unique serial number that identifies the client token once the ciphertext is generated it is sent to the lock along with the serial number of the client smart card in a first authentication packet step 405 during authentication the client driver 220 sends a first encrypted random number along with the plaintext serial number of the user 39 s smart card 101 the lock is provisioned with a database of serial numbers of authorized users and their corresponding nk_uids keys when the lock receives the first authentication packet step 415 it uses the serial number of the client smart card contained in the first authentication packet to retrieve the enciphered version of the client smart cards 39 nk_uids in the lock database the lock database contains a mapping of client smart card serial numbers to corresponding nk_uids keys during authentication the user 39 s serial number is utilized to retrieve the enciphered version of the user 39 s nk_uids key from its database and is then written in enciphered form into the lock 39 s smart card 102 where it is automatically deciphered by the lock 39 s smart card 102 at that instant in time the lock 39 s smart card 102 contains exactly the same nk_uids key of the authenticating user then the lock 39 s smart card decrypts the first encrypted random number in step 415 appropriate checks and balances are incorporated to ensure that a successful decryption can be detected in step 420 a second random number is generated by the lock 39 s smart card 102 and encrypted with the same user 39 s nk_uids key still in the lock 39 s smart card the ciphertext is then returned to the user in a second packet step 425 the client driver software 220 utilizes the.