对公钥可搜索加密中内部关键词猜测攻击的研究

Research on Internal Keyword Guessing Attack in Public Key Searchable Encryption

近年来,随着云计算技术的发展和数据隐私保护的要求不断提高,密码学作为保护信息安全的一种必要手段,在生活中应用得越来越广泛。其中可搜索加密技术广受青睐,因为它不仅能够保护用户数据的隐私性,而且还可以实现用户对加密数据进行关键词搜索的功能。后续的很多研究者丰富了可搜索加密的功能和性质,但是也还存在着关键词攻击等问题亟待解决。因为敌手一旦获得了关键词就会威胁到密文数据文件的安全,而且也可能泄露数据接收者的搜索偏好和个人身份等隐私信息,所以解决关键词猜测攻击问题是非常有意义而且十分重要的。目前对于抵抗外部敌手的离线关键词猜测攻击的研究已经日渐成熟,但是对于抵抗内部敌手的离线关键词猜测攻击还有待进一步深化完善。本文阐述了内部关键词猜测攻击的机理,指出敌手可以进行内部关键词猜测攻击的主要原因在于云服务器可以得到关键词密文和陷门信息,并且可以自由地做关键词密文和陷门信息的匹配测试。然后梳理了近年来抗内部关键词猜测攻击的常见解决方案,主要包括使用双服务器模型、认证服务器模型、见证关键词模型、指定发送者模型、模糊关键词模型等五类解决方案,并深入总结和比较了五类方案,归纳出了解决内部关键词猜测攻击的一般思路,并指出未来抵抗内部关键词猜测攻击将会成为公钥可搜索加密方案的一种基本属性,要解决内部关键词猜测攻击就必须从服务器可以生成密文、获取陷门和独立运行测试算法三个方面入手,最后提出了现阶段内部关键词猜测攻击需要解决的问题以及未来的三个研究思路,能够为进一步解决公钥可搜索加密中的内部关键词猜测攻击问题有所帮助,使得公钥可搜索协议真正为实际所用。

In recent years,with the flourishing of cloud computing,data privacy receives more and more attention and cryptography is a widely used method in daily life to prevent data leakage.Searchable encryption can protect data from leaking and retain the search functionality over encrypted data simultaneously.Although there are many followed works on the expressive query and higher security,the keyword guessing attack(KGA)is one of the problems to be more explored.The keyword guessing attack makes adversaries infer the meaning of keyword ciphertext,so data privacy is compromised by leaking users’search preferences even the personal information of data receivers.Therefore,it is very meaningful and important to solve the keyword guessing attack problem.Specifically,pay more attention to how to solve the offline keyword guessing attack against internal adversaries under the fact that the research of resisting offline keyword guessing attacks against external adversaries has become mature gradually.In this paper,we expound on the mechanism of an internal keyword guessing attack,that is,the cloud server can test whether the keyword ciphertext and the trapdoor match at will.Then,we summarize and compare the solutions against internal keyword guessing attack in recent years.More specifically,there are five kinds of solutions on the dual-server model,authentication server model,witness keywords model,designated sender model,and fuzzy keywords model respectively.Then,we point out that the general way to solve internal keyword guessing attacks is by hindering ability of the server to generate ciphertext,get trapdoor,and run test algorithms independently.Moreover,resistance to internal keyword guessing attack should be a basic attribute of the public key searchable encryption scheme.Finally,left problems on internal keyword guessing attacks and further works are discussed.It is helpful to further solve the internal keyword guessing attack problem in the public key searchable encryption,so that the public key searchable protocol is used in practice.