Quantum key distribution system, key management device, key management method, and control program

Abstract

To provide a quantum key distribution system, key management device, key management method, and control program capable of efficiently utilizing an encryption key.SOLUTION: In a quantum key distribution system, each key management device comprises: a storage section; a monitoring section for monitoring whether or not a QKDN management device is in operation; and a registration control section that when it is determined by the monitoring section that operation of the QKDN management device is stopped, stores an encryption key before generation by a key generation device managed by the key management device is registered with the QKDN management device as life cycle information in the storage section and, when it is determined by the monitoring section that the operation of the QKDN management device is started, registers life cycle information on the encryption key stored in the storage section with the QKDN management device.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a quantum key distribution system, a key management device, a key management method, and a control program. [Background technology]

[0002] In encrypted communication of messages from a sending server to a receiving server, the message is encrypted at the sending server and decrypted at the receiving server using an encryption key that is shared in advance between the sending server and the receiving server. In particular, encryption communication in which a new encryption key is generated for each message communication is called one-time pad encryption communication.

[0003] Furthermore, in recent years, the development of quantum cryptography communication has been progressing. Quantum cryptography communication is a type of cryptographic communication using a one-time pad method, and enables more secure cryptographic communication by transmitting a cryptographic key generated by a transmitter on the sending server side from the transmitter to a receiver on the receiving server side on photons (particles of light), which are the smallest units of light, or on weak light. Technology related to quantum cryptography communication is disclosed in Patent Document 1, for example.

[0004] Patent Document 1 discloses a quantum key distribution network device for independently operating a data transmission path and a quantum key consumption path that consumes a quantum key for encrypting the corresponding data in a quantum key distribution network. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-175604 Summary of the Invention [Problem to be solved by the invention]

[0006] In quantum cryptography communication, it is required to efficiently use the encryption keys generated by key generation devices installed at each node of the quantum key distribution network.

[0007] One of the objects of the present disclosure is to provide a quantum key distribution system, a key management device, a key management method, and a control program that solve the above-mentioned problems. [Means for solving the problem]

[0008] A quantum key distribution system according to one aspect of the present disclosure includes a plurality of key generation devices provided at a plurality of bases, each of which is connected to another by an optical fiber, and which generate encryption keys; a plurality of key management devices provided corresponding to the plurality of key generation devices and which manage the encryption keys generated by each of the plurality of key generation devices; a plurality of key supply devices provided corresponding to the plurality of key management devices and which supply the encryption keys managed by the plurality of key management devices to an application that performs quantum cryptography communication; and a processing status of the encryption keys by each of the plurality of key generation devices, the plurality of key management devices, and the plurality of key supply devices. and a QKDN management device that acquires and manages the above-mentioned life cycle information, and each of the key management devices comprises a memory unit, a monitoring unit that monitors whether the QKDN management device is operating, and a registration control unit that, if the monitoring unit determines that the operation of the QKDN management device is stopped, stores in the memory unit an encryption key that was generated by a key generation device managed by the key management device before being registered in the QKDN management device as life cycle information, and, if the monitoring unit determines that the operation of the QKDN management device has started, registers in the QKDN management device the life cycle information for the encryption key stored in the memory unit.

[0009] A key management device according to one aspect of the present disclosure is a key management device that manages encryption keys generated by a key generation device connected to other key generation devices via optical fiber, and includes: a memory unit; a monitoring unit that monitors whether a QKDN management device that acquires and manages information about encryption keys generated by each of a plurality of key generation devices as lifecycle information of the encryption keys is operating; and a registration control unit that, if the monitoring unit determines that the operation of the QKDN management device is stopped, stores in the memory unit the encryption key that was generated by a key generation device managed by the key management device before it was registered in the QKDN management device as lifecycle information; and, if the monitoring unit determines that the operation of the QKDN management device has started, registers in the QKDN management device the lifecycle information about the encryption key stored in the memory unit.

[0010] A key management method according to one aspect of the present disclosure is a key management method for a key management device that manages encryption keys generated by a key generation device connected to other key generation devices via optical fiber, and monitors whether a QKDN management device that acquires and manages information about encryption keys generated by each of a plurality of key generation devices as lifecycle information of the encryption keys is in operation.If it is determined that the operation of the QKDN management device is stopped, the encryption key before being registered in the QKDN management device is stored in a memory unit as lifecycle information that it was generated by a key generation device managed by the key management device, and if it is determined that operation of the QKDN management device has started, the lifecycle information for the encryption key stored in the memory unit is registered in the QKDN management device.

[0011] A control program according to one aspect of the present disclosure is a control program that causes a computer to execute key management processing by a key management device that manages encryption keys generated by a key generation device connected to other key generation devices via optical fiber, and causes the computer to execute the following processes: monitoring whether a QKDN management device that acquires and manages information about encryption keys generated by each of multiple key generation devices as lifecycle information of the encryption keys is in operation; if it is determined that the operation of the QKDN management device is stopped, storing in a memory unit the encryption key before it was registered in the QKDN management device as lifecycle information that it was generated by a key generation device managed by the key management device; and if it is determined that the operation of the QKDN management device has started, registering in the QKDN management device the lifecycle information about the encryption key stored in the memory unit. [Effects of the Invention]

[0012] The present disclosure can provide a quantum key distribution system, a key management device, a key management method, and a control program that can efficiently use encryption keys. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an example configuration of a quantum key distribution system according to the present disclosure. [Figure 2] FIG. 1 is a diagram showing the relationship between the transmission distance, the key generation probability, and the key generation rate in quantum key distribution. [Figure 3] FIG. 1 is a block diagram illustrating an example of the configuration of a key management device provided in a quantum key distribution system according to the present disclosure. [Figure 4] 10 is a flowchart illustrating the operation of a key management device provided in the quantum key distribution system according to the present disclosure. [Figure 5] FIG. 10 is a sequence diagram showing an example of the operation of the quantum key distribution system according to the present disclosure. [Figure 6] FIG. 10 is a sequence diagram showing another example of the operation of the quantum key distribution system according to the present disclosure. [Figure 7]FIG. 10 is a sequence diagram showing another example of the operation of the quantum key distribution system according to the present disclosure. [Figure 8] FIG. 2 is a block diagram illustrating an example of a hardware configuration for implementing a key management function of a key management device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments will be described with reference to the drawings. Note that the drawings are simplified, and the technical scope of the embodiments should not be narrowly interpreted based on the description in the drawings. Furthermore, identical elements are given the same reference numerals, and duplicate explanations will be omitted.

[0015] In the following embodiments, when necessary for convenience, the description will be divided into multiple sections or embodiments. However, unless otherwise specified, they are not unrelated to each other, and one is a partial or complete modification, application example, detailed explanation, supplementary explanation, etc. of the other. Furthermore, in the following embodiments, when the number of elements (including the number, numerical value, amount, range, etc.) is mentioned, it is not limited to that specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited to a specific number in principle.

[0016] Furthermore, in the following embodiments, the components (including operational steps, etc.) are not necessarily essential unless otherwise specified or considered to be clearly essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., it is intended to include those that are substantially similar or approximate to the shape, etc., unless otherwise specified or considered to be clearly not essential in principle. The same applies to the above numbers, etc. (including numbers, numerical values, amounts, ranges, etc.).

[0017] <First Embodiment> Fig. 1 is a diagram showing an example of the configuration of a quantum key distribution system according to the present disclosure. As shown in Fig. 1, the quantum key distribution system 1 is a system that manages and operates encryption keys used in quantum cryptography communication in a QKDN (Quantum Key Distribution Network) platform, and includes at least a plurality of key generation devices (QKD devices) 11, a plurality of key management devices 12, a plurality of key supply devices 13, and a QKDN management device 14.

[0018] Each of the plurality of key generation devices 11 generates an encryption key. The plurality of key generation devices 11 are provided at different locations and are connected to each other by optical fibers 50.

[0019] The quantum key distribution system 1 is used for quantum cryptography communication using a quantum key distribution method called CV-QKD, for example. In the application layer, in cryptographic communication of a message from a sending server to a receiving server, the message is encrypted at the sending server and decrypted at the receiving server using an encryption key shared in advance between the sending server and the receiving server. In particular, cryptographic communication in which a new encryption key is generated for each message communication is called one-time pad cryptography.

[0020] Quantum cryptography communication is a type of cryptographic communication using a one-time pad method, and the quantum key distribution system 1 enables more secure cryptographic communication by transmitting an encryption key generated by a key generation device 11 (transmitter 11_1) provided corresponding to a transmission server from the transmitter to a key generation device 11 (receiver 11_2) provided corresponding to a receiving server, using weak light. Note that the weak light is, for example, light (quantum light) whose typical intensity is about one photon, and whose quantum mechanical state change can be detected.

[0021] The transmitter 11_1 (key generation device 11 on the transmitting side) transmits a plurality of weak lights including randomly assigned transmission bits and information on transmission bases to the receiver 11_2 (key generation device 11 on the receiving side) via the optical fiber 50. In other words, the transmitter 11_1 phase-modulates each of the plurality of weak lights using the randomly assigned transmission bits and transmission bases, and transmits the phase-modulated light to the receiver 11_2 via the optical fiber 50.

[0022] For example, if the bit value of the transmission bit is "0", a phase modulation amount of 0 degrees is assigned, and if the bit value of the transmission bit is "1", a phase modulation amount of 180 degrees is assigned. Also, if the base value of the transmission basis is "X", a phase modulation amount of 0 degrees is assigned, and if the base value of the transmission basis is "Y", a phase modulation amount of 90 degrees is assigned. Each weak light is phase-modulated with a phase modulation amount obtained by adding the phase modulation amount corresponding to the bit value and the phase modulation amount corresponding to the base value. Therefore, weak light phase-modulated using a transmission basis with a base value of "X" ideally appears on the real axis, and weak light phase-modulated using a transmission basis with a base value of "Y" ideally appears on the imaginary axis.

[0023] The receiver 11_2 phase-modulates the reference light using a randomly assigned reception basis corresponding to a transmission basis randomly assigned to each of the plurality of received weak light beams. Thereafter, the receiver 11_2 performs basis matching for the plurality of received weak light beams using, for example, a homodyne detector. Specifically, the receiver 11_2 causes interference between the plurality of weak light beams and the phase-modulated reference light beam, thereby detecting information of a plurality of bit values ​​(bit information) from each of the plurality of weak light beams interfered by the reference light of the reception basis whose basis value matches the transmission basis, among the plurality of weak light beams. Note that the bit information includes a phase component representing the bit value and an amplitude component representing the intensity of the bit value.

[0024] For example, if the basis value of the receiving basis is "X", a phase modulation amount of 0 degrees is assigned, and if the basis value of the receiving basis is "Y", a phase modulation amount of 90 degrees is assigned. Therefore, the desired bit information can be detected only when interference occurs between weak light and reference light whose transmitting basis and receiving basis match each other.

[0025] Thereafter, the transmitter 11_1 and the receiver 11_2 perform error correction processing and privacy amplification processing on the bit string after error correction, and as a result, encryption keys (i.e., shared encryption keys) whose bit strings match each other are individually generated.

[0026] 2 is a diagram showing the relationship between transmission distance and key generation probability and key generation rate in quantum key distribution. As shown in FIG. 2, the longer the transmission distance, the lower the key generation rate and the lower the key generation probability. In particular, when the transmission distance exceeds 50 km, the key generation rate drops sharply. Therefore, the length of each optical fiber 50 connecting multiple key generation devices 11 is, for example, 50 km or less.

[0027] When quantum cryptography communication is performed between two locations separated by a long distance, such as more than 50 km, or when quantum cryptography communication is performed while avoiding transmission routes that may be susceptible to eavesdropping, the quantum cryptography communication (sharing of encryption keys) is performed via a location other than the two locations (a relay location). Key relay technology is used to share encryption keys between two locations via a relay location.

[0028] For example, when an encryption key is shared between points A and B via a relay point C, first, the key generation device 11 at point A generates an encryption key Kab to be shared with point B. Then, the key generation device 11 at point A and the key generation device 11 at relay point C generate a common encryption key Kac using the above-mentioned quantum key distribution technology. Then, the key Kab generated at point A is encrypted with the encryption key Kac and transferred from point A to relay point C. At relay point C, the encrypted key Kab is decrypted with the encryption key Kac. Then, the key generation device 11 at relay point C and the key generation device 11 at point B generate a common encryption key Kcb using the above-mentioned quantum key distribution technology. Then, the decrypted key Kac at relay point C is encrypted with the encryption key Kcb and transferred from relay point C to point B. At point B, the encrypted key Kab is decrypted with the encryption key Kcb. In this way, by using the key relay technology, the encryption key is shared between the sites A and B via the site C.

[0029] The multiple key management devices 12 are provided corresponding to the multiple key generation devices 11, and manage the encryption keys generated by each of the multiple key generation devices 11. For example, each key management device 12 stores the encryption key generated by the corresponding key generation device 11 in a storage unit, and manages the consumption of encryption keys by a key supply device (described later). Each key management device 12 also encrypts and decrypts an encryption key (corresponding to the above-mentioned encryption key Kab) shared between two locations by key relay. Other functions of each key management device 12 will be described later.

[0030] The plurality of key supply devices 13 are provided corresponding to the plurality of key management devices 12, and supply encryption keys managed by the plurality of key management devices 12 to applications in which quantum cryptography communication is performed.

[0031] The QKDN management device 14 acquires the processing status of the encryption keys by each of the multiple key generation devices 11, multiple key management devices 12, and multiple key supply devices 13 as life cycle information, and centrally manages it.

[0032] For example, when an encryption key is generated by key generation device 11, QKDN management device 14 accepts a registration request from key management device 12 that manages this key generation device 11, and registers the fact that the encryption key has been generated by this key generation device 11 as life cycle information for the encryption key. Note that the life cycle information for the encryption key at this time includes the generation time of the encryption key, identification information for key generation device 11 that generated the encryption key, identification information for the encryption key (for example, a combination of identification information for key management device 12 and a serial number), etc.

[0033] Furthermore, for example, when an encryption key is supplied to an application by the key supplying device 13, the QKDN management device 14 accepts a registration request from the key management device 12 that manages the key supplying device 13, and registers the fact that the encryption key has been supplied (consumed) to the application by the key supplying device 13 as life cycle information for the encryption key. Note that the life cycle information for the encryption key at this time includes the consumption time of the encryption key, identification information of the key supplying device 13 that consumed the encryption key, identification information of the encryption key (for example, a combination of identification information of the key management device 12 and a serial number), etc.

[0034] (Details of the key management device 12) 3 is a block diagram showing an example of the configuration of a key management device according to the present disclosure. As shown in FIG. 3, the key management device 12 includes at least a monitoring unit 121, a registration control unit 122, and a storage unit 123.

[0035] The monitoring unit 121 monitors whether the QKDN management device 14 is in operation. The registration control unit 122 controls the registration of life cycle information about encryption keys in the QKDN management device 14 based on the monitoring results of the QKDN management device 14 by the monitoring unit 121.

[0036] For example, the monitoring unit 121 monitors whether the QKDN management device 14 is in operation based on the processing status of the QKDN management device 14.

[0037] Alternatively, the monitoring unit 121 may monitor whether the QKDN management device 14 is operating based on the response status of the QKDN management device 14. Specifically, the monitoring unit 121 periodically monitors whether the QKDN management device 14 is operating based on whether the QKDN management device 14 responds to a request from the registration control unit 122 to periodically register life cycle information about the encryption key. For example, if the registration control unit 122's request to register life cycle information about the encryption key in the QKDN management device 14 is not accepted, the monitoring unit 121 determines that the operation of the QKDN management device 14 is stopped, and if the registration control unit 122's request to register life cycle information about the encryption key in the QKDN management device 14 is accepted, the monitoring unit 121 determines that the operation of the QKDN management device 14 has started.

[0038] Alternatively, the monitoring unit 121 may receive a notification from the QKDN management device 14 that operation has been stopped or a notification from the QKDN management device 14 that operation has started, and determine whether the QKDN management device 14 is operating or not from the content of the notification.

[0039] If monitoring unit 121 determines that operation of QKDN management device 14 is stopped, registration control unit 122 stores in memory unit 123 the encryption key before it was registered in QKDN management device 14, as lifecycle information indicating that it was generated by key generation device 11 under the management of key management device 12. Thereafter, if monitoring unit 121 determines that operation of QKDN management device 14 has started, registration control unit 122 registers in QKDN management device 14 the lifecycle information about the encryption key before it was registered, stored in memory unit 123.

[0040] If monitoring unit 121 determines that operation of QKDN management device 14 is stopped, registration control unit 122 may further store in storage unit 123 life cycle information about the encryption key before it was registered in QKDN management device 14, indicating that it was supplied to an application by key supply device 13 under the management of key management device 12. Even in this case, if monitoring unit 121 subsequently determines that operation of QKDN management device 14 has started, registration control unit 122 registers in QKDN management device 14 the life cycle information about the encryption key before it was registered that is stored in storage unit 123.

[0041] Next, the operation of the key management device 12 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the operation of the key management device according to the present disclosure.

[0042] 4, first, the key management device 12 monitors whether the QKDN management device 14 is operating (step S11). For example, the key management device 12 periodically monitors whether the QKDN management device 14 is operating, based on whether or not the QKDN management device 14 responds to a request for periodic registration of life cycle information about an encryption key generated by the key generation device 11 under its management. For example, if the key management device 12 does not accept registration of life cycle information about an encryption key in the QKDN management device 14, the key management device 12 determines that operation of the QKDN management device 14 is stopped, and if the key management device 12 accepts registration of life cycle information about an encryption key in the QKDN management device 14, the key management device 12 determines that operation of the QKDN management device 14 has started.

[0043] Here, if the key management device 12 determines that the operation of the QKDN management device 14 is stopped, it stores in a memory unit the encryption key before it was registered in the QKDN management device 14 as lifecycle information indicating that it was generated by the key generation device 11 under its management (step S12).

[0044] Thereafter, when the key management device 12 determines that the operation of the QKDN management device 14 has started, it registers the life cycle information about the encryption key before registration that is stored in the storage unit in the QKDN management device 14 (step S13).

[0045] In this way, when the operation of the QKDN management device 14 is stopped, the key management device 12 according to the present disclosure stores in a memory unit the encryption keys generated by the key generation devices 11 under its management, and when the operation of the QKDN management device 14 starts, registers in the QKDN management device 14 the life cycle information for the encryption keys before registration stored in the memory unit. This allows the key management device 12 according to the present disclosure to re-register and use encryption keys whose life cycle information has not been registered in the QKDN management device 14 without discarding them, thereby enabling efficient use of encryption keys.

[0046] (An example of the operation of quantum key distribution system 1) Next, an example of the operation of the quantum key distribution system 1 will be described with reference to Fig. 5. Fig. 5 is a sequence diagram showing an example of the operation of the quantum key distribution system according to the present disclosure. Note that in the example of Fig. 5, among the multiple key generation devices 11, key generation devices 11_1 and 11_2 that share an encryption key are shown, and among the multiple key management devices 12, key management devices 12_1 and 12_2 that manage the key generation devices 11_1 and 11_2 are shown.

[0047] First, the key generating devices 11_1, 11_1 generate a common encryption key (steps S101, S102). At this time, the QKDN management device 14 stops its operation for reasons such as periodic inspection (step S301).

[0048] Thereafter, the key management device 12_1 attempts to register life cycle information about the encryption key generated by the key generation device 11_1 in the QKDN management device 14 (step S102). However, since the QKDN management device 14 is in a stopped state, it does not accept the registration of life cycle information about the encryption key by the key management device 12_1.

[0049] In this case, the key management device 12_1 stores the encryption key that has not been registered in the QKDN management device 14 in a storage unit without discarding it (step S103). Thereafter, the key management device 12_1 periodically monitors whether the QKDN management device 14 is operating or not (steps S104 to S105). Then, when the QKDN management device 14 starts operating (step S302), the key management device 12_1 registers life cycle information about the encryption key stored in the storage unit in the QKDN management device 14 (step S106). This allows the key management device 12_1 to re-register and use the encryption key whose life cycle information has not been registered in the QKDN management device 14 without discarding it, thereby enabling efficient use of the encryption key.

[0050] Similarly, the key management device 12_2 attempts to register life cycle information about the encryption key generated by the key generating device 11_2 in the QKDN management device 14 (step S202). However, since the QKDN management device 14 is out of operation, it does not accept the registration of life cycle information about the encryption key by the key management device 12_2.

[0051] In this case, the key management device 12_2 stores the encryption key that has not been registered in the QKDN management device 14 in the storage unit without discarding it (step S203). Thereafter, the key management device 12_2 periodically monitors whether the QKDN management device 14 is operating or not (steps S204 to S205). Then, when the QKDN management device 14 starts operating (step S302), the key management device 12_2 registers life cycle information about the encryption key stored in the storage unit in the QKDN management device 14 (step S206). This allows the key management device 12_2 to re-register and use the encryption key whose life cycle information has not been registered in the QKDN management device 14 without discarding it, thereby enabling efficient use of the encryption key.

[0052] (Another example of the operation of quantum key distribution system 1) Next, another example of the operation of the quantum key distribution system 1 will be described with reference to Fig. 6. Fig. 6 is a sequence diagram showing another example of the operation of the quantum key distribution system according to the present disclosure. Note that in the example of Fig. 6, among the multiple key generation devices 11, key generation devices 11_1 and 11_2 that share an encryption key are shown, and among the multiple key management devices 12, key management devices 12_1 and 12_2 that manage the key generation devices 11_1 and 11_2 are shown.

[0053] In the example of Fig. 6, an encryption key whose life cycle information is not registered is used as an encryption key for key relay. Other processes shown in Fig. 6 are the same as those shown in Fig. 5.

[0054] First, the key generating devices 11_1, 11_1 generate a common encryption key (steps S101, S102). At this time, the QKDN management device 14 stops its operation for reasons such as periodic inspection (step S301).

[0055] Thereafter, the key management device 12_1 attempts to register life cycle information about the encryption key generated by the key generation device 11_1 in the QKDN management device 14 (step S102). However, since the QKDN management device 14 is in a stopped state, it does not accept the registration of life cycle information about the encryption key by the key management device 12_1.

[0056] In this case, the key management device 12_1 may use the encryption key not registered in the QKDN management device 14 for a purpose other than supplying it to an application, for example, as a key to be distributed by a key relay (corresponding to the above-mentioned key Kab), without discarding it. Alternatively, the key may be used as an encryption key for encrypting a key to be distributed by a key relay (corresponding to the above-mentioned keys Kac, Kcb, etc.). Lifecycle information about the fact that an encryption key not registered in the QKDN management device 14 has been distributed by a key relay or has been used to encrypt a key to be distributed by a key relay is stored in the storage unit 123 (step S103a). The lifecycle information about the fact that an encryption key has been distributed by a key relay or has been used to encrypt a key to be distributed by a key relay includes the use time of the encryption key, identification information of the key generation device 11 that generated the encryption key, etc.

[0057] Thereafter, the key management device 12_1 periodically monitors whether the QKDN management device 14 is operating or not (steps S104 to S105). Then, when the QKDN management device 14 starts operating (step S302), the key management device 12_1 registers, in the QKDN management device 14, life cycle information that indicates that the encryption key stored in the storage unit has been distributed by the key relay or that the encryption key has been used to encrypt the key distributed by the key relay (step S106). This allows the key management device 12_1 to re-register and use the encryption key whose life cycle information has not been registered in the QKDN management device 14 without discarding it, thereby enabling efficient use of the encryption key.

[0058] Similarly, the key management device 12_2 attempts to register life cycle information about the encryption key generated by the key generating device 11_2 in the QKDN management device 14 (step S202). However, since the QKDN management device 14 is out of operation, it does not accept the registration of life cycle information about the encryption key by the key management device 12_2.

[0059] In this case, the key management device 12_2 may use the encryption key not registered in the QKDN management device 14 for a purpose other than supplying it to an application, for example, as a key to be distributed by a key relay (corresponding to the above-mentioned key Kab), without discarding it. Alternatively, the key may be used as an encryption key for encrypting a key to be distributed by a key relay (corresponding to the above-mentioned keys Kac, Kcb, etc.). Lifecycle information about the fact that an encryption key not registered in the QKDN management device 14 has been distributed by a key relay or has been used to encrypt a key to be distributed by a key relay is stored in the storage unit 123 (step S203a). The lifecycle information about the fact that an encryption key has been distributed by a key relay or has been used to encrypt a key to be distributed by a key relay includes the time of use of the encryption key, identification information of the key generation device 11 that generated the encryption key, etc.

[0060] Thereafter, the key management device 12_2 periodically monitors whether the QKDN management device 14 is operating or not (steps S204 to S205). Then, when the QKDN management device 14 starts operating (step S302), the key management device 12_2 registers, in the QKDN management device 14, life cycle information that indicates that the encryption key stored in the storage unit has been distributed by the key relay or that the encryption key has been used to encrypt the key distributed by the key relay (step S206). This allows the key management device 12_2 to re-register and use the encryption key whose life cycle information has not been registered in the QKDN management device 14 without discarding it, thereby enabling efficient use of the encryption key.

[0061] However, if the QKDN management device 14 determines that there is a contradiction in the encryption key used for the key relay (YES in step S301), the key management devices 12_1 and 12_2 delete the encryption key distributed by the key relay (steps S107 and S207). On the other hand, if the QKDN management device 14 determines that there is no contradiction in the encryption key used for the key relay (NO in step S301), the encryption key distributed by the key relay becomes valid.

[0062] (Another example of the operation of quantum key distribution system 1) Next, another example of the operation of the quantum key distribution system 1 will be described with reference to Fig. 7. Fig. 7 is a sequence diagram showing another example of the operation of the quantum key distribution system according to the present disclosure. Note that the example of Fig. 7 shows key management devices 12_1 and 12_2, among the multiple key management devices 12, that share an encryption key, and shows terminals 21 and 22, among the multiple terminals of an application that performs quantum cryptography communication, to which encryption keys are supplied by the key management devices 12_1 and 12_2. In addition, hereinafter, the key supplying devices 13 corresponding to the key management devices 12_1 and 12_2 will be referred to as key supplying devices 13_1 and 13_2, respectively.

[0063] First, the terminal 21 requests the key management device 12_1 for an encryption key for performing quantum cryptography communication with the terminal 22 (step S401). In response, the key management device 12_1 supplies the encryption key to the terminal 21 using the key supply device 13_1 (step S402). Upon receiving the encryption key, the terminal 21 requests the terminal 22, which performs quantum cryptography communication, to share key information (step S403). In response, the terminal 22 requests the key management device 12_2 for an encryption key for performing quantum cryptography communication with the terminal 21 (step S501). In response, the key management device 12_2 supplies the encryption key to the terminal 22 using the key supply device 13_2 (step S502).

[0064] At this time, the QKDN management device 14 also stops operation due to reasons such as periodic inspection (step S601).

[0065] Here, with regard to the encryption key supplied to terminal 21, life cycle information indicating that it was generated by key generation device 11_1 has been registered in the QKDN management device 14, but life cycle information indicating that it was supplied to terminal 21 by key supply device 13_1 has not been registered and therefore needs to be registered. Similarly, with regard to the encryption key supplied to terminal 22, life cycle information indicating that it was generated by key generation device 11_2 has been registered in the QKDN management device 14, but life cycle information indicating that it was supplied to terminal 22 by key supply device 13_2 has not been registered and therefore needs to be registered.

[0066] Therefore, the key management device 12_1 attempts to register, in the QKDN management device 14, life cycle information about the encryption key supplied to the terminal 21 by the key supply device 13_1 (step S404). However, since the QKDN management device 14 is out of operation, it does not accept the registration of life cycle information about the encryption key by the key management device 12_1.

[0067] In this case, the key management device 12_1 stores in a storage unit life cycle information about the encryption key supplied to the terminal 21 by the key supplying device 13_1 (step S405). Thereafter, the key management device 12_1 periodically monitors whether the QKDN management device 14 is operating or not (steps S406 to S407). Then, when the QKDN management device 14 starts operating (step S602), the key management device 12_1 registers in the QKDN management device 14 the life cycle information about the encryption key stored in the storage unit (step S408). In other words, the key management device 12_1 can supply the encryption key already registered in the QKDN management device 14 to the application terminal 21 even when the operation of the QKDN management device 14 is stopped, on the condition that the encryption key is re-registered after recovery. In other words, the key management device 12_1 can efficiently use the encryption key.

[0068] Similarly, the key management device 12_2 attempts to register, in the QKDN management device 14, life cycle information about the encryption key supplied to the terminal 22 by the key supplying device 13_2 (step S504). However, since the QKDN management device 14 is out of operation, it does not accept the registration of the life cycle information about the encryption key by the key management device 12_2.

[0069] In this case, the key management device 12_2 stores in a storage unit life cycle information about the encryption key supplied to the terminal 22 by the key supplying device 13_2 (step S505). Thereafter, the key management device 12_2 periodically monitors whether or not the QKDN management device 14 is operating (steps S506 to S507). Then, when the QKDN management device 14 starts operating (step S602), the key management device 12_2 registers in the QKDN management device 14 the life cycle information about the encryption key stored in the storage unit (step S508). That is, the key management device 12_2 can supply the encryption key already registered in the QKDN management device 14 to the application terminal 22 even when the operation of the QKDN management device 14 is stopped, on the condition that the encryption key is re-registered after recovery. That is, the key management device 12_2 can efficiently use the encryption key.

[0070] Thus, in the quantum key distribution system 1 according to the present disclosure, when the operation of the QKDN management device 14 is stopped, each key management device 12 stores in a memory unit the encryption key generated by the key generation device 11 under its management, and when the operation of the QKDN management device 14 starts, registers in the QKDN management device 14 the life cycle information for the encryption key before registration stored in the memory unit. This allows the key management device 12 according to the present disclosure to re-register and use encryption keys whose life cycle information has not been registered in the QKDN management device 14 without discarding them, thereby enabling efficient use of encryption keys.

[0071] (Hardware configuration for realizing the key management function of the key management device 12) The key management process performed by the key management device 12 can be realized by a general-purpose computer system, which will be briefly explained below with reference to FIG.

[0072] 8 is a block diagram showing an example of a hardware configuration that realizes the key management function of the key management device 12. The computer 300 includes, for example, a CPU (Central Processing Unit) 301, which is a control device, a RAM (Random Access Memory) 302, and a ROM (Read Only Memory) 303. The computer 300 further includes an IF (Interface) 304, which is an interface with the outside, and an HDD (Hard Disk Drive) 305, which is an example of a non-volatile storage device. The computer 300 may also include input devices such as a keyboard and a mouse, and a display device such as a display, as other components not shown.

[0073] The HDD 305 stores an OS (Operating System) (not shown) and a control program 306. The control program 306 is a computer program in which the key management process of the key management device 12 is implemented.

[0074] The CPU 301 controls various processes in the computer 300, and access to the RAM 302, ROM 303, IF 304, and HDD 305. In the computer 300, the CPU 301 reads and executes the OS and control program 306 stored in the HDD 305. In this way, the computer 300 realizes the key management function of the key management device 12.

[0075] The above-mentioned program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in this disclosure. The program may be stored on a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable medium or tangible storage medium includes RAM, ROM, flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disc (DVD), Blu-ray disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0076] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0077] Each drawing is merely an example for describing one or more embodiments. Each drawing may relate not only to one particular embodiment, but also to one or more other embodiments. As will be understood by those skilled in the art, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings to create, for example, an embodiment not explicitly shown or described. Not all features or steps shown in any one drawing are necessary to describe an exemplary embodiment, and some features or steps may be omitted. The order of steps described in any drawing may be changed as appropriate.

[0078] Furthermore, some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes.

[0079] (Appendix 1) a plurality of key generation devices that generate encryption keys and are provided at a plurality of locations and are connected to each other by optical fibers; a plurality of key management devices provided corresponding to the plurality of key generation devices and managing the encryption keys generated by the plurality of key generation devices; a plurality of key supply devices provided corresponding to the plurality of key management devices and configured to supply encryption keys managed by the plurality of key management devices to an application that performs quantum cryptography communication; a QKDN management device that acquires and manages lifecycle information on the processing status of encryption keys by each of the plurality of key generation devices, the plurality of key management devices, and the plurality of key supply devices; Equipped with Each of the key management devices A memory unit; a monitoring unit that monitors whether the QKDN management device is operating; a registration control unit that, when the monitoring unit determines that operation of the QKDN management device is stopped, stores in the storage unit an encryption key before it was registered in the QKDN management device, indicating that it was generated by a key generation device managed by the key management device as lifecycle information, and, when the monitoring unit determines that operation of the QKDN management device has started, registers in the QKDN management device lifecycle information about the encryption key stored in the storage unit; A quantum key distribution system comprising:

[0080] (Appendix 2) In each of the key management devices, the monitoring unit determines that the operation of the QKDN management device is stopped when the registration control unit has not accepted the registration of life cycle information about the encryption key in the QKDN management device. 10. The quantum key distribution system of claim 1.

[0081] (Appendix 3) In each of the key management devices, the monitoring unit periodically monitors whether the QKDN management device is in operation in response to a request from the registration control unit for periodic registration of life cycle information about the encryption key; 1. A quantum key distribution system as described in Appendix 2.

[0082] (Appendix 4) In each of the key management devices, The monitoring unit determines whether the QKDN management device is operating based on either a notification from the QKDN management device that the device is out of operation or a notification from the QKDN management device that the device has started operating. 10. The quantum key distribution system of claim 1.

[0083] (Appendix 5) In each of the key management devices, When the monitoring unit determines that the operation of the QKDN management device is stopped, the registration control unit stores in the memory unit life cycle information about the encryption key before it was registered in the QKDN management device, indicating that it was supplied to an application by a key supply device managed by the key management device, and when the monitoring unit determines that the operation of the QKDN management device has started, registers in the QKDN management device the life cycle information about the encryption key stored in the memory unit. 10. The quantum key distribution system of claim 1.

[0084] (Appendix 6) In each of the key management devices, When the monitoring unit determines that the operation of the QKDN management device is stopped, an encryption key before its generation by a key generation device managed by the key management device is registered in the QKDN management device as lifecycle information is used as a key distributed by a key relay or as an encryption key for encrypting a key distributed by a key relay. 10. The quantum key distribution system of claim 1.

[0085] (Appendix 7) In each of the key management devices, When the monitoring unit determines that the QKDN management device has started operating, the registration control unit registers with the QKDN management device life cycle information indicating that an encryption key generated by a key generation device managed by the key management device before being registered as life cycle information in the QKDN management device was distributed by a key relay or was used to encrypt a key distributed by a key relay. 10. The quantum key distribution system of claim 6.

[0086] (Appendix 8) If the QKDN management device determines that there is a contradiction in the life cycle information of an encryption key distributed by a key relay that has been applied for registration, or an encryption key used to encrypt a key distributed by a key relay, the QKDN management device deletes the encryption key distributed by the key relay. 8. The quantum key distribution system of claim 7.

[0087] (Appendix 9) A key management device that manages encryption keys generated by a key generation device connected to another key generation device by an optical fiber, A memory unit; a monitoring unit that monitors whether a QKDN management device that acquires and manages information indicating that an encryption key has been generated by each of a plurality of key generation devices as life cycle information of the encryption key is in operation; a registration control unit that, when the monitoring unit determines that operation of the QKDN management device is stopped, stores in the storage unit an encryption key before it was registered in the QKDN management device, indicating that it was generated by a key generation device managed by the key management device as lifecycle information, and, when the monitoring unit determines that operation of the QKDN management device has started, registers in the QKDN management device lifecycle information about the encryption key stored in the storage unit; A key management device comprising:

[0088] (Appendix 10) A key management method for a key management device that manages encryption keys generated by a key generation device connected to another key generation device via an optical fiber, comprising: a QKDN management device that acquires and manages information indicating that an encryption key has been generated by each of a plurality of key generation devices as life cycle information of the encryption key; and If it is determined that the operation of the QKDN management device is stopped, the encryption key before being registered in the QKDN management device is stored in a storage unit as lifecycle information indicating that the encryption key was generated by a key generation device managed by the key management device; When it is determined that the operation of the QKDN management device has started, life cycle information about the encryption key stored in the storage unit is registered in the QKDN management device. Key management method.

[0089] (Appendix 11) A control program that causes a computer to execute key management processing by a key management device that manages encryption keys generated by a key generation device connected to another key generation device via an optical fiber, the control program comprising: a process of monitoring whether a QKDN management device, which acquires and manages information indicating that an encryption key has been generated by each of a plurality of key generation devices as life cycle information of the encryption key, is in operation; When it is determined that the operation of the QKDN management device is stopped, a process of storing in a storage unit the encryption key before it was registered in the QKDN management device as lifecycle information indicating that it was generated by a key generation device managed by the key management device; When it is determined that the operation of the QKDN management device has started, a process of registering life cycle information about the encryption key stored in the storage unit in the QKDN management device; A control program that causes a computer to execute the above.

[0090] Some or all of the elements (e.g., configurations and functions) described in Supplementary Notes 2 to 8 that are dependent on Supplementary Notes 1 may also be dependent on Supplementary Notes 9, 10, and 11 in the same dependency relationship as Supplementary Notes 2 to 8. Some or all of the elements described in any Supplementary Note may be applied to various hardware, software, recording means for recording software, systems, and methods. [Explanation of symbols]

[0091] 1. Quantum key distribution system 11 Key generation device 12 Key management device 13 Key supply device 14 QKDN management device 121 Monitoring Department 122 Registration control section 123 Storage section 50 Optical Fiber

Claims

1. a plurality of key generation devices that generate encryption keys and are provided at a plurality of locations and are connected to each other by optical fibers; a plurality of key management devices provided corresponding to the plurality of key generation devices and managing the encryption keys generated by the plurality of key generation devices; a plurality of key supply devices provided corresponding to the plurality of key management devices and configured to supply encryption keys managed by the plurality of key management devices to an application that performs quantum cryptography communication; a QKDN management device that acquires and manages lifecycle information on the processing status of encryption keys by each of the plurality of key generation devices, the plurality of key management devices, and the plurality of key supply devices; Equipped with Each of the key management devices A memory unit; a monitoring unit that monitors whether the QKDN management device is in operation; a registration control unit that, when the monitoring unit determines that operation of the QKDN management device is stopped, stores in the memory unit the encryption key before it was registered in the QKDN management device, indicating that it was generated by a key generation device managed by the key management device, as life cycle information, and, when the monitoring unit determines that operation of the QKDN management device has started, registers in the QKDN management device the life cycle information for the encryption key stored in the memory unit; A quantum key distribution system comprising:

2. In each of the key management devices, The monitoring unit determines that the operation of the QKDN management device is stopped when the registration control unit has not accepted the registration of life cycle information about the encryption key in the QKDN management device. The quantum key distribution system of claim 1 .

3. In each of the key management devices, The monitoring unit periodically monitors whether the QKDN management device is in operation in response to a request from the registration control unit for periodic registration of life cycle information about the encryption key. The quantum key distribution system according to claim 2 .

4. In each of the key management devices, The monitoring unit determines whether the QKDN management device is in operation based on either a notification from the QKDN management device that the device is in operation stoppage or a notification from the QKDN management device that the device has started operation. The quantum key distribution system of claim 1 .

5. In each of the key management devices, When the monitoring unit determines that the operation of the QKDN management device is stopped, the registration control unit stores in the memory unit life cycle information about the encryption key before it was registered in the QKDN management device, indicating that it was supplied to an application by a key supply device managed by the key management device, and when the monitoring unit determines that the operation of the QKDN management device has started, registers in the QKDN management device the life cycle information about the encryption key stored in the memory unit. The quantum key distribution system of claim 1 .

6. In each of the key management devices, When the monitoring unit determines that the operation of the QKDN management device is stopped, the encryption key before the fact that it was generated by a key generation device managed by the key management device is registered in the QKDN management device as lifecycle information is used as a key to be distributed by a key relay or as an encryption key for encrypting a key to be distributed by a key relay. The quantum key distribution system of claim 1 .

7. In each of the key management devices, When the monitoring unit determines that the QKDN management device has started operating, the registration control unit registers with the QKDN management device life cycle information indicating that the encryption key before being registered with the QKDN management device was generated by a key generation device managed by the key management device as life cycle information, and that the encryption key was distributed by a key relay or was used to encrypt the key distributed by the key relay. The quantum key distribution system according to claim 6 .

8. If the QKDN management device determines that there is a contradiction in the life cycle information of an encryption key distributed by a key relay that has been applied for registration, or an encryption key used to encrypt a key distributed by a key relay, the QKDN management device deletes the encryption key distributed by the key relay. The quantum key distribution system according to claim 7.

9. A key management device that manages encryption keys generated by a key generation device connected to another key generation device by an optical fiber, A memory unit; a monitoring unit that monitors whether a QKDN management device that acquires and manages information indicating that an encryption key has been generated by each of a plurality of key generation devices as life cycle information of the encryption key is in operation; a registration control unit that, when the monitoring unit determines that operation of the QKDN management device is stopped, stores in the memory unit the encryption key before it was registered in the QKDN management device, indicating that it was generated by a key generation device managed by the key management device, as life cycle information, and, when the monitoring unit determines that operation of the QKDN management device has started, registers in the QKDN management device the life cycle information for the encryption key stored in the memory unit; A key management device comprising:

10. A key management method for a key management device that manages encryption keys generated by a key generation device connected to another key generation device via an optical fiber, comprising: a QKDN management device that acquires and manages information indicating that an encryption key has been generated by each of the plurality of key generation devices as life cycle information of the encryption key; and monitors whether the QKDN management device is in operation. If it is determined that the operation of the QKDN management device is stopped, the encryption key before being registered in the QKDN management device is stored in a storage unit as life cycle information indicating that the encryption key was generated by a key generation device managed by the key management device; When it is determined that the operation of the QKDN management device has started, life cycle information for the encryption key stored in the storage unit is registered in the QKDN management device. Key management method.

11. A control program that causes a computer to execute key management processing by a key management device that manages encryption keys generated by a key generation device connected to another key generation device via an optical fiber, the control program comprising: a process of monitoring whether a QKDN management device, which acquires and manages information indicating that an encryption key has been generated by each of a plurality of key generation devices as life cycle information of the encryption key, is in operation; When it is determined that the operation of the QKDN management device is stopped, a process of storing in a memory unit the encryption key before it was registered in the QKDN management device as lifecycle information indicating that it was generated by a key generation device managed by the key management device; When it is determined that the operation of the QKDN management device has started, a process of registering life cycle information about the encryption key stored in the storage unit into the QKDN management device; A control program that causes a computer to execute the above.

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