PMTER-ABE: a practical multi-authority CP-ABE with traceability, revocation and outsourcing decryption for secure access control in cloud systems

Attribute-based encryption (ABE) has evolved as an efficient and secure method for storage of data with fine-grained access control in cloud platforms. In recent years, increasing diversification in the design of ABE schemes has led to significant research in the assimilation of properties like traceability, revocation, and outsourcing decryption. However, most of the recent ABE schemes incorporate few of these properties and hence lack in robustness to adapt with varying demands of cloud systems. In modern ABE designs, the notions of forward and backward secrecy have been introduced to accommodate the delegation of a large number of heterogeneous users in the system. In general, these features are realized under the concept of user revocation. On the other hand, to control malicious users in the system, it is necessary to implement traceability in integration with user revocation. Finally, for resource-constrained users, outsourcing decryption to proxy servers is a viable option. Thus, we propose PMTER-ABE, a practical decentralized multi-authority traceable and efficiently revocable attribute-based cryptosystem with outsourcing decryption advantage. The key features of our cryptosystem are (i) incorporating large attribute universe with highly expressive policies, (ii) integrating forward and backward secrecy under user revocation, (iii) implementing white-box traceability to detect malicious users, and (iv) outsourcing decryption to reduce the computational overhead of decryption on users. We present the formal proofs for correctness, security, and traceability of PMTER-ABE along with performance analysis. The efficiency and usability of PMTER-ABE is shown with practical implementation and experimental results.