Efficient revocation in ciphertext-policy attribute-based encryption based cryptographic cloud storage

It is secure for customers to store and share their sensitive data in the cryptographic cloud storage.However,the revocation operation is a sure performance killer in the cryptographic access control system.To optimize the revocation procedure,we present a new efficient revocation scheme which is efficient,secure,and unassisted.In this scheme,the original data are first divided into a number of slices,and then published to the cloud storage.When a revocation occurs,the data owner needs only to retrieve one slice,and re-encrypt and re-publish it.Thus,the revocation process is accelerated by affecting only one slice instead of the whole data.We have applied the efficient revocation scheme to the ciphertext-policy attribute-based encryption(CP-ABE) based cryptographic cloud storage.The security analysis shows that our scheme is computationally secure.The theoretically evaluated and experimentally measured performance results show that the efficient revocation scheme can reduce the data owner’s workload if the revocation occurs frequently.     

A method for trust management in cloud computing: Data coloring by cloud watermarking

With the development of Internet technology and human computing, the computing environment has changed dramatically over the last three decades. Cloud computing emerges as a paradigm of Internet computing in which dynamical, scalable and often virtualized resources are provided as services. With virtualization technology, cloud computing offers diverse services (such as virtual computing, virtual storage, virtual bandwidth, etc.) for the public by means of multi-tenancy mode. Although users are enjoying the capabilities of super-computing and mass storage supplied by cloud computing, cloud security still remains as a hot spot problem, which is in essence the trust management between data owners and storage service providers. In this paper, we propose a data coloring method based on cloud watermarking to recognize and ensure mutual reputations. The experimental results show that the robustness of reverse cloud generator can guarantee users embedded social reputation identifications. Hence, our work provides a reference solution to the critical problem of cloud security.     

NaEPASC: a novel and efficient public auditing scheme for cloud data

Cloud computing is deemed the next-generation information technology （IT） platform, in which a data center is crucial for providing a large amount of computing and storage resources for various service applications with high quality guaranteed. However, cloud users no longer possess their data in a local data storage infrastructure, which would result in auditing for the integrity of outsourced data being a challenging problem, especially for users with constrained computing resources. Therefore, how to help the users complete the verification of the integrity of the outsourced data has become a key issue. Public verification is a critical technique to solve this problem, from which the users can resort to a third-party auditor （TPA） to check the integrity of outsourced data. Moreover, an identity-based （ID-based） public key cryptosystem would be an efficient key management scheme for certificatebased public key setting. In this paper, we combine ID-based aggregate signature and public verification to construct the protocol of provable data integrity. With the proposed mechanism, the TPA not only verifies the integrity of outsourced data on behalf of cloud users, but also alleviates the burden of checking tasks with the help of users＇ identity. Compared to previous research, the proposed scheme greatly reduces the time of auditing a single task on the TPA side. Security analysis and performance evaluation results show the high efficiency and security of the proposed scheme.     

A cost effective fault-tolerant scheme for RAIDs

The rapid progress in mass storage technology has made it possible for designers to implement large data storage systems for a variety of applications.One of the efficient ways to build large storage systems is to use RAIDs only when one error occurs .But in large RAIDs systems ,the fault probability will increase when the number of disks increases ,and the use of disks with big storage capacity will cause the recovering time to prolong,thus the probability of the second disk‘‘‘‘‘‘‘‘s fault will incerease Therefore,it is necessary to develop methods to recover data when two or more errors have occurred In this paper,a fault tolerant scheme is proposed based on extended Reed-Solomon code,a recovery procedure is designed to correct up to two errors which is implemented by software and hardware together,and the scheme is verified by computer simulation,In this scheme,only two redundant disks are used to recover up to two disks‘‘‘‘‘‘‘‘ fault .The encoding and decoding methods,and the implementation based on software and hardware are described.The application of the scheme in software RAIDs that are builit in cluster computers are also described .Compared with the existing methods such as EVENODD and DH ,the proposed scheme has distinct improvement in implementation and redundancy.     

Dynamic data auditing scheme for big data storage

When users store data in big data platforms,the integrity of outsourced data is a major concern for data owners due to the lack of direct control over the data.However,the existing remote data auditing schemes for big data platforms are only applicable to static data.In order to verify the integrity of dynamic data in a Hadoop big data platform,we presents a dynamic auditing scheme meeting the special requirement of Hadoop.Concretely,a new data structure,namely Data Block Index Table,is designed to support dynamic data operations on HDFS(Hadoop distributed file system),including appending,inserting,deleting,and modifying.Then combined with the MapReduce framework,a dynamic auditing algorithm is designed to audit the data on HDFS concurrently.Analysis shows that the proposed scheme is secure enough to resist forge attack,replace attack and replay attack on big data platform.It is also efficient in both computation and communication.     

Data Security Model for Cloud Computing

From the perspective of data security, which has always been an important aspect of quality of service, cloud computing focuses a new challenging security threats. Therefore, a data security model must solve the most challenges of cloud computing security. The proposed data security model provides a single default gateway as a platform. It used to secure sensitive user data across multiple public and private cloud applications, including Salesforce, Chatter, Gmail, and Amazon Web Services, without influencing functionality or performance. Default gateway platform encrypts sensitive data automatically in a real time before sending to the cloud storage without breaking cloud application. It did not effect on user functionality and visibility. If an unauthorized person gets data from cloud storage, he only sees encrypted data. If authorized person accesses successfully in his cloud, the data is decrypted in real time for your use. The default gateway platform must contain strong and fast encryption algorithm, file integrity, malware detection, firewall, tokenization and more. This paper interested about authentication, stronger and faster encryption algorithm, and file integrity.     

An ID-based authenticated dynamic group key agreement with optimal round

Group key agreement protocols are crucial for achieving secure group communications.They are designed to provide a set of users with a shared secret key to achieve cryptographic goal over a public network.When group membership changes,the session key should be refreshed efficiently and securely.Most previous group key agreement protocols need at least two rounds to establish or refresh session keys.In this paper,a dynamic authenticated group key agreement(DAGKA) protocol based on identity-based cryptography is presented.By making use of the members’ values stored in previous sessions,our Join and Leave algorithms reduce the computation and communication costs of members.In the proposed protocol,Setup and Join algorithms need one round.The session key can be refreshed without message exchange among remaining users in Leave algorithm,which makes the protocol more practical.Its security is proved under decisional bilinear Diffie-Hellman(DBDH) assumption in random oracle model.     

A Parallel Implementation of Multiple Secret Image Sharing Based on Cellular Automata

Recently, a multisecret sharing scheme for secret color images among a set of users was proposed, which allows that each participant to share secret color images with the rest of participants in such way that all of them can recover all secret color images only if all participants pool their shares. In this work a parallel implementation of the cellular automata-based multisecret sharing scheme is proposed, in which the technology of CUDA （Compute Unified Device Architecture） is used in parallelization, taking advantage that each cell of cellular automata can be processed independently. The processing time of the proposed scheme is analyzed and it is proved that the proposed parallel algorithm using the CUDA structure is more than 12 times faster than the conventional sequential algorithm. This reduction of temporal complexity allows the practical use of the secret sharing scheme in many information security fields.     

Server-aided access control for cloud computing

With the massive diffusion of cloud computing,more and more sensitive data is being centralized into the cloud for sharing,which brings forth new challenges for the security and privacy of outsourced data.To address these challenges,the server-aided access control (SAAC) system was proposed.The SAAC system builds upon a variant of conditional proxy re-encryption (CPRE) named threshold conditional proxy re-encryption (TCPRE).In TCPRE,t out of n proxies can re-encrypt ciphertexts (satisfying some specified conditions) for the delegator (while up to t?1 proxies cannot),and the correctness of the re-encrypted ciphertexts can be publicly verified.Both features guarantee the trust and reliability on the proxies deployed in the SAAC system.The security models for TCPRE were formalized,several TCPRE constructions were proposed and that our final scheme was secure against chosen-ciphertext attacks was proved.     

Scalable SaaS Indexing Algorithms with Automated Redundancy and Recovery Management

Software-as-a-Service (SaaS) is a new software delivery model with Multi-Tenancy Architecture (MTA). An SaaS system is often mission critical as it often supports a large number of tenants, and each tenant supports a large number of users. This paper proposes a scalable index management algorithm based on B+ tree but with automated redundancy and recovery management as the tree maintains two copies of data. The redundancy and recovery management is done at the SaaS level as data are duplicated with tenant information rather than at the PaaS level where data are duplicated in chunks. Using this approach, an SaaS system can scale out or in based on the dynamic workload. This paper also uses tenant similarity measures to cluster tenants in a multi-level scalability architecture where similar tenants can be grouped together for effcient processing. The scalability mechanism also includes an automated migration strategies to enhance the SaaS performance. The proposed scheme with automated recovery and scalability has been simulated, the results show that the proposed algorithm can scale well with increasing workloads.     

用户可动态撤销及数据可实时更新的云审计方案

随着云存储的出现,越来越多的用户选择将大量数据存储在远程云服务器上,以节约本地存储资源.如何验证用户远程存储在云端数据的完整性,成为近年来学术界的一个研究热点.虽然现已提出了很多云审计方案,但大多数方案都假设个人和企业在使用云存储系统的整个过程中,用户及其公私钥始终不变,且不能高效地对数据进行实时动态更新.为此,提出一种轻量级的支持用户可动态撤销及存储数据可动态更新的云审计方案.首先,该方案允许用户可高效地动态撤销（包括更换公私钥）,在用户撤销阶段,采用了多重单向代理重签名技术,新用户只需计算重签名密钥,而无需从云端下载数据再重新签名后上传到云端;其次,该方案能够保证数据可实时动态更新（插入、删除、修改）,通过在数据块的身份识别码中引入虚拟索引,数据动态更新时,只有被更新数据块的身份识别码发生变化,其余数据块的身份识别码保持不变;最后,在重签名阶段,云服务器代替新用户进行签名,在审计阶段,第三方审计者代表当前用户对存储在远程云服务器上的数据进行完整性验证,减轻了终端用户的计算开销及系统的通信开销（轻量级）.安全性分析和性能分析进一步说明,该方案是安全的和高效的.     

多用户通信机制中支持隐私保护的属性基动态广播加密

云计算和物联网的快速发展使多用户信息共享机制备受关注,然而当用户将个人数据上传到云服务器与不同用户共享时,未经授权的用户和不可信的第三方云服务提供商会窥探这些隐私数据,对数据安全和用户隐私构成严重威胁。此外,多用户共享机制还存在访问控制不灵活、用户撤销和动态管理等问题。为了解决这些问题,文章结合属性基加密与广播加密技术提出一种动态广播加密机制。该方案在保证数据安全的同时,利用不经意传输协议,实现了接收者的匿名,保护了用户隐私。此外,该方案还支持新用户随时动态加入系统,且不影响原用户在系统中的解密能力,并实现了用户撤销和快速解密。性能分析表明,该方案较已有方案在安全性和效率方面有明显优势。     

面向可变用户群体的可搜索属性基加密方案

为解决属性基加密方案中用户撤销繁琐、密文更新计算开销大的问题,提出一种面向可变用户群体的可搜索属性基加密方案.利用二叉树管理撤销列表,当需要撤销用户时,可信中心只要将其加入撤销列表,并通知云服务器更新部分密文,提高了用户撤销的效率.考虑到利用二叉树实现用户撤销会导致系统中用户数量存在上限,当某个二叉树叶结点所代表的用户被撤销后,只要更新二叉树中设置的随机值,其他用户就可以重复使用该结点.基于配对计算为用户提供密文搜索功能,并保证被撤销的用户无法搜索密文.安全性分析表明,该方案在随机谕言模型下满足选择明文不可区分安全性.性能分析和实验数据表明,该方案相比于同类方案,计算开销更小.     

Generic user revocation systems for attribute-based encryption in cloud storage

Cloud-based storage is a service model for businesses and individual users that involves paid or free storage resources. This service model enables on-demand storage capacity and management to users anywhere via the Internet. Because most cloud storage is provided by third-party service providers, the trust required for the cloud storage providers and the shared multi-tenant environment present special challenges for data protection and access control. Attribute-based encryption (ABE) not only protects data secrecy, but also has ciphertexts or decryption keys associated with fine-grained access policies that are automatically enforced during the decryption process. This enforcement puts data access under control at each data item level. However, ABE schemes have practical limitations on dynamic user revocation. In this paper, we propose two generic user revocation systems for ABE with user privacy protection, user revocation via ciphertext re-encryption (UR-CRE) and user revocation via cloud storage providers (UR-CSP), which work with any type of ABE scheme to dynamically revoke users.     

一种支持属性撤销的密文策略属性基加密方案

针对传统属性基加密方案中单授权中心计算开销大以及安全性较差等问题,通过引入多个授权中心以及安全两方计算协议等技术,提出一种支持细粒度属性级撤销和用户级撤销的密文策略属性基加密方案。引入多个属性授权中心以颁发并更新属性版本秘钥,同时秘钥生成中心与云存储服务器之间进行安全两方计算等操作,生成并更新用户密钥,从而进行细粒度属性级撤销。在云存储服务器中,对用户列表中的用户唯一秘值及唯一身份值进行操作以实现用户级撤销,同时通过多个授权中心抵抗合谋攻击,并将部分计算工作外包给云端。分析结果表明,与基于AND、访问树和LSSS策略的方案相比,该方案有效增强了系统的安全功能,同时显著降低了系统的计算复杂度。     

移动医疗系统中的可撤销无证书代理重签名方案

代理重签名在保证委托双方私钥安全的前提下, 通过半可信代理实现了双方签名的转换, 在本文方案中, 通过代理重签名实现了在通信过程中终端用户对于身份的隐私要求。移动医疗服务系统因为其有限的计算和存储能力, 需要借助云服务器来对医疗数据进行计算和存储。然而, 在将医疗数据外包给云服务器后, 数据便脱离了用户的控制, 这给用户隐私带来了极大地安全隐患。现有的无证书代理重签名方案大多都不具有撤销功能, 存在着密钥泄露等安全性问题。为了解决这一问题, 本文提出了一种可撤销的无证书代理重签名方案, 在不相互信任的移动医疗服务系统中, 实现了医疗数据传输过程以及云存储过程中的用户匿名性, 同时, 本文方案具有单向性和非交互性, 更适合在大规模的移动医疗系统中使用。此外, 当用户私钥泄露时, 本文利用 KUNode 算法实现了对用户的高效撤销, 并利用移动边缘计算技术将更新密钥和撤销列表的管理外包给移动边缘计算设备,降低了第三方的计算成本, 使其具有较低的延迟。最后, 在随机谕言机模型下证明了所构造的方案在自适应选择消息攻击下的不可伪造性, 并利用 JPBC 库与其他方案进行计算与通信开销的对比。其结果表明, 本方案在具备更优越的功能的同时, 具有较小的计算成本、通信成本和撤销成本。     

支持错误定位的远程数据完整性批量验证方案

远程数据完整性验证技术是保证云数据安全的一种重要技术,能通过与服务器进行少量交互,验证外包数据是否完整。在现实中,云存储服务通常是在多用户与多服务器之间存在的,最近多用户与多服务器环境下的批处理验证方案陆续被提出。但这些方案在数据出错后,往往于一次挑战中无法判定错误数据的拥有者或所在服务器。利用Merkle Hash Tree（MHT）提出了一种支持错误数据定位的批处理校验方案,可以在批处理校验不通过后,同时定位出错误数据的拥有者与其所存储的服务器。     

基于密文策略属性加密体制的匿名云存储隐私保护方案

针对云存储中数据机密性问题,为解决密钥泄漏与属性撤销问题,从数据的机密性存储以及访问的不可区分性两个方面设计了基于密文策略属性加密体制(CP_ABE)的匿名云存储隐私保护方案。提出了关于密钥泄漏的前向安全的不可逆密钥更新算法;在层次化用户组以及改进的Subset-Difference算法基础上,利用云端数据重加密算法实现属性的细粒度撤销;基于同态加密算法实现k匿名l多样性数据请求,隐藏用户潜在兴趣,并在数据应答中插入数据的二次加密,满足关于密钥泄漏的后向安全。在标准安全模型下,基于l阶双线性Diffie-Hellman(判定性l-BDHE)假设给出所提出方案的选择性安全证明,并分别从计算开销、密钥长度以及安全性等方面验证了方案的性能优势。     

Access control scheme with tracing for outsourced databases

To manage dynamic access control and deter pirate attacks on outsourced databases, a dynamic access control scheme with tracing is proposed. In our scheme, we introduce the traitor tracing idea into outsource databases, and employ a polynomial function and filter function as the basic means of constructing encryption and decryption procedures to reduce computation, communication, and storage overheads. Compared to previous access control schemes for outsourced databases, our scheme can not only protect sensitive data from leaking and perform scalable encryption at the server side without shipping the outsourced data back to the data owner when group membership is changed, but also provide trace-and-revoke features. When malicious users clone and sell their decryption keys for profit, our scheme can trace the decryption keys to the malicious users and revoke them. Furthermore, our scheme avoids massive message exchanges for establishing the decryption key between the data owner and the user. Compared to previously proposed publickey traitor tracing schemes, our scheme can simultaneously achieve full collusion resistance, full recoverability, full revocation, and black-box traceability. The proof of security and analysis of performance show that our scheme is secure and efficient.     

云存储中基于代理重加密的CP-ABE访问控制方案

针对云存储中基于密文策略的属性加密（CP-ABE）访问控制方案存在用户解密开销较大的问题,提出了一种基于代理重加密的CP-ABE （CP-ABE-BPRE）方案,并对密钥的生成方法进行了改进。此方案包含五个组成部分,分别是可信任密钥授权、数据属主、云服务提供商、代理解密服务器和数据访问者,其中云服务器对数据进行重加密,代理解密服务器完成大部分的解密计算。方案能够有效地降低用户的解密开销,在保证数据细粒度访问控制的同时还支持用户属性的直接撤销,并解决了传统CP-ABE方案中因用户私钥被非法盗取带来的数据泄露问题。与其他CP-ABE方案比较,此方案对访问云数据的用户在解密性能方面具有较好的优势。