| 摘要 |
[Problem] To provide a new user authentication method which efficaciously prevents illicit access to a system. [Solution] The present invention is an authentication system which authenticates a user who uses a system subject to use, said authentication system comprising: a database which, for each user, manages user account information including a token ID which identifies a security token; a synchronization server which generates token codes on the basis of the token ID; and an authentication server which carries out an authentication determination with respect to a user authentication request which is transmitted from the system subject to use, and transmits the result of the authentication determination to the system subject to use. If a prior notification of an authentication request which an information communication terminal has transmitted in a state of being capable of communication is received prior to receiving the user authentication request, the authentication server carries out the authentication determination on the basis of a first token code, whereas, if the user authentication request is received without the prior notification of the authentication request being received, the authentication server carries out the authentication determination on the basis of the first token code and a second token code. |
