As the artificial intelligence and the cloud computing thrive, transacting data via clouds has become an increasingly profitable business in recent years. Therefore, provable data possession with data transfer (DT-PDP) is proposed to enable transferable auditing ability on data integrity for data owners without downloading the data. However, we found that existing solutions either fail to guarantee secure multi-ownership confirmation or, when fixing multi-ownership, fail to enable scalable and efficient ownership transfer for group transactions. Even worse, during transactions, they leak secret keys to untrusted entities, leading to integrity audit failures for untransacted data. To address primary conflict between fixed ownership distribution and the dynamic nature of group members, and potential collusion attacks due to untrusted entities during transactions. In this paper, we propose a scalable cloud auditing with efficient ownership transfer for group transactions. Specifically, by refining data transaction framework and carefully elaborating tag design in data integrity auditing, we allow 1) partial ownership transfer without disturbing others, if any remaining, inside the group; and 2) efficient ownership transfer between two totally different groups. Additionally, to prevent the risk of key leakage during data transactions, we have incorporated a random mask to maintain the integrity of the audit. The security analysis and evaluations justify the security level and practicality of our design.

Abstract In certain cloud Electronic Medical Records (EMRs) applications, the data ownership may need to be transferred. In practice, not only the data but also the auditing ability should be transferred securely and efficiently. However, we investigate and find that most of the existing data ownership transfer protocols only work well between two individuals, and they become inefficient when dealing between two communities. The proposals for transferring tags between communities are problematic as well since, they require all members get involved or a fully trusted aggregator facilitates ownership transfer, which are unrealistic in certain scenarios. To alleviate these problems, in this paper we develop a secure auditing protocol with decentralized (t, n)-threshold ownership transfer for cloud EMRs. This protocol is designed to operate efficiently without requiring the mandatory participation of every user or the involvement of any trusted third-party. It is achieved by employing the threshold signature. Rigorous security analyses and comprehensive performance evaluations illustrate the security and practicality of our protocol. Specifically, according to the evaluations and comparisons, the communication and computational consumption is independent of the file size, i.e., it is constant in our protocol for both communities.