Never too old to learn …

I have seen quite a number of Lips Keso keys, but the image Han mailed me yesterday did cause me to raise an eyebrow …

Special lips keso key with specially milled out flat part

What you see here is a dimple key with a part of the tip milled out (flattened). Han tried to insert a normal blank key, but that would not go in all the way. The lock really ‘checks’ for the key to be flat on the tip.

At first this really puzzled Han, but when asking around he learned that this was done for large master key installations when they ran out of combinations. (imagine, fifteen pins and four possible depths per position … that must have been some master key system!).

This is a pretty old system, yet it is interesting to still learn new things about it ….

9 Responses to “Never too old to learn …”

  1. Lockpicker says:

    4^15 = 1 073 741 824 One key for each person in China!

    The true is that they have not installed all of the 15 pins, due to the cost.

  2. mercurial says:

    Whilst 4^15 is the total number of differs available assuming all pin chambersw are utilised, this does not translate to being able to make a masterkey system with 4^15 differs available.

    Issues such as preventing cross-keying and ‘ghost masters’ are a very important issue in masterkey systems, and this greatly restricts the total keyspace available within a masterkey system. Ensuring the grand master key has at least one cut position that is higher when compared to any other key in the system is also preferable, to make it impossible to file down into a change key to make a master – again restricting the available keyspace.

    Also, if poor records have been kept, or records of the masterkey system are not available(often a real nightmare!), then the ability to create a new ‘key profile’ within and compatible with the existing system certainly provides a way to ensure there will be no cross-keying between existing locks in the system, and new cylinders which only allow insertion of the keys with the flat.

  3. mercurial says:

    Some ideas – I hope I’ve managed to be clear and understandable :

    Assume all pin positions in the lock are filled, because otherwise it would be possible to extend the masterkey system by utilising the unused chambers.

    Adding a lock with this flat to the masterkey system means that all keys prior to this upgrade will not fit into the new locks. This would mean even the grand master key of the original system won’t fit into the new plugs. Cutting the flat onto the grand master would remove the bitting that is there, which would surely render the key useless as a grandmaster in the original system.

    So, what if the new plugs were only used for adding extra change keys to the system? These locks will have keys that will fit into any other cylinder in the system, but the flat on these keys will mean that they will not operate in any of these original locks.

    This doesnt make sense either, because these new locks that have a flat on the key, supposedly at the bottom of the masterkey systems will be locks that cannot be opened by the grand master key – as it will not fit into the keyway, since it lacks the flat.

    Adding the flat to the grandmaster key also means repinning all original locks in the system so that section of the bitting where the flat is such that the flat aligns those pins to the shear line.

    However, this would sesem to be of no use, as this would mean that any holder of a change key from the original system could file the flat into their key, and they would know for sure that this section of their key now has the same bitting as the new grand master key. Eliminating these pin stacks from the availablek eyspace would seem to considerably restrict the available differs for the system, not increase it.

    Additionally, the possibility of an existing key having the flat filed into it seems means that all keyspace used in the original keysystem must be avoided, as filing down a key from the original system will create a key that will operate a lock in the new system that has matching bitting in the remaining chambers.

    All of this is assuming that all the pin positions in the lock are used. However, if all the pin positions in the locks are not used, then why not populate those chambers extend the keyspace in the system?

    I can see a use of this where it is desirable to have locks that cannot be opened by the grand master key (although that tends to contradict the whole idea of a masterkey system), but beyond that, I find it hard to understand how this would help to increase the available differs in an existing masterkey system. I guess this could also be used to ‘split’ a masterkey system into two separate systems, but again the system using keys with the flats would have to avoid all keyspace used by the system without the flats, to avoid a key with the flat filed into it being able to operate locks in the separated part of the system.

    Is it possible that this is not so much for masterkeying, but is a simple way of creating a new ‘key profile’ ?

  4. mh says:

    It seems to me that there is actually a dimple / “cut” in the thinner section of the key.
    Yes, this is equivalent to a different profile, much the same as Abloy is doing it with different profile discs in the middle (and I’ve seen similar techniques on similar keys like DOM ix as well).

    And as such, it can be used just like different profiles in masterkeyed systems, with the master key being the “thinnest” key,
    and of of course with a rather low protection against rights amplification.


  5. mercurial says:

    mh – you are right, I had a good look at the picture at home (much better screen), and it does look like there is a dimple/cut in the thinner section of the key. I was assuming it was simply a flat.

    Even if the flat can hold bitting, it can only hold a limited number of depths (and there are only 4 to begin with).

    Rights amplification certainly does seem relatively easy under this system.

  6. RL says:

    Has anybody seen masterpins being used in this system? The smaller kesosystems i’ve seen didn’t use them so it was easy to make a masterkey out of an changekey if you knew the bitting and had tools to do it. This was also happened a few times in a system i have replaced recently, i kept some artpieces of the not-ment-to-be-masterkeys in my collection. A changekey just had less dimples used then a submaster or a grandmaster, it suprised me.

  7. zeke79 says:


    You mentioned that a changekey had less dimple cuts than a submaster or a grandmaster key. This is called a positional master system and was not uncommon several years ago though I am not sure if it is still a common practice or not. The problem with positional master systems as you have noticed is ease of rights amplification. Starting with any changekey, one only needs to see a submaster or grandmaster key to note all of the positions used and with 4 cut depths possible a trained eye can note the most probable cut in each position used. This weakness of positional master systems from my understanding is the cause for security conscious locksmiths and security experts to advise against them or to flat out refuse to install a system of this sort.

    As you mentioned the flat section of the key makes it easier to decode that position by sight as there is likely only one or two possible depth of cut for that position. I could be wrong about that however, as if the lock is constructed properly and the plug is broached in a way that the flat is broached into the keyway then it may allow for 3 or 4 cut depths. It would be nice to get my hands on one of these locks with the flat sectioned keys so I could take a closer look. I am with mercurial and agree that I see only limited function of the new key and locks utilizing the flat section other than using it as a new key profile. Again, it would be nice to find a lock of this sort and do some comparative research between it and a standard keso system.

    Great job on the blog Barry! Keep up the great work 😉

  8. Lambert says:

    This key system was special made for one custumor, Philips in Eindhoven.

  9. Thomaswhite says:

    Hi, gentlemen, when i read this discussion i feel need to make some little remark about mentioned no. of combinations, i was worked in company what sell keso keys and locks, and what i know about KESO keys, there are two (flat side) rows with 4 dephts (5+5pins ) and 1 row pins with 3 depths that is 4on10 x 3on5: 254803968 mathematically differs
    and in some models of cylinders i discover less no. of pins in some or all rows (5+5+4: keso 10 RS or 4+4+4+omega pin: KESO 2000S omega)
    Sincerely Thomas

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