Identity-Preserving Public Integrity Checking with Dynamic Groups for Cloud Storage

Despite a variety of security threats, cloud storage is on the increase especially when a group of users need to store and share data. Identity-privacy and user dynamic operation are of growing concern in public integrity checking (PIC) scheme. In this paper, we develop an identity-preserving public integrity checking scheme with dynamic groups (IPIC-DG) for cloud storage. Firstly, our scheme can realize the whole anonymity. On the one hand, no one except the group manager can discover the real identity of users. On the other hand, even the manager, who issues user's secret key, is not capable of forging signatures on behalf of others. Secondly, we propose an anonymous public integrity verification protocol that not only supports integrity checking without retrieving whole data from the cloud, but also protects the signer's identity during the whole process. We utilize group signature to construct a homomorphic authenticator on each file block to guarantee the anonymous remote data integrity checking. Thirdly, our scheme supports a way of dynamic user operation that greatly improves the efficiency and feasibility of user revocation. At last, we formally prove our IPIC-DG scheme is IND-CCA security. Experimental results show that our work performs well in practical application.