In WW2, Berlin-based company Heimsoeth & Rinke not only produced the Enigma, but also a cipher cylinder, about which as good as nothing is known. Can my readers help to research the history of this device?

In the Second World War, the Germans used or designed some 20 encryption machines, including the Enigma, the Lorenz machine and the T-52 (Geheimschreiber). If you want to know more, check the blog article about German WW2 encryption machines I published last year.


The HR cylinder

Among all these designs, one German encryption device from WW2 is especially puzzling: a cipher cylinder, about which as good as nothing is known. It bears a label of Berlin-based company Heimsoeth & Rinke, which is known to have manufactured the Enigma. I call this device “HR cylinder”. Only one copy of the HR cylinder is known to exist. It is owned by the National Cryptologic Museum in Fort Meade near Washington. Here is a picture I took there:

Heimsoeth-Zylinder (3)

Five years ago, I published my first blog post about the HR cylinder (in German). This article received many page hits and my readers published a few interesting comments. Anyway, the background of this device remained a mystery. It is not known when exactly it was built and who was supposed to use it. I am not aware of a written source that mentions the HR cylinder (except for a Cryptologia article by Louis Kruh and my book Codeknacker gegen Codemacher, but both contain no additional information).


Cipher cylinders

I don’t know how the HR cylinder was used. It probably worked like any other cipher cylinder (here’s a picture that explains how a text is encrypted). The history of cipher cylinders goes back to the 15th century, but this type of encryption gained popularity only after the First World War. The most successful cipher cylinder variant is the M-94, which was used by the US military in the 1920s:


The HR cylinder is bigger and includes more rings than the M-94, which was designed as a pocket device. Here is a closer shot:

Heimsoeth-Zylinder (4)

On the following picture, the name of the producer can be seen :

Heimsoeth-Zylinder (2)

Apart from the Enigma and the HR cylinder, I don’t know of any other cipher device Heimsoeth & Rinke produced.


A prototype?

The HR cylinder certainly was not designed as a high-security cryptograph and was not meant to encrypt long messages. Its cryptographic strength is probably lower than the one of the Enigma. As the HR cylinder doesn’t have a keyboard, encrypting a message with it is less convenient than with other encryption machines of the time. On the other hand, the HR cylinder was cheaper to produce and more robust than the Enigma and similar devices.

The HR cylinder of the National Cryptologic Museum comes in the following case:

Heimsoeth-Zylinder (5)

The fact that the HR cylinder owned by the National Cryptologic Museum is the only one known suggests that this copy is a prototype. If so, it must be an advanced prototype, as it bears a serial number, comes in a case and bears a producer label. It looks pretty mature to me.

Heimsoeth-Zylinder (1)

In the Cryptologia article mentioned above, Louis Kruh stated that the HR cylinder was probably not used by the military or the diplomacy. Then he wrote: “There remains (unlikely) RLM Forschungsamt, RSHA, Gestapo (Secret Police) and SD. Cryptographically mediocre institutions like Parteikanzlei (Nazi Party organizations), Reichskanzlei (Civil Administration), Railroad, Post Office which were denied unrestricted use of the Enigma and might have looked for other devices.”

Richard SantaColoma wrote: “This one looks to me… just a guess of course… that it was intended to be attached to some standard typewriter, and used as a ‘cipher guide’. The clamps at the ends point to this, as does the high number of wheels… maybe, one for each typewriter column? If this is correct, then the operation would be very slow, and manual. But also, it might make sense because the user would not have to carry a whole, big and heavy, typewriter to a remote location (or an enigma). They would only need to find a typewriter to use once they got there… and convert it to a cipher machine, with this. The accessory wheels could be adapters for different models?”


A few new questions

There are two interesting aspects I didn’t cover in my first blog post about the HR cylinder:

  • According to the German Wikipedia entry about Heimsoeth & Rinke, the devices produced by this company didn’t bear a producer label any more after 1940 (because knowing who produced such a device was an interesting information for a spy). Does this mean that the HR cylinder was built before 1940?

  • The HR cylinder owned by the National Cryptologic Museum bears two inscriptions: RDM 291 and 118. What does this mean?

Can a reader say more about this device?

Further reading: The Schlüsselrad: New information about a little known German WW2 cipher device


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Kommentare (6)

  1. #1 Richard SantaColoma
    29. April 2019

    This one continues to drive me nuts. I actually open the high res pictures I took of it, once in awhile, and try finding some new clue in them.

    The confounding thing about it is that it is a contrasting combination of seemingly careful and complex engineering, but then with only the simplest of outward information. I mean, to show what it shows, it could be built much simpler than it is.

    I think this points to their being another layer of complexity, either within the unit, or when it is attached to a parent device. The problem with that, though, is that there does not seem to be any means of linking with another device… no gears or cogs, for instance, that might interface with another unit.

    And there doesn’t seem to be any electrical or mechanical linkage between the rings, which might cause them to interact with each other. At least, this cannot be seen from the outside.

    I do wonder if, if it were allowed, that a bit of dis assembly might offer an important clue. If there is certainly no connection between the rings, that leaves it as a display only. But if there are cogs or pins which cause the rings to interact in some way, with each other, then it would be valuable to know that, too.

    Maybe the museum would allow that, or perhaps someone on staff would be interested in trying to take a ring or two off, themselves.

  2. #2 Thomas
    29. April 2019

    This ist a pre-WWII device: It was produced between March 1936 and December 1938, since Heimsoeth und Rinke had the adress “Ludendorffstraße 6” only in this period,

  3. #3 Dan Durham
    29. April 2019

    It appears that the order of the characters on each wheel is different. Are the wheels numbered or marked in some other way to facilitate changing the order of the wheels?

  4. #4 David A Wilson
    30. April 2019

    How easy is it to change the order of the wheels?

  5. #5 Richard SantaColoma
    30. April 2019

    Dan wrote:
    “It appears that the order of the characters on each wheel is different.”

    Yes they are. And it seems that on the main wheels, the first half of the alphabet, to “m”, is all in red, and the second half, in white. Here is a close up I had taken of the device, in which you can see this, clearly:

    But also note that, on the left end, there are a set of four disks, two with different sets of numbers, but then next to two of the (seemingly) same main letter disks. I’d guess they serve some purpose different than the main row of disks, but?

    “Are the wheels numbered or marked in some other way to facilitate changing the order of the wheels?”

    I haven’t noted any such markings, but then such numbering marks could be on the sides of the disks, where they are hidden.

    One thing to note: In another picture I have, it shows the other side of that large knurled and plain aluminum ring shown above… and there is an embossed, red arrow pointing to one row of the letters on the disks.

  6. #6 Richard SantaColoma
    30. April 2019

    David wrote:

    “How easy is it to change the order of the wheels?”

    I don’t know if Klaus, or a staff at the museum, ever tried to take it apart, but of course I did not. However, the “kit” contains two unmarked disks, which the NSA labled, “2 spare spacer disks”. They are held under little canvas straps, with snaps, ready to use. This seems to imply that it can be disassembled by the user. Just a guess (again), but perhaps one or both of the aluminum ends are knurled so that one could get a grip on the, for unscrewing.

    One other thing to note: In my picture linked in the comment above, you can see one of the disks tilted slightly, and what looks like an aluminum pin in the side of it. The question would be the purpose of such a pin: Is it to fix the disks into a relationship once that relationship and order is chosen, so that they cannot move? Or is it a cog to actuate the neighboring disk, when they are rotated? That is, is this an active arrangement of disks, constantly advancing while being used; or is it a static display of the key of the moment?