可验证外包解密的离线/在线属性基加密方案

属性基加密可以为雾-云计算中的数据提供机密性保护和细粒度访问控制,但雾-云计算系统中的移动设备难以承担属性基加密的繁重计算负担。为解决该问题,该文提出一种可验证外包解密的离线/在线属性基加密方案。该方案能够实现离线/在线的密钥生成和数据加密,同时支持可验证外包解密。然后,给出方案的选择明文攻击的安全证明和可验证性的安全证明。之后,该文将转换阶段所需双线性对的计算量降为恒定常数。最后,从理论和实验两方面对所提方案进行性能分析,实验结果表明该方案是有效且实用的。     

基于属性加密的云存储方案研究

云存储中往往采用属性加密方案来实现细粒度的访问控制,为了进一步保护访问控制策略中的敏感信息,并解决授权中心单独为用户生成密钥而产生的密钥托管问题。该文对访问控制策略中的属性进行重新映射,以实现其隐私性。另外在密钥生成算法中设计一个双方计算协议,由用户产生密钥的部分组件,与授权中心共同生成密钥以解决密钥托管问题。最后在标准模型下对方案进行了安全证明,并进行了性能分析与实验验证,实验结果表明,与已有相关方案相比,虽然为了实现访问控制策略隐藏并且解决密钥托管问题增加了额外的计算负载, 但是由于该文将大部分解密工作授权给云存储中心来执行,因此数据访问者的计算负载较小。     

支持属性撤销的可验证多关键词搜索加密方案

近年来,可搜索加密技术及细粒度访问控制的属性加密在云存储环境下得到广泛应用。考虑到现存的基于属性的可搜索加密方案存在仅支持单关键词搜索而不支持属性撤销的问题,以及单关键词搜索可能造成返回搜索结果部分错误并导致计算和宽带资源浪费的缺陷,该文提出一种支持属性撤销的可验证多关键词搜索加密方案。该方案允许用户检测云服务器搜索结果的正确性,同时在细粒度访问控制结构中支持用户属性的撤销,且在属性撤销过程中不需要更新密钥和重加密密文。该文在随机预言机模型下基于判定性线性假设被证明具有抵抗选择关键词集攻击安全性及关键词隐私性,同时从理论和实验两方面分析验证了该方案具有较高的计算效率与存储效率。     

多云服务提供者环境下的一种用户密钥撤销方法

密钥信息泄露是互联云服务难题之一,为解决该问题,该文提出一种基于属性环签名的用户密钥撤销方案。该方案以互联云的用户密文访问方法为研究对象,论述了无属性泄露的密文矩阵映射机制,多授权者自主扩展属性集生成密钥,从而令云服务提供者(CSP)无法获得用户完整属性,达到消除属性存储负载的目的。另外,该方案以撤销环与单调张成算法为基础设计用户签名验证撤销机制,令CSP、授权者与用户共同组成属性环,接受CSP定义密文访问结构,用户签名只有通过源CSP验证才能访问密文,授权者撤销部分属性失效用户解密密钥,从而达到权限撤销不影响其它用户访问的目的。该方案以密文策略属性基加密(CP-ABE)与单调张成算法为基础设计多用户组合属性共谋抵抗机制,用以保护属性的机密性。最后,给出该方案通信成本和计算效率的性能分析,用以验证该方法的有效性。     

基于属性加密的高效密文去重和审计方案

针对当前支持去重的属性加密方案既不支持云存储数据审计,又不支持过期用户撤销,且去重搜索和用户解密效率较低的问题,该文提出一种支持高效去重和审计的属性加密方案。该方案引入了第3方审计者对云存储数据的完整性进行检验,利用代理辅助用户撤销机制对过期用户进行撤销,又提出高效去重搜索树技术来提高去重搜索效率,并通过代理解密机制辅助用户解密。安全性分析表明该方案通过采用混合云架构,在公有云达到IND-CPA安全性,在私有云达到PRV-CDA安全性。性能分析表明该方案的去重搜索效率更高,用户的解密计算量较小。     

雾计算中细粒度属性更新的外包计算访问控制方案

针对基于密文策略的属性加密(CP-ABE)在低时延需求较高的雾计算环境中,存在加解密开销大、属性更新效率低的问题,提出了一种雾计算中细粒度属性更新的外包计算访问控制方案,使用模加法一致性秘密(密钥)分享技术构建访问控制树,将加解密计算操作外包给雾节点,降低用户加解密开销;结合重加密机制,在雾节点建立组密钥二叉树对密文进行重加密,实现对用户属性的灵活更新。安全性分析表明,所提方案在决策双线性Diffie-Hellman假设下是安全的。仿真实验结果表明,所提方案中用户加解密时间开销相比其他方案更小,属性更新效率更高。     

基于理想格的高效密文策略属性基加密方案

已有的基于格的密文策略属性基(CP-ABE)方案只能通过矩阵运算方法进行加解密,加解密效率不高,而效率较高的基于理想格的密钥策略属性基(KP-ABE)方案又存在对各类实际应用场景适应性较差的问题。为解决上述问题,该文利用理想格上的算法生成主密钥和密钥,同时在多项式环上进行运算,极大地提高了加解密效率;通过在原属性集合中添加虚拟属性,方案成功结合访问结构生成密文,同时授权用户可以构建出满足解密条件的子集,从而实现方案的正确解密;还利用单个陷门矩阵生成密钥,有效降低了公共参数和主密钥的数量。最终该文构建了一个基于理想格的支持门限访问结构的高效CP-ABE方案,并证明方案在环上容错学习(R-LWE)假设下是选择性安全的。与现有支持门限访问结构的方案的对比分析表明,该文方案公共参数数量更少、效率更高,且对实际应用场景有更好的适应性。     

属性可撤销且密文长度恒定的属性基加密方案

密文策略属性基加密（ciphertext-policy attribute-based encryption,CP-ABE）类似于基于角色访问控制,可以为云存储系统提供灵活细粒度的访问控制.但大多数CP-ABE方案中,密文长度与访问策略复杂度成正相关,系统属性同时被多个用户共享而导致属性难以被撤销.针对上述问题,本文提出一种支持属性撤销且密文长度恒定的属性基加密方案.该方案中每个用户的属性群密钥不能通用,可以有效抵抗撤销用户与未撤销用户的合谋攻击.为减少属性授权机构和数据拥有者的计算负担,属性撤销过程所需的计算量外包给数据服务管理者;同时该方案采用支持多值属性和通配符的"AND"门策略,实现了密文长度恒定.所提方案基于决策性q-BDHE（q-bilinear Diffie-Hellman exponent）假设对方案进行了选择明文攻击的安全性证明.最后对方案进行了理论分析与实验验证,分析结果表明本文方案可以有效抵制用户合谋攻击,增加了方案的安全性.同时所提方案在功能和计算效率方面具有一定优势,适用于实际应用情况.     

基于NTRU的多密钥同态代理重加密方案及其应用

为了提高同态加密算法在多用户云计算场景下的实用性,构造了一个基于NTRU的多密钥同态代理重加密方案。首先利用密文扩张思想提出了一种新的NTRU型多密钥同态密文形式,并基于此设计了相应的同态运算和重线性化过程,从而形成一个支持分布式解密的NTRU型多密钥同态加密方案;然后借助于密钥交换思想设计了重加密密钥和重加密过程,将代理重加密功能集成到该NTRU型多密钥同态加密方案中。所提方案保留了多密钥同态加密和代理重加密的特性,而且在用户端的计算开销较低。将所提方案应用于联邦学习中的隐私保护问题并进行了实验,结果表明,所提方案基本不影响联邦训练的准确率,加解密、同态运算和重加密等过程的计算开销也可接受。     

支持直接撤销的密文策略属性基加密方案

提出一种支持直接撤销的属性基加密方案,首先给出支持直接撤销的属性基加密定义和安全模型,其次给出具体的支持撤销的密文策略——属性基加密方案并对安全性进行证明,最后,与其他方案对比显示,该方案在密文和密钥长度方面都有所减少。该方案可以实现对用户进行即时撤销,当且仅当用户所拥有的属性满足密文的访问结构且不在用户撤销列表内时,才能使用自己的私钥解密出明文。     

Attribute-based encryption scheme supporting attribute revocation in cloud storage environment

Attribute-based encryption (ABE) scheme is widely used in the cloud storage due to its fine-grained access control.Each attribute in ABE may be shared by multiple users at the same time.Therefore,how to achieve attribute-level user revocation is currently facing an important challenge.Through research,it has been found that some attribute-level user revocation schemes currently can’t resist the collusion attack between the revoked user and the existing user.To solve this problem,an attribute-based encryption scheme that supported the immediate attribute revocation was proposed.The scheme could achieve attribute-level user revocation and could effectively resist collusion attacks between the revoked users and the existing users.At the same time,this scheme outsourced complex decryption calculations to cloud service providers with powerful computing ability,which reduced the computational burden of the data user.The scheme was proved secure based on computational Diffie-Hellman assumption in the standard model.Finally,the functionality and efficiency of the proposed scheme were analyzed and verified.The experimental results show that the proposed scheme can safely implement attribute-level user revocation and has the ability to quickly decrypt,which greatly improves the system efficiency.     

SecCloudSharing: Secure data sharing in public cloud using ciphertext‐policy attribute‐based proxy re‐encryption with revocation

An efficient cryptography mechanism should enforce an access control policy over the encrypted data to provide flexible, fine‐grained, and secure data access control for secure sharing of data in cloud storage. To make a secure cloud data sharing solution, we propose a ciphertext‐policy attribute‐based proxy re‐encryption scheme. In the proposed scheme, we design an efficient fine‐grained revocation mechanism, which enables not only efficient attribute‐level revocation but also efficient policy‐level revocation to achieve backward secrecy and forward secrecy. Moreover, we use a multiauthority key attribute center in the key generation phase to overcome the single‐point performance bottleneck problem and the key escrow problem. By formal security analysis, we illustrate that our proposed scheme achieves confidentiality, secure key distribution, multiple collusions resistance, and policy‐ or attribute‐revocation security. By comprehensive performance and implementation analysis, we illustrate that our proposed scheme improves the practical efficiency of storage, computation cost, and communication cost compared to the other related schemes.     

云存储系统中支持用户隐私保护的细粒度访问控制

从云存储实际需求出发,设计了一个云存储环境下支持用户隐私保护和用户属性撤销的多属性权威的属性加密机制,为了保证系统实现的效率和减轻数据持有者的负担,在属性撤销中,复杂的计算任务都委托给可信第三方或云服务器完成。所提方案在DBDH假设下被证明是安全的。     

Searchable ciphertext‐policy attribute‐based encryption with revocation in cloud storage

To protect the sensitive data outsourced to cloud server, outsourcing data in an encrypted way has become popular nowadays. However, it is not easy to find the corresponding ciphertext efficiently, especially the large ciphertext stored on cloud server. Besides, some data owners do not want those users who attempt to decrypt to know the sensitive access structure of the ciphertext because of some business or private reasons. In addition, the user attributes revocation and key updating are important issues, which affect application of ciphertext‐policy attribute‐based encryption (CP‐ABE) in cloud storage systems. To overcome the previous problems in cloud storage, we present a searchable CP‐ABE with attribute revocation, where access structures are partially hidden so that receivers cannot extract sensitive information from the ciphertext. The security of our scheme can be reduced to the decisional bilinear Diffie–Hellman (DBDH) assumption and decisional linear (DL) assumption. Copyright © 2015 John Wiley & Sons, Ltd.     

支持属性撤销的适应性安全属性基加密方案

Attribute revocation is inevitable and also important for Attribute-Based Encryption (ABE) in practice. However, little attention has been paid to this issue, and it remains one of the main obstacles for the application of ABE. Most of existing ABE schemes support attribute revocation work under indirect revocation model such that all the user's private keys will be affected when the revocation events occur. Though some ABE schemes have realized revocation under direct revocation model such that the revocation list is embedded in the ciphertext and none of the user's private keys will be affected by revocation, they mostly focused on the user revocation that revokes the user's whole attributes, or they can only be proven to be selectively secure. In this paper, we first define a model of adaptively secure ABE supporting the attribute revocation under direct revocation model. Then we propose a Key-Policy ABE (KP-ABE) scheme and a Ciphertext-Policy ABE (CP-ABE) scheme on composite order bilinear groups. Finally, we prove our schemes to be adaptively secure by employing the methodology of dual system encryption.     

Access control scheme with attribute revocation for SWIM

Access control scheme is proposed for System Wide Information Management (SWIM) to address the problem of attribute revocation in practical applications. Based on the attribute based encryption (ABE), this scheme introduces the proxy re-encryption mechanism and key encrypting key (KEK) tree to realize fine-grained access control with attribute revocation. This paper defines the attributes according to the status quo of civil aviation. Compared with some other schemes proposed before, this scheme not only shortens the length of ciphertext (CT) and private key but also improves the efficiency of encryption and decryption. The scheme can resist collusion attacks and ensure the security of data in SWIM.