Quantum key distribution method, network, communication node and storage medium

Abstract

The invention relates to the field of communication, and discloses a quantum key distribution method, a network, a communication node and a storage medium, and the method comprises the steps: determining a target communication node and a quantum key; determining all paths taking the starting communication node as a starting point and taking the target communication node as an ending point; determining a plurality of quantum key distribution paths according to all the paths and the key splitting parameters; according to a splitting quantity value in the key splitting parameter, splitting the quantum key to obtain a plurality of key components with the quantity of the splitting quantity value; a plurality of key components and key splitting parameters are respectively transmitted through a plurality of quantum key distribution paths, a target communication node generates a quantum key after receiving the plurality of key components and the key splitting parameters, and the plurality of split key components are respectively transmitted to the target communication node through different paths. The communication nodes in different paths transmit not complete quantum keys, and the communication nodes on each path cannot see the complete quantum keys, so that the security of quantum key distribution is improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of communications, and in particular to a quantum key distribution method, network, communication node and storage medium. Background Art

[0002] A network composed of multiple communication nodes for quantum key distribution is called a quantum key distribution network. In a quantum key distribution network, communication nodes that share the same quantum key can communicate with each other. Normally, adjacent communication nodes share the same quantum key, but non-adjacent communication nodes need to distribute quantum keys before they can communicate.

[0003] In the prior art, quantum keys can be distributed through intermediate nodes, but the intermediate nodes can see the complete quantum keys, and the security of the quantum keys is poor. Therefore, an additional quantum key management center is set up in the quantum key distribution network. The quantum key management center has all the quantum keys of each communication node in the quantum key distribution network. The quantum key is distributed through the quantum key management center, which prevents the intermediate nodes from seeing the complete quantum key. However, the cost is high, and when the quantum key management center encounters security risks, it may threaten the security of the entire quantum key distribution network, and there is a risk of quantum key leakage. The security of quantum key distribution is still poor. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a quantum key distribution method, network, communication node and storage medium to improve the security in the quantum key distribution process.

[0005] In order to solve the above technical problems, an embodiment of the present application provides a quantum key distribution method, comprising:

[0006] Determine the target communication nodes and quantum keys;

[0007] Determine all paths starting from the starting communication node and ending at the target communication node;

[0008] Determine multiple quantum key distribution paths according to all the paths and key splitting parameters; the key splitting parameters include: a splitting quantity value;

[0009] Splitting the quantum key according to the split quantity value to obtain a plurality of key components of the split quantity value;

[0010] The multiple key components and the key splitting parameters are transmitted respectively through the multiple quantum key distribution paths, so that after the target communication node receives the multiple key components and the key splitting parameters, it generates the quantum key.

[0011] The embodiment of the present application further provides a quantum key distribution method, wherein the method of determining multiple quantum key distribution paths according to all the paths and the key splitting parameters comprises:

[0012] According to the intersection of communication nodes in all the paths and the split quantity value, multiple quantum key distribution paths are determined.

[0013] An embodiment of the present application further provides a quantum key distribution method, wherein the method determines multiple quantum key distribution paths according to the intersection of communication nodes in all the paths and the split quantity value, including:

[0014] According to the intersection conditions and network conditions of the communication nodes in all the paths and the split quantity value, multiple quantum key distribution paths are determined.

[0015] The embodiment of the present application also provides a quantum key distribution method, wherein the method for determining the key splitting parameter includes:

[0016] The key splitting parameter is determined according to the crossover conditions of the communication nodes in all the paths and / or the network conditions of the communication nodes in all the paths.

[0017] The embodiment of the present application further provides a quantum key distribution method, wherein the key splitting parameter further includes: a threshold value, wherein the threshold value is less than the splitting quantity value; after determining all paths starting from the starting communication node and ending at the target communication node, the method includes:

[0018] Determining multiple quantum key distribution paths according to all the paths and the split quantity values;

[0019] Performing secret sharing splitting of the key splitting parameter on the quantum key to obtain a plurality of key components of the number of splitting values;

[0020] The multiple key components and the threshold value are transmitted respectively through the multiple quantum key distribution paths, so that the target communication node generates the quantum key after receiving the multiple key components of the threshold value.

[0021] An embodiment of the present application further provides a quantum key distribution method, wherein the quantum key is subjected to secret sharing splitting of the key splitting parameter to obtain a plurality of key components of the splitting quantity value, including:

[0022] The quantum key is subjected to secret sharing splitting of the key splitting parameter using the Shamir threshold algorithm to obtain a plurality of key components of the splitting quantity value.

[0023] An embodiment of the present application also provides a quantum key distribution method, wherein the threshold value is determined according to the split quantity value.

[0024] The embodiment of the present application also provides a quantum key distribution network, comprising: a plurality of communication nodes; communication interconnection of the plurality of communication nodes;

[0025] The starting communication node is any one of the multiple communication nodes, and the initial communication node is used to execute any of the quantum key distribution methods described above.

[0026] An embodiment of the present application also provides a starting communication node, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute any one of the quantum key distribution methods described above.

[0027] An embodiment of the present application further provides a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the quantum key distribution method described in any one of the above items is implemented.

[0028] In the present application, when the quantum key is distributed from the starting communication node to the target communication node, the quantum key is split, and the multiple quantum key components after the split are transmitted to the target communication node through different paths respectively. The communication nodes in different paths do not transmit the complete quantum key, and the communication nodes on each path cannot see the complete quantum key, which can improve the security of quantum key distribution, and do not introduce an additional quantum key management center, which can reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] One or more embodiments are exemplarily described by the pictures in the corresponding drawings, and these exemplary descriptions do not constitute limitations on the embodiments.

[0030] Figure 1 It is a schematic diagram of the structure of a quantum key distribution network provided in an embodiment of the present application;

[0031] Figure 2 This is a flow chart of the first quantum key distribution method provided in an embodiment of the present application;

[0032] Figure 3 is a flow chart of a second quantum key distribution method provided in an embodiment of the present application;

[0033] Figure 4 is a schematic diagram of quantum key distribution provided by an embodiment of the present application;

[0034] Figure 5 It is a structural diagram of the starting communication node provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the present application, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The division of the following embodiments is for the convenience of description, and the specific implementation of the present application should not be construed as any limitation, and the various embodiments can be combined and referenced with each other under the premise of no contradiction.

[0036] In order to solve the technical problem of poor security in the process of quantum key distribution, the embodiment of the present application provides a quantum key distribution network, Figure 1 is a schematic diagram of the structure of a quantum key distribution network provided in an embodiment of the present application, such as Figure 1 As shown, the quantum key distribution network includes: multiple communication nodes, and communication interconnection between the multiple communication nodes.

[0037] The communication between communication nodes depends on human settings. The communication can also be understood as network communication. The quantum key distribution network can also be called a quantum key distribution secure communication network.

[0038] In the embodiment of the present application, the communication and intercommunication of multiple communication nodes can be understood as each communication node communicating and intercommunication with at least one other communication node in the quantum key distribution network.

[0039] The starting communication node is any one of the multiple communication nodes in the quantum key distribution network, and the starting communication node wants to distribute the quantum key to the target communication node, so that the starting communication node can exchange data with the target communication node based on the quantum key. The target communication node can be another communication node in the quantum key distribution network determined by the starting communication node according to business requirements. For example, the initial communication node can be communication node 1, and the target communication node can be communication node 10.

[0040] Each communication node has a shared quantum key with the adjacent communication node and can communicate directly, but non-adjacent communication nodes need to distribute quantum keys before they can communicate. For example, communication node 1 and communication node 2 share a quantum key K. i To communicate, communication node 5 and communication node 7 share the quantum key K m+1However, there is no direct connection between communication node 1 and communication node 10, and they are not adjacent communication nodes. Therefore, communication node 1 needs to distribute the quantum key to communication node 10 before communication node 1 can communicate with communication node 10 through the quantum key.

[0041] The quantum key distribution network in the embodiment of the present application does not need to add a quantum key management center, which can reduce costs, and there is no risk of quantum key leakage due to security risks in the quantum key management center.

[0042] Based on the quantum key distribution network provided in the above embodiment, the embodiment of the present application further provides a quantum key distribution method. Figure 2 is a flow chart of the first quantum key distribution method provided in the embodiment of the present application, such as Figure 2 As shown, the quantum key distribution method is applied to the starting communication node in the above-mentioned quantum key distribution network, and specifically includes the following steps.

[0043] Step 201, determine the target communication node and quantum key.

[0044] The initial communication node can determine the target communication node and quantum key according to business requirements. Of course, the target communication node and quantum key can also be determined according to other requirements or requests, information, etc., which is not specifically limited in the embodiments of the present application.

[0045] The quantum key needs to be distributed from the initial communication node to the target communication node.

[0046] Step 202, determine all paths starting from the start communication node and ending at the target communication node.

[0047] After the starting communication node and the target communication node are determined, all paths in the quantum key distribution network starting from the starting communication node and ending at the target communication node can be determined.

[0048] For example, Figure 1 In the quantum key distribution network shown, if the initial communication node is communication node 1 and the target communication node is communication node 10, all corresponding paths include: communication node 1->communication node 2->communication node 3->communication node 10, communication node 1->communication node 4->communication node 8->communication node 10, communication node 1->communication node 5->communication node 7->communication node 8->communication node 10, communication node 1->communication node 5->communication node 7->communication node 8->communication node 10, communication node 1->communication node 5->communication node 7->communication node 9->communication node 10, communication node 1->communication node 6->communication node 7->communication node 8->communication node 10, and communication node 1->communication node 6->communication node 7->communication node 9->communication node 10.

[0049] Step 203, determining multiple quantum key distribution paths based on all paths and key splitting parameters.

[0050] The key splitting parameter includes: a splitting number value. The key splitting parameter can be a preset value, such as the splitting number value is preset to 4.

[0051] According to the split number value in the key splitting parameter, multiple quantum key distribution paths with the same number of splits are selected from all paths. For example, Figure 1 In the quantum key distribution network shown, if the initial communication node is communication node 1, the target communication node is communication node 10, the number of all paths is 6, and the split number value is preset to 4, 4 paths are selected from the 6 paths as quantum key distribution paths.

[0052] When selecting multiple quantum key distribution paths with the same split quantity value from all paths, random selection can be performed according to the split quantity value, or multiple quantum key distribution paths with the smallest number of nodes can be selected from all paths according to the split quantity value. Multiple quantum key distribution paths can also be determined by other methods, which are not specifically limited in the embodiments of the present application.

[0053] Step 204: split the key according to the split quantity value to obtain a plurality of key components of the same number as the split quantity value.

[0054] The key is equally divided into multiple key components corresponding to the split quantity value. Of course, it can also be unequally divided, and divided into multiple key components of different lengths in proportion. The key can also be divided by other methods to obtain multiple key components, which is not specifically limited in the embodiments of the present application.

[0055] Step 205: Transmit multiple key components and key splitting parameters respectively through multiple quantum key distribution paths.

[0056] A key component and a key splitting parameter are transmitted to each quantum key distribution path. The target communication node can receive multiple key components and key splitting parameters transmitted by multiple target paths. When the number of key components counted by the target communication node is equal to the split number value in the key splitting parameter, a key is generated according to the multiple key components. The key generation operation can be a merging operation, etc.

[0057] For example, if the multiple quantum key distribution paths are quantum key distribution path 1, quantum key distribution path 2, quantum key distribution path 3, and quantum key distribution path 4, and the multiple key components are key component 1, key component 2, key component 3, and key component 4, key component 1 and key splitting parameters can be transmitted to quantum key distribution path 1, key component 2 and key splitting parameters can be transmitted to quantum key distribution path 2, key component 3 and key splitting parameters can be transmitted to quantum key distribution path 3, and key component 4 and key splitting parameters can be transmitted to quantum key distribution path 4. When the number of key components received by the target communication node is 4, which is equal to the split number value 4 in the key splitting parameter, the target communication node generates a quantum key according to the multiple key components.

[0058] A quantum key distribution method provided in an embodiment of the present application splits a quantum key, and transmits the multiple key components after the split to a target communication node through different quantum key distribution paths respectively. The communication nodes in different paths do not transmit a complete quantum key, and the communication nodes on each quantum key distribution path cannot see the complete quantum key, which can improve the security of quantum key distribution and reduce costs without introducing an additional quantum key management center.

[0059] In the above Figure 2 Based on the quantum key distribution method shown, an embodiment of the present application also provides another quantum key distribution method. The above step 203 determines multiple quantum key distribution paths according to all paths and key splitting parameters, which specifically includes the following steps.

[0060] Multiple quantum key distribution paths are determined based on the intersection of communication nodes in all paths and the split quantity value.

[0061] If the split number value is 4, according to the crossover of communication nodes in all paths and the multiple quantum key distribution paths determined by the split number value, there cannot be at least four quantum key distribution paths that pass through the same communication node, that is, any four quantum key distribution paths cannot have any crossover node, that is, the four key components cannot all pass through a communication node. This is because once the four key components all pass through a communication node, the communication node can generate a complete quantum key based on the four key components, resulting in a decrease in the security of quantum key distribution.

[0062] A quantum key distribution method provided in an embodiment of the present application does not allow all key components to pass through a communication node, which can further improve the security of quantum key distribution.

[0063] On the basis of the above embodiments, the embodiments of the present application further provide another quantum key distribution method. The steps in the above embodiments specifically include the following steps.

[0064] Multiple quantum key distribution paths are determined based on the intersection and network conditions of communication nodes in all paths and the number of split values.

[0065] On the basis of not allowing all key components to pass through one communication node, the embodiment of the present application also determines multiple quantum key distribution paths according to the network conditions of the communication nodes in all paths.

[0066] If there is a problem of poor network conditions of communication nodes in at least one path among all the paths, the path where the communication node with poor network conditions is located will be abandoned, so that the network conditions of the communication nodes in the multiple quantum key distribution paths finally determined are all good, which can respond to network emergencies of communication nodes in a timely manner and improve the stability of quantum key distribution.

[0067] It is also possible to determine multiple quantum key distribution paths based on the intersection of communication nodes in all paths, other problem conditions, and split quantity values.

[0068] A quantum key distribution method provided in an embodiment of the present application does not allow all key components to pass through a communication node, and takes into account the network conditions of the communication node, thereby improving the stability of quantum key distribution.

[0069] In the above Figure 2 Based on the quantum key distribution method shown, an embodiment of the present application also provides another quantum key distribution method. The method for determining the key splitting parameters in step 203 in the above embodiment specifically includes the following steps.

[0070] The key splitting parameters are determined according to the cross-conditions of the communication nodes in all the paths and / or the network conditions of the communication nodes in all the paths.

[0071] Discard the communication nodes with poor network conditions in all paths, regenerate the paths, and then determine the partial paths that meet the intersection requirements based on the intersection of the communication nodes in the regenerated paths. Then, based on the number of partial paths, determine the number of splits in the key splitting parameter, which should be less than or equal to the number of partial paths.

[0072] A quantum key distribution method provided in an embodiment of the present application determines the key splitting parameters through the intersection conditions and / or network conditions of communication nodes in all paths, so that multiple key components can be transmitted separately through multiple quantum key distribution paths, and the stability and security of quantum key distribution can be improved.

[0073] In the above Figure 2 Based on the quantum key distribution method shown in FIG. 1 , an embodiment of the present application further provides another quantum key distribution method. Figure 3 is a flow chart of a second quantum key distribution method provided in an embodiment of the present application, such as Figure 3 As shown, the key splitting parameters also include: a threshold value, the threshold value is less than the splitting quantity value; the above step 202, after determining all paths starting from the starting communication node and ending at the target communication node, specifically includes the following steps.

[0074] Step 301, determining multiple quantum key distribution paths according to all paths and split quantity values.

[0075] The specific implementation of this step is the same as the specific implementation of the above step 203, and will not be described in detail here.

[0076] It is also possible to determine multiple quantum key distribution paths based on the crossover of communication nodes in all paths and the split quantity value. It is also possible to determine multiple quantum key distribution paths based on the crossover of communication nodes in all paths, network conditions, and split quantity values.

[0077] Step 302: Perform secret sharing splitting of key splitting parameters on the quantum key to obtain a plurality of key components of the same number of splitting values.

[0078] In the embodiment of the present application, the Shamir threshold algorithm can be used to perform secret sharing splitting of key splitting parameters on the quantum key. For example, the Shamir threshold algorithm can be used to perform (3, 4) sharing splitting on the key, 3 is the threshold value, 4 is the splitting number value, that is, the quantum key is divided into four key components, and only three of the key components are needed to restore the original overall quantum key.

[0079] After determining the split number value, the threshold value can be determined according to the split number value. For example, when the split number value is 4, the threshold value can be 3 or 2; when the split number value is 5, the threshold value can be 4, 3 or 2.

[0080] Of course, other secret sharing schemes can also be used to split the quantum key, which is not specifically limited in the embodiments of the present application.

[0081] Step 303: transmit multiple key components and threshold values ​​through multiple quantum key distribution paths respectively.

[0082] After the target communication node receives a threshold number of key components, it can generate a quantum key.

[0083] A key component and a threshold value are transmitted to each quantum key distribution path. After receiving multiple key components of the threshold value, the target communication node can generate a quantum key based on the multiple key components. The key generation operation can restore the complete quantum key for the target communication node using the Shamir threshold algorithm.

[0084] For example, if the threshold value is 3 and the split number value is 4, although there are four quantum key distribution paths transmitting different key components, after the target communication node receives the three key components, it can use the Shamir threshold algorithm to recover the complete quantum key based on these three key components.

[0085] For example, if the initial communication node is communication node 1, the target communication node is communication node 10, and the four key components are K1, K2, K3, and K4 respectively, the starting communication node determines four quantum key distribution paths based on the network conditions and cross-conditions of the communication nodes in all paths and the number of split values, which are: communication node 1->communication node 2->communication node 3->communication node 10, communication node 1->communication node 4->communication node 8->communication node 10, communication node 1->communication node 5->communication node 7->communication node 8->communication node 10, communication node 1->communication node 6->communication node 7->communication node 9->communication node 10. Figure 4 is a schematic diagram of quantum key distribution provided by an embodiment of the present application, such as Figure 4 As shown, the initial communication node transmits K1, K2, K3, and K4 to these four paths respectively. Each quantum key distribution path adopts the single-hop relay principle to relay the key component to the target communication node. In the single-hop relay, each relay node only forwards the data without processing or modifying the data. When the target communication node receives the three key components, it can use the Shamir threshold algorithm to recover the complete quantum key and complete the quantum key distribution.

[0086] A quantum key distribution method provided by an embodiment of the present application, the quantum key to be distributed is split using the Shamir threshold algorithm, and after setting a suitable network routing strategy, it is relayed to the target communication node via different network paths. Since the quantum key transmitted is not a complete quantum key, the loss of control of a single relay node during the relay process will not cause the quantum key to be distributed to lose control. The selection of multiple routing paths makes it possible to restore the complete quantum key as long as the number of key components received by the target communication node is greater than or equal to the threshold value, even if there are failed relay nodes during the relay process. This solution does not require the addition of an additional management center to the existing quantum key distribution confidentiality system, reducing management costs. At the same time, the flexible selection of network paths can also greatly increase the reliability of quantum key distribution. At the same time, the flexible selection of routing strategies solves the problem of low efficiency of quantum key transmission in single-hop solutions.

[0087] The step division of the above methods is only for the purpose of clear description. When implemented, they can be combined into one step or some steps can be split and decomposed into multiple steps. As long as they include the same logical relationship, they are all within the scope of protection of this patent; adding insignificant modifications to the algorithm or process or introducing insignificant designs without changing the core design of the algorithm and process are all within the scope of protection of this patent.

[0088] The present application embodiment relates to an initial communication node, Figure 5 is a schematic diagram of the structure of the starting communication node provided in the embodiment of the present application, such as Figure 5 As shown, it includes: at least one processor 501; and a memory 502 that is communicatively connected to the at least one processor 501; wherein the memory 502 stores instructions that can be executed by the at least one processor 501, and the instructions are executed by the at least one processor 501, so that the at least one processor 501 can execute the quantum key distribution method in the above-mentioned embodiments.

[0089] The memory 502 and the processor 501 are connected in a bus manner. The bus may include any number of interconnected buses and bridges. The bus connects various circuits of one or more processors and memories together.

[0090] The embodiment of the present application relates to a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the above method embodiment is implemented.

[0091] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0092] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present application, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present application.

Claims

1. A quantum key distribution method, characterized in that: The method comprises: Determine the target communication nodes and quantum keys; Determine all paths starting from the starting communication node and ending at the target communication node; Determine multiple quantum key distribution paths according to all the paths and key splitting parameters; the key splitting parameters include: a splitting quantity value; Splitting the quantum key according to the split quantity value to obtain a plurality of key components of the split quantity value; The multiple key components and the key splitting parameters are transmitted respectively through the multiple quantum key distribution paths, so that after the target communication node receives the multiple key components and the key splitting parameters, it generates the quantum key.

2. The quantum key distribution method according to claim 1, characterized in that: Determining multiple quantum key distribution paths according to all the paths and the key splitting parameters includes: According to the intersection of communication nodes in all the paths and the split quantity value, multiple quantum key distribution paths are determined.

3. The quantum key distribution method according to claim 2, characterized in that: Determining multiple quantum key distribution paths according to the intersection of communication nodes in all the paths and the split quantity value includes: According to the intersection conditions and network conditions of the communication nodes in all the paths and the split quantity value, multiple quantum key distribution paths are determined.

4. The quantum key distribution method according to claim 1, characterized in that: The method for determining the key splitting parameters includes: The key splitting parameter is determined according to the cross-conditions of the communication nodes in all the paths and / or the network conditions of the communication nodes in all the paths.

5. The quantum key distribution method according to claim 1, characterized in that: The key splitting parameter further includes: a threshold value, the threshold value is less than the splitting quantity value; after determining all paths starting from the starting communication node and ending at the target communication node, the method includes: Determining multiple quantum key distribution paths according to all the paths and the split quantity values; Performing secret sharing splitting of the key splitting parameter on the quantum key to obtain a plurality of key components of the number of splitting values; The multiple key components and the threshold value are transmitted respectively through the multiple quantum key distribution paths, so that the target communication node generates the quantum key after receiving the multiple key components of the threshold value.

6. The quantum key distribution method according to claim 5, characterized in that: The step of performing secret sharing splitting of the key splitting parameter on the quantum key to obtain a plurality of key components of the number of splitting values ​​includes: The quantum key is subjected to secret sharing splitting of the key splitting parameter using the Shamir threshold algorithm to obtain a plurality of key components of the splitting quantity value.

7. The quantum key distribution method according to claim 5, characterized in that: The threshold value is determined according to the split quantity value.

8. A quantum key distribution network, characterized in that: include: A plurality of communication nodes; communication intercommunication between the plurality of communication nodes; The starting communication node is any one of the multiple communication nodes, and the starting communication node is used to execute the quantum key distribution method described in any one of claims 1 to 7.

9. A starting communication node, characterized in that: include: at least one processor; as well as, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the quantum key distribution method described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the quantum key distribution method according to any one of claims 1 to 7 is implemented.

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