INDIVIDUAL AUTHENTIFICATION DEVICE

摘要

Attack for authentication by a false user is usually tried a plurality of times because only one trial seldom results in successful authentication. The invention has been made considering this situation as a key point. If a user is once judged as a non-registered person from a non-registered person judging threshold, the registered person judging threshold is dynamically changed to a stricter one, and the user is subjected to the identification judgment using this changed threshold thereafter. With this, attack by a false user can be detected at high probability, thereby improving the security degree. The registered person judging threshold after the change, if a predetermined time has passed or if the user is authenticated, is returned to the original threshold, thereby reducing the possibility of wrongly rejecting the registered user while the usability is ensured.