Is a lock easier to pick if it has a master key?

[scrapheap]

My understanding of how a master key works for a set of locks is the following (For pin tumblers).

Each pin in the lock has two breaks in it rather than the normal one.
One of the breaks is moved to the shear line by the normal key, the other break is moved to the shear line by the master key.

The breaks for the master key will be the same in each lock that the master key is for, the breaks for the normal keys will be different so normal keys only open their specific lock.

My question is this, if there are two positions that each pin can be set in , does it make it easier to pick a lock which has a master key as well as the normal key?

[Varjeal]

Each pin in the lock has two breaks in it rather than the normal one.

Incorrect. Not always will this occur. In fact, for simple master key systems this is highly unlikely.

One or two stacks may have an extra master pin, but it's not likely that all will unless poorly done, or a very complex master system. Also, a particular chamber may possibly have more that one master pin in it.

Does it make it easier to pick? Heck ya...the more keys that can work in a lock, the less secure it is against picking. (There are exceptions, but not within pin tumbler locks as far as I can recall atm.)

[scrapheap]

Thanks, it makes much more sense to me now.

I had assumed that each stack would have and extra pin as that way the master key could be completely different.

Just realised though that the stack with the master pin does not have to be the same in each lock so that while each normal key will be a variation on the master key they will not always vary in the same part of the key.

[Cat]

A neat thing to know about master keys is that the way they are cut, they usually have more material on them. Why is this? Because its easier to slowly file down the key to create a master, than it is to add material. So when you take a master keyed lock apart, the lower break will typically be for the individual key, and the top break will typically be for the master key.

[Chucklz]

I find this a rather foolish generalization. The reasoning is sound, ie a good Master bitting should be chosen so that none of the change keys can be filed down to give a high level key (Not that a change key couldnt be filed down to give phantom masters for certain locks). A good system, in my opionion, will have at least one rather low cut on the master, so that the high level master bitting isn't obvious from one dissassembled cylinder.

[CaptHook]

I find this a rather foolish generalization. The reasoning is sound, ie a good Master bitting should be chosen so that none of the change keys can be filed down to give a high level key

Chucklz is right, there should be differences in depths on boths sides of the imaginary line (some higher, some lower).
As a note, the more shearlines created generally make it easier to pick due to more "chances" if you will. Flip side of this is a sfic cylinder, where the more shearlines you create, the more chances you create to give a false set on the operating shearline.
Chuck

[Cat]

Thanks for adding that.

[Chucklz]

I hope you didnt take my comments as an insult or a slight. I meant that to generalize like this was foolish, not that you were foolish.

[Cat]

Oops, I got disconnected

Anyway, if some one is going to disassemble and measure the pins in a lock to gain info on the master key, since they have the time to do that, they are going to be able to figure it out. Just take the plug out and keep all the pins except the top/driver pins.. Stick your key in while being careful that it doesn't completely push out any of the pins, and observe where the sheer line is. Your suggestion of having a low cut on the master key doesn't complicate things at all. The only way it would is if you purposelly put a low cut in the master key, and all the individual keys happened to have the exact same low spot. Then you could stick a fake sheer line by adding an extra pin. This might trick someone in to thinking the fake sheer line was for the master key. But then what locksmith is going to go to that trouble.

[Cat]

No, even if you did call me foolish, Marines tend to have thick skin, ya know

Too bad its hard to talk about this without illustrations. Nonetheless I find it interesting if you can follow my ... unclear theories.

[Cat]

That fake sheer line would have to be at varying heights in every lock so it'd only work on a handful of locks. Way too much trouble.

[PickPick]

With some of the newer locks, they try to avoid this 'weakening' of the lock by doing the master keying not through the pins themself but through the sidebar, Evva DPX/DPI for example or sometimes in Abus XP1 systems.
Here, the bitting can be the same for all locks, just the sidebars are different.
The trouble with some of these systems is just that they use passive elements as added security, things which block the lock when a bitting is missing in the key but not when an extra bitting exist. Therefore a file can be used for access rights escalation.

[Cat]

Good info.