抗关键词猜测攻击的可搜索公钥加密的研究

Searchable public key encryption scheme is a useful primitive that provides searchable ciphertexts for some predefined keywords. It enables one to search for publicly encrypted keywords without revealing any information about the original data contents and the keywords. Searchable public key encryption scheme overcomes the shortcoming in traditional public key encryption scheme that it cannot operate directly on the ciphertext data and thus provides a promising solution for the encrypted data retrieval in the data storage systems. In recent years, searchable public key encryption scheme has been extensive researched and applied due to its unique advantages. But, there are still many shortcomings and imperfections in the previous searchable public key encryption schemes. Many open problems remain, especially the keyword guessing attack problem. The research of this project focuses on secure-channel free searchable public key encryption against keyword guessing attacks. Aimed at the keyword guessing attack problem and the secure-channel problem in the previous searchable public key encryption schemes, it will first design a new framework and security model for searchable public key encryption, and then develop probably secure and efficient searchable public key encryption schemes that provides resistance to the keyword guessing attack and can send the keyword trapdoors via public channel. On this basis, it will futher solve several key technical issues in the design of searchable public key encryption, such as complicated certificate management problem, keyword-trapdoor revocation, expressive multi-keyword search and receiver-update in multi-user setting. The research of this project will further promote the development and improvement of the theory and architecture of searchable public key encryption, and accelerate the actual application of searchable public key encryption. Therefore, it has great theoretical and practical significance.

可搜索公钥加密体制颠覆了传统公钥加密无法对密文直接操作的缺陷，能够在不泄露密文中的原始数据信息以及关键词信息的情况下让存储服务提供者搜索密文中是否包含某个加密后的关键词，因此该体制为密文搜索问题的解决提供了理想的方法。近年来，可搜索公钥加密的研究取得了不少成果，但仍存在诸多问题亟待解决，尤其是关键词猜测攻击问题。本项目研究无安全信道抗关键词猜测攻击的可搜索公钥加密体制的设计与实现。针对已有可搜索公钥加密中的关键词猜测攻击和安全信道等问题，本项目首先对无安全信道抗关键词猜测攻击的可搜索公钥加密方案的构造方法展开研究。在此基础上，进一步解决复杂的证书管理、关键词陷门撤销、具有强表达能力的多关键词搜索以及多用户场景下的接收者更新等关键问题，以增强可搜索公钥加密的功能，提升其实用性。本项目的研究将完善可搜索公钥加密体制的理论与体系，促进其在云存储等领域的实际应用，因此具有非常重要的理论与现实意义。

可搜索公钥加密为密文搜索问题的解决提供了理想的方法。针对已有可搜索公钥加密方法存在的易受关键词猜测攻击、算法执行效率低、搜索模式不够灵活等问题，本项目重点研究高效实用的抗关键词猜测攻击的可搜索公钥加密方法。首先，充分考虑针对可搜索公钥加密的各类敌手的攻击能力和已知关键词猜测攻击的特点，建立了抗关键词猜测攻击的可搜索公钥加密的方案框架和安全模型；其次，研究抗关键词猜测攻击的可搜索公钥加密方案的设计，分别提出了高效的基于双线性对运算的和轻量级的不依赖双线性对的抗关键词猜测攻击的可搜索公钥加密方案；然后，面向实际应用对可搜索公钥加密进行拓展性研究，分别提出了富于表达的可搜索公钥加密方案、支持隐证书机制的基于证书可搜索公钥加密方案、搜索陷门可限时撤销的可搜索公钥加密方案、多接收者的无证书可搜索公钥加密方案、支持多关键词模糊搜索的可搜索公钥加密方案等更为实用的方案。对于所提出方案，本项目在标准模型或随机预言模型下严格证明了其安全性，并分析其计算代价和通信代价。本项目研究致力于提升可搜索公钥加密的安全性和实用性，解决了可搜索公钥加密在实际应用中所面临的关键词猜测攻击、搜索模式不灵活、复杂证书管理、搜索陷门滥用等现实问题，具有重要的理论意义和实用价值。