Security Research On Quantum Key Distribution

Communication security has a vital significance in the current highly developed information era.The traditional cryptographic systems,which rely on computational complexity,are facing more challenges due to the exponential growth of computer processing power and the emergence of quantum computers.Therefore,quantum key distribution(QKD),which builds its theoretically unconditional security on the principles of quantum physics has become a key area of research.Since the proposal of the BB84 protocol in 1984,QKD has made significant progress both theoretically and experimentally.However,unavoidable flaws in the preparation and measurement of quantum states in realworld devices not only impede the optimization and improvement of efficiency performance but also lead to security loopholes in practical QKD systems.The thesis discusses how to analyze imperfections during quantum state preparation and measurement,and how to consider these identified flaws in the security proof of quantum key distribution.The main research topics can be summarized as following points:(1)The effects of non-qubit quantum source flaws and reference frame deviation on QKD:the thesis considers non-qubit quantum source flaws,such as state preparation flaws,high-dimensional information leakage,and Trojan horse attacks,into the security analysis of reference frame independent(RFI)QKD protocols.To improve the system’s security,a four-state RFI-QKD protocol is proposed based on non-qubit quantum source flaws,which reduces the complexity of the system by decreasing the number of quantum states to be prepared from six to four.(2)The security of the RFI-MDI-QKD protocol for universal RFI measurement:this thesis estimate the phase error rates of different bases using the equivalent entanglement process to prove that source flaws,eavesdropping,and reference frame deviation are irrelevant.The maximum amount of information that may be leaked using a semi-definite program is also estimated.It is noted that the advantage of the protocol is that it only requires characterization of the inner product of the prepared quantum states on both sides,further reducing the requirements for quantum state preparation.(3)RFI-MDI-QKD protocol without uncharacterized qubit sources:the protocol is proposed and demonstrated to eliminate the need for detecting encoded quantum states.This removes rigorous trust in the encoding devices used by the communicating parties.The protocol also utilizes data from mismatched bases,which are typically discarded in traditional quantum communication protocols.Furthermore,it accounts for collective attacks on the system without any modifications to the existing experimental setup.