Privacy-Preserving Public Auditing for Shared Data in Mobile Cloud Storage

With the mobile cloud storage services, mobile users can easily form a group and share data with each other. Given the fact that the cloud are not trustable, a third party public auditor can be introduced to audit data integrity, and supporting group dynamics and protecting the privacy of the original user of shared data from the public auditor is a fundamental issue during the auditing. In this paper, we propose a new identity privacy preserving public auditing scheme for the integrity of group data with efficient group dynamics utilizing the multilinear maps based Diffie-Hellman Key Exchange protocol. With our proposed scheme, a third party auditor is able to audit the integrity of shared data without learning private identity information of the group members, and proxy re-signatures are used here to allow the cloud to do the re-computing to support group dynamics (user join and user revocation). Besides, our scheme also supports secure and efficient public auditing due to our improved polynomial-based authentication tags. The security and performance analysis shows that our proposed scheme is secure and highly efficient.