CLIENT DEVICE, KEY DEVICE, SERVICE PROVIDING DEVICE, USER AUTHENTICATION SYSTEM, USER AUTHENTICATION METHOD, PROGRAM, AND RECORDING MEDIUM

摘要

When registering a user in a user authentication system, a client device performs a signature for a user ID, a password, and a public key by using a secret key which constitutes a pair together with the public key and transmits user information containing the signature and the respective information items to a service providing device. The service providing device verifies the signature by using the public key and stores the user information in which the password is correlated with the public key. Even if the service authentication method is any of a password authentication, a public key authentication, or a combination of the password and the public key authentication upon making a service request, the client device can perform an authentication process by transmitting the authentication reply containing the user ID and the password authentication information or the signature for the challenge from the service providing device or the signature for the password and the challenge.