The Research Of Key Technologies For Secure Key Distillation In Satellite-to-ground Quantum Secure Communication

Quantum key distribution(QKD)technology,based on the uncertainty theory,nocloning theorem and other quantum mechanics,by encoding,transmitting and measuring the information included in quantum states,can generate information-theoretical secure keys for the communication parties.Since C.H.Bennett and G.Brassard proposed the first QKD protocol in 1984(BB84 protocol),research on QKD has attracted worldwide attention.Especially,the achievement of China Backbone Quantum Network from Beijing to Shanghai and also the ”Micius” quantum Scientific experimental satellite extends the quantum communication network from a ground-based regional network to a global-scale quantum communication network relayed by the quantum satellite.Nowadays QKD technology is rapidly developed and almost ready for the commercial application,but there are still some potential security threats existed,which may be caused by the technical limitations or imperfect design and implementation of the protocols.The research on security threats of the realistic QKD system mainly and also the research on the design of QKD protocols mainly focus on quantum physical communication phase,while only few researches is focused on the secure key extraction phase.Also,some obvious flaws,such as the chosed random string in privacy amplification procedure cannot meet the system security requirement and some systems haven't realized the information-theoretical-secure authentication procedure,are existed in the design of key extraction in many realistic QKD systems.The research of key distillation technologies has to towards the high relatively moving,high channel loss,and limited computational and storage resource satellite-ground quantum secure communication system in the future.Towards to the satellite-to-ground QKD experiment between Micius and Graz ground station,this paper mainly focuses on the fundamental research and application tests about the secure key distillation technologies in QKD,including time synchronization,privacy amplification and information-theoretical secure authentication.The main achievements are shown as follows:1.Research on the high accurate time synchronization technology.Firstly,towards to the entanglement based QKD system with fixed spatial relationship,we propose a time synchronization scheme working with PPS signals.Secondly,in this paper,we design and implement a time-synchronization algorithm working with synchronization pulses,which can automatically correct the communication delay in the satellite-to-ground QKD system with dynamic spatial relationship,called as Peak-tracking algorithm.The results show that the proposed algorithm can fast and accurate map the detected pluses to the transmitted ones.2.Research on privacy amplification technology.Firstly,we propose and implement a novel certified privacy amplification technology.which has great potential application value in satellite based QKD system.Secondly,we propose a Fixed scale FFT based privacy amplification algorithm(Fit-PA),and firstly optimize the implement of Fit-PA algorithm in the multi-core platform.Experimental results show that Fit-PA algorithm can meet the performance requirements of GHz high-speed QKD systems.3.Research on the information-theoretical secure(ITS)authentication technology.Based on the fast Number-theoretic transforms(NTT)technology,we propose an almost strongly universal(N-ASU)hash function.Based on N-ASU hash function,we design and implement the NTT based ITS authentication algorithm,called as N-Auth.Results show that N-Auth algorithm are around thousand times faster than the classical algorithms.4.Free space QKD experiment.Towards the secure communication between Micius and Graz ground station,firstly,combining the previous technologies,we proposed and implemented the secure key extraction scheme between Micius satellite and Graz ground station,and finished the application tests and very nice results were achieved.Secondly,we proposed the calculation method of basis deviation angle for the ground stations,which ensured the real-time polarization alignment between Micius and the ground station and kept the stabilization of the satellite-to-ground QKD system.Finally,we proposed the implementation scheme of certified privacy amplification algorithm and N-Auth algorithm for quantum satellites and evaluated the performance of the algorithms.The results show that our proposed secure key distillation technologies can meet the security and performance requirements very well for the resource limited satellite based QKD systems.This work effectively and successfully supported the first intercontinental quantum secure video conference.The achievements of this paper,have huge theoretical significance and application value,and can be used for the design and implementation of the realistic QKD systems in the future,especially in the high-speed satellite-to-ground QKD systems with limited resources.