Paper 2025/2021

TreeCast: Multi-Party Key Establishment Protocol for IoT Devices

Abstract

Secure communication in the Internet of Things (IoT) requires lightweight protocols that scale across unicast, multicast, and broadcast settings. Existing solutions typically depend on centralized gateways, which introduce single points of failure and scalability limitations. We present TreeCast, a decentralized group key establishment protocol that organizes devices in a binary tree and derives communication keys through hybrid key exchange. The protocol achieves efficient and scalable key management, supporting dynamic membership with localized rekeying. We provide a formal security analysis and proof, showing that TreeCast achieves authentication, session key confidentiality, post-compromise security, and partial forward secrecy. In addition, we evaluate computational and storage costs of the protocol, demonstrating logarithmic scalability in both communication overhead and device state. By enabling a single framework for unicast, multicast, and broadcast communication, our approach bridges the gap between cryptographic rigor and practical IoT deployment. TreeCast provides a deployable, communication-oriented solution to secure large-scale IoT networks.