KEY EXCHANGE SYSTEM, QKD APPARATUS, HUB APPARATUS, METHOD, AND PROGRAM

1 . A key exchange system comprising:

a quantum key distribution (QKD) network including

a plurality of QKD apparatuses that performs exchange of a key by using a quantum key distribution protocol, and

a key management apparatus that relays the key; and

a plurality of hub apparatuses that performs encrypted communication by using the key received from the key management apparatus, wherein

each of the QKD apparatuses includes

a first processor, and

a first memory storing first program instructions that cause the first processor to

encrypt the key by using a public key of one of the hub apparatuses in a case where the key is exchanged with another QKD apparatus by using the quantum key distribution protocol, and

transmit the encrypted key to the key management apparatus, and

each of the hub apparatuses includes

a second processor, and

a second memory storing second program instructions that cause the second processor to

decrypt the encrypted key by using a secret key corresponding to the public key in a case where the encrypted key is received from the key management apparatus.

2 . The key exchange system according to claim 1 , wherein the public key and the secret key are keys of post-quantum cryptography.

3 . The key exchange system according to claim 1 , wherein the second program instructions further cause the second processor to share the secret key with another hub apparatus by using a key encapsulation mechanism based on post-quantum cryptography.

4 . A quantum key distribution (QKD) apparatus in a key exchange system including: a QKD network including a plurality of QKD apparatuses that performs exchange of a key by using a quantum key distribution protocol and a key management apparatus that relays the key; and a plurality of hub apparatuses that performs encrypted communication by using the key received from the key management apparatus, the QKD apparatus comprising:

a processor; and

a memory storing program instructions that cause the processor to:

encrypt the key by using a public key of one of the hub apparatuses in a case where the key is exchanged with another QKD apparatus by using the quantum key distribution protocol; and

transmit the encrypted key to the key management apparatus.

5 . A hub apparatus in a key exchange system including: a quantum key distribution (QKD) network including a plurality of QKD apparatuses that performs exchange of a key by using a quantum key distribution protocol and a key management apparatus that relays the key; and a plurality of hub apparatuses that performs encrypted communication by using the key received from the key management apparatus, the hub apparatus comprising:

a processor; and

a memory storing program instructions that cause the processor to:

generate a public key and a secret key by using predetermined public key cryptography;

distribute the public key to the plurality of QKD apparatuses; and

decrypt the key by using the secret key in a case where the key encrypted by a corresponding one of the QKD apparatuses by using the public key is received from the key management apparatus.

6 . (canceled)

7 . A non-transitory computer-readable recording medium storing a program for causing a computer to function as the QKD apparatus of claim 4 .

8 . A non-transitory computer-readable recording medium storing a program for causing a computer to function as the hub apparatus of claim 5 .