Remote device authentication system

This invention relates to an authentication system and, more particularly, to an authentication system for ensuring the validity of a remote device, for example, a wireless telephone or smartcard. Method and system for authenticating a remote device are disclosed by an arrangement in which the remote device and an authentication center each contain an identical key code index, which includes a plurality of key code numbers. When a remote device identifies itself to the authentication center by sending identification information, the authentication center generates a first key using a portion of the received identification information and a first random number that specifies a first key code number. The remote device determines the first key code number from the first key. If the remote device recognizes the first key code number from among the stored plurality of key code numbers, the remote device generates a second key, which includes a second random number that specifies a second key code number, and a portion of the identification information. From the second key, the authentication center determines a second key code number. If the first and second key code numbers match the remote device is authenticated, otherwise the remote device is not authenticated.