【作者】 陈曦；

【导师】 吕家国；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2020， 博士

【摘要】 云计算、物联网和移动计算等信息技术为数据的存储、获取和处理提供了强有力的支撑,使得构建基于第三方数据平台的密文共享系统成为可能。但是,由于第三方数据平台具有开放性,在为用户提供便利数据共享服务的同时,也带来了一系列安全风险与挑战。例如,在复杂的用户组织结构中,如何为大量用户提供安全可靠的密钥授权;随着共享用户数量的不断增多,如何对多用户进行合理、高效而又灵活的授权;以及在多域数据访问环境下,如何实现高效地跨域认证等,这些问题都是在实现密文安全共享时亟待解决的。采用授权和认证机制,可以验证用户身份的合法性,是密文安全共享的重要基础。本论文围绕支持密文数据安全共享的授权和认证若干关键技术问题开展研究工作,以期解决等级属性加密中的密钥授权滥用及密钥泄露问题、多代理场景中如何为多用户灵活授权访问的问题、云计算跨域场景下外域用户的认证问题。论文的主要工作和创新性成果如下:1.在等级属性加密中,提出了存在密钥授权滥用的问题,给出了一种安全密钥授权的等级属性加密解决方案。在分析了密钥授权滥用问题成因的基础上,关联密钥生成的必需条件,采用有向图提出了一个可以抵御密钥授权滥用的等级属性加密方案有效构造。通过规约证明的方法,分析了该方案在一般群模型和选择性策略下,具有选择明文攻击安全性和密钥滥用攻击安全性。针对密钥被泄露后,泄密者身份无法被确认的问题,又提出了一个具有白盒可追踪性的等级属性加密方案。该方案既可抵御密钥的授权滥用,又兼具白盒可追踪性,实现了对密钥泄露者的身份追踪识别。进一步安全分析表明,在l阶强Diffie-Hellman假设下,方案满足白盒可追踪性。效率分析表明,当属性空间固定时,可以高效地构造该方案。2.针对如何同时支持多条件细粒度授权和抵御合谋攻击的问题,提出了一种基于属性条件门限代理重加密方案。该方案的主旨思想是:基于门限秘密共享,将单个代理扩充到多个代理,避免了单一代理与用户的合谋攻击,提高了系统健壮性。进一步地,通过引入多关键词的设置,结合Lan等人提出的条件代理重加密和经典的基于密文策略属性加密,给出了方案的有效构造方法。该方案支持多个关键词授权条件下的密文数据细粒度访问,以及灵活的用户撤销,防止密文未经授权被合谋转换情况的出现,保护了数据所有者的敏感信息。通过可证明安全分析,表明在一般群模型下,该方案具有选择明文攻击安全性;与其他条件代理重加密方案相比,其所支持的功能更具有多样性。3.提出了一种不依赖双线性对的安全授权门限代理重签名算法,并给出了其双向跨域认证的实现方案。基于Harn等人的群门限签名,通过引入ELGamal签名和门限秘密共享,分别给出单向和双向的情况下算法的具体构造。证明了在随机预言模型下,基于离散对数问题,所构造的算法具有抗合谋选择明文攻击安全性。在混合云跨域场景下,基于PKI体系和双向门限代理重签名算法,给出了双向跨域身份认证方案的实现方法。结果表明:采用多代理重签名的门限转换机制,可以提高数字证书的跨域认证效率。更多还原

【Abstract】 Information technologies such as Cloud Computing,Internet of Things,and mobile computing have provided strong support for data storage,acquisition,and processing,which make it possible to build ciphertext sharing systems based on the third-party data platforms.However,due to the openness of the third-party data platform,while providing users with convenient data sharing services,it also brings a series of security risks and challenges,for example,in the complex user organization structure,how to provide secure and reliable key-delegation for a large number of users;with the increasing number of shared users,how to authorize multiple users in a reasonable,efficient and flexible manner;and how to achieve efficient cross-domain authentication in the multi-domain data accessing environment.These problems are urgent to be solved in the implementation of ciphertext secure sharing.The adoption of authorization and authentication mechanism can verify the legitimacy of user identity,which is the important foundation of secure ciphertext sharing.This dissertation focuses on some critical issues of secure sharing and authentication of ciphertext data based on third-party platforms,in order to solve the problems,such as the key-delegation abuse and key leakage in the hierarchical attribute-based encryption,how to flexibly authorize access to multiple users in a multi-agent scenario,and the authentication problem of external domain users in cloud computing cross-domain scenario.The main contributions of this dissertation can be summarized as follows:1.In the hierarchical attribute-based encryption,the problem of key-delegation abuse is raised,and one hierarchical attribute-based encryption solution with secure key-delegation is presented.Based on analyzing the causes of key-delegation abuse,a hierarchical attribute-based encryption scheme against key-delegation abuse is constructed by introducing the directed graph and associating the two requirements of key generation.Through the reduction and proof,the scheme is proved to be secure against chosen-plaintext attack and resistant to key abuse attack under the selective access strategy and generic group model.To solve the problem that the identity of the leaker cannot be confirmed after the key is leaked,a hierarchical attribute-based encryption scheme with white box traceability.The proposed scheme not only can resist key-delegation abuse,but also has the white box traceability,which realizes the identity tracking and identification of the key leaker.Further security analysis shows that under the l-strong Diffie-Hellman assumption,the scheme satisfies the white box traceability.The efficiency analysis shows that when the attribute universe is fixed,the constructed schemes are efficient.2.Aiming at the problem of how to support multi-conditional fine-grained authorization and resists the collusion attack simultaneously,an attribute-based conditional threshold proxy re-encryption scheme is proposed.The main idea of the scheme is: based on threshold secret sharing,the single proxy is extended to multiple proxies,which avoids the collusion attack between the single proxy and users,and improves the robustness of the system.Further,by introducing the multi-keyword setting,an effective structure of the scheme is presented,with the combination between the conditional proxy re-encryption scheme proposed by Lan et al.and the classic ciphertext-policy attribute-based encryption.This solution achieves fine-grained access to ciphertext data under multiple keyword authorization conditions,supports flexible user revocation,prevents unauthorized ciphertext from being collusive transformed,and protects sensitive information of data owners.The provable security analysis shows that the scheme is proved to be secure against chosen-plaintext attack under the generic group model.Compared with other conditional proxy re-encryption schemes,the proposed scheme supports more diverse functions.3.A threshold proxy re-signature algorithm with secure authorization is proposed,which is independent of bilinear pairings,and its implementation scheme for bi-directional cross-domain authentication protocol is given.By introducing El Gamal signature and threshold secret sharing,the unidirectional and bidirectional threshold proxy re-signature algorithms are proposed respectively based on Harn’s group-oriented threshold signature schemes.It is proved that the proposed algorithms are secure against chosen-plaintext attack with collusion based on discrete logarithm assumption under random orac le model.A multi-proxy cross-domain authentication protocol based on bidirectional threshold proxy re-signature algorithm and PKI is presented under the cross-domain scene of hybrid cloud.The results show that the threshold conversion mechanism of multi-proxy re-signature can improve the cross domain authentication efficiency of digital certificate.更多还原