Optimizing Attribute-Based Encryption for Fine-Grained Access Control in Cloud Environments: An Adaptively Secure, Offline/Online, and Outsourcing Framework

Attribute-Based Encryption (ABE) is an advanced public-key encryption paradigm that enforces fine-grained access control over encrypted data. For instance, the data owner can generate the ciphertext associated with ((”Cardiology” OR ”Critical Care Medicine”) AND ”Consultant Physician”), which can only be decrypted by other data users whose attributes satisfy this access policy. However, a major efficiency drawback of ABE is that ciphertext size, encryption time, and decryption time grow with the complexity of the access policy and the number of attributes. To address this issue, we propose an adaptively secure, offline/online and outsourcing ABE scheme under the Generic Group Model. The majority of encryption operation is performed during the offline phase, while ABE ciphertext is quickly assembled during the online phase. Decryption outsourcing enables the edge node to convert the original ABE ciphertext into an ElGamal-style ciphertext using a transformation key without revealing the plaintext message to the edge node. Our approach is efficient and suitable for mobile devices. Performance evaluation demonstrates the system can balance computation and power consumption over an extended period, effectively addressing challenges in data sharing.