Identify key in a multiple keys, single lock system
You will find that multi-keyed locks become ridiculously complex (and expensive) the more keys it is made to accept. And there are practical limits.

An easier, non "wireless" solution would be two factor authentication. Well, an idea similar to it anyway. An electronic keypad lock paired with a regular lock (that cannot be left unlocked if the key is removed). Each person gets a unique keycode, but still requires the physical key to get in.  (Something you know, something you have). Regular key could be copied and the keypad code can be spied on, so it's not foolproof.

Other options are a Mag-Stripe door lock. Easy to make unique cards, but easy to copy as well. Slightly harder to clone are Smart card locks (They have contacts like a SIM card does). Frankly, RFID is the way to go.