A Hierarchical User Online/Offline Revocable Encryption Scheme in End-Edge-Cloud Networks

The rapid development of end-edge-cloud networks significantly improves data storage and sharing efficiency by offloading computational tasks from the central cloud to the network edge. However, this architecture also introduces new security and privacy challenges. To address these issues, this paper proposes a hierarchical user online/offline revocable encryption (HUOORE) scheme that enhances both system security and computational efficiency. A trust level (TL) is defined to enforce fine-grained access control, allowing only authorized users to decrypt data based on their trust levels. The proposed HUOORE scheme divides encryption and decryption into online and offline phases, where most complex pairing operations are executed offline, leaving only lightweight computations for the user side. Moreover, an efficient key revocation mechanism is designed to prevent unauthorized access and simplify key management. Formal security analysis demonstrates that HUOORE achieves CPA security under the q-parallel Bilinear Diffie-Hellman Exponent (BDHE) assumption and ensures privacy-preserving access policies. Experimental results demonstrate that the proposed scheme significantly reduces user-side computation overhead with acceptable storage cost, making it suitable for secure data sharing in resource-constrained end-edge-cloud environments.