Cipher Machines and Cryptology

Here’s a trip down memory lane for some of you, particularly those of you who served in the RFA back in the day.  No doubt you will remember the KL-7 crypto machine.  What a beast that was…

If you’d like to revisit the KL-7 you’ll find an excellent simulator on the Cipher Machines and Cryptology website build by Dirk Rijmenants, here:  He’s made the simulator as true to life as possible, complete with the sound of the machine’s motor-generator and the hearty clunking noise of the rotors turning with each key press.  The only thing the simulator doesn’t do that the real machine often did is to stop working in the middle of a long decrypt due to dirty contacts under the keyboard!

There’s a lot more fascinating stuff on the site if you’re interested in the history, technical and operational aspects of cryptology, including a section on the Enigma machine (an excellent simulator is available for that, too) and several other mechanical and hand-cipher systems.



  1. Martin Seymour.
    And there I was thinking all that was still Classified. My only method of communication in 1982 (Falklands islands) was CW, Morse Code and a KL7. I was a RFA Radio Officer seconded to a Ship Taken Up From Trade (well and trult STUFT).

  2. Sorry – that should read Geestport

  3. By Dennis Harker

    History:- Radio Officer with RFA from Nov 1966 to 1993.
    Systems Engineer with RFA from 1993 to 2005 (early retirement).

    Having used the KL-7 for a good number of the above years I felt that the posts might benefit from a little clarification.

    I joined my first ship (RFA Lyness) during build on the Tyne in Nov 1966. As I was a “first tripper” the duty of cleaning the KL-7 rotor contacts and setting them up for the following day fell to me during the evening 12-4 watch once we were operational. Some ships carried two machines and, indeed, at one stage in that first trip we were running both machines in order to cope with the amount of traffic. If the rotors started stalling I had to clean them again. It was the rotor contacts that had to be kept clean. I can’t remember exactly when the machine was taken out of service but it had earned its retirement!

    I was on Fort Grange for the excursion down south in 1982 and we weren’t using KL-7 by then. Racket in the radio rooms? Try 2 x broadcast T/Ps, 2 x intership T/Ps, Inmarsat T/P/Telephone and all the UHF/HF circuits for the Flight (3 x Sea Kings) plus a listening watch on 500Khz and other circuits that I won’t mention. We were manned with 5 x R.O.s and on 6 hour watches to give the capability of 2 Ros on watch at a time . I was the radio maintainer and helped out with the watchkeeping as needed.

    With regard to the supply of fresh water Fort Grange’s complement (peacetime) was around 200. That was with one Sea King embarked – we had 3. There were others embarked which took the above numbers quite a bit higher but all needed and were thankful for, the fresh water. Fort Grange was equipped with a reverse osmosis plant but couldn’t use it as the inlet for the plant was on the same side, forward, of the outlet of the sewage plant. This meant the plant could be used whilst underway but not when not moving – good design eh? Especially when there was an abundance of good water available to use.

    We did appreciate the FW believe you me. During the fracas we would raft up alongside Geesport and take water. I can’t speak for the warships but I would imagine that they might not have had space for a plant in those days which I would expect to be fitted these nowadays.

  4. As far as I can remember the water was for the task force. As you say, ships need water and I don’t know how the RN dealt with this other than chartering a chemical tanker (very clean coated tanks.)
    I went and had a look at the Fort Toronto’s radio room, which had plenty of space for the naval stuff all piled on what was basically the work bench at the far end. She had the full fit for the MOD charter whereas we were just on a spot charter to top her up, so no extra fittings … (war was over at that point anyway.)
    There’s a pix of us going alongside her on this site gallery.

  5. Hi Bob, and sorry it’s been months since I last logged in, so I missed your reply to my original post.

    Yes the KL7 was used on the Merchant ships engaged (STUFT) in the Falkland Islands Task Force. That would have been almost the last, if not the last, operational use of the machine before it was officially retired. Imagine the racket in the radio room, with a mechanical teleprinter rattling away one one side and the KL7 clunking on the other!

    Loading water? For the Task Force, or to supply the islands?

    That reminds me of another thing the Royal Navy didn’t know about Merchant ships… the fact that we had evaporators and could make as much fresh water as we needed. Once that was discovered, we ran our evaporator 24/7 and every RAS included a transfer of fresh water. On a couple of occasions we had warships alongside and supplied them direct rather than via an RFA.

    We were equally surprised to discover that the Navy didn’t have this capability themselves, either on warships or on RFAs. It seems fairly fundamental, doesn’t it. I wonder if they do now.

  6. Thanks for that link. Very interesting, downloaded the KL-7 on got it working on Windows 11 using compatibility settings. I seem to remember seeing one on the Fort Toronto (but I will stand corrected on that, it was a long time ago) in the Falklands, CP Ships Class 3 chemical tanker being used as a water carrier. We were there on sister ship Fort Rouge just after the war ended topping her up with more water. Good from our point of view as we were a week in Rio loading water. 🙂

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