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.     

云存储环境下无密钥托管可撤销属性基加密方案研究

属性基加密因其细粒度访问控制在云存储中得到广泛应用。但原始属性基加密方案存在密钥托管和属性撤销问题。为解决上述问题,该文提出一种密文策略的属性基加密方案。该方案中属性权威与中央控制通过安全两方计算技术构建无密钥托管密钥分发协议解决密钥托管问题。通过更新属性版本密钥的方式达到属性级用户撤销,同时通过中央控制可以实现系统级用户撤销。为减少用户解密过程的计算负担,将解密运算过程中复杂对运算外包给云服务商,提高解密效率。该文基于q-Parallel BDHE假设在随机预言机模型下对方案进行了选择访问结构明文攻击的安全性证明。最后从理论和实验两方面对所提方案的效率与功能性进行了分析。实验结果表明所提方案无密钥托管问题,且具有较高系统效率。     

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。     

Public integrity verification for data sharing in cloud with asynchronous revocation

Cloud data sharing service, which allows a group of people to access and modify the shared data, is one of the most popular and efficient working styles in enterprises. Recently, there is an uprising trend that enterprises tend to move their IT service from local to cloud to ease the management and reduce the cost. Under the new cloud environment, the cloud users require the data integrity verification to inspect the data service at the cloud side. Several recent studies have focused on this application scenario. In these studies, each user within a group is required to sign a data block created or modified by him. While a user is revoked, all the data previously signed by him should be resigned. In the existing research, the resigning process is dependent on the revoked user. However, cloud users are autonomous. They may exit the system at any time without notifying the system admin and even are revoked due to misbehaviors. As the developers in the cloud-based software development platform, they are voluntary and not strictly controlled by the system. Due to this feature, cloud users may not always follow the cloud service protocol. They may not participate in generating the resigning key and may even expose their secret keys after being revoked. If the signature is not resigned in time, the subsequent verification will be affected. And if the secret key is exposed, the shared data will be maliciously modified by the attacker who grasps the key. Therefore, forcing a revoked user to participate in the revocation process will lead to efficiency and security problems. As a result, designing a practical and efficient integrity verification scheme that supports this scenario is highly desirable. In this paper, we identify this challenging problem as the asynchronous revocation, in which the revocation operations (i.e., re-signing key generation and resigning process) and the user's revocation are asynchronous. All the revocation operations must be able to be performed without the participation of the revoked user. Even more ambitiously, the revocation process should not rely on any special entity, such as the data owner or a trusted agency. To address this problem, we propose a novel public data integrity verification mechanism in which the data blocks signed by the revoked user will be resigned by another valid user. From the perspectives of security and practicality, the revoked user does not participate in the resigning process and the re-signing key generation. Our scheme allows anyone in the cloud computing system to act as the verifier to publicly and efficiently verify the integrity of the shared data using Homomorphic Verifiable Tags (HVTs). Moreover, the proposed scheme resists the collusion attack between the cloud server and the malicious revoked users. The numerical analysis and experimental results further validate the high efficiency and scalability of the proposed scheme. The experimental results manifest that re-signing 10,000 data blocks only takes 3.815 ?s and a user can finish the verification in 300 ?ms with a 99% error detection probability.     

One-way hash chain-based self-healing group key distribution scheme with collusion resistance capability in wireless sensor networks

In order to resolve the collusion resistance problem in the one-way hash chain-based self-healing group key distribution schemes and improve the performance of previous self-healing group key distribution schemes, we propose a self-healing group key distribution scheme based on the revocation polynomial and a special one-way hash key chain for wireless sensor networks (WSNs) in this paper. In our proposed scheme, by binding the time at which the user joins the group with the capability of recovering previous group session keys, a new method is addressed to provide the capability of resisting the collusion attack between revoked users and new joined users, and a special one-way hash chain utilization method and some new methods to construct the personal secret, the revocation polynomial and the key updating broadcast packet are presented. Compared with existing schemes under same conditions, our proposed scheme not only supports more revoked users and sessions, but also provides a stronger security. Moreover, our proposed scheme reduces the communication overhead, and is especially suited for a large scale WSN in bad environments where a strong collusion attack resistance capability is required and many users will be revoked.     

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。     

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.     

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。     

Secure personal data sharing in cloud computing using attribute-based broadcast encryption

The ciphertext-policy (CP) attribute-based encryption (ABE) (CP-ABE) emergings as a promising technology for allowing users to conveniently access data in cloud computing. Unfortunately, it suffers from several drawbacks such as decryption overhead, user revocation and privacy preserving. The authors proposed a new efficient and privacy-preserving attribute-based broadcast encryption (BE) (ABBE) named EP-ABBE, that can reduce the decryption computation overhead by partial decryption, and protect user privacy by obfuscating access policy of ciphertext and user's attributes. Based on EP-ABBE, a secure and flexible personal data sharing scheme in cloud computing was presented, in which the data owner can enjoy the flexibly of encrypting personal data using a specified access policy together with an implicit user index set. With the proposed scheme, efficient user revocation is achieved by dropping revoked user's index from the user index set, which is with very low computation cost. Moreover, the privacy of user can well be protected in the scheme. The security and performance analysis show that the scheme is secure, efficient and privacy-preserving.     

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。     

Multi-authority attribute-based encryption scheme with policy dynamic updating

Attribute-based encryption (ABE) is a new cryptographic technique which guarantees fine-grained access control of outsourced encrypted data in the cloud environment.However,a key limitation remains,namely policy updating.Thus,a multi-authority attribute-based encryption scheme with policy dynamic updating was proposed.In the scheme,an anonymous key issuing protocol was introduced to protect users’ privacy and resist collusion attack of attribute authority.The scheme with dynamic policy updating technique was secure against chosen plaintext attack under the standard model and can support any types of policy updating.Compared to the existing related schemes,the size of ciphertext and users’ secret key is reduced and can significantly reduce the computation and communication costs of updating ciphertext.It is more effective in the practical application.     

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.     

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.     

A based on blinded CP‐ABE searchable encryption cloud storage service scheme

Cloud computing has great economical advantages and wide application, more and more data owners store their data in the cloud storage server (CSS) to avoid tedious local data management and insufficient storage resources. But the privacy of data owners faces enormous challenges. The most recent searchable encryption technology adopts the ciphertext‐policy attribute‐based encryption (CP‐ABE), which is one good method to deal with this security issue. However, the access attributes of the users are transmitted and assigned in plaintext form. In this paper, we propose a based on blinded CP‐ABE searchable encryption cloud storage service (BCP‐ABE‐SECSS) scheme, which can blind the access attributes of the users in order to prevent the collusion attacks of the CSS and the users. Data encryption and keyword index generation are performed by the data owners; meanwhile, we construct that CSS not only executes the access control policy of the data but also performs the pre‐decryption operation about the encrypted data to solve higher time cost of decryption calculation to the data users. Security proof results show that this scheme has access attribute security, data confidentiality, indistinguishable security against chosen keyword attack, and resisting the collusion attack between the data user and the CSS. Performance analysis and the experimental results show that this scheme can effectively reduce the computation time cost of the data owners and the data users.     

Multiuser access control searchable privacy‐preserving scheme in cloud storage

Searchable encryption scheme‐based ciphertext‐policy attribute‐based encryption (CP‐ABE) is a effective scheme for providing multiuser to search over the encrypted data on cloud storage environment. However, most of the existing search schemes lack the privacy protection of the data owner and have higher computation time cost. In this paper, we propose a multiuser access control searchable privacy‐preserving scheme in cloud storage. First, the data owner only encrypts the data file and sets the access control list of multiuser and multiattribute for search data file. And the computing operation, which generates the attribute keys of the users' access control and the keyword index, is given trusted third party to perform for reducing the computation time of the data owner. Second, using CP‐ABE scheme, trusted third party embeds the users' access control attributes into their attribute keys. Only when those embedded attributes satisfy the access control list, the ciphertext can be decrypted accordingly. Finally, when the user searches data file, the keyword trap door is no longer generated by the user, and it is handed to the proxy server to finish. Also, the ciphertext is predecrypted by the proxy sever before the user performs decryption. In this way, the flaw of the client's limited computation resource can be solved. Security analysis results show that this scheme has the data privacy, the privacy of the search process, and the collusion‐resistance attack, and experimental results demonstrate that the proposed scheme can effectively reduce the computation time of the data owner and the users.     

Efficient revocable attribute-based encryption scheme

In the existing solutions,the time-based scheme is difficult to achieve immediate revocation,and the third-party-based scheme often requires re-encryption,which needs large amount of calculation and doesn’t apply to mas-sive data.To solve the problem,an efficient and immediate CP-ABE scheme was proposed to support user and attribute lev-els revocation.The scheme was based on the classic LSSS access structure,introducing RSA key management mechanism and attribute authentication.By means of a semi-trusted third party,the user could be authenticated before decryption.Com-pared with the existing revocation schemes,The proposed scheme didn’t need the user to update the key or re-encrypt the ciphertext.The semi-trusted third party wasn’t required to update the RSA attribute authentication key.The scheme greatly reduced the amount of computation and traffic caused by revocation,while ensuring anti-collusion attacks and forward and backward security.Finally,the security analysis and experimental simulation show that the scheme has higher revocation ef-ficiency.     

云端数据访问控制中基于中间代理的用户撤销新方法

基于属性的加密机制是云端大数据细粒度访问控制的重要方法,其中的用户撤销是访问控制的重要一环,但现有的用户撤销方法因为仅仅重新加密对称密钥或者需要重新加密原始数据,所以存在安全性差或效率低的问题。针对上述问题,提出了一种基于中间代理的用户撤销方法,来解决在细粒度访问控制环境下用户撤销所带来的安全和效率问题。该用户撤销方法主要思想是利用中间代理辅助处理原始密文,继而由用户完成转化后密文的解密。由于用户没有单独解密密文的能力,因此不需要重新加密共享数据,从而在用户撤销后保证了数据的安全性,又解决了效率问题。理论分析以及实验结果表明,所提出的方法相较现有方法能够在细粒度访问控制环境下达到安全且高效的用户撤销。     

Data sharing scheme supporting secure outsourced computation in wireless body area network

How to effectively protect the security of data sharing in WBAN was a key problem to be solved urgently.The traditional CP-ABE mechanism had a 〝one to many〝 data security communication function which was suitable for access control in WBAN,but it had high computational complexity and did not support attribute revocation.Fully considering of limitations on computation and storage of sensor nodes and dynamic user attribute in WBAN,a CP-ABE scheme was proposed which was provably secure against CPA under the standard model and supported attributes revocation,outsourced encryption and decryption.Compared with the proposed schemes,the computation burden on senor nodes is greatly reduced and the user's attribution can be revoked immediately and fine grained while meeting the demand of its security in the proposed scheme.     

MACPABE: Multi-Authority-based CP-ABE with efficient attribute revocation for IoT-enabled healthcare infrastructure

The Internet of Things (IoT) technology along with cloud computing has gained much attention in recent years for its potential to upgrade conventional healthcare systems. Outsourcing healthcare data to a cloud environment from IoT devices is very essential as IoT devices are lightweight. To maintain confidentiality and to achieve fine-grained access control, the ciphertext policy attribute-based encryption (CP-ABE) technique is utilized very often in an IoT-based healthcare system for encrypting patients' healthcare data. However, an attribute revocation may affect the other users with the same attribute set, as well as the entire system due to its security concerns. This paper proposes a novel CP-ABE-based fine-grained access control scheme to solve the attribute revocation problem. The proposed technique includes multiple attribute authorities to reduce the work overhead of having a single authority in the traditional CP-ABE systems. In addition, the proposed scheme outsources the decryption process to a decryption assistant entity to reduce the decryption overhead of the end-users. To prove the efficiency of the proposed scheme, both formal security analysis and performance comparisons are presented in this paper. Results and discussion prove the effectiveness of the proposed scheme over some well-known schemes.     

数据外包环境下一种支持撤销的属性基加密方案

In order to support fine-grained attribute revocation in data outsourcing systems,an attribute-based encryption scheme with efficient revocation in indirect revocation model was proposed.The model of ABE supporting attribute revocation was given,and a concrete scheme was constructed which proved its security under the standard model.Compared to the existing related schemes,the size of ciphertext and private/secret key is reduced,and the new scheme achieves fine-grained and immediate attribute revocation which is more suitable for the practical applications.