QUOTE (suoq @ Sep 11 2010, 11:52 AM)

I fail to see how the bolded statement is affected by either keys or combination locks.
You can bypass any access control method by:
1) Forcible entry- Go to town with sledge hammers, power tools, plasma cutters, etc.
2) Extortion - I'll tell your secrets unless you give me X.
3) Kidnapping - I'll kill you or your kids if you don't open the vault.
4) Bribes - I'll pay you a million bucks for the Coke recipe.
A decent security system includes features to attempt to counter all of these if they are considered viable threats by the threat model. Since these are common, let's look at the differences.
On the entry to the room/container that contains a valuable item a typical electronic access system (as in prox card or similar) has the following weaknesses that a combination lock doesn't have.
I can copy the credential by it's RF signature.
I can get into the space (typically less sensitive then the controlled area) where the EAC controllers for the floor lives and make the lock open.
I can interrupt power to the maglock/strike.
I can steal the credential.
I can hack the computer controlling the EAC and have it open the lock for me.
I can mess with the logs of an EAC and have it forget that the lock opened or say it was opened by an authorized user at a different time.
Key locks are subject to having the key stolen (but they are normally only carried on the job and locked up in a key container otherwise) and having the key visually decoded. But they are subject to various well understood attacks and are normally used for non-critical areas where they are more subject to physical attacks than subtle attacks, as you can make padlocks that are very difficult to cut. Picking isn't obvious, but it normally leaves "some" forensic signs to a trained expert.
Good quality combination locks require that you know the combination to open it without force. As these are supposed to be memorized there isn't anything to steal without planting video cameras. In theory purely mechanical ones are subject to x-ray attack so you can decode the dials remotely. Supposedly the KGB had portable equipment (for some value of "portable") to do that on USG S&G 8500s. Plus you can use electronic dialers to attack them. So in theory you can open the container, photograph the secret plans and sneak back out without anyone knowing. Or you could drill the container, decode the lock and replace it with an identical lock that has the correct combination, repair and repaint the hole and sneak back out.
The modern versions with some electronic components has retry penalties and logs accessible on the dial and various elements other elements (like limited view angles) to make it a lot harder to attack successfully. In theory the best way to attack an X-09 that you don't know the combination to is to drill it, but it's designed so you can't recover the combination after you destroy the lock to open the container. So at best you leave the container with a lock that won't open, at which point they call in a tech and the security officer who look at why the container isn't opening. The security officer should find that the lock serial number doesn't match and/or the tech should see the traces of the drilling.
Which is why Kaba Mas sells something like 10 million bucks a year of these to the feds.