Biblio

As the public cloud becomes one of the leading ways in data sharing nowadays, data confidentiality and user privacy are increasingly critical. Partially policy-hidden ciphertext policy attribute-based encryption (CP-ABE) can effectively protect data confidentiality while reducing privacy leakage by hiding part of the access structure. However, it cannot satisfy the need of data sharing in the public cloud with complex users and large amounts of data, both in terms of less expressive access structures and limited granularity of policy hiding. Moreover, the verification of access right to shared data and correctness of decryption are ignored or conducted by an untrusted third party, and the prime-order groups are seldom considered in the expressive policy-hidden schemes. This paper proposes a fully policy-hidden CP-ABE scheme constructed on LSSS access structure and prime-order groups for public cloud data sharing. To help users decrypt, HVE with a ``convert step'' is applied, which is more compatible with CP-ABE. Meanwhile, decentralized credible verification of access right to shared data and correctness of decryption based on blockchain are also provided. We prove the security of our scheme rigorously and compare the scheme with others comprehensively. The results show that our scheme performs better.

With the popularity of cloud computing, cloud storage technology has also been widely used. Among them, data integrity verification is a hot research topic. At present, the realization of public auditing has become the development trend of integrity verification. Most existing public auditing schemes rarely consider some indispensable functions at the same time. Thus, in this paper, we propose a comprehensive public auditing scheme (PDBPA) that can simultaneously realize data block privacy protection, data dynamics, and multi- user batch auditing. Our PDBPA scheme is implemented in bilinear pairing. By adding random masking in the audit phase, with the help of the characteristics of homomorphic verifiable tags (HVTs), it can not only ensure that the TPA performs the audit work correctly, but also prevent it from exploring the user’s sensitive data. In addition, by utilizing the modified index hash table (MIHT), data dynamics can be effectively achieved. Furthermore, we provide a specific process for the TPA to perform batch audits for multiple users. Moreover, we formally prove the security of the scheme; while achieving the audit correctness, it can resist three types of attacks.