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Hagelin C-52 and CX-52
Advanced pin-and-lug cipher machine

The C-52 and the later CX-52 were small mechanical cipher machines, developed by Hagelin around 1952 as a replacement for the C-446 and the earlier M-209. It is probably Hagelin's most successful mechanical cipher machine, both commercially and technically, as it is difficult to break, even by today's standards. It is crypto-compatible with the truely portable CD-57.
The C-52 is a so-called pin-and-lug machine, just like the earlier M-209 and C-446, but is cryptographically far more advanced and secure. It comes in many flavours, sometimes with customized 'specials', many of which are not compatible with each other. Civil versions were generally painted grey, while the military variant was mostly green. They were otherwise identical.

The image on the right shows a typical (civil) CX-52 machine with numbered wheels. The machine was also available in an Arabic version and with One-Time Tape (the so-called RT/CX or CX/RT).
CX-52 with cover open

The machine could also by expanded with a motorized keyboard, such as the B-52 or the B-62. The combination of a C-52 plus the B-52 or B-62 keyboard was known as: BC-52. By the mid-1950s, the C-52 was already in use in about 50 countries [3]. Although the Hagelin pin-wheel machines were succeeded in the late 1960s by the electro-mechanical H-4605 and later by the fully-electronic HC-500 CRYPTOMATIC series, many CX-52 machines were kept as backup during the Cold War until the 1980s. In some countries, such as Belgium, even well into the 1990s.
Standard (civil) version of the CX-52 CX-52 One-Time Tape version of the CX-52 (with RT extension) RT/CX Arabic version of the CX-52 Arabic Operational cut-away version, used for instruction. Cut-away Optional B-621b keyboard B-621b BC-52 Simulator for Windows Simulator

When the C-52 was introduced, it caused ripples throughout the cryptanalytic community [2]. 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.
CX-52 cipher wheel with 31 pins removed from the machine

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.
Removing the axle Removing the pin-wheels from a CX-52 Each wheel has a different number of steps and has numbers on its circumference. Left side of wheel 31 Right side of wheel 31 CX-52 cipher wheel with 31 pins removed from the machine Perspective view of wheel 31 The 6 pin-wheels of a military CX-52, with alternating letters and numbers.

M-209 compatibility
Although the C-52 was far more advanced and less predictable that the M-209 (C-38), it was still possible to make it backwards compatible. For this, one would use the following wheels:

C-52: 34 38 42 46 25 26
C-38: 17 19 21 23 25 26

Note that the first 4 wheels of the C-52 have twice the number of steps of the C-38 wheels. With carefully chosen pin-settings it was therefore possible to make the two models interoperable. In this mode, the first five bars of the cage (1-5) were not used, so that the remaining 27 bars could act like the 27 bars of the M-209/C-38.
CX-52 with cover open Each wheel has a different number of steps and has numbers on its circumference. Standard (civil) version of the CX-52

CX-52 standard version
This is the standard version of the CX-52. It's a 6-wheel cipher machine of the 'pin-and-lug' type that is very difficult to break, even today. This is mainly because of the very high number of configurable options, such as the removable configurable wheels.

Click any of the images below for a hi-res view.

Perspective view of the CX-52 Full view of the CX-52 The tools stored inside the top lid The tools of the CX-52 View of the wheels inside the machine Complete view of the opened machine The print wheel and the cipher wheels The key inserted from the right

Random Tape version (CX/RT)
This is a more secure version of the CX-52, in which the wheels have been replaced by a 5-level punched-tape reader. The tape contains random characters that are 'added' to the clear text and 'subtracted' at the other end. They were often used by embassies for diplomatic traffic.
When the key tape contains truely random characters, the system is in fact a One-Time Pad (OTP) (sometimes called One-Time Tape or OTT) and the machine is known as a Mixer. The image on the right shows a typical CX/RT machine with its key tape loaded and ready for use.

When used correctly, OTP/OTT machines are unbreakable. For this to work, the characters on the key tape had to be truely random. In practice, however, the tape was often created with a pseudo-random number generator (PRN) with makes it more vulnerable to attacks.

The same princple was used in the OTP-version of the earlier C-446, the so-called C-446-RT. It was also used in the contempory and later electro-mechanical Hagelin machines, such as the online/offline TC-52, the TC-55 and the ULES-64.
Close-up of the random tape in the tape reader Perspective view from the left Perspective view from the right

Arabic version
This version is identical to the standard CX-52 shown at the top of this page, except for the fact that the standard alphabet is replaced by Arabic characters. This is visible on the print wheel as well as on the six cipher wheels.

Machines like this were sold to the Arab countries such as Saudi-Arabia and Iran.

The print wheela and the cipher wheels Close-up of the cipher wheels Front view of the Arabic CX-52 Perspective view of the Arabic CX-52

Cut-Away version
This machine was probably used for instruction and training of technical staff. Various parts of the outer body of the machine have been cut-away so that the interior becomes visible. The machine is fully functional and has been painted hamerite blue. The cut-out parts have been highlighted with red paint.   


B-62 Keyboard
The C-52 and CX-52 could be converted into a fully automatic fast electro-mechanical cipher machine, by adding an optional motorized keyboard. The first version was developed at the same time as the C-52 and was known as B-52. It was later replaced by the fully transistorized B-62.
By adding the keyboard to the CX-52, messages could be enciphered and deciphered much faster than before, whilst the output was printed immediately on the cipher machine's printer. It was particularly popular in command centres.

The B-62 was introduced around 1962 and had the same form-factor as the B-52. It consisted of a large metal base with a keyboard at the front and the bay for the CX-52 behind the keyboard. The cipher machine would be installed in such a way that it could be drived by the mechanical axles of the B-62 at the left.

The image above shows a typical B-62 keyboard. Hagelin experienced a lot of trouble with the design. There were many problems with the letter-encoder at the left and with synchronization of the mechanical parts. Trying to drive a blocked CX-52 machine, could easily cause permanent damage to either the machine or the keyboard. As a result, Hagelin made many different revisions of the B-62 keyboard, often identified by a extra digit in the model number.

The B-62 variant shown here is known as the B-621. The B-62 keyboard was also manufactured by HELL in Kiel (Germany), for use with the HELL H-54 cipher machine (a copy of the Hagelin CX-52). HELL improved the design in a number of ways, both electronically and mechanically.

BC-52 Simulator for Windows
Dirk Rijmenants in Belgium has once again created a very realistic simulation of the BC-52 that runs under Windows. 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)
Click here to download Dirk Rijmentants' BC-52 Simulator for Windows (off-site)

  1. Crypto AG, The Hagelin Cryptographer, Type CX-52
    User Manual in English, French and German. 36-page booklet. 1 January 1962.

  2. Crypto AG, The Hagelin Cryptographer, Type CX-52 (Photographs
    Photographs belonging to the above manual. 4 pages. 16 January 1951.

  3. Crypto AG, Instructions for the tape controlled cryptographer CX/RT
    User Manual for the CX-52 with random tape (RT) in English. 7 pages. June 1968.

  4. Crypto AG, Spare parts catalogue CX-52 (No 21101 etc)
    Spare parts list with instructions in English, French and German.
    35 pages. 1 January 1962.

  5. Crypto AG, RT/CX One Time Tape auxiliary device
    CX-52/RT sales brochure (English). 3 pages. December 1958.

  6. Crypto AG, Appareillage pour Chiffrement à Bandes Perforées
    French instructions for CX-52/RT (RT/CX), B-621 (keyboard) and PEB-61.
    5 pages. February 1969.

  1. Crypto AG, The Hagelin Cryptographer, Type CX-52
    User Manual in English, French and German. 36-page booklet. 1 January 1962.

  2. Deavours and Kruth, Machine Cryptography and Modern Cryptanalysis
    ISBN 0-89006-161-0. 1985, p. 197.

  3. Boris Hagelin, Die Geschichte der Hagelin-Cryptos
    Original manuscript by Boris Hagelin in German language. Zug, Fall 1979.1

  1. This story was later translated by Boris Hagelin into English. It can be downloaded here.
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