In another embodiment, each electronic key 20, 120 may include a security code and a serial number for one or more security devices 40, 140. For example, a key 20, 120 may only be able to lock or unlock a security device 40, 140 where the security codes and the serial numbers match one another. In one example, each serial number is unique to a security device 40, 140 and could be programmed at the time of manufacture or by the retailer. Individual electronic keys 20, 120 may then be assigned particular serial numbers for authorized security devices 40, 140 (e.g., user 1 includes serial numbers 1, 2, 3; user 2 includes serial numbers 1, 4, 5). Each of the electronic keys 20, 120 may be programmed with the same security code using a programming station 60. In order to lock or unlock a merchandise security device 40, 140, the electronic key 20, 120 may communicate with a particular security device and determine whether the security codes and the serial numbers match. If the codes match, the electronic key 20, 120 then locks or unlocks the security device 40, 140.