Terminal device, information processing method, and computer-readable recording medium storing program for authentication

1. A terminal device, comprising:

a processor comprising:

an authentication information acquirer configured to acquire a plurality of pieces of authentication information;

an authentication determiner configured to determine whether or not authentication is successful based on, among the plurality of pieces of authentication information acquired by the authentication information acquirer, at least one piece of authentication information; and

an authentication information updater configured to, when the authentication determiner determines that authentication is successful, update a plurality of pieces of saved authentication information with the plurality of pieces of authentication information acquired by the authentication information acquirer,

wherein the authentication determiner is configured to, in a background,

determine that authentication is successful when first authentication information acquired by the authentication information acquirer falls below a predetermined authentication threshold,

when the first authentication information is greater than or equal to the authentication threshold and less than or equal to a predetermined authentication permissible value, determine whether or not authentication is successful based on second authentication information acquired by the authentication information acquirer, and

change an authentication interval according to a result of the determination based on the second authentication information.

2. The terminal device according to claim 1 , wherein, when the authentication determiner determines that the first authentication information is greater than or equal to the authentication permissible value or determines that authentication is failure based on the second authentication information, the authentication determiner further determines whether or not authentication is successful based on third authentication information acquired by the authentication information acquirer.

3. The terminal device according to claim 2 , wherein

the terminal device includes a tilt detector configured to detect an angle of tilt of a terminal device, and

when, while a user is using the terminal device, an angle of the terminal device detected by the tilt detector is different from a saved angle or the authentication interval has elapsed, the authentication determiner determines whether or not authentication is successful based on, among the plurality of pieces of authentication information acquired by the authentication information acquirer, at least a piece of authentication information or a plurality of pieces of authentication information.

4. The terminal device according to claim 1 , wherein

the terminal device includes a tilt detector configured to detect an angle of tilt of a terminal device, and

when, while a user is using the terminal device, an angle of the terminal device detected by the tilt detector is different from a saved angle or the authentication interval has elapsed, the authentication determiner determines whether or not authentication is successful based on, among the plurality of pieces of authentication information acquired by the authentication information acquirer, at least a piece of authentication information or a plurality of pieces of authentication information.

5. A terminal device, comprising:

an authentication information acquirer configured to acquire a plurality of pieces of authentication information;

a tilt detector configured to detect an angle of tilt of the terminal device;

an authentication determiner configured to determine whether or not authentication is successful based on, among the plurality of pieces of authentication information acquired by the authentication information acquirer, at least one piece of authentication information; and

an authentication information updater configured to, when the authentication determiner determines that authentication is successful, update a plurality of pieces of saved authentication information with the plurality of pieces of authentication information acquired by the authentication information acquirer,

wherein the authentication determiner is configured to, in a background,

when, while a user is using the terminal device, an angle of the terminal device detected by the tilt detector is different from a saved angle or a predetermined authentication interval has elapsed,

determine that authentication is successful when first authentication information acquired by the authentication information acquirer falls below a predetermined authentication threshold,

when the first authentication information is greater than or equal to the authentication threshold and less than or equal to a predetermined authentication permissible value, determine whether or not authentication is successful based on second authentication information acquired by the authentication information acquirer.

6. An information processing method executable by a terminal device, the information processing method comprising:

acquiring a plurality of pieces of authentication information;

determining whether or not authentication is successful based on, among the acquired plurality of pieces of authentication information, at least one piece of authentication information;

when the authentication is determined to be successful, updating a plurality of pieces of saved authentication information with the plurality of pieces of acquired authentication information; and

in a background,

determining that authentication is successful when acquired first authentication information falls below a predetermined authentication threshold, and

when the first authentication information is greater than or equal to the authentication threshold and less than or equal to a predetermined authentication permissible value, determining whether or not authentication is successful based on acquired second authentication information, and changing an authentication interval according to a result of the determination based on the second authentication information.

7. A non-transitory computer-readable recording medium storing a program for causing a computer to perform:

acquiring a plurality of pieces of authentication information;

determining whether or not authentication is successful based on, among the plurality of pieces of acquired authentication information, at least one piece of authentication information;

when the authentication is determined to be successful, updating a plurality of pieces of saved authentication information with the plurality of pieces of acquired authentication information; and

in a background,

determining that authentication is successful when acquired first authentication information falls below a predetermined authentication threshold, and

when the first authentication information is greater than or equal to the authentication threshold and less than or equal to a predetermined authentication permissible value, determining whether or not authentication is successful based on acquired second authentication information.