To easily manage secret information while securing the safety of a one-time password concerning user authentication using the one-time password in an information communication network system.

A hush generation part 113 in a portable telephone set 101 obtains a hush value by using a user ID, present time information and common secret information and generates the one-time password. In a user authentication server 103 receiving the user ID and the one-time password from a user PC 102, a hush generation part 124 generates the one-time password similarly by using the received user ID, the present time information and the common secret information to use it for verification by a one-time password verification part.