Advanced pin-and-lug cipher machine
CX-52 was a mechanical
pin-and-lug cipher machine,
developed around 1952 by Boris Hagelin
and manufactured by Crypto AG in Zug (Switzerland).
It was intended as a replacement for earlier machines, like
the C-446 and
CX-52 is a more secure version of the C-52,
and has an irregular movement of the cipher wheels, which made it virtually
unbreakable by NSA at the time.
Compared to earlier designs, it offers several improvements.
It has six interchangeable cipher wheels that can be
by pulling out the main spindle from the right side. Each of the wheels
has a different number of steps on its circumference, which ideally
should be coprimes.
The wheels were normally black, as shown in the image on the right.
In some cases, users had six additional wheels,
which were usually white.
Of the total set of 12 wheels, six were placed in the machine, subject to the
current KEY, whilst the remaining six were
stowed in a metal container.
The machine was available in a civil (grey) and military (green) variant,
which were functionally identical. When used properly, the CX-52 was highly
secure and very difficult to break by the US
National Security Agency (NSA).
It was possible however, to set it up in such a way that it had a
short cycle (period), in which case it was easy to break.
This was fixed in the CX-52M,
which was modified by NSA
cryptomathematician Peter Jenks, to always produce a long cycle,
albeit one that was predictable by NSA. It looked safe from the outside,
but was in fact weaker than before .
For customers who did not move from the CX-52 to the CX-52M,
were available to learn them how to make 'proper' (secure)
use of the machine.
By supplying different manuals to different customers, this too
became a way of manipulating the strength in favour of the NSA.
For use in base stations, the CX-52 could be expanded with a
B-52 or B-62 keyboard unit, in which case the function of the
advance lever was taken over by a motor. This greatly improved the
throughput of the machine. The combination of CX-52 and a B-52/B-62
was known as BCX-52.
The machine was also available in a
Random-Tape (RT) version (shown above),
in which case the cipher wheels had been replaced by a
5-level tape reader.
As these machines are based on the
One-Time Tape (OTT) principle, they are
theoretically unbreakable. For this reason they were only advertised and sold
to friendly nations 1 like NATO countries, Switzerland and Sweden. This was
part of a secret deal between Hagelin
and NSA, today known as
The Gentleman's Agreement
Despite a slow start – mainly caused by the implementation of the
The Gentleman's Agreement –
the machine became very popular. By the mid-1950s, it was already in use
in 50 countries .
In 1970, the CX-52 was succeeded by the
electronic H-460. Nevertheless, many of them were kept as
backups during the Cold War,
well into the 1980s — in Belgium even well into the 1990s.
As NSA refused to tell Hagelin which countries were on their target
list, Hagelin assumed he could also sell these machines to South
American countries, like Argentina and Brasil.
When in 1960, the CIA Licencing Agreement came into effect,
he learned that this was not the case .
The diagram below provides a quick overview of the many controls and
settings on the CX-52. Note that many versions and variants exist, and
that not all controls are available on all versions. The machine is shown
here with it cover open, revealing the six removable cipher wheels (at
the front) and the revolving cage with sideways movable (sliding)
bars behind them. At the front left is a strip printer with a
settable letter wheel at the top. It is used as the input/output device.
Setting they cryptographic KEY, involves setting the pins on each of the
wheels, and inserting the selected wheels in the machine in the desired order,
as instructed by the (daily) KEY sheet. Next, the MODE selector at the left
side is set to C – for ciphering – or D for deciphering.
A message is enciphered letter-by-letter, by setting the letter selection
disc at the front left to the input letter,
and operating the advance lever at the right.
Input and output letter are then printed on the paper strip at the left rear.
A built-in rotating knife, automatically
cuts the paper strip in two halves.
Standard (initial) version of the machine. Very secure when used properly,
and extremely difficult to break by NSA at the time. It defeated the
existing methods for solving Hagelin ciphers. NSA tried to
persuade Hagelin not to sell these machines to denied countries,
but refused to share the denied-list with him, as they didn't want
to reveal their targets .
It was possible to setup this machine in such as way that it produced a short
cycle, as a result of which it became easier to break. Unwitting
users could easily select a weak setting. For this reason, the CX-52
was never adopted for use by the US Army and NATO.
This version was marketed by Crypto AG as the improved – more secure –
version of the CX-52, which always produced a long cycle (period).
The modification was developed by Peter Jenks at NSA.
In reality, the cycle was predictable, and allowed NSA to break it
This is the most secure version of the CX-52, in which the cipher wheels
are replaced by a 5-level reader for punched paper tape. It is also
known at the RT/CX or
It was only advertised and sold to friendly nations,
auch as the NATO countries, Switzerland and Sweden.
When used properly, this machine is theoretically
unbreakable, as it is based on the
One-Time Pad (OTP) cipher.
In 1960, Hagelin had sold a large batch of CX-52/RT machines to Brasil,
but this met with fierce opposition from NSA/CIA, as Brasil was on the
proscribed list (the list of countries to which secure machine had to
be denied) — which Hagelin didn't have. Hagelin acted immediately and
persuaded the Brasilians to swap the
RT-machines for the (exploitable) CX-52-M-27.
He also stopped advertising this model below the Mexican border
According to the
The Gentleman's Agreement –
which controlled which machines could be sold to whom –
Hagelin had secretly designated a range of version and variant
numbers, which were not printed on the machine's label. He identified the
CX-52 as a Class-2 machine. It was more advanced than the C-52,
which was a Class-1 machine. The following designators are known:
This model is supplied with Standard A slide bars, which
produce irregular or varying angular displacements of the key wheels,
each wheel advancing 0, 1, 2, 3, 4 or 5 steps on each operation.
This is the default and most secure version of the machine.
This model is supplied with Standard B slide bars, which
produce regular or fixed anglular displacements of the key wheels,
all advancing the same number of steps, but the number of steps may
be any one from 1 to 32. It is weaker than the a-variant.
This model is compatible with the old types of C-machines, the M-209, the
C-446 and a certain version of the C-52. It is the weakest of the models.
This is basicially a CX-52a that is enhanced with the so-called
Complementary feature (here written as 'Komplimentary'),
also known as the Hüttenhain 1 feature.
This is a CX-52b that is enhanced with the Hüttenhain 1 feature.
This variant is built by HELL
(licenced by Hagelin) for the German and
Austrian market, for which HELL had an exclusive contract.
It is the only version that is approved by
Dr. Erich Hüttenhain 1
for use by the German Bundeswehr (Army), where it is known as the
CX-52c with Hüttenhain 1 feature.
This is a 10-digit numerical-only variant of the CX-52.
These machines can be of the a, b or c type and may have the complementary
feature as well. For example: CX-52ak/10.
This is a 30 character version of the CX-52, suitable for the Arabic
(and possibly Russian) alphabets.
It is similar to the C-52/30 Arab.
This is the Random Tape or
One-Time Tape (OTT) variant of the machine.
The basic version of the machine was sold in a grey painted
enclosure. It is also known as the civil version, although the
military version was identical (apart from the colour).
Note that there are many versions and variants of this machine,
with different locks, print heads, reconfigurable letter selection
discs and with or without certain features. The version shown here
does not have the F/V selector at its left side.
The image on the right shows a military version of the CX-52.
It is identical to the standard (civil) version,
but it painted in a military green colour.
The case is locked by means of a cross-lock-and-key, whereas the civil
version has a regular cylinder lock. The version shown here has
an F/V selector at the left side (towards the rear) which is missing
from the civil version shown above.
One-Time Tape version
By far the most secure model of the CX-52 was the
Random Tape (RT) version, commonly known as CX-52/RT or RT/CX.
It a One-Time Tape (OTT) machine, or
mixer, that is based
on the principle of the One-Time Pad (OTP).
When correctly used, OTT machines are unbreakable.
This version was only advertised and sold to friendly nations,
such as all NATO countries, Switzerland, Sweden and very few others.
The image on the right shows a modified CX-52, of which part of
the body has been removed, so that the inner mechanics have become
This item was found on eBay in 2009, and was probably made for
instruction purposes, or just for fun. The machine has been repainted
in blue hamerite, and the edges of the cut-out sections have been
highlighted in red.
In the mid-1950s, the German company HELL was contracted by the
German Army — Bundeswehr — to build this CX-52 clone.
At the time, Germany was not allowed to develop its own encryption
devices, but building them under licence from a foreign developer
The machine was designated H-54,
has has several improvements over
the original CX-52, including one that was developed by
Dr. Erich Hüttenhain,
the head of the
German cipher authority ZfCh
(and former head of OKW-Chi).
➤ More information
Over the years, many mechanical Hagelin cipher machines like the CX-52,
found their way to the Netherlands, where they were used by the Army,
the Air Force, the Navy and the Foreign Office.
In later years, when mechanical cipher machines had been replaced by
electronic ones, it became common practice to give former crypto-users
or decision makers, a silver-painted Hagelin cipher machine as a retirement
present. The one shown here was given as a farewell present to the (then)
head of the Dutch cipher authority.
B-52, B-62, B-621
The basic CX-52 is a fully mechanical device, that requires a text to
be encrypted letter-by-letter. As this is a very time-consuming task,
it was possible to use a special motor-drive with keyboard, that had
a bay for the CX-52.
The expansion, or B-unit, was mainly used in base stations
and command centres. The design faced many mechanical and electrical
problems, as a result of which there are many production variants,
designated B-52, B-62, B-621, etc.
The combination CX-52/B-52 was known as BCX-52.
Each CX-52 was supplied with six (usually black) cipher wheels, that
had 25, 26, 29, 31, 34 and 37 steps respectively. It could be
extended with six further (usually white) cipher wheels,
with 38, 41, 42, 43, 46 and 47 steps respectively.
The additional wheels were stored in a slimline metal container, such
as the one shown in the image on the right.
Each CX-52 came with a blue printed manual in three languages.
Note however, that there were different manuals for each variant,
customer and/or country, and that some manuals may have been rigged,
to prevent the machine from being used properly (i.e. make it breakable).
In addition, there was a wide range of service manuals, parts lists,
application notes, leaflets, brochures, etc., some of which are available from
the Documentation section below.
➤ CX-52 documentation
When the C-52 was introduced, it caused ripples throughout the
cryptanalytic community .
Basically, the C-52 has 6 pin-wheels, chosen from a set of 12 different
wheels. Each wheel has a different number of steps (and hence pins)
to complete a full revolution, all of which are relative prime numbers
in order to achieve the maximum possible cryptographic period.
The wheels carried a number that corresponded to the number of steps:
25 26 29 31 34 37 38 41 42 43 46 47
The 6 wheels are removable, making it easier to swap them and to
configure the pin-settings. The higher number of steps on each wheel
increased the cipher period drastically, reducing the probability
of key sequence overlap. The wheels were numbered from 01 to the number
of steps, e.g. 47, but there were also wheels with interleaved letters
and numbers (A-02-B-04-C-06 etc.).
In addition, the cage of the C-52 has 32 bars whereas the M-209/C-38
only has 27 bars. The extra five bars (1-5) control the irregular
stepping of the rightmost five wheels. The downside of this design is
that the rightmost wheel either moves continuously or is hardly ever moved
at all during encipherment.
This problem was more or less solved in two further variants,
the CX-52 and in the CX-52M, which had an improved stepping mechanism.
The CX-52 was in fact so strong that agencies had to
develop new methods of attack.
An extra feature of the machine was the possibility to scramble the
final output alphabet by swapping the individual letters on the selector (the
large rotating knob on the left) into any possible order.
This improved cipher security and posed an extra challenge for cryptanalists.
BC-52 Simulator for Windows
Crypto researcher Dirk Rijmenants in Belgium has created a very realistic
simulation of the BC-52 that runs on the Windows™ operating system.
The BC-52 is actually a C-52 that is seated on a B-52 keyboard, hence the
name BC-52. The software allows you to select between C-52 and CX-52 simulation,
and customize the machine in various ways. Full instructions are included
with the program.
The image on the right shows a screenshot of the BC-52 simulator
running on Windows. It can also be used on Linux (WINE) and Mac (Parallels).
➤ Download (off-site)
- The Hagelin Cryptographer, Type CX-52
User Manual in English, French and German. 36 pages.
Crypto AG. 1 January 1962.
- The Hagelin Cryptographer, Type CX-52 (photographs)
Photographs belonging to the above manual [A]. 4 pages.
Crypto AG. 16 January 1951.
- Instructions for the tape controlled cryptographer CX/RT
User Manual for the CX-52 with random tape (RT) (English). 7 pages.
Crypto AG. June 1968.
- Spare parts catalogue CX-52 (No 21101 etc)
Spare parts list with instructions in English, French and German. 35 pages.
Crypto AG. 1 January 1962.
- RT/CX One Time Tape auxiliary device
CX-52/RT sales brochure (English). 3 pages.
Crypto AG. December 1958.
- Appareillage pour Chiffrement à Bandes Perforées
Instructions for CX-52/RT (RT/CX), B-621 and PEB-61 (French).
Doc. 2268. Crypto AG, Oskar Sturzinger. February 1969. 5 pages.
- Die Klaviatur B-621 (B-62)
B-621 (B-62) keyboard attachment for CX-52 (German). 14 pages (with schematics).
Doc. 1188a. Crypto AG, Oskar Sturzinger. June 1968.
- CX-52 Condensed Instructions
Doc. 3035b. Crypto AG, BH. November 1957.
- CX-52 Description
Doc. 3027. Crypto AG, Oskar Stürzinger, August 1956.
- CX-52 Service Instructions and Maintenance
Doc. 3099. Crypto AG, BH, January 1959.
- CX-52 Spare parts catalogue
Doc. L-013. Crypto AG, May 1956.
- CX-52 Specification
Doc. I-3006c. Crypto AG, Oskar Stürzinger, November 1957.
- B-52 Service Instructions
Doc. E-3121a. Crypto AG, Oskar Stürzinger, 12 November 1956 — July 1961.
- B-52 Ersatzteilkatalog (spare parts catalogue)
Doc. L-027. Crypto AG, 10 October 1957.
- B-52 Keyboard attachment unit
Doc. 3052a. Crypto AG, Sn, January 1958.
- C-52 Trouble Shooting
Doc. 3225a. Crypto AG, date unknown.
- Usage of Hagelin cryptographer CX-52
Doc. <unknown>. 25 November 1964.
This story was later translated by Boris Hagelin into English. It can be downloaded here.
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© Crypto Museum. Created: Tuesday 04 August 2009. Last changed: Monday, 02 March 2020 - 11:39 CET.