不经意传输在密码学中有着重要的应用。量子保密查询用来解决N取1的不经意传输问题，它能够在用户访问数据库的同时保护通信双方的隐私。实用量子保密查询协议基于量子密钥分配技术即可实现，具有很强的应用潜力，已经引起了广泛关注。本项目研究实用量子保密查询中的若干关键理论问题，主要包括：研究如何提高实用量子保密查询协议抵御联合攻击的能力；探索新的实用量子保密查询模型，尝试改变现有协议中Alice平均可得条目数和协议失败概率相互制约、不能同时达到理想的现状；研究当前实际应用中普遍采用的非理想单光子源对协议安全性的潜在影响，设计适用于非理想单光子源的实用量子保密查询方案；设计设备无关或测量设备无关的实用量子保密查询方案。项目研究成果将为今后量子保密查询可能的实际应用提供理论支持。

Oblivious transfer has important applications in cryptography. Quantum private query (QPQ) deals with the problem of 1-out-of-N oblivious transfer, and can protect both parties’ privacy when a user tries to obtain an item from the database. Practical QPQ, which is based on similar technology of quantum key distribution, can be easily realized within current technology and has attracted much attention. In this project we study some key theoretical problems in practical QPQ, including: (i) try to find a method to improve the security of such protocols against collective attack; (ii) design new models of practical QPQ which have better trade-off between the expected value of the amount of items Alice can obtain and the protocol’s failure probability; (iii) analyze the effect of using non-ideal photon resources on the security, and give secure QPQ protocols with such resources; (iv) design device- independent or measurement- device- independent QPQ protocols. The results will promote the development of practical QPQ, and provide theoretical support for its possible implementation in the future.