master keys vs keyed alike

[powercity]

Can someone tell me the difference between master keys and keyed alike?

Please

[CitySpider]

In a master key system, you have two locks, locks B and C. You also have key A, which can open both of them, and key B, which can open B, and key C, which can open C. C can not open B, and vice versa.

If you have two locks that are keyed alike, essentially, you have locks A and B, and keys A and B, and key A can open A or B, and key B can open B or A. They're the exact same key and the exact same lock.

[marso]

Cityspider is right on the money. On the internals of the locks this is what is occuring.

Keyed alike - Two locks have the same sized pins put in the same order so that the one key works on both locks.

Master key - The pin stack has instead of two (top and bottom) there is another small pin placed in the stack so that there is now another "key cut" that can be used on this position.

A good paper on master key can be found at the link below.
http://www.crypto.com/papers/mk.pdf it is by Matt Blaze

[Mad Mick]

A good paper on master key can be found at the link below.
http://www.crypto.com/papers/mk.pdf it is by Matt Blaze

Beat me to it!!

Aussies, always get there first!

[Chucklz]

If you are considering purchasing a MK/KA system, carefully review your security needs. The loss/unauthorized duplication of one key in the KA system, well then your whole system falls apart. MK systems have their own weaknesses, as shown in the Blaze paper.

[Luke]

To anyone here who has designed a master system consisting of more that 10 locks congrats to you. Took me 2 hours to figure out how to design. 10 mins to put into action. Bloody master key has low cuts where as, the others have the medium and higher ones. Maths you need it ...

[Chucklz]

Luke,

A good MK should have at least one cut in one position higher than all the cuts in that position for every change key, so that someone cannot just file down a change key to get a MK.


I have to go now, but Ill post more later on the RC progression system.

[Luke]

That is true but like i said first system

[Chucklz]

Here is a bit about creating an easy to do MK system. First pick a TMK (Top Master Key). This system still has security flaws, as in users could still probably generate a MK with a little knowledge etc. but its better than haphazard guessing. Lets design a GMK system. You would have one GMK that would open all the locks, and then two groups controlled by seperate Master keys.

Ok, so lets pick 60423 as the GMK

For the First Master Key system
Pick a constant for the change keys. You could pick something like 15xxx. Your change keys will all have 15 for the first two cuts. The Master Key for this level would be 15423


For the Second Master Key system
Pick a different constant, for example 42xxx . Your Master key for this system would be 42423

For the change keys, you can progress the remaining three positions. Try starting with 511 . This again will help to prevent a user filing down a key to make a MK. You can continue with 512, 514, 515, 516. You could skip the 513 because it shares a bitting with the TMK. This way, you could easily make a simple GMK system with about 200 or more change keys in each system. Happily you could resuse bittings if you need to. You can use the 512, 514 etc bittings in both MK systems.

Im sure Varjeal will have many more suggestions and tips for you.