The Research Of Key Technologies For Networking Of Low-Orbit Quantum Key Distribution Constellation Based On Decoy States BB84 Protocol

Quantum key distribution(QKD)technology uses the basic principles of quantum mechanics such as the principle of quantum uncertainty and the non cloning of unknown quantum states to encode,transmit and measure the information of quantum states,so as to distribute the key of information-theoretical security for both sides of communication.With the development of quantum computing,the security of public key cryptosystem based on complex mathematical computing is in threat.Since the first practical QKD protocol,BB84 protocol,was proposed,QKD technology has attracted extensive attentions all over the world because of its unconditional security.In particular,China’s Beijing-to-Shanghai quantum line and Micius Quantum Science Experimental satellites represent milestones in ground and space QKD applications respectively.The two quantum application projects have laid a solid foundation for the progress of China’s quantum network in the future,and will play an important role in national defense,government affairs,finance,commerce and other fields.QKD technology makes use of the characteristics of quantum mechanics,which can generate unconditionally secure keys in information theory for both communication parties to ensure the communication security.It is of great significance in combating quantum computing and ensuring the security of future communication.However,the QKD technology based on ground communication network is difficult to build an intercontinental QKD network because the coverage is shortened caused by optical channel loss.The in-orbit experiment of Micius has successfully proved the feasibility of intercontinental QKD using satellites.Therefore,the deployment of QKD constellation has become an important way to establish a global QKD network.The research on the networking of QKD constellation is of great significance for the construction of global QKD network.At present,in the actual deployment of QKD constellation,there are the following problems:1.Bad weather conditions increase the channel attenuation of satellite-to-ground QKD,which makes it too low to meet the needs of users.Improving the satellite-toground QKD key rates under meteorological interference is an important problem faced by QKD constellation.2.Satellite resources and user geographical location limit the access efficiency of constellation to ground users.The research on the access between constellation and ground users is of great significance to improve the total key sizes of constellation-toground.3.The key resource of inter-satellite link seriously restricts the traffic and scope of inter-satellite key routing.The existing QKD network routing algorithm is difficult to solve this problem.The research on the routing algorithm based on inter-satellite link key resource distribution is an important basis to support the networking of QKD constellation.4.The key sizes of satellite-to-ground and inter-satellite QKD is closely related to the constellation configuration.Optimizing the constellation configuration can improve the key sizes of satellite-to-ground and inter-satellite QKD,which is of great significance to improve the networking ability of QKD constellation.Based on the above problems,this paper has carried out the following research:1.The optimization technology of key size per revolution of satellite-to-ground QKD based on decoy states BB84 protocol is studied.Firstly,the key rate per revolution model under satellite-to-ground dynamic channel is established;Then,the QKD key size optimization algorithm of decoy states BB84 protocol based on coordinate descent method is proposed;Finally,the key size per revolution of satellite-to-ground QKD under different meteorological attenuation conditions is simulated.The results show that the optimized satellite-toground QKD can better adapt to the changes of meteorological conditions.In the case of no meteorological attenuation,the key size per revolution is about 150%higher than that of Micius,while in the case of meteorological attenuation of 10dB,the key size per revolution is nearly 200% higher than that of Micius.2.The user access selection algorithm of low Earth orbit(LEO)QKD constellation is studied.Firstly,an optimization method of QKD constellation user access problem based on sliding time window mechanism is proposed;Secondly,according to the exponential explosion characteristics of QKD constellation user access selection problem,a QKD constellation user access solution algorithm is proposed-the constellation to ground user access selection problem is decomposed into multiple subproblems,and each subproblem can be solved by the longest path algorithm;Finally,the user access of LEO QKD constellation is simulated.The results show that the algorithm can select the appropriate satellite access for each ground station,which shows that the access with large amount of satellite ground QKD key sizes per revolution is selected with a large frequency.3.The routing algorithm of LEO QKD constellation based on inter-satellite key resources is studied.Firstly,an information dissemination mechanism of LEO QKD constellation network state based on state request and hybrid update strategy is proposed;Secondly,a graph theory model of inter-satellite multipath routing in QKD constellation is proposed;Then,a traffic control algorithm of QKD constellation based on link load is proposed;Finally,the inter-satellite routing algorithm of QKD constellation is simulated.The results show that the routing algorithm can stably exchange keys for ground users and meet the key exchange needs of most users.The main reason for limiting the key exchange needs is that the key sizes per revolution of inter-satellite QKD is too low,so that the key can not be relayed in a large range through the inter-satellite link.4.The configuration optimization of LEO constellation based on night QKD is studied.Firstly,the effect of orbit parameters on the key sizes per revolution of satelliteto-ground QKD is analyzed.In order to ensure that the satellite can generate quantum key with the ground station during a year,the satellite should operate in low orbit sunsynchronous orbit;Then,the optimization of QKD satellite key sizes per revolution based on sub-satellite point trajectory of sun-synchronous repeating orbit is studied;Finally,the relationship between inter-atellite QKD key sizes per revolution and constellation configuration is analyzed and simulated.A method to increase the inter-planar QKD key sizes per revolution by adjusting the phase difference between satellites is proposed.