Multi-user QKD system and method with priority sorting function

Abstract

The present invention discloses a multi-user QKD system and method with a priority sorting function, and relates to the field of communication technology. It includes a user center, a quantum security gateway, a control center, and a quantum key distribution center. The terminal device in the user center will submit a quantum key request when there is a demand. The user center packages multiple key requests into a data packet, and the quantum security gateway generates a quantum key shared with the control center to encrypt the quantum key request data packet and then send it to the control center. The control center compares the number of key requests with the number of remaining keys stored in the key pool in the quantum key distribution center at the current moment, and distributes keys to the different key request numbers of each user terminal in the user center according to the priority. The present invention effectively improves the work efficiency of the entire quantum key distribution process while ensuring safety and reliability by packaging multiple quantum key requests and encrypting them with quantum keys.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a multi-user QKD system and method with a priority sorting function. Background Art

[0002] Quantum communication is one of the scientific and technological focuses of international attention in today's era. Quantum technology uses artificial observation and control of microscopic particle systems such as photons and electrons and their quantum states, and uses unique physical phenomena such as quantum superposition and quantum entanglement to obtain, transmit and process information in a way that cannot be achieved by classical theory. Quantum key distribution is the most popular and most widely used technology in quantum communication. Since the publication of the BB84 protocol in 1984, quantum key distribution technology has developed rapidly in the past 30 years, and has been combined with many fields to derive many applications.

[0003] The current quantum communication network architecture basically combines quantum keys with the user data transmission process to ensure that eavesdroppers cannot use their own technology to crack the data packets when they intercept them, thus achieving the purpose of secure transmission. Although quantum keys do play a protective role in the data encryption process, since the quantum communication network still uses classical equipment and some links, these places may also become vulnerabilities for eavesdroppers to attack.

[0004] In 2022, Chen et al. proposed a quantum key distribution network routing scheme based on application-level sorting, in which quantum key distribution, or QKD, uses the characteristics of quantum mechanics to ensure communication security. It enables both communicating parties to generate and share a random, secure key to encrypt and decrypt messages. This scheme can handle the situation where the quantum key distribution network has different key quantity requirements under multiple users in parallel. Compared with the general scheme, this scheme improves the efficiency of key distribution, but fails to take into account the confidentiality issues of users when transmitting data and requesting instructions between modules. Eavesdroppers can achieve the purpose of destroying key distribution by directly attacking the transmission link or node.

[0005] Therefore, there is an urgent need to propose a multi-user QKD system and method with priority sorting function to solve the above problems. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a multi-user QKD system and method with a priority sorting function.

[0007] The technical solution of the present invention is achieved in this way:

[0008] Multi-user QKD system with prioritization,

[0009] Includes user center, quantum security gateway, control center and quantum key distribution center;

[0010] The user center, the quantum security gateway, the control center, the quantum key distribution center, and the user center are connected in sequence through classical channels to form a ring network structure;

[0011] A quantum channel is provided between the quantum security gateway and the control center, and a quantum channel is provided between the quantum key distribution center and the user center;

[0012] The user center includes multiple user end devices, and the user center collects quantum key requests from multiple user end devices and packages them into quantum key request data packets and sends them to the quantum security gateway;

[0013] The quantum security gateway encrypts the quantum key request data packet into an encrypted data packet using the quantum key, and sends the encrypted data packet to the control center;

[0014] The control center decrypts the encrypted data packet into a quantum key request data packet, prioritizes the user terminal devices according to the number of quantum key requests of each user terminal device in the quantum key request data packet, obtains the ranking result and sends it to the quantum key distribution center;

[0015] The quantum key distribution center generates quantum keys and sends the quantum keys to user end devices in sequence according to the sorting results.

[0016] Classical channels are used to transmit routine requests, data with low confidentiality requirements, or data encrypted by quantum keys, while quantum keys can be transmitted through dedicated, highly secure quantum channels.

[0017] As a further optimization of the above solution, each user-end device is connected to each other through classical channels and quantum channels to achieve signal transmission. At the same time, the transmitted information is encrypted through the quantum channel using quantum keys.

[0018] As a further optimization of the above solution, the quantum security gateway includes a first quantum key distribution device and a gateway. The gateway here refers to a conventional gateway.

[0019] The gateway receives a quantum key request data packet from the user center and sends it to the first quantum key distribution device through a classical channel; the first quantum key distribution device generates a quantum key according to the quantum key request, and then sends the quantum key to the gateway through a quantum channel; the gateway uses the quantum key to pack the quantum key request data packet into an encrypted data packet, and sends the encrypted data packet to the control center.

[0020] As a further optimization of the above solution, the control center includes a data analysis module, a priority sorting module and a failure retry module;

[0021] Any two modules among the data analysis module, the priority sorting module and the failure retry module are connected to each other, the data analysis module sends signals to the priority sorting module and the failure retry module in one direction, the priority sorting module sends signals to the failure retry module in one direction, and the failure retry module does not send signals to the other two modules;

[0022] The data analysis module is used to analyze the quantum key request data packet and the number of quantum key requests in the key pool, and control the priority sorting module and the failure retry module;

[0023] The priority sorting module is based on the analysis results of the data analysis module.

[0024] The priority sorting module prioritizes a plurality of user terminal devices according to the analysis result of the data analysis module and the number of quantum key requests; wherein, if the number of quantum key requests is smaller, the priority of the corresponding user terminal device is higher, and vice versa, the priority of the user terminal device is lower;

[0025] The failure retry module is used to receive a failure signal sent from the data analysis module or the priority sorting module, and send a request to the quantum security gateway to re-acquire the encrypted data packet.

[0026] As a further optimization of the above scheme,

[0027] The quantum key distribution center includes a key pool and a plurality of second quantum key distribution devices; the key pool is connected to the second quantum key distribution device via a quantum channel;

[0028] The key pool stores a plurality of quantum keys; when the number of quantum keys in the key pool is less than the number of quantum key requests in the quantum key request data packet, the second quantum key distribution device generates a quantum key and transmits it to the key pool through a quantum channel.

[0029] The present invention also discloses a multi-user QKD method with a priority sorting function, which is applied to the multi-user QKD system with a priority sorting function mentioned above;

[0030] The steps include:

[0031] Step 1, submit a request: the user terminal device in the user center sends a quantum key request, and the quantum key requests sent by different user terminal devices at the same time are aggregated and packaged into a quantum key request data packet, and sent to the quantum security gateway; compared to executing communication between devices once for one request, packaging multiple requests and then sending them out can reduce the loss caused when the device is connected, reduce the occupancy of the communication channel, and effectively improve the working efficiency of the device.

[0032] Step 2: Data packet encryption: After receiving the quantum key request data packet, the quantum security gateway generates a quantum key through the first quantum key distribution device, and the gateway shares the quantum key with the control center through the quantum channel;

[0033] At the same time, the gateway uses the quantum key to encrypt the quantum key request data packet to obtain an encrypted data packet, and sends the encrypted data packet to the control center through a classical channel;

[0034] Encrypting request data packets with quantum keys can prevent network eavesdroppers from maliciously tampering with or stealing data, and improve the security, confidentiality, and reliability of quantum key request data packets during transmission.

[0035] Step 3, data analysis: the control center uses the quantum key shared by the quantum security gateway to decrypt the encrypted data packet to obtain the key request data in the quantum key request data packet;

[0036] At the same time, the control center queries the number of remaining keys in the key pool in the quantum key distribution center;

[0037] Step 4, data comparison: the control center compares the number of quantum key requests in the quantum key request data packet and the number of remaining keys in the key pool through the data analysis module;

[0038] If the number of quantum key requests is less than or equal to the number of remaining keys, the quantum key request data packet is directly sent to the quantum key distribution center and step six is ​​executed; otherwise, step five is executed;

[0039] Step 5: Prioritization: The control center uses the priority sorting module to prioritize the user terminal devices, and then sends the quantum key request data packet and the priority sorting result to the quantum key distribution center, and executes step 6;

[0040] Step 6, key distribution: if the quantum key distribution center only receives the quantum key request data packet, it distributes the quantum key in the key pool to the user terminal device of the user center through the quantum channel according to the quantum key request in the quantum key request data packet;

[0041] Otherwise, the quantum key distribution center distributes the existing quantum keys to the user terminal devices with high priority through the quantum channel according to the received quantum key request data packets and the priority sorting results; when the number of quantum keys in the key pool is 0, the quantum key distribution center calls multiple second quantum key distribution devices to generate quantum keys according to the remaining quantum key requirements, and distributes them to the user terminal devices that were not originally allocated quantum keys.

[0042] As a further optimization of the above scheme, in step five, the priority sorting method is: prioritize the user-end devices by comparing the number of quantum key requests from different user-end devices, wherein, if the number of quantum key requests is smaller, the priority of the corresponding user-end device is higher, and vice versa, the priority of the user-end device is lower, so as to ensure that more user-end devices can obtain quantum keys as early as possible.

[0043] As a further optimization of the above scheme, the priority is divided into five levels from high to low, from I to V. The system determines the number of second quantum key distribution devices to be called according to the priority. When the priority sorting function is used, there are at least two levels of priority, namely, level I and level II. In this case, the remaining keys in the key pool are used to distribute keys to level I user-end devices, and the remaining requested user-end devices are level II. At this time, 25% of the second quantum key distribution devices are called for quantum key generation operations, and the generated quantum keys are used to distribute to level II user-end devices. Similarly, if the user-end devices are sorted into three priorities, when generating quantum keys, level II and level III call 25% and 50% of the second quantum key distribution devices respectively; four priorities call 25%, 50% and 75% respectively; five priorities call 25%, 50%, 75% and 100% respectively.

[0044] Dynamically calling the number of running second quantum key distribution devices according to priority can also ensure production efficiency while avoiding waste of resources and energy.

[0045] As a further optimization of the above scheme, when the control center fails to perform a decryption operation on the encrypted data packet, or when the data analysis module produces no results, garbled characters, or stuck operations when reading and analyzing the decrypted quantum key request data packet, or when the priority sorting module produces no results in sorting the key request data, the failure retry module is started, and the failure retry module sends a retry request to the quantum security gateway, and the first quantum key distribution device regenerates the quantum key to encrypt the quantum key request data packet, and sends the encrypted data packet and the quantum key to the control center again.

[0046] As a further optimization of the above scheme, if the number of failed retry operations exceeds the preset number, the current quantum key request is terminated, and the quantum security gateway sends a retry request to the user center, which re-initiates the quantum key request to prevent the device from crashing due to continuous resending of requests when errors occur in data transmission.

[0047] Compared with the prior art, the present invention achieves the following beneficial effects:

[0048] (1) In the present invention, the quantum key request is packaged and compressed before transmission, which improves the work efficiency compared to transmitting each request once;

[0049] (2) The present invention uses quantum keys to encrypt request data packets, thus preventing eavesdroppers from attacking the system at this stage and destroying the entire quantum key request process;

[0050] (3) In the present invention, the startup status of the device can be determined according to actual needs, thereby saving power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 is a system block diagram of the quantum key distribution system of the present invention;

[0052] Figure 2 It is a workflow diagram of the quantum key distribution method of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clear, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] like Figure 1 As shown, this embodiment provides a multi-user QKD system with a priority sorting function, including a user center, a quantum security gateway, a control center, and a quantum key distribution center;

[0055] The user center, the quantum security gateway, the control center, the quantum key distribution center, and the user center are connected in sequence through classical channels to form a ring network structure;

[0056] A quantum channel is set up between the quantum security gateway and the control center, and a quantum channel is set up between the quantum key distribution center and the user center;

[0057] Classical channels are used to transmit routine requests, data with low confidentiality requirements, or data encrypted by quantum keys, while quantum keys can be transmitted through dedicated, highly secure quantum channels.

[0058] The user center includes multiple user terminal devices, and the user center collects quantum key requests from multiple users and packages them into quantum key request data packets and sends them to the quantum security gateway; in this embodiment, the user center includes multiple user terminal devices; each user terminal device is connected to each other through a classical channel and a quantum channel to achieve signal transmission, and at the same time, the transmitted information is encrypted through the quantum channel using a quantum key; the user sends a quantum key request and receives a quantum key through the user terminal device.

[0059] The quantum security gateway includes a first quantum key distribution device and a gateway. The gateway here refers to a conventional gateway. The gateway receives a quantum key request data packet from the user center and sends it to the first quantum key distribution device through a classical channel. The first quantum key distribution device generates a quantum key according to the quantum key request, and then sends the quantum key to the gateway through a quantum channel; the gateway uses the quantum key to package the quantum key request data packet into an encrypted data packet, and sends the encrypted data packet to the control center.

[0060] The control center decrypts the encrypted data packet into a quantum key request data packet, prioritizes the user terminal devices according to the number of quantum key requests of each user terminal device in the quantum key request data packet, obtains the ranking result and sends it to the quantum key distribution center;

[0061] In this embodiment, the control center includes a data analysis module, a priority sorting module and a failure retry module;

[0062] Any two modules among the data analysis module, the priority sorting module and the failure retry module are connected to each other, the data analysis module sends signals to the priority sorting module and the failure retry module in one direction, the priority sorting module sends signals to the failure retry module in one direction, and the failure retry module does not send signals to the other two modules;

[0063] The data analysis module is used to analyze the quantum key request data packet and the number of quantum key requests in the key pool, and control the priority sorting module and the failure retry module;

[0064] The priority sorting module prioritizes a plurality of user terminal devices according to the analysis result of the data analysis module and the number of quantum key requests; wherein, if the number of quantum key requests is smaller, the priority of the corresponding user terminal device is higher, and vice versa, the priority of the user terminal device is lower;

[0065] The failure retry module is used to receive a failure signal sent from the data analysis module or the priority sorting module, and send a request to the quantum security gateway to re-acquire the encrypted data packet.

[0066] The quantum key distribution center generates quantum keys and sends the quantum keys to the user end devices in sequence according to the sorting results. In this embodiment, the quantum key distribution center includes a key pool and a plurality of second quantum key distribution devices; the key pool and the second quantum key distribution devices are connected via a quantum channel;

[0067] The key pool stores a plurality of quantum keys; when the number of quantum keys in the key pool is less than the number of quantum key requests in the quantum key request data packet, the second quantum key distribution device generates a quantum key and transmits it to the key pool through a quantum channel.

[0068] This embodiment also discloses a multi-user QKD method with a priority sorting function, which is applied to the above-mentioned multi-user QKD system with a priority sorting function;

[0069] like Figure 2 As shown, the following steps are included:

[0070] Step 1, submit a request: the user terminal device in the user center sends a quantum key request; the quantum key requests sent by different user terminal devices at the same time are aggregated and packaged into a quantum key request data packet, and sent to the quantum security gateway; it is assumed that 1,000 user terminal devices in the user center have sent requests; compared to executing communication between devices once for one request, packaging multiple requests and then sending them out can reduce the loss caused when the devices are connected, reduce the occupancy of the communication channel, and effectively improve the working efficiency of the equipment.

[0071] Step 2: Data packet encryption: After receiving the data packet, the quantum security gateway generates a quantum key through the first quantum key distribution device, and the gateway shares the quantum key with the control center through the quantum channel;

[0072] At the same time, the gateway uses the quantum key to encrypt the quantum key request data packet to obtain an encrypted data packet, and sends the encrypted data packet to the control center through a classical channel;

[0073] Encrypting request data packets with quantum keys can prevent network eavesdroppers from maliciously tampering with or stealing data, and improve the security, confidentiality, and reliability of quantum key request data packets during transmission.

[0074] Step 3: Data analysis: The control center uses the quantum key shared by the quantum security gateway to decrypt the encrypted data packet and obtain the key request data in the data packet;

[0075] At the same time, the control center queries the number of remaining keys in the key pool in the quantum key distribution center;

[0076] In this embodiment, when the control center fails to perform a decryption operation on an encrypted data packet, or when the data analysis module produces no results, garbled characters, or stuck operations when reading and analyzing the decrypted quantum key request data packet, or when the priority sorting module produces no results when sorting the key request data, a failure retry module is started, and the failure retry module sends a retry request to the quantum security gateway, and the first quantum key distribution device regenerates the quantum key to encrypt the quantum key request data packet, and sends the encrypted data packet and the quantum key to the control center again; if the failed retry operation occurs more than three times, the current quantum key request is terminated, and the quantum security gateway sends a retry request to the user center, and the user center re-initiates the quantum key request to prevent the device from crashing due to continuous resending of requests when an error occurs in data transmission.

[0077] Step 4: Data comparison: The control center compares the number of quantum key requests in the quantum key request data packet with the number of remaining keys N in the key pool through the data analysis center;

[0078] If the number of quantum key requests is less than or equal to the number of remaining keys, the data packet is directly sent to the quantum key distribution center and step 6 is executed; otherwise, step 5 is executed;

[0079] Step 5: Prioritization: The control center uses the priority sorting module to prioritize the user-end devices, then sends the data packets and priority sorting results to the quantum key distribution center, and executes step 6;

[0080] In this embodiment, the priority is divided into five levels from I to V from high to low, and the priority sorting method is: the user terminal devices are prioritized by comparing the number of key requests of different user terminal devices, wherein, if the number of quantum key requests is smaller, the priority of the corresponding user terminal device is higher, and vice versa, the priority of the user terminal device is lower, so as to ensure that more user terminal devices can obtain quantum keys as early as possible.

[0081] Step 6: Key distribution: If the quantum key distribution center only receives the quantum key request data packet, it will distribute the quantum key in the key pool to the user terminal device of the user center through the quantum channel according to the quantum key request in the quantum key request data packet;

[0082] Otherwise, the quantum key distribution center distributes the existing quantum keys to the user terminal devices with high priority through the quantum channel according to the received quantum key request data packets and the priority sorting results; when the number of quantum keys in the key pool is 0, the quantum key distribution center calls multiple second quantum key distribution devices to generate quantum keys according to the remaining quantum key requirements (i.e. 1000-N), and distributes them to the user terminal devices that were not originally allocated quantum keys.

[0083] The quantum key distribution method provided in this embodiment packages multiple quantum key requests and encrypts them with quantum keys, thereby effectively improving the work efficiency of the entire quantum key distribution process while ensuring security and reliability.

[0084] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A multi-user QKD system with a prioritization function, characterized in that Includes user center, quantum security gateway, control center and quantum key distribution center; The user center, the quantum security gateway, the control center, the quantum key distribution center, and the user center are connected in sequence through classical channels to form a ring network structure; A quantum channel is provided between the quantum security gateway and the control center, and a quantum channel is provided between the quantum key distribution center and the user center; The user center includes multiple user terminal devices, and the user center collects quantum key requests from multiple user terminal devices and packages them into quantum key request data packets and sends them to the quantum security gateway; The quantum security gateway encrypts the quantum key request data packet into an encrypted data packet using the quantum key, and sends the encrypted data packet to the control center; The control center decrypts the encrypted data packet into a quantum key request data packet, prioritizes the user terminal devices according to the number of quantum key requests of each user terminal device in the quantum key request data packet, obtains the ranking result and sends it to the quantum key distribution center; The quantum key distribution center generates quantum keys and sends the quantum keys to user end devices in sequence according to the sorting results; The control center includes a data analysis module, a priority sorting module and a failure retry module; The data analysis module is used to analyze and compare the number of quantum key requests in the quantum key request data packet and the number of remaining keys in the key pool, and control the priority sorting module and the failure retry module; The priority sorting module prioritizes a plurality of user terminal devices according to the analysis result of the data analysis module and the number of quantum key requests; wherein, if the number of quantum key requests is smaller, the priority of the corresponding user terminal device is higher, and vice versa, the priority of the corresponding user terminal device is lower; The failure retry module is used to receive a failure signal sent from the data analysis module or the priority sorting module, and send a request to the quantum security gateway to re-acquire the encrypted data packet.

2. The multi-user QKD system with priority sorting function according to claim 1, characterized in that: Each user-end device is connected to each other through classical channels and quantum channels.

3. The multi-user QKD system with priority sorting function according to claim 2, characterized in that: The quantum security gateway includes a first quantum key distribution device and a gateway; The gateway receives a quantum key request data packet from the user center and sends it to the first quantum key distribution device through a classical channel; the first quantum key distribution device generates a quantum key according to the quantum key request and then sends the quantum key to the gateway through a quantum channel; The gateway uses the quantum key to pack the quantum key request data packet into an encrypted data packet, and sends the encrypted data packet to the control center.

4. The multi-user QKD system with priority sorting function according to claim 3, characterized in that: The quantum key distribution center includes a key pool and a plurality of second quantum key distribution devices; the key pool is connected to the second quantum key distribution device via a quantum channel; The key pool stores a plurality of quantum keys; when the number of quantum keys in the key pool is less than the number of quantum key requests in the quantum key request data packet, the second quantum key distribution device generates a quantum key and transmits it to the key pool through a quantum channel.

5. A multi-user QKD method with a priority sorting function, characterized in that Applicable to a multi-user QKD system with a priority sorting function as claimed in any one of claims 1 to 4; The steps include: Step 1: Submit a request: The user terminal device in the user center sends a quantum key request, and the quantum key requests sent by different user terminal devices at the same time are aggregated and packaged into a quantum key request data packet, and sent to the quantum security gateway; Step 2: Data packet encryption: After receiving the quantum key request data packet, the quantum security gateway generates a quantum key through a first quantum key distribution device, and the gateway shares the quantum key with the control center through a quantum channel; At the same time, the gateway uses the quantum key to encrypt the quantum key request data packet to obtain an encrypted data packet, and sends the encrypted data packet to the control center through a classical channel; Step 3, data analysis: the control center uses the quantum key shared by the quantum security gateway to decrypt the encrypted data packet to obtain the key request data in the quantum key request data packet; At the same time, the control center queries the number of remaining keys in the key pool in the quantum key distribution center; Step 4, data comparison: the control center compares the number of quantum key requests in the quantum key request data packet and the number of remaining keys in the key pool through the data analysis module; If the number of quantum key requests is less than or equal to the number of remaining keys, the quantum key request data packet is directly sent to the quantum key distribution center and step six is ​​executed; Otherwise, go to step 5; Step 5, Priority sorting: The control center uses the priority sorting module to prioritize the user terminal devices, then sends the quantum key request data packet and the priority sorting result to the quantum key distribution center, and executes step 6; Step 6, key distribution: if the quantum key distribution center only receives the quantum key request data packet, then according to the quantum key request in the quantum key request data packet, the quantum key in the key pool is distributed to the user terminal device of the user center through the quantum channel; Otherwise, the quantum key distribution center distributes the existing quantum keys to the user terminal devices with high priority through the quantum channel according to the received quantum key request data packets and the priority sorting results; when the number of quantum keys in the key pool is 0, the quantum key distribution center calls multiple second quantum key distribution devices to generate quantum keys according to the remaining quantum key requirements, and distributes them to the user terminal devices that were not originally allocated quantum keys.

6. The multi-user QKD method with priority sorting function according to claim 5, characterized in that: In step five, the priority sorting method is: prioritize the user terminal devices by comparing the number of quantum key requests of different user terminal devices, wherein, if the number of quantum key requests is smaller, the priority of the corresponding user terminal device is higher, and vice versa, the priority of the user terminal device is lower.

7. The multi-user QKD method with priority sorting function according to claim 6, characterized in that: The priorities are divided into five levels from I to V from high to low.

8. The multi-user QKD method with priority sorting function according to claim 7, characterized in that: When the control center fails to decrypt the encrypted data packet, or the data analysis module produces no results, garbled characters, or stuck operations when reading and analyzing the decrypted quantum key request data packet, or the priority sorting module produces no results when sorting the key request data, the failure retry module is started, and the failure retry module sends a retry request to the quantum security gateway, and the first quantum key distribution device regenerates the quantum key to encrypt the quantum key request data packet, and sends the encrypted data packet and the quantum key to the control center again.

9. The multi-user QKD method with priority sorting function according to claim 8, characterized in that: If the number of failed retry operations exceeds the preset number, the current quantum key request is terminated, and the quantum security gateway sends a retry request to the user center, which then re-initiates the quantum key request.

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