Data integrity auditing technology serves as an essential tool to ensure the data's integrity with the popularity of remote storage. However, existing data integrity auditing models are unsuitable for a large number of files with interrelationships and heavily depend on a centralized Third-Party Auditor (TPA). To address these issues, in this paper we propose a blockchain-assisted searchable integrity auditing scheme for large-scale similarity data. To broaden the scope of the auditing model and enhance its ability to handle interconnected files, we utilize the keyword to design a search index and a trapdoor to achieve authenticator searchability for the interconnected files. The integrity of the searching result from the cloud side can be guaranteed at the same time. To reduce reliance on centralized TPA and enhance the credibility and transparency of auditing, we integrate blockchain technology along with smart contracts to replace TPA and achieve multitask auditing. We adopt a certificateless cryptosystem to generate the authenticator, while considering the cost reduction. Moreover, an arbitrator is proposed to achieve fairness judge. Theoretical and security analysis demonstrate that the proposed scheme is efficient and secure, making it a promising solution for data auditing in a wide range of applications.

As decentralized storage becomes more prevalent, ensuring data integrity within these systems has gained increasing importance. However, the introduction of a centralized and trustedCloud Combiner(CO) to manage auditing across distributedCloud Servers(CSs) presents several challenges, which not only increases communication costs with independent CSs but also diminishes the credibility of the auditing results. Additionally, traditional approaches often require either certificate and key management or the establishment of secure transmission channels, which incur substantial overhead. Furthermore, the computational cost for index generation to support searchable auditing is often high. To address these challenges, we propose a collaborative and searchable integrity auditing scheme for multi-replica data that eliminates the need for a CO. Specifically, we design a certificate-based authenticator for multi-copy data blocks, which simplifies certificate and key management while removing the need for secure channels. To enable efficient searchable auditing, we introduce a novel index tag that matches authenticators, thereby reducing the computational overhead. Moreover, we leverage blockchain technology to enhance the credibility of the auditing process and ensure the integrity of the search results. Both security and performance analyses demonstrate that the proposed scheme is secure and efficient.

Provable Data Possession (PDP) is an alternative technique that guarantees the integrity of remote data. However, most current PDP schemes are inapplicable to similarity-like data checking with the same attribute, i.e., when there are numerous similar files to be checked by Data Owners (DOs). Some traditional models cannot resist the corrupt auditors who always generate biased challenge information. Besides, a copy-summation attack exists in some schemes, which means the Cloud Server (CS) can bypass the verification by storing the median value instead of initial data via summation operation. To address the issues above, in this work, we propose a keyword searchable PDP scheme for large similar data checking. To achieve searchability, we introduce the notion of a keyword in PDP and design a specific index structure to match the authenticator. The scheme enables all matched files to be auditable and verifiable, while guaranteeing privacy protections. Unlike existing methods, our Third Party Auditor (TPA) checks all similar data containing the same keyword simultaneously. We utilize unpredictable yet verifiable public information on the blockchain to generate challenge information, rather than relying on a centralized TPA. The proposed scheme can resist copy-summation attacks. Theoretical analysis demonstrates that the proposed scheme satisfies the security requirements, and our evaluations demonstrate its efficiency.

Summary Cloud storage provides a convenient way of collaboration and sharing. An increasing number of users are becoming more open to sharing their data with others. Consequently, the integrity of shared data has started to draw significant attention due to the loss control of it. Remote data integrity techniques can solve this problem. To resist the collusion between the third party auditor and the cloud server, existing integrity auditing schemes utilize blockchain to replace the third party auditor to do some work. However, these schemes still involve collusion between the third party auditor and the miners and cannot guarantee the third party auditor to execute the auditing process honestly. Considering this, we propose a blockchain‐based transparent and certificateless data integrity auditing scheme. Specifically, we design the smart contract combining the commitment technology to generate the challenge information and record the auditing information. Besides, we combine certificateless cryptography and the blind technology to achieve the privacy‐preserving. The proposed scheme can resist collusion, improve the transparency of the auditing process, protect the data privacy and reduce the overhead of certificate management and key management. The security analysis and performance evaluation demonstrate the security and efficiency of the scheme.

Data deduplication and integrity auditing based blockchain plays an important role in guaranteeing secure and efficient cloud storage services. However, existing data deduplication schemes support auditing either with the assistance of a trust center (key server or third-party auditor) or bear the waste of computation and storage resources caused by repetitive authenticators storage and key storage. In this paper, we propose a blockchain-based shared data integrity auditing and deduplication scheme. Specifically, we propose a deduplication protocol based on ID-based broadcast encryption without key servers and achieve key deduplication on the user side. Next, we propose a data integrity auditing protocol by using the characteristic of convergent encryption to achieve authenticator deduplication on the cloud service provider side. Besides, we achieve decentralized data integrity auditing based blockchain without relying on a single trusted third-party auditor and improve the credibility of the auditing result. On this basis, we propose two bath auditing protocols for different scenarios to improve efficiency. Security and performance analysis demonstrates that the authenticators' storage cost on the cloud storage provider side can be reduced from${\mathcal {O}}({\mathcal {F}})$to${\mathcal {O}}(1)$and the key storage cost on the user side can be reduced from${\mathcal {O}}({\mathcal {F}})$to${\mathcal {O}}(1)$as well.

J1C2 Presentation Abstract at IEEE SERVICES 2022 for IEEE Transactions on Services Computing, doi: 10.1109/TSC.2021.3086023

Cloud storage service provides a convenient way for users to store massive data. To guarantee the integrity of the outsourced data, provable data possession (PDP) schemes for multi-copy data and multi-cloud have been proposed respectively. To avoid a single point of failure and to increase the security of the outsourced data, many users store multiple copies on multiple cloud servers. However, few protocols support multi-copy data and multi-cloud at the same time. Considering that three entities (third-party auditor, cloud organizer and cloud storage servers) participate in the auditing process, it is difficult for users to locate the position of the faults, including entity position, file position and data block corruption position, when the auditor reports data corruption. In this paper we propose a certificateless multi-copy public auditing protocol in multi-cloud storage, which supports to locate the faults entities and corrupted data blocks. Specifically, instead of relying on a trusted centralized judgement entity to deal with the faults detection, smart contracts combined with the binary search technique are utilized to help achieve the reliability of faults localization result and the accuracy of the judgement. Additionally, the proposed protocol supports data dynamics update, including data modification, insertion and deletion. Theoretical analysis and experiment results show that our protocol is efficient and practical.

Traditional data sharing systems are facing new challenges when implementing access control with more and more complex data sharing requirements. Flexibility of user revocation in completely decentralized environments needs to be taken into account. In this article, we propose a Key-Policy Attribute-Based Encryption scheme with Multiple and Flexible Revocation (MAFR-KP-ABE) to achieve the features of decentralized authorization and flexible revocation. We prove the security of our MAFR-KP-ABE scheme in the standard model and provide the comparison with relevant schemes to demonstrate its efficiency. Then we propose a fine-grained access control system based on MAFR-KP-ABE scheme and blockchain that matches the need of paid data sharing services with several security properties enhanced. Security analysis and system implementation are given subsequently to demonstrate our system efficient and secure.