Personal authentication device, personal authentication method, and recording medium

1. A personal authentication device comprising:

a sensor configured to detect a contact with a propagation path being a part of a head of a person to be authenticated;

at least one memory configured to store instructions; and

at least one processor configured to execute the instructions to:

generate, when the sensor detects the contact, a first acoustical signal including an audible range, and generate a second acoustical signal in an inaudible range having a higher frequency than the audible range;

measure an acoustical signal after the first acoustical signal propagates a part of the head and measures an acoustical signal after the second acoustical signal propagates a part of the head; and

perform first authentication of the person to be authenticated when the measured first acoustical signal satisfies a predetermined condition, and when the second acoustical signal satisfies a predetermined condition after the first authentication, perform second authentication for determining whether a person to be authenticated successful in the first authentication is a same person.

2. The personal authentication device according to claim 1 , wherein

the at least one processor is further configured to execute the instructions to

perform the second authentication when the first authentication is successful, and not perform the second authentication when the first authentication fails.

3. The personal authentication device according to claim 2 , wherein

the at least one processor is further configured to execute the instructions to

permit a predetermined access when a result of the first authentication is successful, or when a result of the first authentication and a result of the second authentication immediately after the first authentication are successful, and continue permission of a predetermined access when a result of the second authentication performed after the second authentication immediately after the first authentication is successful.

4. The personal authentication device according to claim 2 , wherein

the at least one processor is further configured to execute the instructions to:

calculate a first acoustical characteristic from an acoustical signal after propagating the measured first acoustical signal, and calculate a second acoustical characteristic from an acoustical signal after propagating the measured second acoustical signal; and

perform the first authentication, based on information including at least one of the first acoustical characteristic and a first feature quantity extracted from the first acoustical characteristic, and perform the second authentication, based on information including at least one of the second acoustical characteristic and a second feature quantity extracted from the second acoustical characteristic.

5. The personal authentication device according to claim 2 , wherein

the at least one processor is further configured to execute the instructions to

transmit the second acoustical signal after measuring the first acoustical signal.

6. The personal authentication device according to claim 1 , wherein

the at least one processor is further configured to execute the instructions to:

calculate a first acoustical characteristic from an acoustical signal after propagating the measured first acoustical signal, and calculate a second acoustical characteristic from an acoustical signal after propagating the measured second acoustical signal; and

perform the first authentication, based on information including at least one of the first acoustical characteristic and a first feature quantity extracted from the first acoustical characteristic, and perform the second authentication, based on information including at least one of the second acoustical characteristic and a second feature quantity extracted from the second acoustical characteristic.

7. The personal authentication device according to claim 6 further comprising

a storage configured to store at least one of the first and second acoustical characteristics and the first and second feature quantities being associated with one or a plurality of persons in advance, wherein

the at least one processor is further configured to execute the instructions to

identify whether to be a person to be authenticated successful in the first authentication, by comparing the calculated first and second acoustical characteristics with the first and second acoustical characteristics stored in the storage, or by comparing the extracted first and second feature quantities with the first and second feature quantities stored in the storage.

8. The personal authentication device according to claim 6 , wherein

the at least one processor is further configured to execute the instructions to

transmit the second acoustical signal after measuring the first acoustical signal.

9. The personal authentication device according to claim 6 , wherein

the at least one processor is further configured to execute the instructions to

permit a predetermined access when a result of the first authentication is successful, or when a result of the first authentication and a result of the second authentication immediately after the first authentication are successful, and continue permission of a predetermined access when a result of the second authentication performed after the second authentication immediately after the first authentication is successful.

10. The personal authentication device according to claim 1 , wherein

the at least one processor is further configured to execute the instructions to

transmit the second acoustical signal after measuring the first acoustical signal.

11. The personal authentication device according to claim 10 , wherein

the at least one processor is further configured to execute the instructions to

permit a predetermined access when a result of the first authentication is successful, or when a result of the first authentication and a result of the second authentication immediately after the first authentication are successful, and continue permission of a predetermined access when a result of the second authentication performed after the second authentication immediately after the first authentication is successful.

12. The personal authentication device according to claim 1 , wherein

the at least one processor is further configured to execute the instructions to

permit a predetermined access when a result of the first authentication is successful, or when a result of the first authentication and a result of the second authentication immediately after the first authentication are successful, and continue permission of a predetermined access when a result of the second authentication performed after the second authentication immediately after the first authentication is successful.

13. The personal authentication device according to claim 1 , wherein

the at least one processor is further configured to execute the instructions to

count, using a counter, at least one of a number of times of success of the first authentication and a number of times of success of the second authentication, and

the sensor restores a counter value that is counted to an initial value when detecting the contact has been lost.

14. The personal authentication device according to claim 13 further comprising:

the at least one processor is further configured to execute the instructions to

adjust, when the counter acquires a number of times of successful authentication to be counted and determines that the number of times of successful authentication exceeds a predetermined number of times, a time interval after measuring the first acoustical signal until the second acoustical signal is transmitted in such a way as to be longer.

15. A personal authentication method comprising:

detecting a contact with a propagation path being a part of a head of a person to be authenticated;

generating, when detecting the contact, a first acoustical signal including an audible range;

measuring an acoustical signal after the first acoustical signal propagates the propagation path;

generating a second acoustical signal in an inaudible range having a higher frequency than the audible range;

measuring an acoustical signal after the second acoustical signal propagates the propagation path;

performing, when the measured first acoustical signal satisfies a predetermined condition, first authentication of the person to be authenticated; and

performing, when the second acoustical signal satisfies a predetermined condition after the first authentication, second authentication for determining whether a person to be authenticated successful in the first authentication is a same person.

16. A non-transitory computer readable recording medium storing a personal authentication program which causes a computer to perform:

detecting a contact with a propagation path being a part of a head of a person to be authenticated;

generating, when detecting the contact, a first acoustical signal including an audible range;

measuring an acoustical signal after the first acoustical signal propagates the propagation path;

generating a second acoustical signal in an inaudible range having a higher frequency than the audible range;

measuring an acoustical signal after the second acoustical signal propagates the propagation path;

performing, when the measured first acoustical signal satisfies a predetermined condition, first authentication of the person to be authenticated; and

performing, when the second acoustical signal satisfies a predetermined condition after the first authentication, second authentication for determining whether a person to be authenticated successful in the first authentication is a same person.