Key management device, QKDN control device, quantum cryptography communication system, key management method, QKDN control method and program

Abstract

To enable determination of an optimum route for transmitting an encryption key regardless of a scale of a QKDN.SOLUTION: A key management device is connected to a QKD device for generating a link key by QKD, an application of a user network, and a QKDN control device, and includes a communication interface and a processing unit. The communication interface receives, from the QKDN control device, path information for transmitting an application key to a destination key management device. The processing unit specifies a key management device that is located in a first key sharing network to which a key management device connected to an application belongs and connected to the second key sharing network from the path information, determines a path in the first key sharing network based on resource information of the first key sharing network, and causes a communication interface to transmit the application key encrypted with the link key using the path.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a key management device, a QKDN control device, a quantum cryptography communication system, an information processing device, a key management method, a QKDN control method, an information processing method, and a program. [Background technology]

[0002] A technique has been known in the past in which an application obtains a random number shared with another application using quantum key distribution (QKD) from a key management device, and uses this random number as an encryption key to perform encrypted communication with another application. The encrypted communication by this application is performed over a user network, such as the Internet, which is different from the QKD network. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-92987 [Patent Document 2] Patent No. 5784562 [Non-patent literature]

[0004] [Non-Patent Document 1] ITU-T, Y.3800, “Overview networks on supporting quantum key distribution,” 2019. [Non-patent document 2] ETSI GS QKD 014, “Quantum Key Distribution (QKD); Protocol and data format of REST-based key delivery API,” 2019. [Non-patent document 3] IETF, RFC2328, “OSPF Version 2,” 1998. Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional technology, the larger the QKD network, the more difficult it became to determine the optimal route for sending encryption keys. [Means for solving the problem]

[0006] A key management device according to an embodiment is connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application in a user network, and a QKDN (Quantum Key Distribution Network) control device, and includes a communication interface and a processing unit. The communication interface receives, from the QKDN control device, route information for sending an application key used for encrypting or decrypting communications in the user network to a destination key management device. The processing unit identifies, from the route information, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network, determines a route within the first key sharing network from the key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network, and causes the communication interface to send an application key encrypted with the link key using the route. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a quantum cryptography communication system according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an example of a quantum cryptography communication network according to an embodiment. [Figure 3A] FIG. 10 is a diagram showing an example 1 of resource information (bottleneck of remaining link keys) according to the embodiment. [Figure 3B] FIG. 10 is a diagram showing an example 2 (number of hops) of resource information according to the embodiment. [Figure 3C] FIG. 10 is a diagram for explaining an example of a method for determining a key relay route according to an embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the functional configuration of a key management apparatus according to the embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of the functional configuration of a QKDN control device according to the embodiment. [Figure 6] FIG. 2 is a diagram showing an example of the functional configuration of the information processing apparatus according to the embodiment. [Figure 7] FIG. 1 is a diagram for explaining an example of key relay between different types of KSNs according to an embodiment. [Figure 8A] FIG. 1 is a diagram showing an example 1 of a KSN domain according to an embodiment. [Figure 8B] FIG. 10 is a diagram showing an example 2 of a KSN domain according to an embodiment. [Figure 9] FIG. 10 is a diagram for explaining a first calculation example of a first reference value according to the embodiment. [Figure 10] FIG. 10 is a diagram for explaining a second calculation example of the first reference value according to the embodiment. [Figure 11] FIG. 10 is a diagram for explaining an example of a method for determining a key relay route according to an embodiment. [Figure 12] 1 is a flowchart illustrating an example of a QKDN control method according to an embodiment. [Figure 13] FIG. 4 is a diagram showing an example of affiliation information according to the embodiment. [Figure 14] FIG. 4 is a diagram showing an example of connection status information according to the embodiment. [Figure 15] FIG. 4 is a diagram showing an example of first reference value information according to the embodiment. [Figure 16] FIG. 10 is a diagram showing a first example of a header format of a key relay message according to an embodiment. [Figure 17] FIG. 10 is a diagram showing a second example of a header format of a key relay message according to the embodiment. [Figure 18] FIG. 2 is a diagram showing an example of a centralized management configuration according to an embodiment. [Figure 19] FIG. 2 is a diagram showing an example of the hardware configuration of a KM, a QKDN control device, and an information processing device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, with reference to the accompanying drawings, embodiments of a key management device, a QKDN (Quantum Key Distribution Network) control device, a quantum cryptography communication system, an information processing device, a key management method, a QKDN control method, an information processing method, and a program will be described in detail.

[0009] 1 is a diagram showing an example of the configuration of a quantum cryptography communication system according to an embodiment. Viewed from the side, the QKD network architecture is composed of, from the bottom up, a quantum layer, a key management layer, a QKD network control layer, and a QKD network management layer for managing these three layers. These four layers generate an application key (hereinafter referred to as "application key") used to encrypt and decrypt data communications by an application 5, and supply it to the service layer in the top-level user network. Viewed vertically, three nodes 1 (QKD nodes / trusted nodes) comprising the QKD network and user network are installed at points A, B, and C, respectively.

[0010] The quantum layer consists of a QKD module 2 and a QKD link 3. The main function of the quantum layer is to exchange photons and classical information (control information transmitted and received over a normal control link, different from the QKD link) with QKD modules 2 at other locations and share a link key (random number sequence). Furthermore, the quantum layer has the function of supplying random number sequences to key managers (KMs) 10 (10a to 10c). The link key (quantum encryption key) shared over the QKD link 3 is guaranteed to be resistant to eavesdropping based on the principles of quantum mechanics. When encrypted data communication is performed using the shared link key with a cryptographic communication method known as a one-time pad, information theory guarantees that the transmitted and received data cannot be decrypted by an eavesdropper, regardless of their knowledge. The QKD modules 2 (2a, 2b-1, 2b-2, and 2c) are connected by QKD links 3, such as optical fibers.

[0011] However, the method of sharing link keys using QKD technology is limited by the distance over which the link key can be shared, due to the use of single photons as a medium. For example, as shown in the example of the quantum layer in Figure 1, the QKD module 2 is basically one-to-one, but in the case of relaying, at least two QKD modules 2b-1 and 2b-2 are required at the relaying point B. In the example in Figure 1, the application key K is shared between points A and C. A AC At site B, the QKD module 2b-1 encrypts the application key encrypted at site A using the same link key K as site A. L AB (i.e., a common key in which the encryption key and the decryption key are the same). Then, the QKD module 2b-2 converts the decrypted application key into a link key K L BC Then encrypt it again with the encrypted application key K A AC Relay to base C.

[0012] In order to guarantee unconditional security, QKD inevitably sacrifices some communication performance, such as distance and speed. Generally, the link key generation rate within a 50km radius of installed fiber is approximately 200,000 to 300,000 bits per second (200 to 300kbps). If the QKD key distillation process is implemented and optimized in hardware, the key generation speed for QKD over short distances can reach a maximum of 10Mbps.

[0013] To maintain the key generation speed at Mbps, relay nodes must be installed at intervals that allow the speed to be maintained, and key relay must be performed between relay points. However, encryption and decryption processing takes time at relay points.

[0014] The key management layer is composed of key management devices (KM) 10a to 10c and a KM link. The main functions of the key management layer include supplying application keys to the applications 5a and 5c that actually encrypt data, and relaying keys to other locations via the KM link. The key management devices (KM) 10a to 10c are also responsible for overall key management, such as receiving key requests from the applications 5a and 5c and storing interfaces.

[0015] The QKD network control layer is composed of a QKD network controller 4 and links. The QKD network control layer controls the overall services of the QKD network. A QKD network controller may be provided at each location, or as shown in Figure 1, there may be one (or more) QKD network controllers for the entire quantum cryptography communication system. The QKD network controller 4 and KM 10 may also be implemented as an integrated unit.

[0016] The QKD network management layer includes a QKDN control device 6. The QKD network management layer has the function of collecting performance information from each layer, monitoring whether the service is operating properly, and issuing control commands to the QKD network control layer as necessary. There may be multiple QKDN control devices 6 depending on the configuration of the QKD network. The functions of the QKDN control device 6 may also be realized and performed by the KM 10.

[0017] The service layer's configuration varies depending on the user, but it is composed of applications 5a and 5c for implementing encrypted communications, computer modules, etc. The service layer also has the function of encrypting an application key with a link key and transferring it to an adjacent node. Note that the service layer application 5 may also generate an encryption key (application key) separate from the link key from random number information, etc., independently of QKD.

[0018] In the service layer, application keys are primarily used for encryption using symmetric encryption methods. A symmetric encryption method is an encryption method that uses the same application key shared in advance between the sender and receiver to encrypt and decrypt communication data and messages. Specifically, application keys are used in Advanced Encryption Standard (AES) encryption and One Time PAD (OTP) encryption.

[0019] The user network management layer includes a user network control device 7. The user network management layer collects performance information from the service layer and monitors whether the service is operating properly.

[0020] Note that the architecture shown in FIG. 1 shows basic elements. In reality, the configuration of the architecture may change depending on the situation. For example, the number of bases is not limited to three. Also, for example, the number of applications 5 is not limited to two. Also, for example, the number of QKDN control devices 6 in the QKD network management layer is not limited to one.

[0021] The above-mentioned user network is a public network, and is a network in which encrypted communication is performed by an application 5. The application 5 runs on an information processing device 8, such as a personal computer or a smart device. The user network is, for example, a data communication network such as the Internet or a cellular communication network.

[0022] On the other hand, the above-mentioned QKD network (quantum cryptography communication network) is a private network, and nodes (QKD nodes / nodes) are installed according to actual needs. The nodes provide encryption keys for encrypted communication to user networks.

[0023] Fig. 2 is a diagram showing an example of a quantum cryptography communication network 100 according to an embodiment. The example in Fig. 2 is an example of a small-scale QKDN, since the number of KMs is as small as eight. Secure communication is performed between applications A and D in the user network via a data communication network 103.

[0024] A key sharing network (KSN) 102 in the key management layer is made up of KMs 10 and links between the KMs 10. Hereinafter, the key sharing network 102 will be referred to as a KSN 102. A QKDN control device 6 that communicates with the KMs 10 of the KSN 102 is installed in the QKDN management layer.

[0025] In the quantum layer, a network 101 is configured that includes a plurality of QKD modules 2 and a plurality of QKD links 3 between the QKD modules 2. Because the connection between the QKD modules 2 is one-to-one, the QKD modules 2 corresponding to the upper KM 10 are installed according to the number of links connected to the upper KM 10.

[0026] It should be noted that the number of KMs 10, the number of QKD modules 2, and the number of applications are not limited to the example of FIG.

[0027] Note that when the KM 10 encrypts and transmits the application key with the link key, it consumes the link key because it uses the link key as a one-time pad, i.e., it discards the link key once it has been used. Therefore, the KM 10 cannot relay the application key faster than the number of shared link keys or the speed at which the link keys are shared.

[0028] When an application key is transmitted via multiple KMs 10, the speed at which the application key is shared is limited by the link with the fewest link keys or the link with the slowest link key sharing speed. Such links become bottlenecks and restrict the throughput of cryptographic communications in a quantum cryptography communication system. Alternatively, application keys cannot be shared over links where link keys have been depleted. In a quantum cryptography communication system, it is desirable to share application keys by selecting a route with the best possible bottleneck (for example, a route with the largest link bottleneck). The bottleneck of the links included in the route is identified, for example, based on a value calculated for each link included in the route. Specifically, the bottleneck of the links included in the route is identified by the link with the smallest value calculated using, for example, equation (1) described below.

[0029] On the other hand, when looking at the consumption of link keys in the entire quantum cryptography communication system, it can be said that the more links a route passes through, the more link keys are consumed. Link keys are used when sharing application keys, and are therefore a system resource that determines the throughput of application 5. For this reason, it is desirable to reduce the number of links passed through in the entire system and suppress the consumption of link keys.

[0030] The protocol (routing protocol) that determines the route (key relay route) for sharing application keys within the KSN 102 using quantum key distribution is determined by any method. For example, in the case of an IP-based KSN 102, an Interior Gateway Protocol (IGP) communication protocol is used. A widely used IGP communication protocol is, for example, Open Shortest Path Fast (OSPF). OSPF uses distance (the sum of the costs of the links included in each key relay route) as the metric for routing (path control). In the case of a non-IP-based KSN 102, the route for sharing application keys is determined by any method other than the IGP communication protocol.

[0031] The data associated with the links between the KMs 10 that make up the KSN 102 and adjacent KMs 10 is as follows: The data below is assigned a sequence number in chronological order and is updated based on the sequence number.

[0032] Data associated with the link: Remaining key information: Link key holdings Key remaining information: Link key generation speed Key remaining information: Link key consumption rate

[0033] Data mapped to a KM: A database representing the configuration within the KSN domain (link state database) ·Deterministic information about the shortest path tree to a destination KM within the KSN domain Bottleneck from source to destination KM within the KSN domain The number of hops from the source to the destination KM within the KSN domain Next Hop

[0034] The data associated with a link is key remaining information, which includes three types of information (the amount of link keys held, the rate at which link keys are generated, and the rate at which link keys are consumed).

[0035] The link key reserve is the number of keys that have not yet been used among the keys shared through quantum key distribution between adjacent KMs 10. The link key reserve is accumulated (increased) by performing quantum key distribution, and is consumed (decreased) by using a link key in an application key relay between any source KM 10 and destination KM 10.

[0036] The link key generation speed represents the speed at which link keys are shared by performing quantum key distribution between adjacent KMs 10. The link key generation speed differs for each link depending on the setting parameters of the KMs 10 connected to the link and the connection environment, etc.

[0037] The link key consumption rate indicates the rate at which link keys used to share application keys between adjacent KMs 10 are consumed. The link key consumption rate differs for each link depending on factors such as application key requirements and the connection environment.

[0038] Therefore, the remaining amount of keys available for use on each link is calculated, for example, by the following formula (1).

[0039]

number

[0040] Here, k is a number that identifies the KM 10. k current indicates the amount of link keys held, and SKR k indicates the link key generation speed, and C k indicates the link key consumption rate, and T R indicates the reference time interval. The reference time interval (t) is set according to the actual situation.

[0041] For example, Link k current 1000Mbits, SKR k is 3Mbits / sec, C k is 1Mbits / sec, T R When the time is 300 seconds, the remaining link key A available after the reference time of this KM10 k key becomes 1600 (1.6Gbits).

[0042] It should be noted that the method for calculating the remaining key amount information is not limited to the above formula (1). For example, the remaining key amount information may be calculated using only the amount of link keys held. Or, for example, the remaining key amount information may be calculated using only the link key generation rate. Or, for example, the remaining key amount information may be calculated using a combination of the link key generation rate and the amount of link keys held. Or, for example, the remaining key amount information may be calculated using a combination of the link key generation rate and the link key consumption rate. Or, for example, the remaining key amount information may be calculated using a combination of the amount of link keys held and the link key consumption rate. Or, for example, the remaining key amount information may be calculated using a combination of the link key generation rate, the amount of link keys held, and the link key consumption rate.

[0043] For example, in the case of an IP-based KSN, the information required to determine the key relay route within the KSN domain is collected by the following processes (1) to (4) using OSPF, an existing routing protocol.

[0044] (1) In OSPF, KM10 sends messages called link state updates to share information such as the state of the links to which KM10 is connected, the network addresses of those links, and their costs with other KM10. The link state includes information (route information) that indicates how a certain KM10 is connected to other KM10.

[0045] (2) Each KM 10 understands the network configuration within the KSN domain based on the information in the link state update it receives, and then builds a table (link state database) that represents the network configuration within the KSN domain.

[0046] (3) Each KM 10 uses the Dijkstra algorithm from this database to calculate the shortest path tree within the domain with itself as the source, and creates a forwarding table.

[0047] (4) Each KM 10 stores forwarding table information and resource information from one KM 10 to other KMs 10 within the KSN domain.

[0048] As described above, the data associated with KM10 is the link state database, the determined information of the shortest path tree to the destination KM10 within the KSN domain, the bottleneck from the source to the destination KM10 within the KSN domain, the number of hops from the source to the destination KM10 within the KSN domain, and the next hop.

[0049] The link state database represents the network topology (connectivity) within the KSN domain and is used by each KM 10 to calculate the shortest path. The shortest path tree for each destination KM 10 within the KSN domain may or may not be determined.

[0050] For destination KM10, where the shortest path tree is not determined, the key relay route to destination KM10 is merely a shortest path candidate. The bottleneck from the source to destination KM10 within the KSN domain represents the bottleneck in the remaining key capacity of the link when passing through the shortest path candidate to reach destination KM10. The number of hops from the source to destination KM10 within the KSN domain represents the number of hops when passing through the shortest path candidate to reach destination KM10. The next hop represents the next hop that is a shortest path candidate.

[0051] Each KM 10 has a link state database, definitive information on the shortest key relay route tree within the KSN domain, remaining keys for each link from the source KM to each other KM 10, the number of hops from the source to each other KM 10, and the next hop. The remaining keys for each link from the source to each other KM 10 and the number of hops from the source to each other KM 10 are maintained for each other KM 10.

[0052] In the Dijkstra algorithm of OSPF, the metric is distance. In contrast, the key sharing routing protocol of this embodiment uses the bottleneck of remaining keys on the key relay route, rather than distance, to calculate the metric. This keeps the link key reserves and link key generation speed between KMs 10 that share application keys at or above a certain value, preventing any problems in obtaining the amount of application keys required by applications on the user network.

[0053] First, the resource information used to calculate the metric will be described.

[0054] FIG. 3A is a diagram showing example 1 of resource information (bottleneck of remaining link keys) according to an embodiment. A numerical value assigned to each link indicates the remaining link key. The bottleneck is the minimum remaining key value of each link included in the key relay route from the source (S) via the relay (R) to the destination (D). In FIG. 3A, the bottleneck is the minimum remaining key value of each link included in the key relay route, so min{6,5,3}=3. In other words, the bottleneck of the key relay route in FIG. 3A is 3.

[0055] FIG. 3B is a diagram showing example 2 (number of hops) of resource information according to an embodiment. The number of hops is the number of relays KM10 + 1. The number of hops is the number of relays KM10 included in the key relay route from the source (S) via the relay (R) to the destination (D) + 1. In the example of FIG. 3B, the number of hops is the number of relays KM10 + 1, so the number of relays included in the key relay route (2) + 1 = 3. In other words, the number of hops in the key relay route in FIG. 3B is 3.

[0056] 3C is a diagram illustrating an example of a method for determining a key relay path according to an embodiment. In FIG. 3C, the source KM10 is represented by S, the destination KM10 is represented by D, and the relay KM10 for sharing the application key is represented by R. The numerical value attached to the link indicates the remaining key amount of the link.

[0057] Key relay route A has a bottleneck of 3 and a hop count of 2. Key relay route B has a bottleneck of 6 and a hop count of 3. Key relay route C has a bottleneck of 7 and a hop count of 4.

[0058] An example of a method for calculating a reference value based on a bottleneck and the number of hops is shown below. Method 1: Prioritize bottlenecks. When the bottlenecks are equal, compare the number of hops and determine the route with the fewest number of hops as the optimal key relay route. Method 2: Prioritize the number of hops, and when the number of hops is equal, compare the bottlenecks and determine the route with the larger bottleneck as the optimal key relay route. Method 3: The optimal key relay route is determined by a calculation formula for a reference value (RV) that includes a bottleneck (BN) and the number of hops (Hops).

[0059] The calculation is performed, for example, using the following formula. RV=δ×BN+(1-δ)×(1 / Hops) Here, δ is a coefficient, which is a positive real number smaller than 1.

[0060] On the other hand, if the reference value is only the bottleneck, key relay route C is the optimal key relay route. If the reference value is only the number of hops, key relay route A is the optimal key relay route. By setting the coefficients in the above calculation formula, it is possible to achieve a case where only one of the reference values ​​is used. For example, if the reference value is only the bottleneck, set δ=1. Also, if the reference value is only the number of hops, set δ=0.

[0061] Using the example of FIG. 3C, an example in which δ is set to 0.5 and the reference value is calculated according to the above method 3 will be described.

[0062] The reference value of key relay route A is RV = 0.5 × 3 + (1 - 0.5) × (1 / 2) = 1.75. The reference value of key relay route B is RV = 0.5 × 6 + (1 - 0.5) × (1 / 3) = 3.67. The reference value of key relay route C is RV = 0.5 × 7 + (1 - 0.5) × (1 / 4) = 3.625.

[0063] In method 1, the bottleneck and number of hops up to each KM 10 are stored, and the number of hops is compared only when the bottlenecks are equal. In method 2, the bottleneck and number of hops up to each KM 10 are stored, and the bottlenecks are compared only when the number of hops is equal. In method 3, a calculation formula that represents the reference value is created in advance, and the reference value is calculated from the bottleneck and number of hops up to each KM 10.

[0064] The above formula for calculating the reference value is an example and is not limited to this. For example, another formula may be used in which the bottleneck and the number of hops are weighted and added together to obtain the reference value. In this case, the coefficients (weights) applied to the bottleneck and the number of hops are arbitrary.

[0065] [Example of KM function configuration] 4 is a diagram showing an example of the functional configuration of the key management device (KM) 10 of the embodiment. The key management device (KM) 10 of the embodiment includes a communication unit 11, a storage unit 12, and a processing unit 13.

[0066] The communication unit 11 is realized by a communication interface that communicates via at least one of a wireless method and a wired method. The communication unit 11 includes a KM communication unit 111, a control communication unit 112, and an application communication unit 113. The KM communication unit 111 communicates with one or more KMs 10 in the key management layer of the QKDN to share encryption keys (application keys). The control communication unit 112 communicates with a QKDN control device 6 in the QKD network management layer to share information such as key relay path information. The application communication unit 113 communicates with an application 5 of the user network, which is the highest service layer, to share information such as application key requests.

[0067] The communication unit 11 may be realized without being divided into the above three functional components.

[0068] The storage unit 12 is realized by a storage medium such as a hard disk drive (HDD), an optical disk, a memory card, or a random access memory (RAM).

[0069] The storage unit 12 stores route-related information and application keys shared among the KMs 10. The route-related information includes, for example, key relay path information received from the QKDN control device 6.

[0070] The processing unit 13 is realized by at least one processing unit and executes the processing of the KM 10. This processing unit includes, for example, a control unit and an arithmetic unit, and is realized by analog or digital circuits, etc. The processing unit may be a central processing unit (CPU), a general-purpose processor, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof.

[0071] The processing unit 13 includes a calculation unit 131 , a management unit 132 , an information exchange unit 133 , an execution unit 134 , a key processing unit 135 , a provision unit 136 , a control unit 137 , and a platform unit 138 .

[0072] The calculation unit 131 reads route-related information from the storage unit 12, calculates a key relay route within the KSN 102 for implementing a key relay path, and calculates the optimal key relay route to the destination KM 10 and the BKM (Boarder KM) 10 via which the route is passed. Here, the BKM 10 refers to the KM 10 installed at the boundary between KSN domains.

[0073] For example, resource information is used to calculate a key relay route (path) within the KSN 102. For example, the resource information includes link key status information calculated based on at least one of the link key generation speed, remaining amount, and consumption speed calculated for each link included in the path candidate. The calculation unit 131 identifies a bottleneck in the link key status information used in the link included in the path candidate, and determines a path based on the bottleneck.

[0074] The resource information may further include the number of hops to the BKM 10 (the boundary KM 10) that is passed through, calculated for each route candidate. Then, the calculation unit 131 may determine the route further based on the number of hops.

[0075] The calculation unit 131 also stores the calculated key relay route within the KSN 102 in the storage unit 12.

[0076] The management unit 132 manages remaining key information including the key generation speed, key holding amount, key consumption speed, etc. of the link to which the KM 10 is connected.

[0077] The information exchange unit 133 acquires the above-mentioned information from the communication unit 11 and the management unit 132. Furthermore, the information exchange unit 133 shares the information stored in the storage unit 12 with the QKDN control device 6.

[0078] The execution unit 134 executes key relay between KMs 10 according to the key relay route calculated by the calculation unit 131.

[0079] In response to a key request from the application 5, the key processing unit 135 passes the application key to the providing unit 136. Specifically, in response to the request from the application 5, the key processing unit 135 determines the requested amount of the application key, the providing time for providing the application key to the application 5, and the destination indicating the destination to which the application key will be provided.

[0080] Upon receiving the application key from key processing unit 135, providing unit 136 provides the application key to application 5 of the user network of the service layer. For example, providing unit 136 provides the requested amount of application keys determined by key processing unit 135 to the destination determined by key processing unit 135 by the provision time determined by key processing unit 135. Note that the function of providing unit 136 may be included in communication unit 11.

[0081] The control unit 137 controls the processing performed by the KM 10. For example, the control unit 137 is responsible for controlling the activation and operation of each function of the KM 10.

[0082] The platform unit 138 provides computer operating system functions, basic network functions, security functions, and the like required for managing and operating functions on the KM 10 .

[0083] [Example of functional configuration of QKDN control device] 5 is a diagram showing an example of the functional configuration of the QKDN control device 6 of the embodiment. The QKDN control device 6 of the embodiment includes a communication unit 61, a storage unit 62, and a processing unit 63. Note that the communication unit 61, storage unit 62, and processing unit 63 are realized by hardware in the same way as the communication unit 11, storage unit 12, and processing unit 13 of the KM 10.

[0084] The QKDN control device 6 of the embodiment is connected to a plurality of KMs 10 that provide the applications 5 with application keys used for encrypting or decrypting communications between the applications 5 in the user network.

[0085] The communication unit 61 includes a KM communication unit 611 and a control communication unit 612 .

[0086] The KM communication unit 611 communicates with one or more KMs 10. For example, the KM communication unit 611 communicates to share the ID information of the KM 10, the connection status between the BKM 10 and adjacent KSNs 102, remaining key information for links within the KSNs 102, and key relay route related information within the KSNs 102. The key relay route related information is, for example, information belonging to the KM 10, the connection status between the KSNs 102, and a first reference value used to determine whether to go through each KSN 102.

[0087] The control communication unit 612 performs communication to share information such as the ID information of the KM 10, the connection status of the BKM 10, and the above-mentioned first reference value between the QKDN control devices 6. Furthermore, when information such as the above-mentioned first reference value is centrally managed by the authoritative root server device, the control communication unit 612 communicates with the authoritative root server device.

[0088] The communication unit 61 may be realized without being divided into the above two components.

[0089] The storage unit 62 stores KM information, connection information, and path-related information. The KM information includes ID information of the KM 10 and ID information of the KSN 102 to which the KM 10 belongs. The connection information includes ID information of the BKM 10 connected between KSNs 102 and ID information of the KSNs 102. The path-related information includes remaining key information for links between KMs 10, key relay route-related information, and the like. The path-related information is used to calculate the first reference value of each KSN 102.

[0090] The processing unit 63 includes an information exchange unit 631 , a calculation unit 632 , a determination unit 633 , a control unit 634 , a management unit 635 , and a platform unit 636 .

[0091] The information exchange unit 631 acquires the above-mentioned information from the communication unit 61 and stores it in the storage unit 62. The information exchange unit 631 also shares the information stored in the storage unit 62 with other QKDN control devices 6.

[0092] The calculation unit 632 calculates the first reference value of the KSN 102 based on the above-mentioned route-related information (for example, information about the KSN 102 to which the KM 10 belongs, and the connection status between the KSNs 102, etc.). The calculation unit 632 also stores the calculated first reference value in the storage unit 62.

[0093] The determination unit 633 reads out the route-related information from the storage unit 62, calculates second reference values ​​for the multiple key relay routes, and determines the optimal key relay route based on the second reference values. The determination unit 633 notifies the determined optimal key relay route information to the KM 10 associated with the key relay via the communication unit.

[0094] The control unit 634 controls the processing performed by the QKDN control device 6. For example, the control unit 634 is responsible for controlling the activation and operation of each function.

[0095] The management unit 635 manages information about the KMs 10 connected to the QKDN control device 6, the number of KMs 10, and so on.

[0096] The platform unit 636 provides computer operating system functions, basic network functions, security functions, etc. required for managing and operating functions on the QKDN control device 6.

[0097] [Example of functional configuration of information processing device] 6 is a diagram illustrating an example of the functional configuration of the information processing device 8 according to the embodiment. The information processing device 8 according to the embodiment includes a communication unit 81, a storage unit 82, and a processing unit 83. The communication unit 81, the storage unit 82, and the processing unit 83 are realized by hardware in the same manner as the communication unit 11, the storage unit 12, and the processing unit 13 of the KM 10.

[0098] The communication unit 81 receives an application key used to encrypt or decrypt communications of an application 5a (an example of a source application) in the user network from a KM 10a (an example of a first key management device) connected to a QKD module 2a (an example of a QKD device) that generates a link key by QKD. The application key is encrypted and transmitted to KM 10c using route information determined based on a first reference value that determines the KSN 102 to be passed through when relaying from KM 10a belonging to the first KSN 102 to KM 10c belonging to the second KSN 102, and then transmitted from KM 10c to the application 5c.

[0099] The storage unit 82 stores, for example, an application key for each communication destination of the application 5a (an example of a source application).

[0100] The processing unit 83 encrypts communication with the application 5c (an example of a destination application) by running, for example, the application 5a (an example of a source application).

[0101] The configurations of the KM 10, QKDN control device 6, and information processing device 8 in this embodiment are merely examples, and the configurations may be changed as appropriate.

[0102] Multiple KSNs 102 may be configured, each with a different quantum layer quantum key distribution protocol, key management layer mechanism, or key relay method.

[0103] 7 is a diagram illustrating an example of key relay between different types of KSNs 102 according to an embodiment. An application A and an application B perform secure communication via a data communication network 103.

[0104] In the example of Figure 7, identification information for identifying the KM 10 is assigned to the KM 10 and the BKM 10. For example, identification information a011 is assigned to KM 10a. In the example of Figure 7, when each KM 10 and each BKM 10 are to be distinguished and described, this identification information will be used.

[0105] Application A connects to KMa011, which belongs to KSN 102a. Application B connects to KMb333, which belongs to KSN 102b. KSN 102a is an IP-based network, and KSN 102b is a non-IP-based network. KSN 102a and KSN 102b are connected by BKMa00x and BKMb00y, which are physically co-located, or by BKMa9xx and BKMb9yy, which are physically co-located.

[0106] The links (Link#1 and Link#2) between BKMs 102a and 102b are independent of QKD link 3 of QKD links 101a and 101b.

[0107] Furthermore, QKDN control devices 6#a and 6#b are installed in KSN 102a and KSN 102b, respectively, and the QKDN control devices 6 are connected by links other than Link #1 and Link #2. The links between the QKDN control devices 6 may be QDK links or ordinary links secured by a method other than QKD. Note that there may be no links between the QKDN control devices 6. When there is no link between the QKDN control devices 6, information is shared between the BKMs 10 via Link #1 or Link #2.

[0108] In the example of Figure 7, for the sake of simplicity, the KMs 10 in the key sharing networks 102a and 102b and the QKD modules 2 in the networks 101a and 101b of the QKD link 3 are not all shown, but only some of them.

[0109] As shown in Figure 7, when KMa011 connected to application A shares an application key with KMb333 connected to application B, the route to the destination KMb333 cannot be determined. For example, there is a route via Link #1 and a route via Link #2. The route (key relay route) for sharing the application key between different types of KSNs 102a and 102b is determined by a dedicated QKDN control device 6 installed in each KSN 102. For example, the QKDN control device 6a collects internal information about the KSN 102 and shares this information with the QKDN control device 6b to determine the key relay route. The collected internal information about the KSN 102 includes, for example, route information from destination KMa011 to BKMa00x in the KSN 102a, the connection status with the adjacent KSN 102b, and route information from BKMb00y to destination KMb333 in the adjacent KSN 102b.

[0110] [Example of a large-scale QKDN configuration] As the QDKN scales up and the number of KMs 10 increases, it is common for the key sharing network (KSN) 102 to be divided into multiple KSN domains in order to efficiently and easily manage the KSN 102. In a KSN domain, for example, the number of KMs 10 or the number of links between KMs 10 is limited to a certain value (e.g., 1000).

[0111] As mentioned above, each KSN domain is not necessarily limited to the same standard, scale, or quantum protocol. For example, if an upper limit is set on the number of KMs or links in a domain as a partitioned type of KSN 102, many KMs 10 within the KSN domain will have less key relay path information, which shortens processing time. However, when sharing a key with a KM 10 outside the domain, it is necessary to determine the key relay path between domains via a specific KM 10.

[0112] Fig. 8A is a diagram showing Example 1 of KSN domains according to an embodiment. Fig. 8A shows a case where five key sharing networks 102a-102e (five KSN domains of the same type) of the same type (IP-based in the example of Fig. 8A) exist. Note that the number of key sharing networks 102 and the number of QKDN control devices 6 may be any number and are not limited to the example of Fig. 8A.

[0113] The five KSN domains shown in Fig. 8A have an IP-based ID system. A dedicated QKDN control device 6a to 6e in the QKD network management layer is installed for each key sharing network 102a to 102e in the key management layer.

[0114] Each QKDN control device 6 periodically collects information such as the status of holding link keys between KMs 10 from KMs 10 in each key sharing network 102, and manages the collected information.

[0115] Key sharing networks 102 are connected by BKMs 10 installed at the boundaries between domains. The BKMs 10 at the boundaries between domains are physically located in the same place (node). Furthermore, information sharing between BKMs 10 does not depend on the QKD link 3 used to share link keys.

[0116] The QKDN control devices 6a to 6e construct a dedicated network and share the connection status between KSNs 102 (connection information of BKM 10), key relay-related information, etc. The link between the QKDN control devices 6a to 6e may be the above-mentioned QKD link 3, or may be an ordinary link secured by a method other than QKD.

[0117] Fig. 8B is a diagram showing Example 2 of a KSN domain according to an embodiment. Fig. 8B shows an example in which different types of key sharing networks 102 coexist. In the example of Fig. 8B, there are five key sharing networks 102a to 102e. The key sharing networks 102a, 102c, and 102d are IP-based key sharing networks 102, and the key sharing networks 102b and 102e are non-IP-based key sharing networks 102. Note that the number of key sharing networks 102 and the number of QKDN control devices 6 may be any number and are not limited to the example of Fig. 8B.

[0118] When securely communicating from an application (source) connected to KM 10a in KSN 102a to an application (destination) connected to KM 10d in KSN 102d, it is desirable to determine an efficient key relay route to the destination KM 10d via the optimal KSN 102, while avoiding key consumption and depletion, according to the link key status.

[0119] Therefore, the quantum cryptography communication system according to this embodiment minimizes the consumption of link keys, selects the optimal KSN domain to pass through, and determines the key relay route. This makes it possible to reduce the consumption of link keys throughout the system while avoiding the exhaustion of link keys in a specific KM 10 and maintaining the throughput of application key sharing between KSNs 102.

[0120] 9 is a diagram illustrating a first calculation example of the first criterion value according to the embodiment. A method for calculating the first criterion value for KSN domain selection related to key relay path determination will be described using the example of FIG. 9. In FIG. 9, there are five KSNs 102, of which KSNs 102h, 102x, and 102f are IP-based KSNs, and KSNs 102u and 102s are non-IP-based KSNs.

[0121] An appropriate number of KMs 10 are installed in the KSN 102x. In the example of Fig. 9, identification information for identifying the KMs 10 is assigned to the KMs 10 and BKMs 10. In the example of Fig. 9, when each KM 10 and each BKM 10 is to be distinguished and described, this identification information will be used.

[0122] The KMs 10 belonging to KSN 102x are connected by links. Four BKMs, x011, x066, x633, and x857, are installed on the edge side of KSN 102x, and the four BKMs, x011, x066, x633, and x857, connect to the four adjacent KSNs, 102u, 102h, 102f, and 102s.

[0123] It should be noted that the number of KMs 10, the number of links between KMs 10, the number of BKMs 10, the number of KSNs 102, and the number of QKDN control devices 6 are not limited to the example of FIG.

[0124] The following describes how to calculate the first reference value used to determine whether to select the KSN 102x for the key relay path. There are two main methods for calculating the first reference value. Method 1: First baseline based on the entire KSN102 (Options 1 to 4 below) Method 2: Route-based primary reference value within KSN102 (Options 5 to 8 below)

[0125] First, we will explain Method 1. The communication unit 61 of the QKDN control device 6x periodically acquires the remaining link key amounts of the links between each KM 10 (including BKM 10) within the KSN 102. The processing unit 63 of the QKDN control device 6x calculates a first reference value for the entire KSN 102 based on the remaining link key amounts of all links.

[0126] Therefore, in Method 1, it is assumed that all KMs 10 are connected to the QKDN control device 6x. As a method for calculating the first reference value on an overall basis of the KSNs 102x, there are the following calculation methods such as Option 1 to Option 4.

[0127] <Option 1> For example, the total value of the remaining keys available for use in all links in the KSN 102x is set as the first reference value O of the KSN 102x. The total value is calculated, for example, by the following formula (2).

[0128]

number

[0129] where O own denotes the first reference value of KSN 102x. i denotes the number of all links in KSN 102x. A i key indicates the remaining key amount available for link i. Furthermore, because application key sharing is a two-way communication, the remaining key amount available for each link may be divided into one for sending (encryption) and one for receiving (decryption). The remaining key amount available for each link remains the same, but application keys can be shared more efficiently. In this case, the remaining key amount available for one link in the above formula is the sum of the two amounts (for sending (encryption) and receiving (decryption)).

[0130] <Option 2> For example, the average value of the remaining available keys of all links in the KSN 102x is set as the first reference value O of the KSN 102x. The average value is calculated, for example, by the following formula (3). It is served.

[0131]

number

[0132] where O own , i and A i key The meaning of is the same as that of the above formula (2).

[0133] The advantages of using the sum of the remaining available keys on all links (Option 1) or the average value of the remaining available keys on all links (Option 2) as the first reference value O of the KSN102x are as follows: (1) The amount of calculation required for each KM10 is small. (2) The first reference value O can be efficiently calculated based on the link key status periodically acquired by the QKDN control device 6x.

[0134] Another drawback is that if the available key balance of a link is significantly different from the available key balance of other links on the key relay path, the key relay speed is limited by the available key balance of the link with the small key balance.

[0135] For example, suppose there are 50 links in the KSN 102x, one of which has a remaining key capacity of 10 Gbits, and the remaining 49 links all have a remaining key capacity of 0.001 Gbits. In this case, the first reference value, calculated as the total or average value, is higher than the actual remaining key capacity of 0.001 Gbits. If the KSN 102x is selected based on this first reference value, the key relay speed will be limited to the actual remaining key capacity of 0.001 Gbits (bottleneck).

[0136] <Option 3> For example, the minimum value of the remaining link keys available for use in all links in the KSN 102x is set as the first reference value O of the KSN 102x. The minimum value is calculated, for example, by the following formula (4).

[0137]

number

[0138] where O own , i and A i key The meaning of is the same as that of the above formula (2).

[0139] The advantage of setting the minimum remaining link key amount available in all links as the first reference value O of KSN is that: (1) The amount of calculation required for each KM10 is small. (2) The first reference value O can be efficiently calculated based on the link key status periodically acquired by the QKDN control device 6x. (3) When KSN 102x is selected, sharing of application keys equal to or greater than the minimum remaining link key amount is guaranteed.

[0140] Another drawback is that although a link with the minimum remaining link key amount may not actually be used as a key relay path, the first reference value is expressed as this minimum value.

[0141] For example, when an application key is shared from KM10 of KSN 102u to KM10 of KSN 102f via KSN 102x, there are five routes from BKMx011 on the edge side connected to KSN 102u to BKMx633 on the edge side connected to KSN 102f, and the bottleneck of each route has a link key remaining amount greater than the link with the smallest value. In other words, suppose that no route includes a link with the smallest link key remaining amount. Even in this case, the first reference value for determining whether KSN#x is selected is represented by this smallest value.

[0142] <Option 4> For example, the median of the remaining available keys of all links in the KSN 102x is set as the first reference value O of the KSN 102x. When the remaining available link keys of each link are sorted in order of size, for example, {A'1, A'2, A'3, . . . , A' i The median is calculated, for example, by the following formula (5).

[0143]

number

[0144] The advantage of using the median of the remaining available link keys of all links as the first reference value O of KSN102x is that it is a value that is exactly in the middle of the order, so it is not affected by values ​​that are extremely higher (or lower) than the average value.

[0145] The drawback is that the median link key remaining capacity is used as the first reference value, but if the link key remaining capacity of the link actually used in the relay route is smaller than the median, only the available link key remaining capacity smaller than the median will be provided in this relay route.

[0146] The first reference value for the entire KSN 102x can be calculated using the above options 1 to 4. Note that the above methods for calculating the first reference value are merely examples and are not limited to these. The first reference value may be calculated based on at least one of the total, average, minimum, and median remaining amounts of link keys held in multiple KMs 10 and BKMs 10 included in the KSN 102x to be judged.

[0147] Furthermore, because it is an overall first reference value, it is the same regardless of which KSN 102 it is from and which KSN 102 it is from. For example, in the example of Fig. 9, when key relay is performed from KSN 102u to KSN 102f via KSN 102x, when key relay is performed from KSN 102u to KSN 102h via KSN 102x, and when key relay is performed from KSN 102u to KSN 102s via KSN 102x, the same first reference value O is used.

[0148] In addition, when the first reference value based on the entire KSN102x is used, there is an advantage that the amount of calculation for each KM10 (BKM10) is small.

[0149] Next, method 2 will be described.

[0150] 10 is a diagram illustrating a second calculation example of the first reference value according to the embodiment. The communication unit 61 of the QKDN control device 6x periodically acquires key relay routes between the BKMs 10 within the KSN 102x. The processing unit 63 of the QKDN control device 6x calculates the route-based first reference value of the KSN 102x based on the key relay routes within the KSN 102x.

[0151] Therefore, the processing unit 63 of the QKDN control device 6x must calculate the key relay route within the KSN 102x. The key relay route within the KSN 102x is determined using any routing method. For example, in the case of an IP-based KSN 102x, the existing routing protocol OSPF is used to select the key relay route according to the bottleneck of the remaining available keys on each link. The following options 5 to 8 are available as calculation methods for the first reference value of the route base of the KSN 102x.

[0152] <Option 5> For example, the available remaining key bottleneck value of the optimal key relay route between BKMs 10 is set as the first reference value O of KSN 102x.

[0153] In this case, as shown in Fig. 10, for example, when going from KSN 102u to KSN 102f via KSN 102x, there are routes #1 to #j. For example, route #1 is a route consisting of multiple links {Link1, Link2, Link3, . . . , Link k The remaining available key for each link is calculated using the above formula (1), for example, and the remaining available key for Route #1 is A route_id The bottleneck is calculated, for example, by the following formula (6).

[0154]

number

[0155] Furthermore, the processing unit 63 also calculates the remaining available key amount A for other routes #2 to #j from BKMx011 to BKMx633 in the same manner as for route #1. route_id Then, the processing unit 63 selects the optimum route from the routes #1 to #j. The optimum route is calculated, for example, by the following formula (7).

[0156]

number

[0157] Here, the first reference value O From,To Own Specify the source (From), destination (To), and via (Own).

[0158] For example, if the bottleneck of available remaining keys on route #2 is the largest among all key relay routes, the first reference value from KSN 102u to KSN 102f via KSN 102x is represented by the bottleneck of available remaining link keys on route #2.

[0159] The remaining number of available link keys for each link is calculated on the KM 10 side. Other calculations may be performed by, for example, the BKM 10 and periodically reported to the QKDN control device 6x. Also, for example, the QKDN control device 6x periodically collects information and calculates the first reference value O of the optimal route. From,To Own may be calculated.

[0160] <Option 6> For example, the bottleneck value of the remaining available keys for the three best key relay routes between BKM10 is taken as the first reference value O for KSN102x. This calculation method is basically the same as Option 5, but when calculating the best route, the bottlenecks of the remaining available link keys for the second-best and third-best routes are also calculated. The sum and average value of the bottlenecks of the remaining available link keys for the three best routes is then taken as the first reference value O.

[0161] When sharing an application key, it may be possible to use a single route from start to finish, but if the remaining available application keys for the link are insufficient, it is more common to change to a different key relay route and continue sharing the application key rather than waiting for link keys to be replenished.

[0162] The method of calculating the first reference value O for option 6 is considered to take into account the possibility of route changes, and is therefore more appropriate than option 5. The above method of calculating the best three routes is an example, and the number of routes considered is not limited to three.

[0163] Option 5 and Option 6 are calculation methods that take into account only bottlenecks, but resource information other than bottlenecks may also be taken into account.

[0164] <Option 7> For example, the reference value that combines the available remaining key bottleneck and the number of hops in the optimal key relay route between BKMs 10 is set as the first reference value O of KSN 102x. In this case, as shown in FIG. 10, for example, when going from KSN 102u to KSN 102f via KSN 102x, the key relay route #1 from BKMx011 to BKMx633 consists of multiple links {Link1, Link2, Link3, . . . , Link k The remaining available key for each link is calculated using the above formula (1), for example, and the remaining available key for Route #1 is A route_id The bottleneck is calculated, for example, by the above formula (6).

[0165] In addition, the number of hops of the above route #1 is H route = k. Therefore, the reference value RV of the route #1 is calculated, for example, by the following equation (8).

[0166]

number

[0167] Here, α and β are coefficients representing weights and are any real numbers greater than 0. The processing unit 63 calculates reference values ​​RV for other routes #2 to #j from BKMx011 to BKMx633 in the same manner as for route #1. Then, the processing unit 63 selects an optimal route from routes #1 to #j. The optimal route is calculated, for example, by the following equation (9).

[0168]

number

[0169] <Option 8> As with Option 6, the calculation method of Option 7 is used to calculate, for example, a reference value that combines the bottleneck of the remaining available link keys and the number of hops for not only the optimal route but also the second-best and third-best routes.Then, the sum and average of the reference values ​​that combine the bottleneck of the remaining available link keys and the number of hops for the best three routes is set as the first reference value. Note that the above calculation method for the best three routes is just one example, and the number of routes considered is not limited to three.

[0170] The route-based first reference value 0 of the KSN 102x can be calculated using the above options 5 to 8. The methods for calculating the first reference value in the above options 5 to 8 are merely examples and are not limited to these. For example, the first reference value may be calculated based on at least one of a bottleneck of the remaining number of link keys used in links included in a route within the KSN 102x to be determined and the number of hops in the links included in the route. The bottleneck of the remaining number of link keys may be calculated based on at least one of the sum and average value of the bottleneck of the remaining number of link keys used in links of multiple route candidate included in the KSN 102x to be determined. For example, the first reference value may also be calculated based on at least one of the sum and average value of the number of hops in links included in multiple route candidate.

[0171] Compared with Method 1, the calculation amount of BKM10 is larger, but since the route actually used differs depending on the source KSN102 and the destination KSN102, the calculated first reference value of KSN102x also differs. Therefore, a more optimal key relay route can be selected.

[0172] 11 is a diagram illustrating an example of a method for determining a key relay path according to an embodiment. The example in FIG. 11 illustrates a case in which an application key is shared from KMa011 (KM10a) belonging to KSN 102a to KMd616 (KM10d) belonging to KSN 102d.

[0173] First, the QKDN control device 6 dedicated to each KSN 102 collects information used to determine the key relay path. For example, in the case of KSN 102a, the reference value RV from the source KM (KMa011) to the BKM 10 within the KSN domain of KSN 102a is notified to the QKDN control device 6#a.

[0174] Similarly, in the case of the KSN 102d, the reference value RV from the BKM10 to the destination KM10 in the KSN domain of the KSN 102d is notified to the QKDN control device 6#d.

[0175] Furthermore, the processing unit 63 of the QKDN control device 6 of the KSN domain of the KSN 102 to be passed through calculates the first reference value O according to the above calculation method. Next, each QKDN control device 6 shares route-related information (for example, information on the KSN domain to which KM 10 belongs, the connection status between KSNs 102, and the first reference value for determining whether to pass through each KSN 102).

[0176] Finally, the processing unit 63 of the QKDN control device 6a determines a route from among the multiple key relay routes based on, for example, the largest second reference value. That is, when the relay route for the application key includes multiple KSNs 102 to be passed through, the processing unit 63 calculates a second reference value for determining the multiple KSNs 102 to be passed through when transmitting the application key from the first reference value of each KSN 102, and determines a relay route based on the second reference value.

[0177] The second reference value will be explained below.

[0178] For example, multiple KSN domains {KSN1,KSN2,KSN3,...,KSN q}. The number of KSN domains traversed is q = ΣKSNs. Here, this includes KSN 102 to which source KM10 belongs and KSN 102 to which destination KM10 belongs. In the example of Figure 11, in the case of Path#1, since it passes through KSN 102b, KSN 102a and KSN 102d are also included, so q = 3.

[0179] The second reference value of the route passing through multiple KSN domains is calculated by, for example, the determination method (1) according to the following formula (10).

[0180] Determination method (1): The bottleneck of the first reference value of all the KSNs 102 that are passed through is set as the second reference value of the key relay path.

[0181]

number

[0182] where O KSN1 represents the reference value of the KSN 102 to which the source KM 10 belongs. KSNq represents the reference value of the KSN 102 to which the destination KM 10 belongs. The processing unit 63 of the QKDN control device 6 calculates the first reference value O of other KSNs 102 to be passed through. From,To Own For example, calculate using the above eight options.

[0183] Determination method (2): The reference values ​​of the KSN 102 to which the source KM 10 belongs, the KSN 102 to which the destination KM 10 belongs, and the average of the first reference values ​​of all the KSNs 102 along the route are calculated using the following formula (11), and this average is used as the second reference value of the key relay route.

[0184]

number

[0185] In the example of Fig. 11, the processing unit 63 of the QKDN control device 6a calculates the second reference value for Path #1, Path #2, and Path #3 using the above two determination methods. After that, the processing unit 63 of the QKDN control device 6 determines the optimal key relay path, for example, using the following equation (12).

[0186]

number

[0187] The above calculation formula is an example and is not limited to this. For example, the second reference value may be calculated based on at least one of the bottleneck and the average value of the first reference values ​​of multiple KSNs 102 that are passed through.

[0188] [Example of QKDN control method] 12 is a flowchart showing an example of a QKDN control method according to an embodiment. The QKDN control device 6 periodically collects information used to determine a key relay path from the KM 10 of the KSN 102 managed by the QKDN control device 6. The information used to determine a key relay path is also periodically shared among the QKDN control devices 6.

[0189] First, when there is a request to share an application key between KMs 10, the processing unit 63 of the QKDN control device 6 references a table of affiliation information of the KMs 10 (FIG. 13 described later) and determines the destination KSN information (destination KMs 10 and destination KSNs 10) (step S1). Next, the processing unit 63 references a table of connection status information (FIG. 14 described later) and determines the BKMs 10 and KSNs 102 to be passed through on the way to the destination KMs 10 (step S2).

[0190] Next, the processing unit 63 refers to the table of first reference value information (see FIG. 15, which will be described later) and calculates the second reference value for each key relay path (step S3). Next, the processing unit 63 determines the optimal key relay path according to the calculated second reference value (step S4). The optimal key relay path determination up to step S4 changes due to periodic information updates.

[0191] Finally, once the optimal key relay path has been determined, the processing unit 63 transmits the key relay path related information to the associated KM 10 via the network between the QKDN control devices 6 (step S5).

[0192] The processing unit 63 can determine which BKMs 10 and KSNs 102 should be passed through on the key relay path to the destination KM 10 by referring to the connection information table. The key relay route between the BKMs 10 within the KSNs 102 passed through follows the routing method of each KSN 102.

[0193] Fig. 13 is a diagram showing an example of affiliation information according to an embodiment. The table shown in Fig. 13 is a table for the QKDN control device 6a. This table mainly consists of three parts: type, KM ID, and KSN ID. There are two types. ID information collected from the KMs 10 belonging to each KSN 102 and registered is marked with an "i" as inside information. On the other hand, ID information shared between QKDN control devices 6 and registered is marked with an "o" as outside information.

[0194] For example, the ID information of KMa011 is 16.10.1.1 in IPv4 address form. For example, the ID of KSN102 is #a in the case of KSN102a to which KMa011 belongs. The ID information of KM10 may include only the ID of KM10, or may also include the ID of KSN102. In the example of Figure 13, KMa011 has an IP-based ID system, and KMd616 has a non-IP-based ID system.

[0195] Figure 14 is a diagram showing an example of connection status information according to an embodiment. The table shown in Figure 14 is a table for the QKDN control device 6#a. This table mainly consists of five parts: type, a set of IDs for connected KSNs, and a set of IDs for connected BKMs. The type is the same as in Figure 13, so a description thereof will be omitted.

[0196] 14 as an example, KSN 102a and KSN 102b are connected via BKMa 062 and BKMb 053. The information on this first line is, for example, information acquired from BKMa 062.

[0197] FIG. 15 is a diagram showing an example of first reference value information according to an embodiment. The table shown in FIG. 15 is created from information shared between each QKDN control device 6. This table mainly consists of five parts: type, ID of the KSN 102 as the starting point, ID of the KSN 102 to be passed through, ID of the KSN 102 as the end point, and first reference value. Taking the second and third lines of FIG. 15 as an example, when determining a key relay path from KSN 102c to KSN 102d, if KSN 102b is passed through, the second line shows that the first reference value is O. b c,d The third line indicates that if the route is via KSN102e, the first standard value is O. e c,d This indicates that

[0198] Once the key relay path is determined, the application key is shared between the KMs 10. During key relay, there are two types of message configuration examples, depending on whether or not there is interaction with the QKDN control device 6.

[0199] Fig. 16 is a diagram showing example 1 of the header format of a key relay message according to an embodiment. Fig. 16 shows an example of the header format of a key relay message when communicating between QKDN control devices 6. The header portion consists of six fields.

[0200] The Version is a field that indicates the version of the KM 10. For example, in the case of IPv4, 0x04 is stored in the Version, in the case of IPv6, 0x06 is stored in the Version, and in the case of non-IP, 0x10 is stored in the Version.

[0201] "Type" is a field that indicates the type of message. For example, when key relay within KSN 102 is performed, 0x01 is stored in "Type", and when key relay via KSN 102 is performed, 0x10 is stored in "Type".

[0202] Length is a field that indicates the length of the message.

[0203] Checksum is an error checking field.

[0204] The Numbers of KSNs is a field indicating the number of KSNs 102 related to the key relay path, including the KSN 102 to which the source KM 10 belongs and the KSN 102 to which the destination KM 10 belongs.

[0205] Next BKM ID (Optional) is a field that indicates the ID of the BKM 10 of the next KSN 102 to be passed through.

[0206] The Source KM ID is a field that indicates the ID information of the source KM 10 .

[0207] The Destination KM ID is a field that indicates the ID information of the destination KM.

[0208] The "Key information" field indicates application key information. For example, the application key ID and the application key corresponding to that ID are stored in the key information.

[0209] The QKDN control device 6 queries the corresponding QKDN control device 6 for the BKM ID of the next KSN 102 to be passed through, and updates the Next BKM ID field by determining the next BKM 10. This field is not used when key relay within the KSN 102 is performed.

[0210] The Key information field conforms to, for example, ETSI GS QKD 014 (Non-Patent Document 2).

[0211] Fig. 17 is a diagram showing example 2 of the header format of a key relay message in an embodiment. Fig. 17 is an example of the header format of a key relay message when there is no communication between QKDN control devices 6. When a key relay path is determined, path information is included in the header. In the example of Fig. 18, a path information section has been added compared to Fig. 16. The path information section mainly includes the following fields:

[0212] The Numbers of KSNs is a field indicating the number of KSNs 102 related to the key relay path, including the KSN 102 to which the source KM 10 belongs and the KSN 102 to which the destination KM 10 belongs.

[0213] The Current KSN ID is a field that indicates which KSN 102 is currently performing key relay for the application key.

[0214] The Source KSN ID is a field that indicates the ID of the KSN 102 that belongs to the source KM 10.

[0215] The Source KM ID is a field that indicates the ID of the source KM 10 .

[0216] The Relay KSN ID is a field that indicates the ID of the KSN 102 through which the key relay path passes.

[0217] The From BKM ID is a field that indicates the ID of the starting BKM 10 of the KSN 102 through which the key relay path passes.

[0218] The To BKM ID is a field that indicates the ID of the end BKM 10 of the KSN 102 through which the key relay path passes.

[0219] The Destination KSN ID is a field that indicates the ID of the KSN 102 to which the destination KM 10 belongs.

[0220] The Destination KM ID is a field that indicates the ID of the destination KM 10 .

[0221] Note that there may be multiple Relay KSN IDs, From BKM IDs, and To BKM IDs depending on the number of KSNs 102 that are passed through.

[0222] Note that overhead increases depending on the amount of application keys when there is no interaction with the QKDN control device 6. On the other hand, communication with the QKDN control device 6 is not required, and delays can be reduced.

[0223] Fig. 18 is a diagram showing an example of a centralized management configuration according to an embodiment. In the example of Fig. 18, the QKDN control device 6 is connected to the authoritative root server device 9. Related information such as affiliation information, connection status information, and first reference value information (Figs. 13 to 15) is centrally managed by the authoritative root server device 9. When an application 5 in the user network requests an application key, the QKDN control device 6 queries the authoritative root server device 9 for related information. Based on the response message from the authoritative root server device 9, the QKDN control device 6 determines a key relay path.

[0224] Regarding information updates of the authoritative root server device 9, if the information is constantly updated, the authoritative root server device 9 and the QKDN control device 6 assign the same sequence number. If the information of the authoritative root server device 9 is updated only when a key relay route is determined, the related QKDN control device 6 notifies the authoritative root server device 9 of the latest information when an inquiry is made about determining a key relay route.

[0225] The link between the authoritative root server device 9 and the QKDN control device 6 may be a QKD link 3, or may be an ordinary link secured by a method other than QKD.

[0226] As described above, for example, in the KM 10a of the embodiment, the communication unit 11 (an example of a communication interface) receives from the QKDN control device 6a route information for sending an application key used for encrypting or decrypting communications in the user network to the destination KM 10. Then, the processing unit 13 identifies, from the route information, a BKM 10 that is in the KSN 102a (an example of a first key sharing network) to which the KM 10a connected to the application 5a belongs and is connected to the KSN 102b (an example of a second key sharing network), determines a route within the KSN 102a from the KM 10a connected to the application 5a to the BKM 102b connected to the KSN 102b based on the resource information of the KSN 102a, and causes the communication unit 11 to send the application key encrypted with the link key using that route.

[0227] Furthermore, in the QKDN control device 6a of this embodiment, the processing unit 63 calculates a first reference value that determines the KSN 102d through which an application key is to be sent, for example, from KM 10a (an example of a first key management device) belonging to KSN 102a to KM 10d (an example of a second key management device) belonging to KSN 102d (an example of a second key sharing network). The processing unit 63 determines the KSN 102 through which the application key is to be sent from KM 10a to KM 10d based on the first reference value. Then, the communication unit 61 (an example of a communication interface) transmits route information indicating the KSN 102 through which the application key is to be sent to KM 10a.

[0228] As a result, the quantum cryptography communication system of the embodiment can determine the optimal route for transmitting the cryptographic key regardless of the scale of the QKD network.

[0229] Finally, an example of the hardware configuration of the KM 10, the QKDN control device 6, and the information processing device 8 according to this embodiment will be described.

[0230] [Example of hardware configuration] 19 is a diagram showing an example of the hardware configuration of the KM 10, QKDN control device 6, and information processing device 8 according to an embodiment. The KM 10, QKDN control device 6, and information processing device 8 each include a control device such as a CPU 201, storage devices such as a ROM (Read Only Memory) 202 and RAM 203, and a communication I / F 204 that connects to a network and performs communication. The CPU 201, ROM 202, RAM 203, and communication I / F 204 are connected by a bus 205.

[0231] For example, the programs executed by the KM 10, the QKDN control device 6, and the information processing device 8 are provided in a state that they are pre-installed in the ROM 202 or the like.

[0232] Furthermore, for example, the programs executed by KM10, QKDN control device 6, and information processing device 8 may be configured to be provided as a computer program product by being recorded in an installable or executable format on a computer-readable recording medium such as a CD-ROM (Compact Disk Read Only Memory), a flexible disk (FD), a CD-R (Compact Disk Recordable), or a DVD (Digital Versatile Disk).

[0233] Furthermore, the programs executed by the KM 10, the QKDN control device 6, and the information processing device 8 may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the programs executed by the KM 10, the QKDN control device 6, and the information processing device 8 may be provided or distributed via a network such as the Internet.

[0234] The programs executed by the KM 10, the QKDN control device 6, and the information processing device 8 can cause the computer to function as each of the above-mentioned parts of the KM 10, the QKDN control device 6, and the information processing device 8. In this computer, the CPU 201 can read the programs from a computer-readable storage medium onto a main storage device such as the RAM 203 and execute them.

[0235] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0236] (Addendum) The above-described embodiments can be summarized as the following technical proposals.

[0237] Technical proposal 1 A key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application of a user network, and a QKDN (Quantum Key Distribution Network) control device, a communication interface that receives, from the QKDN control device, route information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device; identifying, from the path information, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network; determining a route within the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; a processing unit that causes an application key encrypted with the link key to be sent to the communication interface using the path; A key management device comprising:

[0238] Technical proposal 2 the resource information includes link key status information calculated based on at least one of a generation rate, a holding amount, and a consumption rate of the link key calculated for each link included in the route candidate, the processing unit calculates a value calculated from at least one of a generation rate, a holding amount, and a consumption rate of the link keys for each link included in the candidate route based on status information of the link keys used in the links included in the candidate route, identifies the link for which the value is smallest as a link bottleneck, and determines the route based on the bottleneck of the link included in the candidate route. A key management device as described in Technical Proposal 1.

[0239] Technical proposal 3 the resource information further includes the number of hops to a key management device connected to the second key sharing network, calculated for each of the route candidates; the processing unit determines the route further based on the number of hops. A key management device described in Technical Proposal 2.

[0240] Technical proposal 4 A QKDN (Quantum Key Distribution Network) control device connected to a first key management device that transmits an application key used for encrypting or decrypting communication between applications in a user network to the application, calculating a first reference value for determining a key sharing network via which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; a processing unit that determines, based on the first reference value, a key sharing network through which the application key is sent from the first key management device to the second key management device; a communication interface that transmits routing information indicating the key sharing network to be passed through to the first key management device; A QKDN control device comprising:

[0241] Technical proposal 5 the first reference value is used for at least one of encryption and decryption of communications of links included in the key sharing network to be determined, and is calculated based on at least one of a total value, an average value, a minimum value, and a median value of remaining amounts of link keys held by a plurality of key management devices included in the key sharing network to be determined. The QKDN control device described in Technical Proposal 4.

[0242] Technical plan 6 the first reference value is calculated based on at least one of a bottleneck of remaining link keys used in links included in a route of the key sharing network to be determined and the number of hops of links included in the route; The QKDN control device described in Technical Proposal 4.

[0243] Technical proposal 7 the first reference value is calculated based on at least one of a total value and an average value of bottlenecks of remaining amounts of link keys used in links of candidate routes included in the key sharing network to be determined; The QKDN control device described in Technical Proposal 4.

[0244] Technical proposal 8 The first reference value is calculated based on at least one of a total value and an average value of the number of hops of links included in the plurality of route candidates. The QKDN control device described in Technical Proposal 7.

[0245] Technical proposal 9 when a plurality of the key sharing networks to be passed through are included in the relay route of the application key, the processing unit calculates a second reference value for determining the plurality of key sharing networks to be passed through when transmitting the application key, from a first reference value of each key sharing network, and determines the relay route based on the second reference value. A QKDN control device according to any one of technical proposals 4 to 8.

[0246] Technical proposal 10 The second reference value is calculated based on at least one of a bottleneck and an average value of the first reference values ​​of the plurality of key sharing networks passed through. The QKDN control device described in Technical Proposal 9.

[0247] Technical proposal 11 A first QKDN control device, which is the QKDN control device according to any one of technical proposals 4 to 10; the first key management device belonging to the first key sharing network; a first application that receives the application key from the first key management device; the second key management device belonging to the second key sharing network; a second QKDN control device connected to the second key management device; a second application that receives the application key from the second key management device; A quantum cryptography communication system comprising:

[0248] Technical proposal 12 a first QKD device and a second QKD device that generate a link key by QKD; the first QKD device transmits the link key to the first key management device; the second QKD device transmits the link key to the second key management device; A quantum cryptography communication system as described in Technical Proposal 11.

[0249] Technical proposal 13 a communication interface that receives an application key used for encryption or decryption of communication with a destination application in a user network from a first key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution); a processing unit that operates a source application to encrypt communication with the destination application, the application key is encrypted and transmitted with the link key to the second key management device using route information determined based on a first reference value that determines the key sharing network through which the application key will be transmitted from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network, and then transmitted from the second key management device to the destination application; Information processing device.

[0250] Technical proposal 14 A key management method for a key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application of a user network, and a QKDN (Quantum Key Distribution Network) control device, comprising: a step of receiving, from the QKDN control device, route information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device by the key management device; a step of identifying, by the key management device, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network, from the route information; determining, by the key management device, a route in the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; the key management device causing an application key encrypted with the link key to be sent to a communication interface using the path; A key management method comprising:

[0251] Technical proposal 15 A QKDN (Quantum Key Distribution Network) control method for a QKDN control device connected to a first key management device that transmits an application key used for encrypting or decrypting communications between applications in a user network to the application, comprising: a step in which the QKDN control device calculates a first reference value that determines a key sharing network through which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; determining, based on the first reference value, a key sharing network through which the application key is sent from the first key management device to the second key management device by the QKDN control device; a step of the QKDN control device transmitting route information indicating the key sharing network to be passed through to the first key management device; A QKDN control method including:

[0252] Technical proposal 16 An information processing device receives, by QKD (Quantum Key Distribution), from a first key management device connected to a QKD device that generates a link key, an application key used for encrypting or decrypting communication with a destination application in a user network; the information processing device encrypts communication with the destination application by running a source application; the application key is encrypted and transmitted with the link key to the second key management device using route information determined based on a first reference value that determines the key sharing network through which the application key will be transmitted from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network, and then transmitted from the second key management device to the destination application; Information processing methods.

[0253] Technical proposal 17 A QKD device that generates a link key by QKD (Quantum Key Distribution), a user network application, and a key management device connected to a QKDN (Quantum Key Distribution Network) control device. a communication interface that receives, from the QKDN control device, route information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device; identifying, from the path information, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network; determining a route within the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; a processing unit that causes an application key encrypted with the link key to be sent to the communication interface using the path; A program to function as a

[0254] Technical proposal 18 a QKDN (Quantum Key Distribution Network) control device connected to a first key management device that transmits an application key used for encrypting or decrypting communications between applications in a user network to the application; calculating a first reference value for determining a key sharing network via which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; a processing unit that determines, based on the first reference value, a key sharing network through which the application key is sent from the first key management device to the second key management device; a communication interface that transmits routing information indicating the key sharing network to be passed through to the first key management device; A program to function as a [Explanation of symbols]

[0255] 1 node 2 QKD modules 3 QKD Link 4 QKD Network Controller 5. Applications 6 QKDN control device 7 User network control device 8. Information processing equipment 9 Authoritative root server devices 10 Key management device (KM) 11 Communications Department 12 Storage section 13 Processing section 61 Communications Department 62 Memory section 63 Processing section 81 Communications Department 82 Memory section 83 Processing section 100 Quantum cryptography communication network A network of 101 QKD links 102 Key Sharing Network 103 Data Communication Network 111 KM Communications Department 112 Control and communication unit 113 App Communication Department 131 Calculation Unit 132 Management Department 133 Information Exchange Department 134 Executive Department 135 Key Processing Unit 136 Provision Department 137 Control Unit 138 Platform Section 611 KM Communications Department 612 Control and communication unit 631 Information Exchange Department 632 Calculation Unit 633 Decision Section 634 Control Unit 635 Management Department 636 Platform Section

Claims

1. A key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application of a user network, and a QKDN (Quantum Key Distribution Network) control device, the key management device comprising: a communication interface that receives, from the QKDN control device, routing information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device; identifying, from the path information, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network; determining a route within the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; a processing unit that causes an application key encrypted with the link key to be sent to the communication interface using the path; A key management device comprising:

2. the resource information includes link key status information calculated based on at least one of a generation rate, a holding amount, and a consumption rate of the link key calculated for each link included in the route candidate, the processing unit calculates a value calculated from at least one of a generation rate, a holding amount, and a consumption rate of the link keys for each link included in the candidate route based on status information of the link keys used in the links included in the candidate route, identifies the link for which the value is smallest as a link bottleneck, and determines the route based on the bottleneck of the link included in the candidate route. The key management device according to claim 1 .

3. the resource information further includes a number of hops to a key management device connected to the second key sharing network, calculated for each of the route candidates; the processing unit determines the route further based on the number of hops. The key management device according to claim 2 .

4. A QKDN (Quantum Key Distribution Network) control device connected to a first key management device that transmits, to an application, an application key used for encrypting or decrypting communication between applications in a user network, the application key comprising: calculating a first reference value for determining a key sharing network via which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; a processing unit that determines, based on the first reference value, a key sharing network through which the application key is sent from the first key management device to the second key management device; a communication interface that transmits routing information indicating the key sharing network to be passed through to the first key management device; A QKDN control device comprising:

5. the first reference value is used for at least one of encryption and decryption of communications of links included in the key sharing network to be determined, and is calculated based on at least one of a total value, an average value, a minimum value, and a median value of remaining amounts of link keys held by a plurality of key management devices included in the key sharing network to be determined. The QKDN control device of claim 4.

6. the first reference value is calculated based on at least one of a bottleneck of remaining link keys used in links included in a route of the key sharing network to be determined and the number of hops of links included in the route; The QKDN control device of claim 4.

7. the first reference value is calculated based on at least one of a total value and an average value of bottlenecks of remaining amounts of link keys used in links of candidate routes included in the key sharing network to be determined; The QKDN control device of claim 4.

8. the first reference value is calculated based on at least one of a total value and an average value of the number of hops of links included in the plurality of route candidates; The QKDN control device of claim 7.

9. When a plurality of the key sharing networks to be passed through are included in the relay route of the application key, the processing unit calculates a second reference value for determining the plurality of key sharing networks to be passed through when transmitting the application key, from a first reference value of each key sharing network, and determines the relay route based on the second reference value. A QKDN control device according to any one of claims 4 to 8.

10. the second reference value is calculated based on at least one of a bottleneck and an average value of the first reference values ​​of the plurality of key sharing networks via which the communication is passed; The QKDN control device of claim 9.

11. a first QKDN control device, the first QKDN control device being a QKDN control device according to any one of claims 4 to 8; the first key management device belonging to the first key sharing network; a first application that receives the application key from the first key management device; the second key management device belonging to the second key sharing network; a second QKDN control device connected to the second key management device; a second application that receives the application key from the second key management device; A quantum cryptography communication system comprising:

12. Further comprising a first QKD device and a second QKD device that generate a link key by QKD; the first QKD device transmits the link key to the first key management device; the second QKD device transmits the link key to the second key management device; The quantum cryptography communication system according to claim 11.

13. A key management method for a key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application of a user network, and a QKDN (Quantum Key Distribution Network) control device, the method comprising: a step of receiving, from the QKDN control device, routing information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device by the key management device; a step of identifying, by the key management device, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network, from the route information; determining, by the key management device, a route in the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; the key management device causing an application key encrypted with the link key to be sent to a communication interface using the path; A key management method comprising:

14. A QKDN (Quantum Key Distribution Network) control method for a QKDN control device connected to a first key management device that transmits, to an application, an application key used for encrypting or decrypting communications between applications in a user network, the QKDN control method comprising: a step in which the QKDN control device calculates a first reference value for determining a key sharing network via which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; determining, based on the first reference value, a key sharing network through which the QKDN control device will transmit the application key from the first key management device to the second key management device; a step of the QKDN control device transmitting route information indicating the key sharing network to be passed through to the first key management device; A QKDN control method including:

15. A key management device connected to a QKD device that generates a link key by QKD (Quantum Key Distribution), an application of a user network, and a QKDN (Quantum Key Distribution Network) control device, a communication interface that receives, from the QKDN control device, routing information for sending an application key used for encryption or decryption of communications in the user network to a destination key management device; identifying, from the path information, a key management device that is in a first key sharing network to which a key management device connected to the application belongs and that is connected to a second key sharing network; determining a route within the first key sharing network from a key management device connected to the application to a key management device connected to the second key sharing network based on resource information of the first key sharing network; a processing unit that causes an application key encrypted with the link key to be sent to the communication interface using the path; A program to function as a

16. a QKDN (Quantum Key Distribution Network) control device connected to a first key management device that transmits, to an application, an application key used for encrypting or decrypting communications between applications in a user network; calculating a first reference value for determining a key sharing network via which the application key is sent from the first key management device belonging to a first key sharing network to a second key management device belonging to a second key sharing network; a processing unit that determines, based on the first reference value, a key sharing network through which the application key is sent from the first key management device to the second key management device; a communication interface that transmits routing information indicating the key sharing network to be passed through to the first key management device; A program to function as a

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