While cloud computing offers significant advantages, concerns about the security and privacy of sensitive data persist, primarily due to the lack of user-to-cloud control. To address confidentiality, data owners often outsource encrypted data rather than plaintext. Ciphertext-Policy Attribute-Based Encryption (CP-ABE) is a viable solution for enabling fine-grained, owner-centric access control when sharing these encrypted files. However, existing schemes fall short in safeguarding against various attacks. Notably, they do not empower cloud providers to verify whether a downloader has the necessary decryption rights, leading to potential vulnerabilities. This lack of verification allows malicious attackers to exploit the system by downloading large volumes of files, resulting in Economic Denial of Sustainability (EDoS) attacks that strain cloud resources and impose financial burdens on service payers. Additionally, the dual role of cloud providers as both the accountant and the payee raise transparency issues for data owners regarding resource consumption fees. To address these challenges in real-world public cloud storage environments, we propose a robust solution designed to protect encrypted cloud storage from EDoS attacks while ensuring resource consumption accountability. Our approach utilizes CP-ABE schemes in a black-box manner and adheres to arbitrary access policies defined by CP-ABE. We present two distinct protocols tailored for different scenarios and provide comprehensive performance and security analyses.

Cloud Storage, Combined Compression, Data Access Control