Design And Analysis Of Quantum Private Query Protocol

The combination of classical cryptography and quantum physics forms quantum cryptography.Due to the risk of classical cryptography being cracked by quantum computers and the advantage of quantum cryptography realizing unconditionally security in theory,quantum cryptography has become a research hotspot in recent years.The quantum private query(QPQ)protocol,which is a quantum cryptographic protocol,requires ensuring the security of the privacy of both the database owner and the user in the process of querying the database.Most existing QPQ protocols can only run in an ideal environment without noise.To resist the collective-rotation noise and collective-dephasing noise in reality,scholars use the property of decoherence-free state(DFS)remaining unchanged in the collective noise to propose the QPQ against collective-rotation noise(CRN-QPQ)protocols and QPQ against collective-dephasing noise(CDN-QPQ)protocols.However,these protocols have deficiencies in security,practicability and communication efficiency.In this paper,two novel QPQ protocols are proposed to solve these deficiencies,and the security and practicability of the proposed protocols are proved.The details are as follows:(1)To resist the collective-rotation noise and make up for deficiencies of the existing CRN-QPQ protocols in terms of security and practicability,a QPQ against collective-rotation noise based on non-orthogonal four-qubit decoherence-free states(NOQDFS-CRN-QPQ)protocol is proposed.The NOQDFS-CRN-QPQ protocol has the following advantages: 1)the protocol can perfectly deal with unambiguous state discrimination measurement attacks,can solve the problem of security vulnerabilities in some existing CRN-QPQ protocols when dealing with such measurement attacks,and has stronger database security.2)The measurement basis of NOQDFS-CRN-QPQ protocol used by the user is the rectilinear or the diagonal,which is easy to implement,and solves the measurement basis preparation problem existed in the oneway CRN-QPQ protocols.(2)In practical application scenarios,there are not only collective-rotation noise but also collective-dephasing noise,and the existing CRN-QPQ protocols cannot resist collectivedephasing noise.Therefore,some scholars have proposed CDN-QPQ protocols.A QPQ against collective-dephasing noise based on two sets of non-orthogonal four-qubit decoherence-free states(TSNOQDFS-CDN-QPQ)protocol is proposed since the existing CDN-QPQ protocols have insufficient communication efficiency.The TSNOQDFS-CDN-QPQ protocol not only can completely ensure database security and the user privacy,but also has a lower communication complexity.The lower communication complexity is mainly reflected in: 1)the TSNOQDFSCDN-QPQ protocol only needs to use the quantum channel once;2)compared with the oneway CDN-QPQ protocol,the probability(1/4)that the user obtains the conclusive results of the asymmetric keys in the TSNOQDFS-CDN-QPQ protocol is less than the probability(1/2)in the existing protocol.Therefore,for the same database size N,the TSNOQDFS-CDN-QPQ protocol requires fewer original keys to be transmitted and reduces communication complexity.Specially,based on the NOQDFS-CRN-QPQ protocol and the TSNOQDFS-CDN-QPQ protocol,a QPQ protocol that is able to resist collective-rotation noise and collective-dephasing noise can be proposed in this paper.It will make up for the inadequacy that the existing protocols cannot resist collective-rotation noise and collective-dephasing noise at the same time.