any 2 of 3 keys needed to open lock - does this exist?

[Mr. Keys]

I am an amateur unfamiliar with the terminology, so please excuse me if this is a dumb question. But I have been unable to find the answer by searching forums.

Is there a mechanical system (not an electronic lock) that has three unique locking sections, in which any two of three of the locking sections must be unlocked in order for the mechanism as a whole to open? If so, what is this type of lock called, what models are available and from where, and what do they cost? What are the limitations and vulnerabilities of these locks?

Thank you for any insight you may be able to provide.

[2octops]

If you are talking about a lock that requires one key to be turned before th esecond will turn, yes, they are available.

They are referred to as key retaining devices.



Check them out at

http://home.earthlink.net/~icls/key_ret.htm

[pizarro]

Does that lock in the picture require 3 keys to open?

if it does, then the answer to your question would probably be to get the 2 key version, and use a master key system to enable one of the locks to be opened by one of two (or more) different keys.

[pizarro]

are you sure that that lock does what he wants?

it states

Key Retainer Devices (KRDs) are in the industry forefront as a proven way to prevent crime by providing visual authorized accountability. This means that as a Top Master Key is issued for legitimate purposes, the employee's key is temporarily "retained" in the KRD. When they return and replace the Master Key, the employee's key is released and the Master Key is again locked into place. This procedure accentuates safety since accountability is required and Master Keys stay "on premises." Thus, potential crime and security vulnerability is lessened.

which I think means that you need a key to unlock/release another key, with the first key being locked into the device untill the second key is returned.

What I think he wants is something like you see in films in bank vaults, where the customer has one key and the bank manager has the other, and both are needed to open a box. Or like in war films you need two keys to launch a nuclear missile.

[pizarro]

Excuse the tripple post.....



it all depends on what you want to use it for. A simple mechanical method could be that you have two individual locks, with one and/or both masterkeyed to accept more than 1 key. these two lock would then have to be unlocked before you can turn a handle that throws a bolt enabling the door to be opened.


If this is the kind of device you require, the exact deign of the mechanism would depend on the application that it will be used for.

If you wanted one (or more) of the locks to accept more than 1 possible key, then the security will be affected depending on how you pin the lock in a "master key" setup.

If you don't want the locks to be masterkeyed, then the locking mechanism behind the locks will be more complex than the one explained, but any specific design will greatly depend on factors such as size, weight, cost, purpose of security, level of security required, etc .......



hope this helped

[rakemaster]

A simple but cumbersom way to do it would be with 6 padlocks, 2 of each keyed to keys A, B, C, and a big chain.

Locks A1 and B1 go through one end of the chain and the second 2 locks

Locks A2 and C1 go through the first 2 locks and the 3rd 2 locks

Locks B2 and C2 go through the 2nd 2 locks and the other
end of the chain.

Not vy practical, but 2 of the 3 keys are required to open the chain.
Rakemaster

[TOWCH]

I think more details on the problem will lend to finding a solution.

[raimundo]

given the original question, I can think of no key that works that way, but in the original time restricted bank vaults, there were three and sometimes four clocks, in which the failure of one of the clocks would not obstruct opening if two others agreed that it was time to open

[2octops]

are you sure that that lock does what he wants?

it states

Key Retainer Devices (KRDs) are in the industry forefront as a proven way to prevent crime by providing visual authorized accountability. This means that as a Top Master Key is issued for legitimate purposes, the employee's key is temporarily "retained" in the KRD. When they return and replace the Master Key, the employee's key is released and the Master Key is again locked into place. This procedure accentuates safety since accountability is required and Master Keys stay "on premises." Thus, potential crime and security vulnerability is lessened.

which I think means that you need a key to unlock/release another key, with the first key being locked into the device untill the second key is returned.

What I think he wants is something like you see in films in bank vaults, where the customer has one key and the bank manager has the other, and both are needed to open a box. Or like in war films you need two keys to launch a nuclear missile.

I dunno if it's what he wants or not....he never posted back.

The way these are made, you have to turn one key before you can turn the next to open the lock. Then in order to remove any of the keys, they have to be locked back in order. It's pretty common to have to use 2 keys to open a lock and neither can be removed before it is locked back.

That is NOT the way safe deposit box locks are designed. They use 3 keys, a guard (bank) and renter. You insert the guard first and turn it to line up the levers on that side. Then insert the renter key and turn, lining up the second set of levers and withdrawing the locking bolt back. At this point, the guard key can be removed, but the renters key can remain in the lock with it in the unlocksed position. Once the renter key is turned back, the lockbolt is extended and now requires both keys to reopen.

[TriannaX]

Let me see if I understand this correctly.

You have 3 keys. You have 1 lock. You want that lock set up so that any 2 of those three keys will open the lock?

I don't know if this exists as a commercial product or not, but there would be ways to make it work.

If there is only one of each of the three keys, or if it's ok to have two of the same key, then all you would need is a custom built setup that has two keyholes linked so that both have to turn at the same time to open the lock. Then just key each keyhole to accept any of the three keys.

The one fatal flaw in this system is that someone could duplicate their key and be able to unlock the lock.

The other option that would take a bit more to make work is this:

Have 3 lock boxes. Each lockbox has a key retained that opens the lock. two keys are required to free the key. Say you have keys A, B, and C.

box 1 takes keys A & B
box 2 takes keys A & C
box 3 takes keys B & C

Then that would release a key to open the lock, and still require two keys to get it open.


That sounds like a lot of work if you ask me, but if it is that important, it's what you have to do.

Those key retaining boxes are nice, we use them for master keys where I work so that we know who has their master key since we aren't supposed to just carry them around with us without a reason.

[n2oah]

That is NOT the way safe deposit box locks are designed. They use 3 keys, a guard (bank) and renter.

1 guard key+ 1renter key=2 keys

[Mr. Keys]

Hi,
There seems to be much confusion on what I was looking for. A Key Retaining Device is not it. The application is a theoretical one. I've actually designed a rather simple solution to the problem but I wanted to see if the problem had previously been pondered and solved.

Let me describe the theoretical situation: Say you have three people who all co-own something of great value which requires occasional maintenance. It is of such value that it requires a guard at all times. My estimation is that the minimum number of guard shifts possible is three. Guards on constant 12 hour shifts do not function well.

The valuable device is behind a closed door, with a guard station out side of it. For the sake of argument, let us assume that any two guards will act as an honesty check on each other. Therefore, any maintenance to the machine can occur at a small overlap time where guard shifts change. Therefore, what is needed is a mechanism which allows these two guards, at shift change, to enter the locked room with the valuable machine.

There's no doubt that an electronic key-card system can do this and much more. But perhaps there is concern about flaws or backdoors in such a system, etc. So something that is easily inspectable, mechanical, and reliable is called for. I've come up with such a device. No, I am not going to hold it secret or attempt to patent it. I am writing up a paper describing its operation and it will eventually become public.

[ponsaloti]

Im confused, i think. Can all three owners have a kety to lock A, and all three guard have keys to lock B ?

[unjust]

simple:
three descrete locks on the door.

a lever mechanism that when 2 locks are unlocked it unbolts the door.

balance the lever system well and they have to be opened nearly simultaneously.

now the problem with that system is that there's functionally a prescribed known time lock on teh system, that can be compromised by compromising any 1 guard.

to me a stronger system would be an owner key (since they could need to access any time) each discrete, and a guard key (uniform across) that open 2 locks to throw the bolt.

[TOWCH]

Safety deposit box lock. Guard 1 has the renter key and half the guard key; Guard 2 has the guard key and half the renter key; Guard 3 has the other halves of the guard and renters keys.

If a 2 part key is too complicated, maybe a seperate keysafe with a safety deposit lock that guard 3 has the renter key to and the other 2 guards have guard keys to, and inside this keysafe is both keys. Might as well give guard 3 one of the main keys so the keysafe is only needed half the time.

ANOTHER option would be to have a main safety deposit box lock, Everyone has a guard key, and three keysafes, everyone having their own renters key and guard keys to the keysafes, but the guard keys are masterkeyed so they work on every lock except their own.

ANOTHER option would be to have three main safety deposit locks on the main door, with all three guards having their own renters key, and guards keys for the locks that they don't have the renters key to. Then have the boltwork for the door to where any of the three locks can open the door.

Or if you want to get fancy, you can get in to custom safety deposit box designs. I'm still smoothing out the details but I came up with one that should work.