Rotating constant confusion

[jimu57]

Was watching a video on MasterkeyPro software and using the rotating constant. I am a little confused.

I learned that in a master key system you should not have use certain portions of the master key bitting in the change keys. For instance, in a master 63452, you might have the first 2 positions as constant and create change keys from the last 3 positions, such as a change key being 63214. The last 3 positions for change keys should never use the 452 from the master key.

In the demo for rotating constant, the master used was 63452. the software created 19 changes (rotating only 1 position), leaving out those that violated MACS. I understand how the rotating constant method works, basically, but in the list of changes, keys used cuts from the master and at least 1 change was just a master wafer difference. Master=63452 and change=63432. Doesnt this, especially in a worn system, lend to using the 63432 change key to attempt access to other master keyed doors by "jiggling"?

I may be not fully understanding why and when to not use cuts from the master key, Is the rule only for the position that has been rotated to? Starting with the first position, changes would be 03452, 23452, 43452, 83452. The 6 from the master has been omitted because it is in the master and using cut actually creates the master. Continuing this rotation, you will eventually get to a point in rotation where you will have a change that is 63450, for instance. If this is ok in rotating constant, why is it not ok in the method above, using the first 2 positions as constant? From what I have heard on here, you would never create a change 63450 because the 4 and 5 are part of the master. Why is this ok in one method and not another? I know I am missing something here but not sure what it is.


thanks

[TORCH [of KCK]]

I've seen both sides of this debate...

On 1 hand, not allowing anyone who's not authorized access to a key that's bitted with a partial master key.
-vs-
On the other hand, how massive is the master key system?
(Is there use of sub-master keys?)

In deciding what you are going to use, you have to ask yourself;
*Does allowing a couple of bittings surrendered matter to reduce pickablity?
*How far & thin MUST I SPREAD the combinations?
(How many ways to restrict access)
*Which sets are more likely need rekeying?
*Does this building(s) have an on sight maintenance mechanical staff?
(If known as yes & pertinent to information... make their shop key deeper cut bitting - don't know their knowledge & turnover)
*** there's more variables I just can't think of right now.

But, yes there's distinguishing details to both sides of the same coin.

[Evan]

Was watching a video on MasterkeyPro software and using the rotating constant. I am a little confused.

I learned that in a master key system you should not have use certain portions of the master key bitting in the change keys. For instance, in a master 63452, you might have the first 2 positions as constant and create change keys from the last 3 positions, such as a change key being 63214. The last 3 positions for change keys should never use the 452 from the master key.

In the demo for rotating constant, the master used was 63452. the software created 19 changes (rotating only 1 position), leaving out those that violated MACS. I understand how the rotating constant method works, basically, but in the list of changes, keys used cuts from the master and at least 1 change was just a master wafer difference. Master=63452 and change=63432. Doesnt this, especially in a worn system, lend to using the 63432 change key to attempt access to other master keyed doors by "jiggling"?

I may be not fully understanding why and when to not use cuts from the master key, Is the rule only for the position that has been rotated to? Starting with the first position, changes would be 03452, 23452, 43452, 83452. The 6 from the master has been omitted because it is in the master and using cut actually creates the master. Continuing this rotation, you will eventually get to a point in rotation where you will have a change that is 63450, for instance. If this is ok in rotating constant, why is it not ok in the method above, using the first 2 positions as constant? From what I have heard on here, you would never create a change 63450 because the 4 and 5 are part of the master. Why is this ok in one method and not another? I know I am missing something here but not sure what it is.


thanks

jimu57:

Let's use the example from the first part of your posting: TMK of 63452 and a change key of 63214.

There are two types of master keying systems these keys could be a part of: Total Position Progression - OR - Rotating Constant

The only correct deployment of those two keys at those levels in a master keying system is Rotating Constant. Using a 2-in-5 pattern, meaning every key in the system will have two bittings from the TMK on rotated to prevent key interchange. In the "constant" positions, only one bottom pin is used with no master pins, this is what prevents key interchange from the changes in one "pattern" from operating locks in another.

So the key concepts of Rotating Constant are, the "patterns" being used to generate change keys and making sure every key has the same number of cuts in common with the TMK.

If the those two keys at those levels were used in a Total Position Progression master keying system, you would never be able to expand your system beyond those 64 change keys. Because you used those first two cuts of the TMK on the change keys, you can not create any lower levels of keying without interchange. Say for an example I created the master key 27452 in that system and created a change key under it of 27214. The change key example you listed 63214 would also operate that lock even though it wasn't intended to as all of the change keys with those first two cuts shared with the TMK become "depth master keys".

In a large complicated system where you are dealing with buildings/complexes with identical layouts among many floors or buildings, depth master keys can have uses to key to the function of a room or door, i.e. restrooms, janitor closets, stairwell doors, electrical rooms, etc. Example: XX214 is the stairwell door on each floor, XX676 is the janitor closet on each floor, etc. Where the first two bittings are shared with the master key for the floor in question, but key 63214 would operate the stairwell doors on every floor but no other locks in the system.

Quickly thinking about the Rotating Constant keying system, 2-in-5 with the TMK, there are ten patterns that come to mind:

63XXX
X34XX
XX45X
XXX52
6X4XX
6XX5X
6XXX2
X3X5X
X3XX2
XX4X2

Where you would progress through the other four possible bittings in each chamber to replace X with a number.

The example from the second part of your posting, where you had the TMK of 63452 and the change keys of: 03452, 23452, 43452, 83452. This would be a 4-in-5 Rotating Constant master keying system with the following patterns available:

X3452
6X452
63X52
634X2
6345X

So that system has a maximum of 20 possible keys under the one TMK.

I hope this answers your questions about why sharing bittings with the TMK should ONLY be done in a Rotating Constant keying system. If you have any further questions please post them here.

~~ Evan

[peterwn]

Was watching a video on MasterkeyPro software and using the rotating constant. I am a little confused.

I learned that in a master key system you should not have use certain portions of the master key bitting in the change keys. For instance, in a master 63452, you might have the first 2 positions as constant and create change keys from the last 3 positions, such as a change key being 63214. The last 3 positions for change keys should never use the 452 from the master key.

A more general rule is if a change (ordinary) key shares cuts with a masterkey, then the same number of cuts must be shared throughout the system. If (say) three cuts are shared between the change key and masterkey there is no way any change key can act as an incidental masterkey within the system. If however some change keys share three cuts and others four cuts, then the change keys with four shared cuts could act as incidental masterkeys (that is they would unintentionally fit a subset of locks) with respect to the locks with three shared cuts.
I saw somewhere (probably an old alt.locksmithing posting by Billy Edwards) that Yale pioneered rotating constant masterkeying. A 5 out of 6 rotating constant system can provide more differs than if a master wafer is used in all positions. In a 6 pin system 4096 change keys are normally possible (assuming odd or even levels used with 4 levels for change keys, although some of these would violate MACS limits). With one 'shared' cut, 1024 change keys (less those that violate MACS limits) are available but there are 6 ways the shared cut can be rotated , giving nominal 6144 differs in all, a 50% increase in available differs.
In the days before computer controlled machine tools, the cost of making broaches and the corresponding milling cutters would have been hideously expensive. This limited the number of keyways a manufacturer could economically make - note that the Yale GA etc keyways have survived for over 100 years. So a manufacturer needed to use the same keyway or keyway family for many masterkeying jobs and so some keys form one suite could well operate some locks in another suite although it is unlikely such instances would be discovered. Using rotating constants (eg a 3 out of 6 scheme) would significantly reduce the chance of a key from one suite unintentionally fitting locks from another suite.

[Sinifar]

Trust me it works. In new cylinders this is just fine, in used cylinders, keep a 4 v/s 2 difference in the change keys. I know it limits the number of keys available, but in most systems, unless you are working an apartment of nursing home, you only need about 12 to 15 change keys.

Two step constant rotator or full rotating makes no difference. What does make a difference is the common cut. This eliminates the phantom keys and makes for a ward cut on all keys. So if you use say a 2 in one position like the first, then all keys in the world which could fit would need a 2 in the first position.

Normally I try is dissuade people from using a 5 pin MK system unless it is absolutely necessary, say like Schlage residential locks used in an apartment building. With a 6 pin system you can add in two constants, preferable on each end and then really cut down the number of phantom keys, stop jiggling, and other fun things people do when they go exploring to find out where else their key might fit.

Finally, do not load your cylinders in "order" - that is this one here is say 3, then the next one down is 5 then the next one down is 7 and so on. Mix up the actual loading of your locks so no two close locks are even one or two cuts off. This also eliminates the jiggling problem. most people know this as shotgun loading and it works well.

With computer systems we load every other one on a short sheet of combinations, then return to the top and take the next odd pair and go down the sheet from there. As we would load 1AA, 3AA, 5AA, 7AA, and when we get to the bottom of the list we go back to the top and load 2AA, 4AA, 6AA etc. or you could take it in fours if your puter gives you a full rotation with out the shotgun method.

Confusing? I know, But try it then you will understand.

Hope this helps...

Sinifar
My 50th year in the Trade!