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Hagelin C-446
Pin-and-lug cipher machine

The C-446 was a mechanical cipher machine developed by Boris Hagelin of A.B. Cryptoteknik in Stockholm (Sweden) in 1946. The machine is nearly identical to the earlier C-443 and is based on the design of the C-38 (M-209). It features two printers at the left: one for the plain text and one for the cipher text. The C-446 was used by many armies world-wide, including Norway and The Netherlands. The machine is compatible with the C-38, the M-209, the BC-38 and the later BC-543.
 
The case is similar to that of the M-209, with the tools and the two paper reels stored inside the top lid. The image on the right shows a typical C-446 with its top lid open, ready for use.

Unlike the M-209, that features a rather simple lock, the C-446 is locked with two different keys (see below); one for the user and one for the officer. Three versions of the C-446 are known:
  
Hagelin C-446A

The differences between the C-446 and the C-446-A are currently unknown, but it is likely that the 'A' just refers to some simple manufacturing changes. It is believed that the machines are otherwise identical. The RT-version is quite different however. Rather than pin-and-lug cipher wheels, it features a 5-level paper tape reader, allowing the machine to be used as a One-Time Pad (OTP). Such machines are also known as One-Time Tape (OTT) machines or Mixers.
 
The C-446 came in commercial (grey) and military (green) variants. Apart from the outer colour, these variants are functionally identical. The machines shown on this page are all of the military type and were used by the Dutch Navy, the Dutch Airforce and the Norwegian Army.

The image on the right shows both versions side by side. The one on the right is the standard C-446-A that has six cipher wheels. The leftmost one has a 5-level tape reader instead of the six wheels. When used with a truely random One Time Tape (OTT), it is theoretically unbreakable.
  
The standard C-446A (left) and the special C-446/RT (right) side-by-side

Many C-446 machines that have been found in recent years, appear to be incomplete due to de-militarisation procedures that were followed when they were finally decommissioned. As a result, some of the bars and lugs may be missing from the cage inside the machine. In some cases, even the serial number plates have been removed and the keys are nearly always missing. The C-446 was used throughout the 1950s, when they were gradually replaced by the more powerful CX-52. The C-446 machines were often kept in storage for backup purposes during 1960s and 1970s.
 
The C-446A with its case closed The C-446 opened and ready for use Hagelin C-446A The standard C-446A (left) and the special C-446/RT (right) side-by-side C-446-RT ready for use Left side of the C-446-RT The tools are usually stored inside the top cover. At the right are the screwdriver and the tweezers. Oil and ink are on the left. Hagelin C-446 with Dutch Naval maintenance book (LiIVRET)

 
C-446-A
The machine shown below is a standard C-446-A. At first sight it is very similar to the war-time M-209, which in turn was based on the civil C-38. The machine has six non-removable cipher wheels that protrude the top lid at the front of the machine. At the left is a double printer with two paper strips: one for the plain text and one for the cipher text, plus a small letter counter.
 
Unlike the M-209, the C-446 can be locked properly. It has a lock on the top cover and one on the machine itself. Both locks are different and suitable keys were supplied for both locks, with one key acting as the master key. One key could only open the cover, whilst the master key (a.k.a. the officer's key) could open both locks (see below), allowing the base key to be set.

The machine is operated by a lever at the right. In the image, the lever is shown upright, in the operational position. The mechanism is operated by pulling-down and releasing the lever.
  
The C-446 opened and ready for use

Different versions of the C-446-A are known. The two rightmost images below show two variants. The one on the right has some additional mechanical features just behind the printer at the left. These components were added to support an external keyboard attachment. Strangely, there is no way to discriminate these differences from the model number of the machine.
 
The C-446A with its case closed The C-446 opened and ready for use Hagelin C-446A The interior of the C-446-A, seen from the right. The interior of the C-446-A, seen from the left. Close-up of the printers and the letter-counter The left side of the printer of a standard C-446-A The left side of the printer of an extended C-446-A, showing additional mechanics.

 
C-446-RT
This variant of the C-446 uses a paper tape reader instead of the six cipher wheels. Using a tape reader with a random cipher tape (RT) produces a much stronger cipher. In fact, when the tape is truely random, and the machine is used correctly, the cipher is unbreakable. Such systems are generally known as One-Time Pad (OTP), One-Time Tape (OTT) or Mixer machines.
 
Although most mixer machine are operated electronically or electro-mechanically, the C-446-RT is a fully hand-operated mechanical device. The image on the right show a typical C-446-RT that was used for many years by the Dutch Navy. A 5-level punched paper-tape is fed through the tape reader at the front. Each time the lever is operated, it advances one step.

Unfortunately, most of the bars and lugs are missing from the machine shown here. They were removed as part of the de-militarisation procedure, as can be seen here and here.
  
C-446-RT ready for use

The same principle was later used in the OTP-version of the Hagelin CX-52. It was called the CX/RT. Both machines could be expanded with a motor-operated keyboard, in order to allow faster processing of crypto text. Apart from purely mechanical OTP-machines, Hagelin produced several electro-mechanical OTP/OTT-machines, such as the TC-52, the TC-55 and the ULES-64.
 
The standard C-446A (left) and the special C-446/RT (right) side-by-side C-446-RT ready for use Left side of the C-446-RT Left side of the opened C-446-RT A number of bars taken from the cage of this machine. The other bars are missing. Opening the paper tape holder Loading the paper tape The paper tape mechanism

 
Tools
The C-446 comes with a set of tools that are usually stored inside the top cover. At the right are the screwdriver and the tweezers. At the left are two metal containers, which are held in place by metal clamps. One or of these more tools are often missing from machines found today.
 
The tweezers are needed to feed the paper through the printer and to remove any clotted paper from the mechanism. The screwdriver is needed to disassemble certain parts and to make adjustments to the mechanism. Please note the special cut-out in the tip of the screwdriver.

Also stored in the top cover are two small metal containers. One contains oil that can be applied with a needle that is attached to the cap. The other one contains a set of replacement ink rolls. Please check the images below.
  
The tools of the C-446

 
The tools are usually stored inside the top cover. At the right are the screwdriver and the tweezers. Oil and ink are on the left. The tools of the C-446 The screwdriver supplied with the C-446. Note the special gap in the blade. Tweezers Bottom of the oil container Taking oil from the container Taking ink rolls from the ink container Closing the oil container

 
Keys
The C-446 was usually supplied with a set of four keys: two operator's keys and two officer's keys. They can be identified by the number of gaps in the grip. The operator's key has one gap, whilst the officer's key has two of them. The gaps are clearly visible in the images below.
 
The operator's key can only be used to open the top cover, but the officer's key can be used to open both the top cover and the machine itself. The latter is needed in order to set the position of the pins and lugs as part of the daily key. The operator could only change the starting position of each of the wheels (message key).

The keys of all C-446 machines are different and the chance that a key fits another machine is very small. Furthermore, different versions of the cross-lock have been used: long, small, simple, complex and (unpickable) safety versions.
  
The four keys that were usually supplied with each machine: two operator's keys and two officer's keys.

 
About missing keys
From most ex-Navy versions of the C-446 that ended up on the Dutch surplus market, the keys are missing. And even worse: in most cases the machines are locked. Over the years, we've seen many machines that were severely damaged by a new owner, in an attempt to open the locks.
 
Our C-446-RT, for example, was locked and came without the keys. In this case, we were lucky. We tried the keys of another C-446 unit and, with a little wiggeling, we managed to open both locks. Apparently, the locks of the two machines were nearly identical. Since then, we've tried the keys numerous times on many other machines, but never had the same luck again.

If you ever find a C-446 with the locks closed and without any keys present, please don't attempt to open it yourself as you are likely to cause permanent damage to the machine. The lock is simply too strong and too well built.
  

Instead try to find a good lock-picker. Although cross-locks are rather complex, they can usually be opened relatively quickly, without damage to the lock or to the machine. The image above shows lock-picker Walter Belgers (Netherlands) opening the C-446 of a friend at the Dutch Radio Ham Museum in December 2008. It took him about two minutes to open two machines.
 
The four keys that were usually supplied with each machine: two operator's keys and two officer's keys. The two keys The officer's key The operator's key Another officer's key Keys and serial number plate C-446-A ready for use

 
Maintenance book
All cipher machines that were used by the Dutch Navy, were issued a maintenance book (LIVRET), in which the complete history of the machine was recorded. It contained a checklist, instructions for storing the machine and written records of maintenance, repairs and overseas shipments.
 
It is called LIVRET voor Chiffreermachines (Pocket book for Cipher Machines). It was issued by the Codedienst (Code Department) of the Verbindingsdienst (Signals Department) of the Koninklijke Marine (Royal Dutch Navy).

The image on the right shows an ex-Dutch Navy C-446-A with serial number 5224. In front of the machine is the maintenance book which also carries serial number 5224. The book measures 12 x 16 cm and has 20 pages. It starts with a hand-written checklist followed instructions for storing the machine without revealing the key.
  
Hagelin C-446 with Dutch Naval maintenance book (LiIVRET)

Maintanance books like these are extremely rare. In this case, it enables us to trace the full history of the machine. Page 4 tells us that the machine was received brand new from the factory on 9-6-1949. It was tested and approved a day later by the chief of the technical department of the MCD (Marine Code Department) mr. M. Vonk. The machine was then stored for several months, until it was released to S.O.C. Ned. on 13 April 1950, following a request of 6 April.

On 7 April 1954 the machine was returned to the MCD where it was subsequently refurbished and re-issued. After that, the machine was returned several times for maintenance or repairs. The last major maintenance recorded in the LIVRET is of 9 November 1966. The last entry in the book is of 14 August 1988, which is probably the last check before the machine was released to a museum.
 
The image on the right proves that the Hagelin C-446 was also used by the Dutch Airforce. The LIVRET was issued for a C-446A with serial number 5659, which was received brand new from the factory on 1 January 1950. Five days later it was tested and released for active duty.

According to the booklet, the machine saw heavy use and was repaired and reworked a number of times. The last repair is dated 19 April 1964. After that, the machine was anually oiled and tested. The last entry before the machine was put in storage, is dated 18 March 1966.
  
LIVRET (maintenance book) for C-446 used by the Royal Dutch Airforce

The two written records above, prove that the C-446 was in use with the Dutch Army from the late 1940s to the mid-1960s. After that, the machines received a last checkup and were put in permanent storage for many years, probably as backups for the electronic machines that had entered service. Mechanical machines were considered useful after a nuclear (EMP) blast.
 
Close-up of the LIVRET Checklist Last page with maintenance notes Hagelin C-446 with Dutch Naval maintenance book (LiIVRET) LIVRET (maintenance book) for C-446 used by the Royal Dutch Airforce page 1 of the Airforce LIVRET

 
ID Plates
The C-446 normally has an ID plate that is mounted over the lock in the top cover, at the front of the machine. This ID plate is shown in the second image below. Quite often it is missing, as it was sometimes removed as part of the de-militarisation process before the machines ended on the surplus market. The serial number can also be found at the front of the machine, where it is engraved in the bottom plate. The image below shows the position of the engraved number.
 
Many, if not all, of the C-446 machines that were used by the Dutch Navy, were delivered by a company called Koopman & Co. These machines have an additional manufacturer's plate attached to their side. The Koopman & Co placard is shown here, here and here.

Koopman & Co was a trading company with offices in Amsterdam, Bandoeng and Djakarta (in the former Dutch East-Indies). It is unclear whether, apart from the name tag, they made any modifications to the machine, prior to delivery to the Navy. It is, however, unlikely.
  
Serial number engraved in the bottom plate at the front of the machine.

The C-446 machines used by the Norwegian Armed Forces had a manufacturer tag that was painted to the back of the machine. It shows that the machine was manufactured in Sweden by A.-B Cryptoteknik; Boris Hagelin's company in Sweden before he made the move to Switzerland.
 
Serial number engraved in the bottom plate at the front of the machine. ID plate mounted over the lock Manufacturer's name plate at the rear of the machine. It is in fact pained onto the body of the machine. Name tag, showing Koopman & Co, Amsterdam - Djakarta. Position of the Koopman plate The position of the Koopman & Co plate on the side of the C-446

 
Opening the case
The machine is usually opened with one of the keys (the operator's key or the officier's key). The top cover is hinged at the rear and can not be removed. After opening, the top cover should be locked into position with a special spring-loaded bracket at the left (see picture #1 below).
 
In the images below it is shown how the top cover should be locked into position. At the left of the machine - to the rear of the printer - is a shiny spring-loaded metal bracket. Rotate this bracket clockwise (i.e. towards the rear).

A gap in the bracket should mate with a pin inside the top cover (at the left side). You may have to open the cover a bit further to allow the bracket to pass the pin first. Release the bracket and ensure that the pin has engaged the gap. Do not forget to release the bracket before closing the case again.
  
The spring-loaded bracket should mate with a pin in the top cover.

 
The bracket is visible at the left The spring loaded bracket The spring-loaded bracket is moved into position by rotating it clockwise. The spring-loaded bracket should mate with a pin in the top cover. The top cover locked in place

 
Closing the case
Before the case of a Hagelin machine can be closed again, the handle at the right first has to be pushed down completely. If you are not familiar with Hagelin machines, you may have trouble pushing down the lever to its home position, which sometimes leads to broken handles.
 
Whatever you do, never use excessive force! Although Hagelin machines are very robust and tough, axles can be broken easily when enough force is applied. Once broken, these machines are extremely difficult to repair.

If the lever won't come down, it's probably because the mechanism is blocked. The most common reason for this is the fact that it always blocks after (de)coding a letter. All you should do at this stage is selected another input letter by rotating the letter knob at the left. Now you should be able to bring the handle down.
  
The handle in the upright position

Once pushed down, lock the handle in place with the small lock. Next, pull-out the grip and fold it upright. Please check that the grip is full aligned. Ensure that the top cover is no longer locked in position, by releasing the bracket at the left (see above). You may now close the case.
 
C-446-A in use The handle in the upright position Rotate the knob to release the mechanism The handle fully pushed down and locked into position Pull-out the grip to fold it upwards Pull-out the grip to fold it upwards The grip in storage position. The cover of the case may now be closed. The C-446A with its case closed

 
Loading paper
Depending on the model, a Hagelin machine takes one or two paper reels. In the example below, we are showing how to load paper into a Hagelin C-446 machine. Please note that there are two different types of paper: standard paper tape, and pre-gummed paper tape. The paper is 9.65 mm wide and the hole at the centre of a reel is ±11 mm. A full roll is about 10 cm wide.
 
Please be careful with pre-gummed paper. Over the years, this paper is likely to have become brittle and will easily break. Furthermore, gummed paper has the tendency to attract moist, making it sticky and potentially block the machine. Removing sticking tape is difficult.

Place the rolls in the lid of the machine and load them one at a time. Lock the roll with the metal bracket that 'snaps' into position. Then feed the paper over the first guide, through the second guide, into the printer. Feeding it into the printer may be a bit tricky (use the tweezers for this).
  
Three paper rolls for the Hagelin C-446. The frontmost one is pre-gummed (read the warning).

Make sure the paper tape curls up a little before it is entered through one of two slots at the rear of the printer mechanism, so that it can be fed through the printer easily. This is best done with the tweezers that are usually stored inside the top lid of the machine (see above under tools.
 
Feed the paper through the guides Close-up of the first paper guide Close-up of the second paper guide Make sure that the paper curls up a little, so that it is easily fed through the printer. Two paper slots at the rear of the printer mechanism The paper in the leftmost printer has already been loaded. The paper in the rightmost printer is currently being loaded. Use the tweezers to pull-up the paper from behind the guide Once loaded, guide the paper through the final guides and feed some more paper by turning the feed know counter clockwise.
Three paper rolls for the Hagelin C-446. The frontmost one is pre-gummed (read the warning). Pre-gummed paper (read the warning) This is the back of pre-gummed paper. Please note that, due to age, this paper may be brittle.

The paper used in the C-446 is the same as used in the M-209. It is very difficult to find suitable paper reels these days, and in many cases the pre-gummed tape has either become 'pudding' or brittle. If you have any surplus rolls left, please contact us.
 
Cryptanalysis
The document below describes the Hagelin M-209 and the C-446A in great detail. Not only is the working principle of the machines explained, it also discusses the machine's cryptanalysis and methods for its attack. The document is in Dutch and was released for publication by the Dutch School for Military Intelligence (DIVI) in 2011 [1].
 
References
  1. SMID, C-446A en M-209 Beschrijving en Analyse
    Descryption and analysis of the Hagelin C-446A and M-209 (Dutch).
    Dutch Department of Defence, Military Intelligence School. Date unknown.

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Crypto Museum. Created: Thursday 06 August 2009. Last changed: Saturday, 20 May 2017 - 08:31 CET.
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