Authentication-gaining apparatus, authentication apparatus, authentication request transmitting method, authentication method, and program

1. An authentication-gaining apparatus comprising:

an acquiring device that generates unique information;

an encrypting device that encrypts the unique information using a cryptographic key, thereby generating encrypted information; and

a transmitting device that repeatedly transmits an authentication request containing the encrypted information, to an authentication apparatus, during an authentication period,

wherein multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information are transmitted during the authentication period, the multiple pieces of unique information including pieces of different information from each other, and

wherein the authentication request is used for judging whether or not the authentication-gaining apparatus is legitimate.

2. The authentication-gaining apparatus according to claim 1 , wherein the unique information contains any one of a random number value, a counter value, and time.

3. The authentication-gaining apparatus according to claim 1 , wherein the cryptographic key is a key of common-key cryptography.

4. An authentication apparatus comprising:

a receiving device that repeatedly receives an authentication request containing encrypted information obtained through encryption using a cryptographic key and transmitted from an authentication-gaining apparatus, during an authentication period;

a decrypting device that decrypts the encrypted information, thereby acquiring decrypted information;

an authentication device that judges whether or not the authentication-gaining apparatus is legitimate, using multiple authentication requests received during the authentication period and containing encrypted information that has been decrypted; and

an output device that outputs a judgment result by the authentication device,

wherein the authentication-gaining apparatus that is legitimate transmits multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information generated by the authentication-gaining apparatus, during the authentication period, the multiple pieces of unique information including pieces of different information from each other.

5. The authentication apparatus according to claim 4 , wherein, if there are a predetermined number or more of duplicates in multiple pieces of decrypted information, the authentication device judges that the authentication-gaining apparatus is not legitimate.

6. The authentication apparatus according to claim 4 , wherein, if an authentication request is received more than a predetermined number of times during a predetermined period, the authentication device judges that the authentication-gaining apparatus is not legitimate.

7. The authentication apparatus according to claim 4 , wherein, if authentication request receiving intervals in the authentication period include a receiving interval with a probability that is lower than a threshold, the authentication device judges that the authentication-gaining apparatus is not legitimate.

8. The authentication apparatus according to claim 4 , wherein, if multiple pieces of decrypted information respectively acquired from the multiple authentication requests received during the authentication period do not match the unique information, the authentication device judges that the authentication-gaining apparatus is not legitimate.

9. The authentication apparatus according to claim 4 , wherein the receiving device intermittently receives an authentication request.

10. The authentication apparatus according to claim 4 , wherein the cryptographic key is a key of common-key cryptography.

11. An authentication request transmitting method by an authentication-gaining apparatus, comprising:

a step of generating unique information;

a step of encrypting the unique information using a cryptographic key, thereby generating encrypted information; and

a step of repeatedly transmitting an authentication request containing the encrypted information, to an authentication apparatus, during an authentication period,

wherein multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information are transmitted during the authentication period, the multiple pieces of unique information including pieces of different information from each other, and

wherein the authentication request is used for judging whether or not the authentication-gaining apparatus is legitimate.

12. An authentication method comprising:

a step of repeatedly receiving an authentication request containing encrypted information obtained through encryption using a cryptographic key and transmitted from an authentication-gaining apparatus, during an authentication period;

a step of decrypting the encrypted information, thereby acquiring decrypted information;

a step of judging whether or not the authentication-gaining apparatus is legitimate, using multiple authentication requests received during the authentication period and containing encrypted information that has been decrypted; and

a step of outputting a judgment result in the step of judging whether or not the authentication-gaining apparatus is legitimate,

wherein the authentication-gaining apparatus that is legitimate transmits multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information generated by the authentication-gaining apparatus, during the authentication period, the multiple pieces of unique information including pieces of different information from each other.

13. A non-transitory computer readable medium with instructions thereon that when executed by a processor of an authentication-gaining apparatus cause the processor to:

generate unique information;

encrypt the unique information using a cryptographic key, thereby generating encrypted information; and

repeatedly transmit an authentication request containing the encrypted information, to an authentication apparatus, during an authentication period,

wherein multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information are transmitted during the authentication period, the multiple pieces of unique information including pieces of different information from each other, and

wherein the authentication request is used for judging whether or not the authentication-gaining apparatus is legitimate.

14. A non-transitory computer readable medium with instructions thereon that when executed by a processor cause the processor to:

repeatedly receive an authentication request containing encrypted information obtained through encryption using a cryptographic key and transmitted from an authentication-gaining apparatus, during an authentication period;

decrypt the encrypted information, thereby acquiring decrypted information;

judge whether or not the authentication-gaining apparatus is legitimate, using multiple authentication requests received during the authentication period and containing encrypted information that has been decrypted; and

output a judgment result from judging whether or not the authentication-gaining apparatus is legitimate,

wherein the authentication-gaining apparatus that is legitimate transmits multiple authentication requests respectively containing encrypted information obtained by encrypting multiple pieces of unique information generated by the authentication-gaining apparatus, during the authentication period, the multiple pieces of unique information including pieces of different information from each other.