云存储环境下的密文安全共享机制

With the convenient of storing and sharing data in cloud storage environment,the concerns about data security arised as well.To achieve data security on untrusted servers,user usually stored the encrypted data on the cloud storage environment.How to build a cipertext-based access control scheme became a pot issue.For the access control problems of ciphertext in cloud storage environment,a CP-ABE based data sharing scheme was proposed.Novel key generation and distribution strategies were proposed to reduce the reliance on a trusted third party.Personal information was added in decryption key to resistant conclusion attacks at the same time.Moreover,key revocation scheme was proposed to provide the data backward secrecy.The security and implement analysis proves that proposed scheme is suit for the real application environment.     

云社交网络中安全高效的加密数据共享机制(英文)

Despite that existing data sharing systems in online social networks(OSNs)propose to encrypt data before sharing,the multiparty access control of encrypted data has become a challenging issue.In this paper,we propose a secure data sharing scheme in OSNs based on ciphertext-policy attributebased proxy re-encryption and secret sharing.In order to protect users' sensitive data,our scheme allows users to customize access policies of their data and then outsource encrypted data to the OSNs service provider.Our scheme presents a multiparty access control model,which enables the disseminator to update the access policy of ciphertext if their attributes satisfy the existing access policy.Further,we present a partial decryption construction in which the computation overhead of user is largely reduced by delegating most of the decryption operations to the OSNs service provider.We also provide checkability on the results returned from the OSNs service provider to guarantee the correctness of partial decrypted ciphertext.Moreover,our scheme presents an efficient attribute revocation method that achieves both forward and backward secrecy.The security and performance analysis results indicate that the proposed scheme is secure and efficient in OSNs.     

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.     

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.     

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.     

Pilot allocation based on user location information in massive MIMO systems

In order to so1ve the prob1em of pi1ot contamination in massive MIMO systems，a pi1ot a11ocation scheme based on user 1ocation information was proposed.The proposed scheme arranged the users according to the po1ar ang1e of the user 1ocation in the po1ar coordinate system with the base station of the ce11 as the po1e，and assigned the pi1ots sequentia11y.Combining with the characteristics of directiona1 antenna，the scheme can reduce the pi1ot contamination and improve the achievab1e rate of the system by contro11ing the mu1tip1exing distance of the pi1ot to a far range.Simu1ation resu1ts show that the proposed scheme can not on1y reduce the pi1ot po11ution between users，but a1so reduce the performance gap between different users and improve the fairness of the system.     

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.     

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.     

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.     

云计算平台下基于属性加密的动态版权使用控制方案（英文）

In order to achieve fine-grained access control in cloud computing,existing digital rights management(DRM) schemes adopt attribute-based encryption as the main encryption primitive.However,these schemes suffer from inefficiency and cannot support dynamic updating of usage rights stored in the cloud.In this paper,we propose a novel DRM scheme with secure key management and dynamic usage control in cloud computing.We present a secure key management mechanism based on attribute-based encryption and proxy re-encryption.Only the users whose attributes satisfy the access policy of the encrypted content and who have effective usage rights can be able to recover the content encryption key and further decrypt the content.The attribute based mechanism allows the content provider to selectively provide fine-grained access control of contents among a set of users,and also enables the license server to implement immediate attribute and user revocation.Moreover,our scheme supports privacy-preserving dynamic usage control based on additive homomorphic encryption,which allows the license server in the cloud to update the users' usage rights dynamically without disclosing the plaintext.Extensive analytical results indicate that our proposed scheme is secure and efficient.     

标准模型下可证明安全的支持大规模属性集与属性级用户撤销的CP-ABE方案

密文策略属性加密方案,特别是不受某个特定值限制的大规模属性集下的密文策略属性加密方案在云存储中得到了越来越广泛的应用,它能够实现细粒度的访问控制。但是在原始的属性加密方案中,解决动态的用户与属性撤销,是当前面临的重要挑战。为了解决这一问题,该文提出一个标准模型下可证明安全的支持大规模属性集的密文策略属性加密方案,该方案能够实现属性级的用户撤销,即若用户的某个属性被撤销,不会影响该用户其他合法属性的正常访问。为了实现撤销,将密钥分为两部分：为用户生成的私钥以及为云存储中心生成的授权密钥。在该方案中,若用户的属性被撤销,那么该属性对应的密文将进行更新,只有该属性没有被撤销的用户才能够成功地进行密钥更新而解密密文。该文基于q-type 假设在标准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。最后对方案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,虽然为了实现属性撤销,增加了存储中心的计算负载,但是不需要属性中心的参与,因此降低了属性中心的计算负载,而且用户除了密钥外不需要其它额外参数来实现属性撤销,因此大大节省了存储空间。     

Data access control policy of encrypted deduplication system

To solve the problem that convergent encryption was commonly used in existing encrypted deduplication systems in cloud storage and data owner couldn’t effectively enforce access control on their outsourced data,an encrypted deduplication system was proposed to support access control functions such as identity authentication,authorization deduplication and the update of access control policy.The outsourced data was only deduplicated with the authorized users,and the unauthorized users couldn’t obtain any data information.CP-ABE and the partition of the ElGamal private key were used to update the access control policy of data.Self-control objects was used to encapsulate user’s data and its access policy,providing authentication for data visitors and ensuring the access control policies enforced effectively.Security analysis and simulation results demonstrate that the proposed system enables data access control and executes efficiently.     

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。     

Multi-authority attribute-based encryption with efficient revocation

Multi-authority attribute-based encryption was very suitable for data access control in a cloud storage environment.However,efficient user revocation in multi-authority attribute-based encryption remains a challenging problem that prevents it from practical applications.A multi-authority ciphertext-policy attribute-based encryption scheme with efficient revocation was proposed in prime order bilinear groups,and was further proved statically secure and revocable in the random oracle model.Extensive efficiency analysis results indicate that the proposed scheme significantly reduce the computation cost for the users.In addition,the proposed scheme supports large universe and any monotone access structures,which makes it more flexible for practical applications.     

Encrypted data sharing with multi-owner based on digital rights management in online social networks简

The online social networks（OSNs） offer attractive means for social interactions and data sharing, as well as raise a number of security and privacy issues. Although current solutions propose to encrypt data before sharing, the access control of encrypted data has become a challenging task. Moreover, multiple owners may enforce different access policy to the same data because of their different privacy concerns. A digital rights management（DRM） scheme is proposed for encrypted data in OSNs. In order to protect users＇ sensitive data, the scheme allows users outsource encrypted data to the OSNs service provider for sharing and customize the access policy of their data based on ciphertext-policy attribute-based encryption. Furthermore, the scheme presents a multiparty access control model based on identity-based broadcast encryption and ciphertext-policy attribute-based proxy re-encryption, which enables multiple owners, such as tagged users who appear in a single data, customize the access policy collaboratively, and also allows the disseminators update the access policy if their attributes satisfy the existing access policy. Security analysis and comparison indicate that the proposed scheme is secure and efficient.     

Enhanced secure medical data sharing with traceable anddirect revocation

Sharing of the electronic medical records among different hospitals raises serious concern of the leakage of individual privacy for the adoption of the semi trustworthiness of the medical cloud platform. The tracking and revocation of malicious users have become urgent problems. To solve these problems, this paper proposed a traceable and directly revocable medical data sharing scheme. In the scheme, a unique identity parameter(ID), which was generated and embedded in the private key generation ...     

Fine-grained data access control for distributed sensor networks

Distributed sensor networks are becoming a robust solution that allows users to directly access data generated by individual sensors. In many practical scenarios, fine-grained access control is a pivotal security requirement to enhance usability and protect sensitive sensor information from unauthorized access. Recently, there have been proposed many schemes to adapt public key cryptosystems into sensor systems consisting of high-end sensor nodes in order to enforce security policy efficiently. However, the drawback of these approaches is that the complexity of computation increases linear to the expressiveness of the access policy. Key-policy attribute-based encryption is a promising cryptographic solution to enforce fine-grained access policies on the sensor data. However, the problem of applying it to distributed sensor networks introduces several challenges with regard to the attribute and user revocation. In this paper, we propose an access control scheme using KP-ABE with efficient attribute and user revocation capability for distributed sensor networks that are composed of high-end sensor devices. They can be achieved by the proxy encryption mechanism which takes advantage of attribute-based encryption and selective group key distribution. The analysis results indicate that the proposed scheme achieves efficient user access control while requiring the same computation overhead at each sensor as the previous schemes.     

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。

     

基于PBAC模型和IBE的医疗数据访问控制方案

医疗卫生领域形成的医疗大数据中包含了大量的个人隐私信息,面临着外部攻击和内部泄密的潜在安全隐患。传统的访问控制模型没有考虑用户访问目的在侧重数据隐私的访问控制中的重要作用,现有的对称、非对称加密技术又都存在密钥管理、证书管理复杂的问题。针对这些问题,提出了综合应用PBAC模型和IBE加密技术的访问控制方案,支持针对医疗数据密文的灵活访问控制。通过加入条件目的概念对PBAC模型进行扩展,实现了对目的树的全覆盖;以病患ID、条件访问位和预期目的作为IBE身份公钥进行病患数据加密,只有通过认证并且访问目的符合预期的用户才能获得相应的私钥和加密数据,从而实现对病患信息的访问。实验结果证明,该方案达到了细粒度访问控制和隐私保护的目的,并具有较好的性能。     

具有细粒度访问控制的隐藏关键词可搜索加密方案

针对现有的可搜索加密算法在多用户环境中密钥管理难度大并且缺乏细粒度访问控制机制的问题,利用基于密文策略的属性加密机制(CP-ABE, ciphertext-policy attribute based encryption)实现了对隐藏关键词可搜索加密方案的细粒度访问控制。数据拥有者可以为其在第三方服务器中存储的加密指定灵活的访问策略,只有自身属性满足该访问策略的用户才有权限对数据进行检索和解密。同时还能够实现对用户的增加与撤销。安全性分析表明方案不仅可以有效地防止隐私数据的泄露,还可以隐藏关键词的信息,使得第三方服务器在提供检索功能的同时无法窃取用户的任何敏感信息。方案的效率分析表明,该系统的检索效率仅为数十微秒,适合在大型应用系统中使用。