Quantum key distribution device, quantum key distribution system, and quantum key distribution method

A quantum key distribution device that is connected to another quantum key distribution device by a quantum communication channel and a classical communication channel and that shares a cryptographic key with the another quantum key distribution device, the quantum key distribution device comprising:

• a quantum key sharer configured to share a photon string with the another quantum key distribution device using quantum key distribution via the quantum distribution channel, and that obtain a photon bit string corresponding to the photon string;
• a key distillation processor configured to generate a link key as the cryptographic key from the photon bit string by a key distillation process;
• a first manager configured to store the link key as a link reception key to be used in data decryption in an internal or external storage;
• a second manager configured to
• receive an application key that is the cryptographic key to be used in cryptographic data communication and has a predetermined role decided therefor, from the another quantum key distribution device via the classical communication channel,
• decrypt the received application key using the link reception key, and
• store the decrypted application key in the storage;
• and
• a key manager configured to manage the application key that is stored in the storage for use in encryption or decryption when an application performs data communication.

A quantum key distribution system comprising a first quantum key distribution device and a second quantum key distribution device that are connected by a quantum communication channel and a classical communication channel, a cryptographic key being shared among the first quantum key distribution device and the second quantum key distribution device, wherein

• the first quantum key distribution device includes
• a first quantum key sharer configured to share a photon string with the second quantum key distribution device using quantum key distribution via the quantum distribution channel, and obtain a photon bit string corresponding to the photon string from the second quantum key distribution device using quantum key distribution via the quantum distribution channel,
• a first key distillation processor configured to generate a link key as the cryptographic key from the photon bit string by a key distillation process,
• a first link-key manager configured to store the link key as a link transmission key to be used in data encryption in an internal or external first storage,
• a first application-key manager configured to
• store, in the first storage, a first application key that has a predetermined role decided therefor from an application key that is the cryptographic key to be used in cryptographic data communication,
• encrypt a second application key that has a role corresponding to the first application key decided therefor from the application key, using the link transmission key, and
• send the encrypted second application key to the second quantum key distribution device via the classical communication channel, and
• a first key manager configured to manage the first application key that is stored in the first storage for use in encryption or decryption when an application performs data communication, and
• the second quantum key distribution device includes
• a second quantum-key sharer configured to share the photon string with the first quantum key distribution device using quantum key distribution via the quantum distribution channel, and obtain a photon bit string corresponding to the photon string from the first quantum key distribution device using quantum key distribution via the quantum distribution channel,
• a second key distillation processor configured to generate a link key as the cryptographic key from the photon bit string by a key distillation process,
• a second link-key manager configured to store the link key as a link reception key to be used in data decryption in an internal or external second storage,
• a second application-key manager configured to decrypt the second application key that is received from the first application-key manager via the classical communication channel, using the link reception key, and store the decrypted second application key in the second storage, and
• a second key manager configured to manage the second application key that is stored in the second storage for use in encryption or decryption when an application performs data communication.

A quantum key communication method implemented in a quantum key communication system that includes a first quantum key distribution device and a second quantum key distribution device which are connected by a quantum communication channel and a classical communication channel and which share a cryptographic key, the method comprising:

• obtaining a photon bit string corresponding to a photon string using quantum key distribution via the quantum distribution channel, the photon string being shared among the first quantum key distribution device and the second quantum key distribution device;
• generating a link key as the cryptographic key from the photon bit string by a key distillation process;
• storing the link key as a link transmission key to be used in data encryption in an internal or external first storage;
• storing, in the first storage, a first application key that has a predetermined role decided therefor from an application key that is the cryptographic key to be used in cryptographic data communication;
• encrypting a second application key that has a role corresponding to the first application key decided therefor from the application key, using the link transmission key;
• sending the encrypted second application key to the second quantum key distribution device via the classical communication channel;
• managing the first application key that is stored in the first storage for use in encryption or decryption when an application performs data communication;
• obtaining a photon bit string corresponding to the photon string using quantum key distribution via the quantum distribution channel;
• generating a link key as the cryptographic key from the photon bit string by a key distillation process;
• storing the link key as a link reception key to be used in data decryption in an internal or external second storage;
• decrypting the second application key that is received from the first quantum key distribution device via the classical communication channel, using the link reception key;
• storing the decrypted second application key in the second storage;
• and
• managing the second application key that is stored in the second storage for use in encryption or decryption when an application performs data communication.