To provide a computer system and a user authentication method in the computer system with excellent operability and high security by using a personal information built-in card storing information unique to a user.
The computer system 1 wherein the personal information built-in card 3 stores a private key in compliance with the public key encryption system and the use of the private key by a computer 2 is permitted only for a prescribed valid period when it is authenticated that a password entered to the computer 2 corresponds to the private key, is provided with: a decision means 11 for deciding whether or not an entry unit 4 of the computer system 1 is operated within the valid period; and a setting means 12 for newly setting the valid period from a start point when the entry unit 4 is operated if the decision means 11 decides that the entry unit 4 is operated.
Shigeru Tsuchiya
Masaya Nishiyama
Higuchi Souji