small,
whilst working for the Army Signal Intelligence Service (SIS),
trying to solve the high-level Japanese diplomatic Purple cipher.
It is covered by US Patent 2,984,700
and has since been used at the heart of the high-level
American cipher machine
shown above, that was also adopted by NATO.
Although officially Hagelin should not have been aware of the existence of
in later talks he mentioned that many of its
operators were experiencing contact problems with the rotors. 2
This proves that Hagelin was aware of the existence
of the machine and that he might have been aware of the
re-injection principle that it features.
He also explained how he conceived the idea after
a trip to Bonn in 1952, were he was told something 3 by
followed by discussions with his chief developer
but insists that it was his own idea.
➤ More about the KL-7
The term unreadable means that the algorithm
could not be broken by NSA.
Also known as unfriendly or secure.
algorithms that are breakable by NSA,
are called friendly or readable or exploitable.
This is actually correct; the KL-7 was known for its many contact
problems if the maintenance instruction were not strictly followed.
This proves that Hagelin had knowledge about the KL-7.
It is currently unclear as to what Hüttenhain told Hagelin on this
occasion, or what Hagelin discussed with Stürzinger afterwards,
as the original document is redacted at this point.
It is entirely possible though, that Hüttenhain was talking
about the AFSAM-7.
The same principle was later also used in the
Retrieved from HAMFU History, December 2018.
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© Crypto Museum. Created: Wednesday 01 January 2020. Last changed: Sunday, 14 June 2020 - 12:12 CET.