Abstract: With the rapid development of cloud computing, an increasing number of organizations and individuals store and share their data on clouds. While cloud storage brings people convenience, it also brings a series of problems at the same time. For example, the data uploaded to the cloud may be tampered and damaged. Therefore, shared data auditing has become an important issue in the field of cloud storage, attracting the attention of researchers. However, the state-of-the-art schemes cannot fully meet the performance and security requirements. Therefore, this paper proposes a public audit shared data protocol for cloud storage by using blockchain and Rank-based Merkle AVL tree (RB-MHT) to achieve privacy preserving and batch auditing to reduce system overhead as well as keeping the security of modification record in this blockchain-based scheme. For privacy preserving, the auditing signature is only related to group management during the audit process and data is blind by a random value. Furthermore, the security of the scheme is verified and its performance is evaluated through implementation. The results demonstrate that the proposed scheme is secure and efficient.

Key words: cloud computing, cloud storage, data shared, privacy preserving, blockchain