Abstract Cloud medical treatment provides real-time data sharing in a cost-effective method, making it more practical to create, collect and manage vast amounts of personal health records (PHR) of patients. However, health information is considered highly sensitive. How to securely store and dynamically process massive patients’ PHR data in a public cloud environment has become one of the most important challenges. Therefore, we introduce a novel solution to the problems of privacy exposure, data security and flexible access of storage modules in medical systems. In this paper, we present a privacy-preserving certificateless broadcast encryption with authorization for the PHR system, which is the best approach to effectively solve the above problems and avoid key escrow. In our work, users (patients) outsource their encrypted data to the cloud server and reallocate data accessing rights of recipients through an authorization set, sharing with a group of authorized receivers (doctors) in a secure and efficient manner. In addition, it is shown to be capable of achieving both plaintext confidentiality and receiver anonymity under the random oracle model. Moreover, the experimental evaluation shows that the proposed scheme enjoys low computational and communication overhead, indicating the feasibility and practicality of the scheme.

In a data auditing scheme, the data owner authorizes a third-party auditor (TPA) to check whether the data stored in the cloud remains intact. Researchers have given many data auditing schemes. However, there are still three significant shortcomings in these schemes. First of all, the security proofs of these schemes are completed in the random oracle model (ROM). As we all know, a scheme with provably security in ROM may be insecure in practical applications. Secondly, TPA in most known schemes is set to be completely reliable. However, TPA in reality may attempt to extract the data owner's data. These schemes cannot resist the malicious behavior of TPA. Third, most known schemes require hash-to-point operations and enjoy high computation cost, so they are not suitable for computing constrained environments. In this paper, we first presented the system model and security demands for an identity-based data auditing (IBDA) scheme. We then came up with a new IBDA scheme and showed the security proofs in the standard model (SM).Finally, we made an analysis on performance for seven data auditing schemes. In our scheme, the computation cost required by TPA is a constant, independent of the number of data blocks participating in the challenge. Therefore, our scheme requires low computation cost and is suitable for computing-constrained environments

Abstract Identity‐based encryption (IBE) is a public key cryptosystem on purpose to remove the traditional certificate management. How to realize efficient user revocation in the IBE is of great importance when considering its application. The drawback of most existing works is that the revoked user can still access the ciphertext prior to revocation. One possible solution proposed by Sun et al. is to evolve the ciphertext in the cloud. However, it is unfortunate that the master time key in their scheme is kept by the private key generator (PKG), which means it is sustained extra burden. In this article, we present an efficient revocable IBE with ciphertext evolution in the cloud‐assisted system and the ciphertext remains constant size. The cloud server keeps only one secret master time update key sent by the PKG in a private channel, and thus our scheme offers scalability. In the meantime, our detailed analysis demonstrates that our proposed scheme is semantically secure against ciphertext chosen attacks based on the k‐CAA problem and enjoys better efficiency in computation and communication costs compared with previous works.

Safe and efficient collection of users’ electronic consumption data is a basic function of the smart grid. Anonymous aggregate signature is a fine option to realize this feature, which can not only reduce the computing cost of the data center (DC) but also protect the user’s identity information from leaking. The security proofs of all known identity-based aggregate signature (IBAS) schemes were completed in the random oracle model (ROM). Regrettably, these schemes are not necessarily secure in real life. In this article, we first propose the system model and security demands of an identity-based designated verifier anonymous aggregate signature (IB-DVAAS) scheme for smart grids. We then come up with a concrete scheme, only the designated DC can check the validity of an aggregate signature, but it cannot recognize the real identity of the signers. Next, we display the security proofs in the standard model. Finally, we conduct an analysis on performance for six aggregate signature schemes. Only three pairing operations are required and hash-to-point operations are not used, the calculation cost of the new scheme is lower than that of other schemes.

Provable data possession (PDP) solves the problem of determining whether the data stored in the cloud is maintained in its entirety. Certificateless cryptography simultaneously tackles two challenges: certificate management and key escrow. There are still three deficiencies in the current known certificateless provable data possession (CL-PDP) schemes. First, security proofs are typically conducted in the random oracle model (ROM). Second, some schemes are incapable of preventing third-party auditor (TPA) from recovering user data blocks. Third, most schemes require hash-to-point operations, which result in lower computational efficiency. In this article, we demonstrated two kinds of attacks targeting the scheme Ji et al. 2020. Subsequently, we put forward a new CL-PDP scheme and showed security proofs in the standard model (SM). Finally, we conducted performance analysis on ten CL-PDP schemes. Our scheme outperforms others in terms of efficiency, as it minimizes computational overhead by requiring only three pairing operations and eliminating the need for hash-to-point operations.