Patent ID: 7631186

Claim:
An authentication method for use in a mobile wireless communication system which includes a mobile terminal, a plurality of radio access points, and an authentication server, wherein said mobile terminal makes communications through one of said radio access points, said method comprising the steps of: said authentication server transmitting a challenge word to said mobile terminal; said mobile terminal holding the challenge word sent from said authentication server, and transmitting an N-th authentication key to said authentication server when an N-th handover occurs, said N-th authentication key being generated by applying a hash function to the held challenge word a number of times different by a predetermined number of times from an (N−1)th authentication key transmitted when an (N−1)th handover has occurred; said authentication server authenticating the validity of said mobile terminal when the N-th authentication key is sent from said mobile terminal, based on whether or not the N-th authentication key and the held (N−1)th authentication key have a predetermined relationship, and holding the N-th authentication key in place of the (N−1)th authentication key when the authentication is successful; and said authentication server generating a new challenge word after an N-th authentication is completed but prior to an (N+1)th handover.