Master key systems in apartments - safe?

[vitti]

I got curious today and wondered if the locks in my apartment were master keyed. I opened up my balcony deadbolt and sure enough it is master keyed (on 3 pins). I realize that most people out there would have no idea how to go about creating a key by opening up the lock but it really seems like this could be a bit unsafe. It would be too easy to make each of the possible master keys. Of course I have no idea if the complex is master keyed by building, building group, or entire complex (I hope not, it's a 500+ unit complex).

Are master key systems generally considered safe for large multi-unit applications?

[bumber]

They are safe in places that dont let you take off the deadbolts to make master keys

But more than likely they are like one floor to a master key or 50 rooms or whatever, because if the real master key was lost, stolen or broke they would have to redo all the rooms.

In alot of master systems they use high security locks that are hard to get keys for, because they think no one will be able to do what you are talking about doingif they cant get a blank. You could make a master out of a key that works one of the locks, but the better the lock is the harder it is to make the key work good, if at all

[mh]

You don't really need to disassemble the lock to come up with the other keys that fit to it, you just need a few blanks.
Matt Blaze has written a paper on this, you'll find it with google.

So - no, it's not safe.

Cheers,
mh

[linty]

master systems in general are convenient for the owner but don't take into consideration security issues. This is one of my big frustrations as a locksmith. Here are the reasons they suck.

Master keys get lost and nothing is done about it.

tenants move out and locks are swapped from one door to another instead of rekeyed.

Customers often come to a locksmith with a key and ask for locks to be mastered to it. This is done without any proper tracking of bittings and often requires the locksmith to use bottom pins instead of top pins to allow the lock to work on cuts that are too close together to allow use of a master wafer. (the smallest master wafer you'd ever want to use is .025 thousandths, in most locks this translates to a little less than two cut depths. These customers don't care that I personally guarantee to them that there will be cross-keying and security issues.

Lazy locksmiths set up systems for these cheap customers by creating a master key that is all deep cuts. By cutting a weiser key to 98898 or something stupid like that you can usually take a brand new lock and re-use the pins inside adding only master wafers because the new lock is unlikely to have deeper cuts than the master.

There are more that i can't think of right now I'm sure. But the point is, master systems are done for the benefit of the landlord. period.


Also if you have only 3 master wafers in your lock it is unlikely that it is keyed to the entire 500+ complex. Even using a rotating constant system you probably couldn't get 500 valid changes on 3 chambers.

Also, mh is right about matt blaze's paper. Actually I tried that myself once a long time ago and had no luck at all. When I actually took a lock apart to check I found that my complex was one of those where the customer brings a locksmith a key and asks for a lock to be mastered to it. The method didn't work because I had assumed that the master key would have proper depths and would follow proper master system keying rules.

[raimundo]

masterkeying is a security compromise for the convenience of the landlord who dosent want to have to use large keyrings. it is inherently insecure. masterkeying a lock reduces the security against picking by putting mulitple shearlines in the collumns.

that said, if your lock only had three collumns mastered, this would indicate that you are on a small system that has been done right, leaving two collumns un tampered with for security.

Many landlords will have the hardware store kid masterkey the whole lock even when the system is not so large that its necessary to do them all.

Masterkeyed locks are easier to pick, they have some real key control issues when master keys are lost, and there is the significant security flaw pointed out in mattblase 'amplifiying rights' paper

masterkeying is low security. there are a lot of holes, and some of them open all the doors. there are even a higher number of random key cuts that satisfy the various combinations, because they can chose either of several shearlines in each column.

where possible, a common key is the answer, such as on the front door of a complex where all tenants have the same key, this will also fit all exterior doors to the general area and some service doors, such as laundry etc.

[maintenanceguy]

We're all interested in, and spend a lot of time with picking locks, impressioning locks, and generally trying to learn about locks. I think we tend to over emphasize the security problems of imperfect lock systems. When you're a hammer, everything looks like a nail.

Criminals don't pick locks, don't decode locks, and don't generally know anything about locks. Criminals kick in doors or climb in open windows. And the criminal that could make a master key by decoding an existing lock system is sophisticated enough to figure out a way in even if the building isn't masterkeyed.

If you're trying to keep out the CIA, install a good lock. That way you'll at least know they were there because they'll have to kick down the door. If you're trying to keep out common criminals make your door and frame stronger, and install an alarm system.