Using a single key on multiple locks? How common is it?

[haykuro]

Just an odd question that popped up in my head.. It's obvious that a single key may work for various locks, but is there some sort of "distribution model" to prevent the success rate being too high?

[femurat]

http://www.lockpicking101.com/viewtopic.php?f=10&t=10321

Enjoy it

[raimundo]

Sometimes locks are key alike so that the person dosent' have to carry many keys, if your house has different keys on each lock you may find it convienient to have them KA (keyalike) and if the locks are the same keyway and the same number of pins, you could do this yourself with knowlege and experience. You may also buy padlocks keyed alike.
When you see dumpsters with locks on them these are very likely KA with a lot of other dumpsters from the same hauler, or in some cities, it may be handled by locksmiths, you could just ask a locksmith for a dumpster key, he may know exactly what you want, whether he would sell you one without selling you a lock with it I don't know, ask by phone to find out, or call a garbage hauler to find out where to buy the lock.

If you are asking about locks that randomly open to the same key, this is also quite common, in the past, it was not uncommon to find that old worn keys to automobiles, especially the GM briggs and stratton wafer sidebar lock.

If a building has five pin locks master keyed in all five columns, each lock will open to the master key and the individual key and probaby 16 or 32 other keys

consider this simplified example

master key cuts 11111
individual key cuts 99999

this will open also with keys cut to

11119
11191
11911
19111
91111
11199
11991
19911
99111
99911
99991
91919
19191
91119
19991
and probably more, its been decades since I remember working out masterkey progressions with a pencil. Oh, and before someone brings up MACS, one cuts beside nine cuts, you can just use a number that dosent serve arguementativeness, I thought of that after putting the numbers here as an example.


In any case, a fully mastekeyed lock has many keys beside the intended ones that will open it.

If a lock has x number of possible combinations, there are many of them that should not be used, including 11111 or the bump key 99999 also 12345 or any permutation that is steped down like that including 12223 or whatever, a stepped down key can leave the lock picked.
I once had an apartment key that was stepped down and found the lock in a picked condition when returning, I discovered that when I locked it, I was turning away from the lock while simply pulling out the key so rather than returning to top dead center, it was slightly off that and picked in the direction of locking.

So in answer to your question, it happens a lot more commonly than you might think. especially in masterkeyed systems,
masterkey progessions done properly will attempt avoid these bittings so that tenants will not have interchangeable keys, but this is still vulnerable to keys of the same keyway that come from sources outside the system.
In any case, masterkeyed systems in older apartments are probably set up by some guy at the hardware store who has no idea of the other keys on the system. If you want a masterkey system set up properly, you cant get the cheap job from the hardware store, you need to go to the locksmith who uses a modern computer progression chart.

[Evan]

Sometimes locks are key alike so that the person dosent' have to carry many keys, if your house has different keys on each lock you may find it convienient to have them KA (keyalike) and if the locks are the same keyway and the same number of pins, you could do this yourself with knowlege and experience. You may also buy padlocks keyed alike.

Correct... Which is why it is not recommended to purchase a padlock at a big box home center like HD or Lowe's, as many of their padlocks are KA with the same 10 or 12 key codes to pick from... Which means you and your neighbor may have the same padlock with the same key code on your gate or shed if you both purchased the same padlock from the same big box home center...

When you see dumpsters with locks on them these are very likely KA with a lot of other dumpsters from the same hauler, or in some cities, it may be handled by locksmiths, you could just ask a locksmith for a dumpster key, he may know exactly what you want, whether he would sell you one without selling you a lock with it I don't know, ask by phone to find out, or call a garbage hauler to find out where to buy the lock.

I wouldn't agree with you on this in general... The situations in which this explanation would apply are very rare since in the situation you described anyone with such a key could dump trash in any dumpster... Trash haulers charge money for two things: the number of times they empty the containers (pickups) and by the weight (per ton) of the trash collected... It is much more likely is that the route driver for that hauler has a copy of the key for the lock on that specific dumpster, or the lock in question is part of a masterkeyed padlock scheme issued by the hauler for which the hauler's key opens all the locks and the individual customer keys will only unlock their own dumpsters...

If you are asking about locks that randomly open to the same key, this is also quite common

It is more common than you would think today if you as a homeowner go out and buy your locks at a big box home center... Those KA codes you find on the packages to buy a matching set of locks for your entire house to the same key without having to use a locksmith will allow anyone who ever bought a lock from that manufacturer with the same KA keycode to open your house as well... The big box home centers purchase their locks KA like that for contractors and builders so they can purchase those matched sets of locks for homes they have built...

This is why you should spend a little bit more money to purchase locks RK (randomly keyed) from a locksmith who would then match the locks to one key as they are installed on your home...

In any case, a fully mastekeyed lock has many keys beside the intended ones that will open it.

If a lock has x number of possible combinations, there are many of them that should not be used, including 11111 or the bump key 99999 also 12345 or any permutation that is steped down like that including 12223 or whatever, a stepped down key can leave the lock picked.

Agreed... Someone who has the correct set of knowledge and skills to properly master key locks using proper masterkeying techniques will be able to select the proper bitting combinations to key locks in a system without key interchange... Features like selective keying and cross keying in large complicated systems often involve double pinning which would allow even more random key combinations from outside the system to operate a given lock... But the keys from within the system would only work in their intended lock or group of locks if they have been properly selected...

I once had an apartment key that was stepped down and found the lock in a picked condition when returning, I discovered that when I locked it, I was turning away from the lock while simply pulling out the key so rather than returning to top dead center, it was slightly off that and picked in the direction of locking.

It sounds like the lock on your apartment door was not part of a system that was designed and installed by someone with the proper training and experience to safely master key locks...

So in answer to your question, it happens a lot more commonly than you might think. especially in masterkeyed systems, masterkey progessions done properly will attempt avoid these bittings so that tenants will not have interchangeable keys, but this is still vulnerable to keys of the same keyway that come from sources outside the system.

In any case, masterkeyed systems in older apartments are probably set up by some guy at the hardware store who has no idea of the other keys on the system. If you want a masterkey system set up properly, you cant get the cheap job from the hardware store, you need to go to the locksmith who uses a modern computer progression chart.

You bring up a good point... Masterkeying locks on a common keyway is generally something which will weaken security even more as there are a plethora of keys out there which will fit into your lock which might operate your locks...

I personally am wary of "hardware stores" which offer masterkeying locks for which they know nothing about any other keys in the system other than the landlord's master key and the random key they select for the new tenant's door... This is a "shoebox" type system and offers no real security or safety against key interchange which could occur with any future additions to such a system...

Also noteworthy are the landlords which do their own keying with pre-made system charts on the common keyways... In a densely populated area there have to be at least 5 or 6 identical pre-made masterkey systems on the same keyway using the same master key and change key bittings... That is a scary thing to think about...

Although you have offered some great advice here raimundo, I would disagree that a computer running a software program is REQUIRED to generate and progress safe master key systems without interchange... Anyone who knows how to do it properly doesn't need a computer program to do it for them, they use the computer program because it allows for data entry of the door numbers or room names/numbers assigned to each key combination in a large system which can then be printed out quickly and neatly to keep accurate records and provide copies to the customer...

~~ Evan

[raimundo]

reading Evans answers, makes me think that master key systems are even more insecure than I had previously thought,

think of the implications of that second to last paragraph for someone who lives in an apartment building on the schlage C keyway.

I knew that a lot of master key systems are insecure but after reading that, its worse than I thought.

[Evan]

reading Evans answers, makes me think that master key systems are even more insecure than I had previously thought,

think of the implications of that second to last paragraph for someone who lives in an apartment building on the schlage C keyway.

I knew that a lot of master key systems are insecure but after reading that, its worse than I thought.

Which is exactly the reason why Schlage stopped selling the "C" keyway as its default keyway quite a while ago, if you had ordered factory masterkeyed locks from Schlage prior to the introduction of the Everest keyway families you would have received the "E" keyway... But the same worries apply as the "E" keyway is also very common... What do you think will become of the new Everest C123 and C145 keyways in about 10 more years or so ? They will become as ubiquitous as the Schlage classic keyways by then and there is NO restriction as to who can buy those open C family blanks...

When you use a well established locksmith shop for your masterkeying you will be sure that you are not getting a duplication of any other system which that shop has set up in your area... When you invest in a dealer only keyway on a lock product they can guarantee that no one else in your area will have keys which will open your locks...

True security with masterkeyed locks is something which needs to be investigated at the manufacturer level to seek out either a restricted or patented keyway rather than the default, stock or standard keyways you will get from a hardware distributor or general contractor...

I can think of a few keyways I would NEVER use or specify for masterkeyed locks:

Arrow "A" keyway or the 1C and 1D SFIC keyways;
Best SFIC single letter keyways which are all old and widely available;
Corbin-Russwin L, D, H, or 59 keyway families;
Kwikset KW1 or KW10;
Sargent L, R, or C keyway families;
Schlage Classic anything;
Yale paracentric E1R keyway, or the GA multiplex keyway...

If you have masterkeyed locks on any of those keyways you have taken your life in your hands because they are very popular pretty much anywhere and you can not expect to have any sort of key control whatsoever as such keys can be duplicated anywhere there is a key machine...

It is better to use something along these lines:

Arrow: one of the 6-pin sectional keyways, for SFIC they have many others besides the two default available;
Best: "Premium" keyways which are Wx or Wxx, or "Peaks" or the latest offering "CORMAX";
Corbin-Russwin: Pyramid keyways or the F, J, 62, 39, 93 factory restricted keyway families;
Sargent: any one of the A, B, G, K, N, or V factory restricted keyway families;
Schlage: an Everest Primus D restricted keyway, Everest D restricted or Everest Primus C open family keyway;
Yale: something from the S, T, V, Y or Z keyway families or their "security" product with the side bar...

There really isn't any valid excuse to install or specify the default keyway when you are constructing a new building... Ordering a more obscure or factory restricted keyway will require slightly more lead time from order to delivery but will allow the physical locks you use to have a longer useful lifespan... Using an "open" or "stock" or "default" keyway means that your locking hardware will offer much less security than if you had invested a little time and energy in exploring your options with the lock manufacturer you chose to create a restricted keyway system... It often costs no more than the normal stock keyways and will allow you a more secure "hardware" platform for your master keying system "software"...

You have to at least give yourself and your building a fighting chance of your keyblanks not being available at Home Depot or Walmart for 15 or so years... If you buy and install locks using keyways which are widely available immediately upon installation then you will never have a secure keying system and those to whom you issue keys can have them copied anywhere that has a key machine...

It is recommended that even a successfully controlled and managed master key system be totally replaced after about 15 years in service which is considered the maximum usable lifespan for a keying system... Frequently used "high traffic" cylinders should be inspected and re-pinned even if it is to the same bitting at least every other year to maintain security of that cylinder... During assessment for replacing the keying system you can physically inspect a sample of your cylinders for wear and decide whether or not to replace the cylinders also (which means upgrading to a new keyway or new high security product which is still under patent) or accommodate the cylinder wear into the design for the new keying system (which might mean using a 3-increment progression and reducing the total capacity of the new system)...

~~ Evan