Lightweight Scheme for Secure Communication in Power Distribution Ring Main Units

With the growing deployment of smart grids, the security of distribution ring main units (RMUs) has become increasingly important. Due to limited computing resources and unstable communication, RMUs are vulnerable to cyber and physical attacks. This paper proposes a Lightweight Hybrid Entropy-based Security (LHES) scheme designed for RMUs. LHES combines entropy sources, such as PUFs, QRNGs, timestamps, and device IDs, to generate high-entropy seeds for cryptographic keys using an enhanced HMAC-based Key Derivation Function (HKDF). The scheme enables paragraph-level encryption with AES-GCM or ChaCha20-Poly1305 and ensures key continuity via a dual-controller failover model. Security analysis shows LHES effectively defends against key reuse, replay, rollback, and substitution attacks, while remaining efficient for embedded systems. LHES offers a scalable and practical solution for securing next-generation distribution networks.