A LIGHTWEIGHT EDGE-LAYER GROUP KEY AGREEMENT PROTOCOL FOR IOT USING ELLIPTIC CURVE CRYPTOGRAPHY AND SHAMIR’S SECRET SHARING

A Group Key Agreement Protocol enables secure multi-party communication by establishing a common cryptographic key, which is especially critical at the edge layer of IoT networks where devices often operate in decentralized and resource-constrained environments. However, existing protocols face several challenges, including high computational overhead, single points of failure, and a lack of integrity validation during the Distribution of the Group Key. To address these challenges, we propose a lightweight edge-layer protocol that combines Shamir’s Secret Sharing Scheme (SSS) and Elliptic Curve Cryptography (ECC) for secure and efficient group key distribution among IoT edge devices. ECC (Curve25519) is used for secure peer-to-peer sharing, with key sizes that are 12 times smaller and operations that are four times faster than traditional RSA. SSS splits the group key into shares and reconstructs it using a threshold, reducing computation and eliminating the need for full key generation on each device. It also removes single points of failure because no device retains the complete key. ECC enables secure peer-to-peer exchange of encrypted shares using ChaCha20 for efficient confidentiality. ChaCha20 enhances encryption speed, performing nearly three times faster than AES on resource-constrained devices. To ensure shared authenticity and detect tampering, HMAC is applied. This offers a lightweight integrity check suitable for constrained IoT devices. The proposed protocol is quantitatively validated through entropy and key-strength analysis, confirming 128-bit equivalent security and O(n) scalability up to 100 nodes. Communication-cost evaluation demonstrates low bandwidth overhead, while formal verification using BAN Logic and ProVerif under the Dolev–Yao adversarial model establishes confidentiality, authenticity, and forward secrecy with provable resilience against replay, impersonation, and man-in-the-middle attacks.