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Crypto Rotor Crypto AG Hagelin H-460 → ← CX-52
Offline rotor cipher machine
- under construction
HX-63 was an electromechanical
rotor-based cipher machine,
introduced in 1963 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 uses a principle – patented by
Boris Hagelin –
that is very similar to the – also patented –
re-entry principle
of the American AFSAM-7 (KL-7).
It is arguably the most sophisticated and secure rotor machine
ever to be taken into production.
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The machine has nine cipher rotors (from a set of 12), 1 mounted on a common spindle.
Each rotor has 41 contacts, and moves in an irregular stepping pattern,
under control of configurable pins and a set of user configurable modifiers 2
that are part of the internal cryptographic KEY.
Text should be entered on the keyboard, which has a
teleprinter layout.
The wiring between the keyboard and the rotor stack can be altered with
41 modifiers that are also part of the internal KEY.
The current position of the rotors can be altered
quickly as part of the external KEY.
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The output is available on a double paper strip printer, that prints
plaintext and ciphertext simultaneously. The device can optionally be
expanded with the PEH-61 tape reader/puncher.
The HX-63 uses a novel principle known as re-entry,
or re-injection.
As each wheel has 41 contacts, whilst only 26 are needed for encryption of the
alphabet, the remaining 15 lines are looped around. Hagelin developed
the idea for re-entry in 1952 after a
visit to Bonn (Germany)
where he discussed the American KL-7 cipher machine
with Dr. Erich Hüttenhain 3 [10].
Development of the machine started in 1954 and took almost 10 years,
during which time it was renamed several times (HX-54, HX-55, HX-56, etc.).
An intermediate design, with fewer features and hand-crank operation, was
released in 1960 as the HX-61. When the final design was ready, in 1963,
it received the name HX-63. The first 12 machines
were sold to a French government agency in 1964 [7]. The HX-63 was in production
until at least 1967. 4
Based on surviving serial numbers,
it is likely that between 50 and 200 units were made.
It is the only rotor machine series
ever made by Crypto AG, 5 and
was succeeded in 1970 6 by the fully electronic HC-460.
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The machine came with 9 rotors, but according to the manual
12 rotors were optionally available [A].
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In his memoirs [7], Hagelin uses the word Modificators for this, but
as this is not a proper English word — it does not appear in the Oxford
English Dictionary — we have replaced it with Modifier.
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During WWII, Dr. Erich Hüttenhain
had been the chief cryptographer of OKW/Chi; the cipher bureau of the
Third Reich (Nazi Germany).
After the war, he worked for the Society of Scientific Work,
which later became the
Zentralstelle für das Chiffrierwesen (ZfCh)
(now: BSI) of which he was the director until 1970.
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Deduced from the date codes on various electronic components inside the
HX-63 in our collection.
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Boris Hagelin had previously worked on
the TKG-35, a rotor machine that
he co-developed in 1951 with Dr. Edgar Gretener
from the Swiss company Gretag,
but that was before Crypto AG had been established.
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The H-460 was withdrawn immediately after the
initial release in 1970, because of electrical and mechanical reliability
issues, and was re-released in 1972.
➤ More
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PLEASE HELP —
We are still looking for original documentation of the HX-63, such as
user manuals, service documentation and circuit diagrams. All we have
at the moment is a 1964 draft description.
You can help us to improve and expand this page by providing additional
information on this topic.
➤ Contact us
The machine is housed in a grey/greenish enforced polyester enclosure
that consists of two case shells: a bottom part and a top part.
The upper part can be removed by pressing a hidden button under the front
left corner of the case.
This is necessary when accessing the internal KEY settings.
At the front left is a large black five-position knob
that is used to select the desired mode of operation.
To its right is the
keyboard, which has a layout
that is similar to that of a teleprinter. 1
In plaintext mode (K) the device supports most (but not all) characters
of the ITA-2 teleprinter alphabet.
In cipher mode (C) the letters J and X are given up to provide
letter-shift, figure-shift and SPACE. J and X are only
available in figure-shift mode, but may also be substituded by other
letters. 2 In decipher mode (D), only the 26 letters of
the Latin alphabet (A-Z) can be entered.
At the top right is a narrow window
through which the current positions of the rotors are visible.
The rotor positions are numbered 1-9 from right to left.
At the top left is the outlet of the built-in double printer,
which prints plaintext and ciphertext simultaneously.
At the centre is a 5-digit counter that shows the number of
characters that have been entered on the keyboard.
➤ Look inside the machine
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Different layouts were available for different countries.
In this case, the keyboard has a German QWERTZ layout, but there are
also machines with the more common QWERTY layout [13].
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The letter J can commonly be replaced by I without affecting the
readability, whilst the letter
X can be replaced by a 2-letter combination such as KS.
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The mode of operation is selected with the large knob at the left.
It has 5 possible settings:
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O Off E Ein (on) — set external key K Klar (plain) C Chiffrieren (cipher) D Dechiffrieren (decipher)
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All connections are at the rear. At the left is a 2-pin socket for
connection of an external 12V DC power supply, such as the battery
of a car. To its right is the 110 or 220V AC power inlet that is
used when the device is powered from the mains (default).
At the right are two multi-pin sockets
for connection of an external (optional)
PEH-61 five level paper tape reader/puncher.
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The HX-63 was available in a number of versions with full or reduced
fuctionality [A]:
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- HX-63
This is the most complete version of the machine, that has all of the
(optional) features. It offers a speed of 8-10 cps and
has a useful key space of > 10409 (~1359 bits).
- HX-63 without stepping modifiers
In this version the stepping behaviour of the rotors was fixed and
could not be modified by the user. The M/MM selector might also be
omitted in this case. The irregular stepping pattern could still be
changed with the pin-settings however (41 on each rotor).
- HX-63 without modifier block
In this version, the modifier block at the rear was not present
and could be replaced by a fix-wired dummy. This significantly
reduced the cost of the machine.
- HX-63 without connection for the tape device
The two wide centronics connectors at the rear – intended for
connection of a PEH-61 paper tape reader/puncher
– were omitted
from this version. This reduced the complexity of the internal
wiring and therefore also the cost of the machine.
- HX-61
This is an earlier version of the HX-63 that was probably introduced
in 1960 [A][16]. It is a spin-off from the HX-63 development and allows
manual operation by means of a hand-crank. It has a reduced speed
of 5 cps (or 1 cps in manual mode).
The crank was later dropped from the final HX-63 design.
- HR-61
Motor-driven variant (like HX-63) without M/MM feature,
and with a single 41-point modifier. It is likely that this is a
combination of the 26-point and the 15-point modifier.
Delivered with 9 cipher rotors with straight through wiring (to be
modified by the customer) [16].
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Tape reader/puncher
PEH-61
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Below is the block diagram of the HX-63, as printed in the manual [A].
There are 9 rotors, each of which has 41 contacts at
either side. The contacts at the left side of a rotor are connected to the
contacts at the right in a randomised (scrambled) order.
The rotor set, or scrambler, is terminated at both ends with a circular
contact plate with 41 contacts, that acts as the entry or exit disc.
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The scrambler of the HX-63 — 9 rotors on a spindle with a contact disc at either end
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At the contact discs, 26 contacts are used for enciphering the 26 letters
of the Latin alphabet. The remaining 15 contacts are looped back to the
other side of the drum. This is known as re-entry or
feed back or re-injection. 1
It was patented by Boris Hagelin
in 1953 and before him in 1944
by Albert Small, but that was unknown
to Hagelin as it was registered as a secret patent [3].
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Simplified block diagram of the HX-63, shown in Cipher mode (C)
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Apart from the wiring inside the rotors and the order in which the rotors
can be placed on the spindle, there are other modifiers 1 that have an
effect on the encryption algorithm. The 26 wires of the input matrix can
be altered in 26! ways (4 · 1026), the 15 re-entry wires can
be swapped in 15! ways (1.3 · 1012) and the rotor drive unit
can be altered in 9! ways (362880).
In addition, there are two rotor stepping methods
that can be selected with the M/MM switch.
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The HX-63 has a wide variety of key settings, some of which are changed more
frequently than others. In the draft manual [A],
the key variables are split into two groups: the internal key and
the external key. The external key can be set by the
operator and is therefore also known as the message key.
The internal key on the other hand, requires the case to be
opened. Some of the internal key settings however, require
components to be taken apart, and may in reality only be changed, say,
once a year (if they are changed at all). We will call these the
basic key settings.
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Typically changed once a year, or just once in the
machine's lifetime:
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- Exit disc wiring (41!)
- Wiring order of each rotor (9 × 41!)
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Typically changed once a day:
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- Rotor order (9!) (or 12!/3!) 1
- Pin configuration of each rotor (41!9)
- Input wiring modifiers (26!)
- Re-entry modifiers (15!)
- Stepping modifiers (9!)
- Rotor stepping method M or MM (2)
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Also known as the message key. Typically changed before each new message:
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- Start position of each rotor (419)
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Depending on the number of rotors that came with the machine (9 or 12).
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The machine uses nine electrically wired cipher rotors that are
placed in a variable order on a common axle, or spindle, that
should be installed in the rotor bay.
When lowering the locking bar, the rotor stack will be
embraced by two fixed contact discs: the
entry disc at the right, and
the exit disc at the left.
The wiring of the entry disc can be
changed with the input modifiers, whilst the wiring of the
exit disc can only be changed
by opening the disc and swapping its wires.
The rotor positions are numbered 1-9 from right to left, as shown
in the image above. Each rotor is identified by a red letter
that is engraved in its left side.
The first nine rotors are identified with the letters
A B C D E F G H J (note that the 'I' is omitted).
The optional rotors had the letters K L M.
Each wheel has 41 divisions that are numbered 01 to 41. For each
division there is a pin that can be set to the left (inactive)
or right (active), in the same way as on the earlier
CX-52. The pins are sensed by a micro-switch
at a certain position on the circumference of the rotor,
and control the stepping of one of the other rotors, subject to the
current settings of the stepping modifiers.
When the rotor stack is removed from the machine, the rotors can
be removed from both sides of the spindle, as shown the image
above. They are held in place by a series of springs that are
embedded in the spindle. This way, the order of the rotors can be
changed in less than a minute.
Changing the wiring order inside a rotor
is more difficult. It
involves the removal of the retaining clip and the pertinax
cover plate. The numbered contacts at
the right side of the rotor can then be swapped as required, after
which the rotor can be reassembled. It is likely that a special
tool was supplied to make contact swapping easier, but this tool
is currently missing. It is unlikely that the rotor wiring was changed
very often, as the wires are fragile and could easily break.
The wiring of the exit disc – at the left
side of the rotor bay –
can be changed in the same manner.
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The modifiers — Hagelin calls them modificators — are located at
the rear of the machine. To alter their settings,
the upper case shell must be removed and the machine must be reversed.
The modifier block is removable, to allow a second (optional) unit to be
prepaired in advance with the KEY settings for the next day,
so that changing the daily KEY would only be a matter of seconds.
At the bottom are the input wiring modifiers. It is bascially a contact matrix
that controls how the 26 lines from the keyboard are connected to the
entry disc.
For each wire, a 26-position thumb-wheel is available, marked A-Z.
The top row shows the current setting.
To avoid short circuits and open lines, and each letter must occur precisely
once. This is a typical permutation feature.
At the top left are the re-entry modifiers, numbered 27 to 41. They are
similar to the input wiring modifiers, but control how the 15 surplus
wires from the exit disc are looped back to
the entry disc. Although each selector has
26 positions, only the first 15 (A-O) are used.
The top row shows the current setting.
As it is also a matrix, each letter (A-O) must occur precisely once.
At the top right are the nine stepping modifiers. Each one is connected
to a rotor-pin sensing switch, and controls which rotor will advance
when an active pin is encountered. Each selector can be set in 9 different
positions (1-9). Like the other modifiers, it is an electric matrix, which
means that each number (1-9) must occur precisely once.
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The table below provides a calculation of the maximum number of
possible key settings of the machine. As not all settings will be
equally useful — there may be doubles, conflicting settings and settings
that produce a weak key — the number of useful settings
is also given, based on information from Hagelin's chief developer
Oskar Stürzinger in the
1964 draft description [A].
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Setting
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Possible 1
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Useful 2
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9 rotors
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12 rotors 3
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Wiring modifiers
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26!×15! ≈ 5 × 1038
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1 × 1030
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1 × 1030
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1 × 1030
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Internal rotor wiring
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41! ≈ 3.3 · 1049
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1 × 1030
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1 × 10270
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1 × 10270
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Rotor order
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9! or 12!/3!
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all
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3.6 × 105
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8 × 107
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Pin settings
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241 ≈ 2.2 × 1012
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106
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1 × 1054
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1 × 1054
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Stepping method M/MM
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2
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2 × 100
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2 × 100
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2 × 100
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Stepping modifiers
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9! ≈ 3.6 × 105
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3.6 × 105
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3.6 × 105
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3.6 × 105
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Exit disc wiring
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41! ≈ 3.3 × 1049
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1 × 1030
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1 × 1030
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1 × 1030
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Initial rotor position
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419 ≈ 3.3 × 1014
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3.3 × 1014
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3.3 × 1014
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3.3 × 1014
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↳
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Possible
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7.8 × 10640
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1.7 × 10643
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Useful
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8.5 × 10409
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1.9 × 10412
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= Probably never altered
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Realistic
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8.5 × 10109
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1.9 × 10112
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In his memoires [7 p.49], where Hagelin says that 10600 settings
were theoreticaly possible, he is probably referring to the maximum
number of 10640 (when using 9 rotors) or 10643 (when using 9 rotors
from a total set of 12). In reality,
the number of useful settings was closer to 10409 (the equivalent
of ~ 1359 bits), but this is still quite an impressive number for the era.
However, as altering the wiring of the rotors and the exit disc is
tedious and time consuming, it is likely that in practice they were
never changed. This means that if a machine had been captured, the internal
wiring would have become known to the enemy. This reduces the number
of useful settings to a more realistic value of > 10109
(~ 366 bits), which is still much more than the Enigma (~ 72 bits or less),
and the later Data Encryption Standard (DES)
which had only 56 bits.
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The UK used Typex and the USA
had its SIGABA. Furthermore, the US had just
introduced the KL-7, a machine that was also
used by NATO. Rotor machines seemed to be the way forward, and
Hagelin dreamed of making
the best one ever:
a super rotor machine that surpassed all others.
The idea for the machine was born in 1952, shortly after
Hagelin
had made a trip to Bonn, where he spoke with
Dr. Erich Hüttenhain
of the Society of Scientific Work. 1
It is likely that they discussed the recently introduced
KL-7 cipher machine
and the reported reliability issues. 2
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On the way back to Zug (Switzerland), Hagelin prompted the idea of a
super rotor machine to his chief engineer
Oskar Stürzinger.
It would have more rotors and more possibile settings than any of
the high-end rotor machines that were in use at the time, such as
Enigma, SIGABA,
AFSAM-7 (KL-7)
and Typex.
In addition, the machine would feature the irregular rotor stepping
of his CX machines.
He also wanted each rotor to have more contact points than needed,
using the surplus contacts for re-entry.
He asked Stürzinger to find
out whether the re-entry principle could work.
After several experiments, development of the HX started in
1954 and took almost a decade, during which time various improvements and
enhancements were made. The number of rotors changed several times,
as did the number of contact points on each rotor.
Using more than four rotors appeared to be a mechanical challenge.
During the development of the HX, Hagelin kept his contact
at the NSA – William Friedman –
informed of the progress.
At least twice — in 1955 and 1957 — Friedman mentioned the HX-machine in
reports to his superiors [9][10].
When Friedman
visited Hagelin in Switzerland in February 1955 [9],
Hagelin told him that he had several
prototypes in mind, such as HX-54, HX-55, HX-56 and THX-55.
The number of rotors was not finalised at that point, but he had already
shown him an early lab model with 5 rotors, and mentioned that the
HX-54 would have 10 rotors with 32 contacts each, which is more than
the 26 contacts needed for the Latin alphabet.
When Friedman asked him what he was planning to do with the extra
6 contacts, Hagelin replied that he would be using them for
re-entry. 3
In April 1956, Hagelin
wrote in a personal letter to
Friedman that two
prototypes of the machine – by then known as HX-56 – were about to
be released to the French Government for evaluation. Apparently
the French had promised Hagelin to demonstrate the machine
to their NATO partners. Although Hagelin was confident that the machine
would survive the evaluation, he confirmed that there were still problems
with the construction of the rotors, which he would address later [14].
When Friedman
visited Hagelin again in September 1957, the HX-machine
was still in the prototype stage, but progress had been made with
respect to the reliability of the rotor contacts. When Friedman
argued that the new machine might be too expensive for the customers,
Sture Nyberg – Hagelin's plant manager – commented that it would cost
less than US$ 3000 [10].
After this, neither the HX-machine nor any sales
restrictions were ever discussed again between Friedman and Hagelin.
It is possible that Friedman
regarded it a 'dead end', as electronic cipher machines were about
to take over. Shortly afterwards,
Friedman
left the stage to enjoy his retirement. 4
In 1961, an intermediate version of the machine was released.
It was known as the HX-61 and could be operated with a hand-crank
as well as by an internal motor; driven from the AC mains or
an external 12V DC source [A]. It is believed that some of these
were released to the French.
By the time the HX-63 was ready for production, in 1963,
the first electronic cipher machines were already appearing on the market,
and rotor machines would soon be something of the past.
Nevertheless, Hagelin managed to secure orders from
a French Government agency, the German intelligence service BND
and possibly several others, and produced a modest quantity of them.
According to some sources 5 only 12 to 15 units were made, but
judging from the build quality and the serial numbers of the surviving
machines, a quantity of 50 - 200 seems more likely.
In his memoirs [7 p.49], Hagelin wrote:
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A number of these rotor machines were supplied together with
the tape punch device PEH-61 to a French government agency. [...]
Due to the development of electronic machines, the manufacture of
he HX-63 and the PEH-61 machines was discontinued. We manufactured
for another firm a sizeable number of high-speed printers and tape
readers originally developed for this machine.
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For NSA and CIA this was a fortunate coincidence.
The HX-63 was probably a cryptographically secure machine – arguably one of the
most sophisticated rotor machines ever to be taken into production –
which would have been very difficult to manipulate.
Electronic cipher machines on the other hand, were based on
shift registers, and could be manipulated much easier.
A few years later, NSA would develop the cryptologic 6
for Hagelin's all-new electronic H-460 machine.
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The Society of Scientific Work was the predecessor of the
Zentralstelle für das Chiffrierwesen (ZfCh),
today known as the BSI. During WWII,
Hüttenhain had been the
chief cryptologist of OKW/Chi.
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The contents of this meeting are still classified, but it is likely that
they discussed the KL-7 (AFSAM-7), as shortly
afterwards Hagelin came up with the idea of the re-entry principle.
It is also likely that they discussed the reliability issues of the KL-7,
as Hagelin later discussed these with Friedman [9][10 p.4].
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This was an interference with a secret American patent, but Hagelin
wasn't aware of that, and Friedman didn't tell him either.
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Friedman had already retired in August 1955 after suffering a heart
attack, but was recalled from retirement in the summer of 1957 to
fix the broken relationship between Hagelin and the NSA [2].
After his second retirement, Friedman's health steeply declined
until his death in November 1969.
➤ More
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Various publications quote the book Machine Cryptography and
Modern Analysis of Deavours and Kruh (1985) as source for the
quantity of 12 units, but we believe this to be incorrect. The
book only briefly mentions the HX-63 and does not discuss production
quantities at all.
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In this context, the term cryptologic refers to the electronic
circuit that implements the cryptographic algorithm. It is also known as
the crypto heart.
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During the 1950s, the US
National Security Agency (NSA)
had a secret deal with
Boris Hagelin,
the owner of Crypto AG,
that controlled to which countries he could sell
unreadable 1 machines. This was known as the
Gentleman's Agreement.
In this period, NSA's chief cryptologist
William Friedman
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) [2][10].
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 had been declined in Japan,
and Hagelin was wondering why.
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The patent describes a cipher machine in which the cipher rotors have more
contacts 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 was going to be used in Hagelin's new HX-machine
that was underway.
Friedman was shocked when he saw the patent, but didn't tell
Hagelin. The re-injection principle had already been registered in the US
in 1944 in a secret patent [15],
so Hagelin's attempt should have
raised a declaration of interference [10].
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The re-entry principle was conceived during WWII by Albert Small — who
worked for the Army Signals Intelligence Service (SIS) —
when 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
AFSAM-7
(later: KL-7), that had also been adopted by NATO.
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Although officially Hagelin should not have been aware of the existence of
the AFSAM-7,
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 its
re-injection principle.
He explained how he conceived the idea after
a trip to Bonn in 1952 were he was told something by
Erich Huttenhain 3
followed by discussions with
Oskar Stürzinger –
his chief developer – but insisted that re-injection
was his own idea [10].
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The re-entry principle was also used in the
Russian M-125-3 (Fialka).
Introduced in 1965 4 it was used in the former USSR
and in the countries of the former Warsaw Pact.
It features 10 cipher rotors, irregular stepping, a card reader
that replaces the modifiers, a printer, a tape puncher and a
tape reader. Yet it was much smaller than the HX-63.
Fialka was used until the early 1990s.
➤ More about the KL-7
➤ More about Fialka
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The term unreadable means that the algorithm
could not be broken by NSA.
Also known as unfriendly or secure.
In contrast:
algorithms that are breakable by NSA,
are called friendly or readable or exploitable.
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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
AFSAM-7 (KL-7) [10 p. 4].
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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, if not likely, that Hüttenhain was talking
about the AFSAM-7.
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Fialka was originally introduced in 1956
(before the HX-63) as the M-125,
but that model did not yet feature re-entry.
The M-125-3 version, released in
1965 (after the HX-63), introduced re-entry, but only when the
device was placed in numbers-only mode.
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Possible misunderstandings
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Not much has been published about the HX-63 in the past, mainly because
very few machines have survived and hardly any documentation is available
in the public domain. As a result, some claims in other publications are
incorrect, or at least do not apply to the final version of the machine.
Here are some examples:
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- Two wiring sets in each rotor
In the book Codeknacker gegen Codemacher [12 p. 122],
author Klaus Schmeh suggests that each rotor has two sets of wiring
of which the selection is under control of the user.
This is not the case.
Each rotor has only one set of 41 electric circuits.
The confusion is probably caused by the fact that Deavours and Kruh
explain in [11] that the current takes one of two paths. However, they
are referring to the re-entry principle.
- Hand crank operation
In the IEEE publication The Scandalous History of the Last Rotor
Machine [13],
author Jon D. Paul shows an early prototype of the HX-63 on which a hand
crank can be inserted at the right side of the machine; alledgedly for
manual operation in case of a motor failure. This feature is not present
on the final machine. It is likely that the machine featured in
the article is an early prototype,
or that it is the earlier HX-61.
- Withdrawn at request of NSA
In the IEEE publication The Scandalous History of the Last Rotor
Machine [13],
author Jon D. Paul claims that the HX-63 was taken off the market
at the request of NSA's
William Friedman,
but none of the quoted sources support this claim.
By 1963/64, Friedman was no longer working for the NSA;
he had retired in 1957 [2].
It is more likely that the HX-63 was withdrawn
because electronic cipher machines were rapidly taken over from
rotor machines, as confirmed by Boris Hagelin in [7 p.49].
In other words: it came too late.
- Only 12 units produced
In many publications, such as [5] and [13] it is claimed that
only 12 to 15 units were ever made. Although this might be correct,
we have yet to find a source that confirms it. In any case, the
book that is commonly referred to as the source –
Machine Cryptography and Modern Cryptanalysis by Deavours
& Kruh [11] – does not reveal the production quantity.
Given the professional build quality and the range of the
surviving serial numbers,
a production quantity of 50 to 200 seems more realistic.
- Plugboard
It is claimed in a number of publications,
for example on Wikipedia (2024) [5],
that the HX-63 had one or two plugboards,
similar to the Steckerbrett of the
Enigma cipher machine. This is not the case.
Rather than plugboards, it has two (optional) thumbwheel-operated matrices:
one for the 26 letters of the alphabet and one for the 15 re-entry lines.
Although their function is similar to
Enigma's plugboard,
they are more advanced and offer many more possible settings. 1
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In fact, the operation of the HX-63 input wiring modifiers can
better be compared to the operation of the card reader of the
Russian M-125 (Fialka), because of its
single-ended nature. The double-ended plugboard of the Enigma
always swapped letters in pairs, which greatly reduced its strength.
➤ More
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The machine is housed in an enforced polyester enclosure that consists
of two shells.
To access the interior, the user only has to press a button
at the bottom of the front left corner, after which the upper case shell
is released. This reveals the interior as shown in the image below.
The machine consists of a large heavy die-cast aluminium frame to which all parts
and sub-circuits are mounted. The frame itself is bolted to the bottom case
shell with four large bolts that are accessible from the bottom of the case.
The five sub-systems are directly visible: the MODE selector,
the keyboard, the scrambler (rotor set),
the printer and the modifier block (at the rear).
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In order to alter the settings of the modifiers, the open machine must be
turned around as shown in the image below. At the top left is a removable
block that holds three sets of thumb-operated switches: 26 for the altering
the wiring of the entry disc, 15 for altering the order of the re-entry
wires, and 9 for altering the wheel stepping pattern. Note that not all
settings are useful.
➤ More
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The image below shows the bottom side of the machine after the frame has been
removed from the bottom case shell. This section holds the mains transformer,
the DC motor that drives the gears, and most of the wiring. At the left is
a 4-deck rotary switch that is operated by the
MODE selector. It moves in tandem with the
plain/cipher/decipher selector below the keyboard contacts.
The 12V DC motor that drives the machine is housed in the die-cast
aluminium compartment at the centre, together with appropriate filtering
parts. Bolted to the compartment is an aluminium panel that holds
two large 1000µF/35V capacitors. This was probably a last-minute upgrade.
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When repairing or restoring an HX-63, it might be necessary to take the
machine (partially) apart. Whilst most of the items at the bottom side are
fixed, the two major building blocks at the top – the scrambler and the
printer – can easily be removed.
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When we received the machine featured here in September 2021, it was
in unknown condition. It had not been switched on since it was
decommissioned in the 1970s or 80s. With a machine of this vintage,
it is always important to carry out a thorough inspection before
connecting it to the mains power. Dried out capacitors and binding
mechanical parts may cause serious problems.
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After opening the case, we noticed that some parts of the
4-deck MODE-selector were floating around
in the bottom case shell. Apparently, one of its swiper contacts
had been blocking the selector, after which a previous owner had used
excessive force to get the selector going again.
In doing so, one of the flat-faced contacts on deck #3 had broken off,
as shown n the image on the right. The swiper contact and its spring
had fallen out, but the (damaged) plastic holder was still in place.
Ceramic four-deck switches of this type are hard to find and
difficult to repair.
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Removing the switch and taking it apart was not a tempting option
— it is fully integrated with the chassis and the wiring —
so we had to come up with a different solution. In the end we fixed it
by wiring the affected segment in parallel to an
unused segment on the adjacent deck #4.
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For this we needed access to the rear side of the switch, which involved
removing the scrambler and the printer from the top side of the frame.
Next, the two 1000µF/35V electrolytic capacitors that are bolted
to the motor compartment were checked. They were both gone and had
to be replaced. The problem however, was that capacitors of this
type are no longer available.
This was solved invisibly by emptying the
existing aluminium enclosures
and placing modern high-quality
capacitors inside them.
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At the moment, the restoration of this machine is still in progress.
Additional information about this process will be added here in due
course.
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Mains cable missing One contact of 4-deck rotary switch broken off Two 1000µF capacitors in DC circuit gone - Rubber rollers inside printer desintegrated
- Clutch not always released
- Mains earth leakage circuit breaker occasionally trips
- Clear/Cipher lamps do not come on
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- New power cable made
- Broken segment of 4-deck rotary switch routed to unused segment
- Modern capacitors placed inside old 1000µF enclosures
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The device can be powered directly from the AC mains, but you should
always check the voltage selector first, to ensure that it matches the
local mains voltage.
Below is the pinout of the mains receptacle at the rear side of the device,
when looking into the receptacle.
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- 220V AC (1)
- 220V AC (2)
- Ground
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The device can also be powered by an external 12V DC source, such as
the battery of a car. Below is the pinout of the 12V receptacle at the rear
of the machine, when looking into the receptacle.
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- +12V (+ terminal)
- 0V (- terminal)
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Device Cipher machine Class Rotor-based cipher machine Model HX-63 Years 1963-1967 Manufacturer Crypto AG (Hagelin) Rotors 9 (selected from an optional set of 12) Stepping Irregular Keys Basic, internal, external Settings > 10640 (2127 bits) - > 10409 (1359 bits)
- > 10109 (366 bits)
Period 419 ≈ 3.3 · 1014 Printer 8 - 10 characters per second (2x) Paper 17.4 mm wide Mains 110 or 220V AC Battery 12V DC (external) Dimensions 400 × 400 × 230 mm Weight 16 kg Quantity 50-200 (est.)
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HX-63 58315 Private collector, Germany HX-63 58316 Crypto Musem, Netherlands HX-63 58317 National Cryptologic Museum (NCM, NSA), USA
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- Oskar Stürzinger, Chiffriertechnik Heute
Vorlesung 'Krieg im Aether' 1976/1977.
ETH Zürich (German). pp.15-16. 1
- Paul Reuvers and Marc Simons, The Gentleman's Agreement
Crypto Museum, 30 July 2015.
- Boris Hagelin, US Patent 2,802,047
Electric switching device for ciphering apparatus.
Filed 16 October 1953.
- Albert W. Small, US Patent 2,984,700
Method and Aparatus for Cryptography.
Filed 22 September 1944. Secret until 16 May 1961.
- Wikipedia, HX-63
Visited January 2020, 27 May 2024.
- Boris Hagelin, Die Geschichte der Hagelin-Cryptos
Original manuscript by Boris Hagelin in German language. Zug, Fall 1979.
- Boris Hagelin, The Story of Hagelin Cryptos 2
English translation of the above. BCW Hagelin, Zug, Spring 1981.
Later edited by David Kahn and published in Cryptologia, Volume 18, Issue 3, July 1994, pp 204-242.
- Paul Reuvers and Marc Simons, Operation RUBICON
Crypto Museum, 19 March 2020.
- William Friedman, Report of Visit to Crypto AG (Hagelin) 21-28 February 1955
28 March 1955. Final version. TOP SECRET.
A2436243. Partly declassified by NSA on 22 July 2014 (EO 13526).
- William Friedman, Hagelin Negotiations (draft)
Report about Friedman's visit to Zug, 18 December 1957.
A60669. Partly declassified by NSA on 20 July 2014 (EO 13526).
- Cipher A. Deavours and Louis Kruh, Machine Cryptography and Modern Cryptanalysis
1985. ISBN 0-89006-161-0. p. 199.
- Klaus Schmeh, Codeknacker gegen Codemacher
2008. ISBN 978-3-937137-89-6. p. 122.
- Jon D. Paul, The Scandalous History of the Last Rotor Machine
IEEE Spectrum, 31 August 2021.
- Boris Hagelin, Letter to William Friedman about HX-56
Zug, 9 April 1956
- Signal Corps Patent Board, Meeting no. 30
22 November 1940.
- Frode Weierud, Production details of Hagelin HX and HR machines
Personal correspondence, 17 September 2023.
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Retrieved from HAMFU History, December 2018.
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The English version of Hagelin's memoirs [7] is less accurate than the
German version [6]. In particular in the description of the HX-63 [7 p.49]
a number of mistakes are made that are not present in
the German version [6 p.48].
For example, he claims that a rotor has 241 possible wirings rather than
41! (41 factorial).
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© Crypto Museum. Created: Wednesday 01 January 2020. Last changed: Monday, 27 May 2024 - 11:35 CET.
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![Photograph of a PEH-61 next to a HX-63. Extracted from [6 p.50]](img/HX63_PEH61_bw.png)
