Privacy-preserving proof of storage in large group

Cloud storage is an important development trend in information technology. To ensure the integrity of data storage in cloud storing, researchers have present some proof of storage (POS) schemes. In some cases, the ability to check data possession is delegated by data owners. Hence, the delegable provable data possession and proxy provable data possession are proposed. However the existing schemes are not secure since the proxy or designated verifier stores some delegation information in cloud storage servers. In this paper, we propose a new POS scheme, which can preserve clients´ privacy and only members in the data shared group to verify the integrity of the outsourced data. In particular, we utilize group signatures and group key exchange to construct homomorphic authenticators, so that only the members in the group is able to check the integrity of shared data for users without retrieving the entire data, and cannot reveal the identities of signers on all blocks in shared data.