DIGITAL SIGNATURE SYSTEM, AND METHOD

20250070985

18/808247

August 19, 2024

A first processing apparatus in a digital signature system receives a first parameter generated using a first signing key and first biometric information; a second parameter generated using a second signing key and second biometric information; and a second signature generated with the second signing key for a message. Using at least the first parameter, the second parameter, and the second signature received, the first processing apparatus computes a first signature for the message that is able to be verified using a first verification key corresponding to the first signing key.

NEC Corporation (Tokyo, JP)

1. A digital signature system comprising: a first processing apparatus that includes at least a first processor and a first communication interface, wherein the first processing apparatus is configured to execute processing comprising: receiving a first parameter generated using a first signing key and first biometric information; receiving a second parameter generated using a second signing key and second biometric information, and a second signature generated with the second signing key for a message; and using at least the first parameter, the second parameter, and the second signature, computing a first signature for the message, wherein the first signature is able to be verified using a first verification key corresponding to the first signing key.

2. The digital signature system according to claim 1, wherein the first processing apparatus is configured to execute processing comprising: computing a differential key that is a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and computing the first signature, using at least the differential key and the second signature.

3. The digital signature system according to claim 1, wherein the first processing apparatus is configured to execute processing comprising: receiving a second verification key corresponding to the second signing key; and verifying the second signature for the message using the second verification key.

4. The digital signature system according to claim 1, wherein the first processing apparatus is configured to execute processing comprising: computing a differential key that is a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and computing a second verification key corresponding to the second signing key, using the differential key and the first verification key.

5. The digital signature system according to claim 1, wherein the first signature is a signature with the first signing key for the message.

6. The digital signature system according to claim 1, further comprising: a second processing apparatus including at least a second processor and a second communication interface; and a third processing apparatus including at least a third processor and a third communication interface, wherein the second processing apparatus i s configured to execute processing comprising: generating the first signing key and the first verification key corresponding to the first signing key; acquiring the first biometric information; generating the first parameter by composing the first signing key and the first biometric information; and transmitting the first parameter to the first processing apparatus, wherein the third processing apparatus is configured to execute processing comprising: acquiring the second biometric information; generating the second signing key and a second verification key corresponding to the second signing key; generating the second parameter by composing the second signing key and the second biometric information; generating the second signature for the message using the second signing key; and transmitting the message, the second parameter, and the second signature to the first processing apparatus.

7. The digital signature system according to claim 6, wherein the second processing apparatus transmits the first verification key to a verification apparatus that verifies a signature or to a Key-server, and the first processing apparatus transmits the first signature to the verification apparatus.

8. The digital signature system according to claim 1, wherein the first processing apparatus is configured to execute processing comprising: computing a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and converting the second signature with the second signing key for the message to the first signature with the first signing key for the message, by a Key homomorphic operation receiving at least the difference between the first signing key and the second signing key and the second signature with the second signing key for the message, as inputs.

9. A signature conversion apparatus comprising: at least one processor; a memory storing program instructions executable by the at least one processor; and a communication interface, wherein the at least one processor, when executing the program instructions, performs processing comprising: receiving a first parameter generated using a first signing key and first biometric information; receiving, as a signature including a parameter, a second parameter generated using a second signing key and second biometric information, and a second signature that is a digital signature generated with the second signing key for a message, together with the message; converting the second signature to a first signature using the first parameter and the second parameter, the first signature being a signature for the message that is able to be verified using a first verification key corresponding to the first signing key; and transmitting the first signature, as a signature not including a parameter that depends on biometric information, to a node that verifies the first signature using the first verification key.

10. A digital signature method comprising: receiving, by a first node, a first parameter generated using a first signing key and first biometric information; receiving, by the first node, a second parameter generated using a second signing key and second biometric information; and a second signature generated with the second signing key for a message; and using at least the first parameter, the second parameter, and the second signature, computing, by the first node, a first signature for the message that is able to be verified using a first verification key corresponding to the first signing key.

11. The digital signature method according to claim 10, comprising: computing, by the first node, a differential key that is a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and computing, by the first node, the first signature, using at least the differential key and the second signature.

12. The digital signature method according to claim 10, comprising: receiving, by the first node, a second verification key corresponding to the second signing key and verifying, by the first node, the second signature for the message, using the second verification key.

13. The digital signature method according to claim 10, comprising: computing, by the first node, a differential key that is a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and computing, by the first node, a second verification key corresponding to the second signing key, using the differential key and the first verification key.

14. The digital signature method according to claim 10, wherein the first signature is a signature with the first signing key for the message.

15. The digital signature method according to claim 10, comprising: generating, by a second node, the first signing key and the first verification key corresponding to the first signing key; acquiring, by the second node, the first biometric information; generating, by the second node, the first parameter by composing the first signing key and the first biometric information; transmitting, by the second node, the first parameter to the first node; acquiring, by a third node, the second biometric information; generating, by the third node, the second signing key and a second verification key corresponding to the second signing key; generating, by the third node, the second parameter by composing the second signing key and the second biometric information; generating, by the third node, the second signature for the message, using the second signing key; and transmitting, by the third node, the message, the second parameter, and the second signature to the first node.

16. The digital signature method according to claim 10, comprising: computing a difference between the first signing key and the second signing key, using the first parameter and the second parameter; and using a Key homomorphic operation receiving at least the difference between the first signing key and the second signing key and the second signature with the second signing key for the message, as inputs, converting the second signature with the second signing key for the message to the first signature with the first signing key for the message.

17. A non-transitory computer-readable medium storing a program causing a computer to execute processing comprising: receiving a first parameter generated using a first signing key and first biometric information; receiving, as a signature including a parameter, a second parameter generated using a second signing key and second biometric information, and a second signature that is a digital signature generated with the second signing key for a message, together with the message; converting the second signature to a first signature using the first parameter and the second parameter, the first signature being a signature for the message that is able to be verified using a first verification key corresponding to the first signing key; and transmitting the first signature, as a signature not including a parameter that depends on biometric information, to a node that verifies the first signature using the first verification key.

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