DRAC: A dynamic fine-grained access control scheme for cloud storage with censorship-coerced resistance

The increasing reliance on cloud storage for data outsourcing raises concerns regarding the security and access to sensitive information and private data. To ensure the security of cloud data, encryption technology is widely applied in cloud storage. However, most existing encryption schemes rely on the assumption that encryption keys remain private, which may become invalid under censorship by unauthorized authorities, potentially leading to data leaks in the cloud. Furthermore, accessing and sharing data in the cloud are crucial for its utilization, and enabling authorized users to achieve fine-grained access control during the dynamic sharing of cloud data poses a significant challenge. To address these issues, this paper proposes a novel fine-grained access control scheme, DRAC. By combining deniable encryption primitives with ciphertext-policy attribute-based encryption technology that supports revocation, the proposed scheme achieves: (1) provide privacy protection for cloud data; (2) resist censorship by unauthorized authorities; and (3) support dynamic fine-grained access control for cloud data. The security and correctness of DRAC are analyzed theoretically, while its performance is evaluated experimentally. The results demonstrate that the system is feasible and effective in practical applications.