Comment on “Privacy-preserving public auditing for non-manager group shared data”

Using cloud storage, users can remotely store their data without the burden on complicated local storage management and maintenance. However, users will no longer physically possess the storage of their data after they upload the data to the cloud. It is very natural for users to suspect whether their data stored in the cloud is intact. To help users efficiently check the integrity of the outsourced data, many public auditing schemes have been proposed. Recently, Huang et al. have proposed a privacy-preserving public auditing scheme for non-manager group shared data. In this paper, we find a security flaw in their auditing scheme. Even if the cloud has deleted or polluted the whole outsourced data, it still can pass the verification of the verifier. And then, we overcome this shortcoming by improving their scheme, which prevents the cloud forging a valid proof to pass the integrity auditing. Last, we perform the concrete implementation of our improved scheme and Huang et al. ’s scheme.

     

具有紧凑标签的基于身份匿名云审计方案

云存储技术具有效率高、可扩展性强等优点。用户可以借助云存储技术节省本地的存储开销,并与他人共享数据。然而,数据存储到云服务器后,用户失去对数据的物理控制,需要有相应的机制保证云中数据的完整性。数据拥有证明（PDP,provable data possession）机制允许用户或用户委托的第三方审计员（TPA,third party auditor）对数据完整性进行验证。但在实际应用中,数据通常由多个用户共同维护,用户在进行完整性验证请求的同时泄露了自己的身份。匿名云审计支持 TPA 在完成数据完整性验证时保证用户的匿名性。在基于身份体制下,匿名云审计方案通常需要借助基于身份的环签名或群签名技术实现,数据标签的构成元素与用户数量相关,使得数据标签不够紧凑,存储效率较低。为了解决这一问题,提出一种基于身份的匿名云审计方案通用构造,使用一个传统体制下的签名方案和一个传统体制下的匿名云审计方案即可构造一个基于身份的匿名云审计方案。基于该通用构造,使用 BLS 签名和一个传统体制下具有紧凑标签的匿名云审计方案设计了具有紧凑标签的基于身份匿名云审计方案。该方案主要优势在于数据标签短,能够减少云服务器的存储压力,提高存储效率。此外,证明了该方案的不可欺骗性和匿名性。     

Security analysis of a publicly verifiable data possession scheme for remote storage

As an essential technology of cloud computing, the cloud storage can exactly satisfy the demand of users with the service of scalability, ubiquitous access and low maintenance cost. However, moving data to the cloud servers will bring some significant security challenges due to the loss of the physical data possession. In order to verify the data integrity, many verifiable data possession schemes have been proposed in last several years. Very recently, Tang and Zhang proposed a new publicly verifiable data possession (PVDP) scheme for remote storage. They claimed that their scheme was suitable for checking the storage correctness and secure against various types of attacks. In this paper, we analyze the security of Tang and Zhang’s PVDP scheme and prove that it is vulnerable to the data recovery attack. We also demonstrate that PVDP scheme works incorrectly with a concrete instance. Our analysis shows that their scheme is not suitable for practical applications. Our work can help cryptographers and engineers design and implement more secure and efficient public auditing schemes for the cloud storage data.     

A Lightweight And privacy-preserving public cloud auditing scheme without bilinear pairings in smart cities

Smart Cities have become a global strategy. However, massive data generated by various smart devices need to be uploaded and stored to the cloud servers. It is critical to ensure the integrity and privacy of the stored data. Quite a few public cloud auditing schemes have been proposed recently. However, most of them use bilinear pairing operations in the audit phase, requiring a significant time cost. Meanwhile, users (may be resource-constrained mobile devices or sensor nodes) still need to perform significant computations, like computing meta data for each data block, which bring a huge burden of calculation for these users. Moreover, those schemes cannot effectively protect users’ data privacy. Thus, we propose a lightweight and privacy-preserving public cloud auditing scheme for smart cities that does not require bilinear pairings. First, the proposed scheme is pairing-free, and allowing a third party auditor to generate authentication meta set on behalf of users. Furthermore, it also protects data privacy against the third party auditor and the cloud service providers. In addition, this new scheme can be easily and naturally extended to batch auditing in a multi-user scenario. Detailed security and performance analyses show that the proposed scheme is more secure and efficient compared to the existing public cloud auditing schemes.     

支持受损数据定位与恢复的动态群用户可证明存储

The outsourced storage mode of cloud computing leads to the separation of data ownership and management rights of data owners, which changes the data storage network model and security model. To effectively deal with the software and hardware failures of the cloud server and the potential dishonest service provider and also ensure the availability of the data owners’ data, the design of secure and efficient data availability and recoverability auditing scheme has both theoretical and practical importance in solving the concern of users and ensuring the security of cloud data. However, most of the existing studies were designed for the security and efficiency of data integrity or recoverability schemes, without considering the fast identification and reliable recovery of damaged data under dynamic group users. Thus, to quickly identify and recover damaged data, a publicly verifiable proof of storage scheme was proposed for dynamic group cloud users. The designed scheme enabled a trusted third-party auditor to efficiently identify the damaged files through a challenge-response protocol and allowed the cloud storage server to effectively recover them when the degree of data damage is less than an error correction ability threshold. The scheme combined association calculation and accumulation calculation, which effectively reduced the number of calculations for the identification of damaged data. By combining erasure coding and shared coding technology, the scheme achieved effective recovery of damaged data of dynamic group users. At the same time, the scheme also supported dynamic user revocation, which ensured the integrity audit and reliable recovery of the collective data after user revocation. The network model and threat model of the designed scheme were defined and the security of the scheme under the corresponding security model was proved. Through the prototype implementation of the scheme in the real environment and the modular performance analysis, it is proved that the proposed scheme can effectively identify the damaged data and reliably recover the cloud data when the data is damaged. Besides, compared with other schemes, it is also proved that the proposed scheme has less computational overhead in identifying and recovering damaged data. © 2022, Beijing Xintong Media Co., Ltd.. All rights reserved.     

Cryptanalysis and improvement of Panda - public auditing for shared data in cloud and internet of things

Cloud computing and internet of things have gained remarkable popularity by a wide spectrum of users recently. Despite of the convenience of cloud storage, security challenges have risen upon the fact that users do not physically possess their data any more. Thus, some auditing schemes are introduced to ensure integrity of the outsourced data. And among them Panda is a public auditing scheme for shared data with efficient and secure user revocation proposed by Wang et al. It argued that it could verify the integrity of shared data with storage correctness and public auditing. In this paper, we analyze this scheme and find some security drawbacks. Firstly, Panda cannot preserve shared data privacy in cloud storage. Furthermore, our analysis shows that Panda is vulnerable to integrity forgery attack, which can be performed by malicious cloud servers to forge a valid auditing proof against any auditing challenge even without correct data storage. Then we pinpoint that the primary cause of the insecurity is the linear combinations of sampled data blocks without random masking properly. Finally, we propose an improvement of Panda together with data privacy preserving and sound public auditing while incurring optimal communication and computation overhead.     

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.     

Privacy-preserving public auditing for educational multimedia data in cloud computing

Nowadays, as distance learning is being widly used, multimedia data becomes an effective way for delivering educational contents in online educational systems. To handle the educational multimedia data efficiently, many distance learning systems adopt a cloud storage service. Cloud computing and storage services provide a secure and reliable access to the outsourced educational multimedia contents for users. However, it brings challenging security issues in terms of data confidentiality and integrity. The straightforward way for the integrity check is to make the user download the entire data for verifying them. But, it is inefficient due to the large size of educational multimedia data in the cloud. Recently many integrity auditing protocols have been proposed, but most of them do not consider the data privacy for the cloud service provider. Additionally, the previous schemes suffer from dynamic management of outsourced data. In this paper, we propose a public auditing protocol for educational multimedia data outsourced in the cloud storage. By using random values and a homomorphic hash function, our proposed protocol ensures data privacy for the cloud and the third party auditor (TPA). Also, it is secure against lose attack and temper attack. Moreover, our protocol is able to support fully dynamic auditing. Security and performance analysis results show that the proposed scheme is secure while guaranteeing minimum extra computation costs.     

A secure and efficient public auditing scheme using RSA algorithm for cloud storage

Cloud storage is widely used by both individual and organizational users due to the many benefits, such as scalability, ubiquitous access, and low maintenance cost (and generally free for individual users). However, there are known security and privacy issues in migrating data to the cloud. To ensure or verify data integrity, a number of cloud data integrity checking schemes with different properties have been presented in the literature. Most existing schemes were subsequently found to be insecure or have high computation and communication costs. More recently in 2016, Yu et al. (Future Gener Comput Syst 62:85–91, 2016) proposed an identity-based auditing scheme for checking the integrity of cloud data. However, in this paper, we reveal that the scheme is vulnerable to data recovery attack. We also present a new identity-based public auditing scheme and formally prove the security of the scheme under the RSA assumption with large public exponents in the random oracle model. We then evaluate the performance of our proposed scheme and demonstrate that in comparison with Yu et al.’s scheme, our proposal is more practical in real-world applications.     

高效可撤销的共享数据云存储审计

共享数据的云存储审计是指对群用户共享的云数据的完整性进行审计. 由于在共享数据云存储审计中, 用户可能因各种原因加入和离开用户群, 因此这种方案通常支持群用户撤销. 在大多数现存的共享数据云审计方案中, 用户撤销的计算开销与用户群要上传的文件块总数成线性关系, 造成很大的计算和通信代价, 如何减少用户撤销产生的计算和通...     

云存储服务中数据完整性审计方案综述

云存储是由云计算提供的一个重要服务,允许数据拥有者将数据远程存储到云服务器上,同时又能够从云服务器上便捷、高效地获取这些数据,没有本地存储和维护数据的负担。然而,这种新的数据存储模式也引发了众多安全问题,一个重要的问题就是如何确保云服务器中数据拥有者数据的完整性。因此,数据拥有者以及云存储服务提供商亟需一个稳定、安全、可信的完整性审计方案,用于审核云服务器中数据的完整性和可用性。不仅如此,一个好的数据完整性审计方案还需满足如下功能需求：支持数据的动态操作,包括插入、删除、修改;支持多用户、多云服务器的批量审计;确保用户数据的隐私性;注重方案的执行效率,尽量减少数据拥有者和云服务器的计算开销与通信开销。为了促进云存储服务的广泛应用与推广,文章重点对云数据完整性审计方案的研究现状进行综述,描述云存储以及数据完整性审计的相关概念、特点,提出云计算环境下数据完整性审计模型和安全需求,阐述云存储数据完整性审计的研究现状,并重点分析部分经典方案,通过方案对比,指出当前方案存在的优点及缺陷。同时,文章还指出了本领域未来的研究方向。     

Cloud data auditing with designated verifier

An auditing scheme is a good way to prove owner’s data outsourced to the cloud are kept intact, and a scheme capable of giving public verifiability service is a good option that some researchers have managed to build for the last few years. However, in a public auditing scheme everybody does verification of data and a possibility of leaking some secrete information to the public verifiers is an issue that data owners are unhappywith this scenario. For example, the data owner does not want anybody else to know he has the data stored in the cloud server. Motivated by the issue of privacy associated with public auditing system, we proposed a designated verifier auditing (DVA) scheme based on Steinfeld et al.’s universal designated verifier (DV) signature scheme. Our DVA scheme authorizes a third party auditor with private verification capability. It provides private verification because the scheme involves private key of the verifier. Moreover, we present the batch auditing scheme to improve auditing efficiency. Through rigorous security analysis we showed that our scheme is provably secure in the random oraclemodel assuming that the computational Diffie-Hellman (CDH) problem is hard over the group of bilinear maps.     

基于区块链的云数据审计方案

云存储凭借高扩展性、高可靠性、低成本的数据管理优点得到用户青睐。然而,如何确保云数据完整性成为亟待解决的安全挑战。目前的云数据完整性审计方案,绝大部分是基于半可信第三方来提供公共审计服务,它们存在单点失效、性能瓶颈以及泄露用户隐私等问题。针对这些缺点提出了基于区块链的审计模型。该模型采用分布式网络、共识算法建立一个去中心化、易扩展的网络解决单点失效问题和计算力瓶颈,利用区块链技术和共识算法加密用户数据保证数据不可窜改和伪造,确保了用户数据的隐私。实验结果表明,与基于半可信第三方云数据审计方案相比,该模型能够保护用户隐私,显著提高了审计效率,减少通信开销。     

Data storage auditing service in cloud computing: challenges,methods and opportunities

Cloud computing is a promising computing model that enables convenient and on-demand network access to a shared pool of configurable computing resources. The first offered cloud service is moving data into the cloud: data owners let cloud service providers host their data on cloud servers and data consumers can access the data from the cloud servers. This new paradigm of data storage service also introduces new security challenges, because data owners and data servers have different identities and different business interests. Therefore, an independent auditing service is required to make sure that the data is correctly hosted in the Cloud. In this paper, we investigate this kind of problem and give an extensive survey of storage auditing methods in the literature. First, we give a set of requirements of the auditing protocol for data storage in cloud computing. Then, we introduce some existing auditing schemes and analyze them in terms of security and performance. Finally, some challenging issues are introduced in the design of efficient auditing protocol for data storage in cloud computing.     

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.     

基于模糊身份的动态数据审计方案

云存储服务的快速发展,也带来众多安全挑战.针对云存储数据的完整性,已有的基于模糊身份的审计方案仅仅支持静态数据,因此很多情况并不适用.本文提出了一种基于模糊身份的动态数据完整性审计方案,结合默克哈希树的动态数据结构,实现用户对云端数据的完全动态操作.该方案采用基于模糊身份的密码体制,与基于公钥基础设施的数据完整性审计方案相比,避免了对公钥证书颁发、管理、吊销的过程,降低了通信代价.并且该方案能够支持批量验证,提高认证效率.最后,本文从安全性和功能上对新方案进行分析,能够抵抗伪造攻击,也保护了数据隐私安全,并且在功能上较其他方案也有一定的优势.     

面向真实云存储环境的数据持有性证明系统

对数据动态更新和第三方审计的支持的实现方式是影响现有数据持有性证明（provable data possession,简称PDP）方案实用性的重要因素.提出面向真实云存储环境的安全、高效的PDP系统IDPA-MF-PDP.通过基于云存储数据更新模式的多文件持有性证明算法MF-PDP,显著减少审计多个文件的开销.通过隐式第三方审计架构和显篡改审计日志,最大限度地减少了对用户在线的需求.用户、云服务器和隐式审计者的三方交互协议,将MF-PDP和隐式第三方审计架构结合.理论分析和实验结果表明：IDPA-MF-PDP具有与单文件PDP方案等同的安全性,且审计日志提供了可信的审计结果历史记录;IDPA-MF-PDP将持有性审计的计算和通信开销由与文件数线性相关减少到接近常数.     

基于数据持有性证明的完整性验证技术综述

在云存储环境中,为确保用户数据的完整性和可用性,用户需要对存储在云服务器中的数据进行完整性验证。现有的数据完整性验证机制主要有两种：数据持有性证明（Provable Data Possession,PDP）与可恢复数据证明（Proof of Retrievability,POR）。重点讨论了基于PDP的云存储数据完整性验证机制。结合PDP验证机制特性,对PDP方案进行分类,并总结了各分类使用的关键技术;根据分类阐述了PDP方案的研究现状,并对典型方案在动态验证、批量审计、计算开销等几个方面进行了对比分析;讨论了基于PDP的云存储数据完整性验证机制未来的发展方向。     

基于智能合约的工业互联网数据公开审计方案

随着工业互联网产生的数据量日益增加,越来越多的企业选择将工业互联网数据外包存储在云服务器上以节省存储开销.为了防止外包存储的数据被篡改或删除,企业需要定期对其进行审计.提出了一种基于智能合约的工业互联网数据公开审计方案.该方案基于博弈论的思想,设计了一系列智能合约,以高效地抵抗参与者恶意行为.与现有抗合谋的公开审计方案相比,该方案不依赖于复杂的密码学工具实现对参与者恶意行为的抵抗,使得其更为高效,进而能够更好地应用于海量且频繁更新的工业互联网数据场景中.特别地,所设计的博弈合约作为一种独立的工具,能够与现有的公开审计方案有效结合,在不降低其审计效率的同时,增加方案的安全性.在本地环境和以太坊公有测试链Ropsten上对博弈合约以及整体方案进行了一系列的测试,结果表明,所设计的合约运行花费低且对运行环境适应性强,对原有完整性审计方案的效率影响小;同时,与其他抗审计者恶意行为的完整性方案相比,该方案更为高效.     

云存储密文访问控制方案

提出了一种在基于密文策略的属性加密(ciphertext-policy attribute-based encryption,CP-ABE)应用场景下,在云存储中实现高效、精细、灵活的密文访问控制的方案。新方案通过引入密钥分割技术和代理重加密技术,在权限撤销时将部分重加密工作转移给云服务提供商执行,大大降低了数据属主的计算代价。与现有方案相比,新方案不仅能够支持多种门限的精细的访问控制策略,而且在权限撤销时,既可以属性集为单位,又可以同一属性集下不同用户为单位。最后分析了方案的安全性,并测试了运行效率。实验结果表明,新方案明显优于一般方案,特别是考虑云存储及多用户情况下,新方案的优势更加明显。