Patent ID: 8625761

Claim:
A user authentication method applied to a user authentication apparatus for authentication using a unique ID that is information unique to a communication apparatus used by a user, the user authentication method comprising: acquiring, from a user, a user ID as information identifying the user; detecting a unique ID corresponding to the user ID acquired at the acquiring from a user ID list indicating a corresponding relationship between the user ID and the unique ID; recording an originating ID in a incoming call history of a communication apparatus having the unique ID detected at the detecting by making a call with a predetermined number of rings to a communication apparatus having the unique ID detected at the detecting; when the call is answered within the predetermined number of rings, disconnecting the call immediately; and when the call is not answered by the user after the predetermined number of rings, and a callback is received, the callback being made by the communication apparatus after the predetermined number of rings of the call in response to the call using the originating ID recorded in the incoming call history, determining whether a unique ID of the communication apparatus having made the callback received at the receiving matches the unique ID of the communication apparatus to which the call has been made, and determining, if there is a match, that the user having the user ID acquired at the acquiring is an authorized user.