A warning re Hotel swipe key cards

[wmah]

Originally Posted by mattincanberra

Hi guys,

Usually the room doors are not connected to any computer system whatsoever but are programmed to accept keys created by a particular computer system (there are rarely wires connecting the locks to a computer).

Matt

I know this is false information there. I've locked myself out of the room many times and have had to go the front desk for replacement cards. They reissue new ones to me and they actually tell me to just throw the other ones out as they are disabled. That also means they don't care what you do with the cards.

Their system has to talk to the room door locks somehow to disable the old key cards. May not be wires so there could be wireless communication.

((On edit: I might play with the locks a little and claim I lost my card and try the old card before using the new card to see what happens.))


Old style cards with the punch holes don't talk to a main system.

[Brian Noble]

Their system has to talk to the room door locks somehow to disable the old key cards.

But, the mechanism could be the key itself. For example, suppose the initial set of key cards are programmed with valid dates/times (possibly using a bit of symmetric cryptography, with perhaps a key rotation schedule, to make things hard to forge). A replacement key can include instructions on the magstripe invalidating a particular old key (again, with a bit of crypto for authentication).