To increase the availability and durability of the outsourced data, many customers store multiple copies on multiple cloud servers. To guarantee the integrity of multi-copies, some provable data possession (PDP) protocols for multi-copy are presented. However, most of previous PDP protocols consider all copies to be stored on only one cloud storage server. In some degree, multi-copy makes little sense in such circumstance. Furthermore, many PDP protocols depend on the technique of public key infrastructure (PKI), which suffers many types of security vulnerabilities and also brings heavy communicational and computational cost. To increase the security and efficiency, we provide a novel identity-based PDP scheme of multi-copy on multiple cloud storage servers. In our scheme, all copies are delivered to different cloud storage servers, which work cooperatively to store the customer's data. By the homomorphic verifiable tags, the integrity of all copies can be checked simultaneously. The system model and security model of our scheme are provided in the paper. The security for our scheme is proved based on the computation Diffie-Hellman (CDH) hard problem. Analysis and experimental evaluation show that our scheme is efficient and practical. The proposed scheme is the first identity-based PDP scheme for multi-copy and multi-cloud servers.

To solve key escrow problem, we utilize the technique of certificateless signature to present a new remote data possession checking (RDPC) protocols protocol for checking the integrity of data shared among a group. In our scheme, user's private key includes two parts: a partial key generated by the group manager and a secret value chosen by herself/himself. To ensure the right public keys are chosen during the data integrity checking, the public key of each user is associated with her unique identity, for example the name or telephone number. Thus, the certificate is not needed and the problem of key escrow is eliminated too. Meanwhile, the data integrity can still be audited by public verifier without downloading the whole data. In addition, our scheme also supports efficient user revocation from the group. The security of our scheme is reduced to the assumptions of computational Diffie-Hellman (CDH) and discrete logarithm (DL). Experiment results exhibit that the new protocol is very efficient and feasible.

Although cloud storage service enables people easily maintain and manage amounts of data with lower cost, it cannot ensure the integrity of people's data. In order to audit the correctness of the data without downloading them, many remote data integrity checking (RDIC) schemes have been presented. Most existing schemes ignore the important issue of data privacy preserving and suffer from complicated certificate management derived from public key infrastructure. To overcome these shortcomings, this article proposes a new Identity-based RDIC scheme that makes use of homomorphic verifiable tag to decrease the system complexity. The original data in proof are masked by random integer addition, which protects the verifier from obtaining any knowledge about the data during the integrity checking process. Our scheme is proved secure under the assumption of computational Diffie–Hellman problem. Experiment result exhibits that our scheme is very efficient and feasible for real-life applications.

Remote data possession checking (RDPC) supplies an efficient manner to verify the integrity of the files stored in cloud storage. Public verification allows anyone to check the integrity of remote data so that it has a wider application in public cloud storage. Private verification just allows the data owner to verify the data integrity, which is mainly applied for the verification of secret data. However, in many real applications, the data owner expects a specific user to check the files in cloud storage, whereas others cannot execute such work. It is obvious that neither public verification nor private verification can satisfy such a requirement. To solve this issue, Ren et al. provided a designated-verifier provable data possession (DV-PDP) protocol. Unfortunately, the DV-PDP is insecure against replay attack launched by the malicious cloud server. To overcome this shortcoming, we present a new RDPC scheme with the designated verifier, in which the data owner specifies a unique verifier to check the data integrity. Based on the computational Diffie–Hellman assumption, we prove the security for our RDPC scheme in a random oracle model. The theoretical analysis and experiment results indicate that our scheme has less communication, storage, and computation overhead while achieving high error detection probability.

Provable Data Possession (PDP) model provides an efficient means for people to audit the integrity of data stored in cloud storage. When sensitive data is shared among multiple users based on cloud storage, it is critical to preserve the anonymity of the data uploader against the auditor. That is, the auditor should not get data uploader's identity through the data audition. To address this problem, many PDP schemes with user identity privacy-persevering are proposed. However, most proposed schemes are designed based on PKI technique which suffers from big burden of certificate management. Moreover, data auditors in most proposed schemes bear heavy computation cost which results to the lower efficiency of the scheme. To overcome the shortcomings, we present a novel identity-based PDP protocol to audit efficiently the integrity of group shared data with uploader's privacy-preserving. Due to the inherent structural advantage of identity-based crypto mechanism, our PDP scheme is able to avoid the problem of certificate management. Different from previous works, our scheme ensures the relationship of the data and the data uploader in the phase of proof generation not the phase of integrity audition. Therefore, the data auditor does not know the relationship at all as well as the extract data uploader of the challenged data. At the same time, establishing the relationship by cloud server in proof generation step can reduce the computational cost of data auditor greatly. Furthermore, the relationship of data uploader and challenged data in the proof is randomized so as to strength the security of the scheme. All these efforts are made in our scheme to efficiently realize the anonymity protection of the data uploader. We give the detailed security proof of our scheme under the computational Diffie-Hellman assumption. Many experiments are performed to evaluate the efficiency of our scheme, the results show that our new scheme is efficient and feasible.

Cloud computing is a fast-growing technology which supplies scalable, innovative, and efficient business models. However, cloud computing is not fully trusted, and the security of the data outsourced in cloud storage needs to be guaranteed. One of the hottest issues is how to ensure the integrity of the data in cloud storage. Until now, many researchers have proposed lots of provable data possession (PDP) schemes to deal with the problem of data integrity audition. Nevertheless, very little effort has been devoted to preserve the data uploader’s privacy while auditing the integrity of data shared in a group. To overcome the shortcoming, we propose a novel certificateless PDP protocol to efficiently audit the integrity of data shared in a workgroup with user privacy preserving. Due to the inherent structural advantage of the certificateless crypto mechanism, our PDP scheme eliminates the key escrow problem and the certificate management problem simultaneously. Moreover, the audition process in our scheme does not need any user’s identity which helps to keep the anonymity of data uploader. We give for our scheme a detailed security proof and efficiency analysis. Experiment results of performance evaluation demonstrate that our new scheme is very efficient and feasible.