Paper 2025/1570 Original: eprint.iacr.org/2025/1570 ↗

Multi-Message Quantum Broadcast with Fine-Grained Access Control

Abstract

Several subscription-based systems require fine-grained, dynamic access control, which traditional broadcast encryption schemes fail to handle efficiently. Attribute-based and policy-based access structures offer a flexible and scalable solution by encoding access rules directly into the encryption mechanism. With the advent and development of quantum networks, attribute-based and policy-based quantum broadcast encryption (PBQBE) becomes necessary for enforcing such controls securely in a post-quantum world. In this paper, we present a general construction of quantum broadcast encryption for multiple messages simultaneously, based on routing and traversing a given attribute-based and, consequently, a policy-based access tree when a user satisfies a unique policy. Our scheme can handle dynamic systems with frequently changing access patterns and can be deployed seamlessly with classical systems. Compared to existing constructions, our scheme offers hierarchical access, policy control, scalability, and revocation while maintaining provable security guarantees.