Theoretical Research On Quantum Private Query Protocol And Quantum Oblivious Transfer Protocol

With the development of quantum parallel algorithms such as Shor factorization and Grover search,the security of cryptographic algorithms based on computational complexity has been severely challenged.In contrast,the security of quantum cryptography is guaranteed by the basic principles of quantum mechanics such as unknown quantum state no-cloning theorem,Heisenberg uncertainty principle,etc.This thesis focuses on the research of quantum private query(QPQ)and quantum oblivious transfer(QOT).QPQ is a new subject that is a combination of classical private query and quantum physics.QPQ is designed to complete database data query between untrusted communication parties and to keep the security of the database and the privacy of the user.QOT transmit information between the sender and receiver of secret information in a hidden way.QOT is a foundation for building other quantum cryptographic protocols.The results of my research work are summarized as below:(1)We propose an relativistic secure QPQ protocol,and evade Lo's no-go theorem negation that unconditional and secure one-way two-sided quantum communication protocol does not exist.Based on Minkowski causality and non-communicating models,in the proposed QPQ model,each party is split up into several agents who cannot communicate with each other during certain phases of the protocol because of their physical separation and the finite speed of light.It is impossible for a single agent that cannot communicate with other agents to tamper with the information without the help of external forces.That is,the use of a non-communicable agent in a relativistic environment avoids Mayers-Lo-Chau no-go theorem.(2)We use a rotation-invariant single-photon quantum state,and solve the problem of transmission error caused by the misalignment of the coordinate system to the QPQ over a long distance.Photon spin angular momentum and orbital angular momentum carry different information to construct a single-photon quantum state that is invariant in the joint rotation noise which overcomes transmission errors due to the relative rotation of the coordinate system,thereby increasing the photon transmission efficiency.(3)We propose a flexible B92-based QPQ protocol.Compared with other SARG04-based QPQ,it can simultaneously obtain better database security and a lower probability with which Bob can correctly guess the address of Alice's query.By introducing entanglement,the proposed QPQ protocol is robust against channel-loss attack,which also implies lower classical communication complexity.The protocol is flexible,practical,and robust against quantum memory attack.(4)We propose a new QPQ protocol with real-time security check,solving the problem that QPQ security detection always occurs after the unhonest activity occurs.An untrusted third party is introduced to propose a framework of one-sided two-party quantum computation protocols with real-time security check.For clarity and without loss of generality,we demonstrate a concrete QPQ example under this framework by improving Gao et al's protocol.We discuss the security of the protocol and show that it really has real-time security check.The proposed framework paves the way for the design of one-sided two-party quantum computation protocols.(5)We study the reduction relationship between QPQ and QOT.It is shown that the existence of secure QPQ is necessary but not sufficient for secure QOT,which provides a strong evidence of nonequivalence of two flavors of oblivious transfer at the quantum level.Meanwhile,we present novel QOT protocol based on a QPQ and unambiguous set discrimination techniques.