A secure and efficient hybrid approach for 5G-AKA in blockchain smart contracts

Next-generation networks (5 G, 6 G, and beyond) require authentication and key-agreement (AKA) protocols that are lightweight, scalable, and resilient to quantum attacks. Current blockchain-based AKA schemes impose heavy on-chain computation, which increases latency, cost, and energy consumption, while providing quantum protection. We introduce SH5-AKA, a hybrid off-chain/on-chain model that offloads expensive cryptographic operations off-chain but yet records tamper-resistant proof Merkle-tree commitments on-chain. SH5-AKA is the first 5G-AKA framework that combines to fuse the post-quantum KEM CRYSTALS-Kyber with Merkle-tree proofs inside a smart contract. The design delivers three main core benefits: (1) off-chain execution reduces gas fees and authentication delay without compromising security, (2) Kyber ensures forward-secure, quantum-resistant key exchange, and (3) Merkle-tree aggregation compresses authentication data, which increases and boosts scalability and mitigates DoS and Replay attacks. We prove the formal security in the Real-or-Random model and validate the protocol with Scyther. Experiments show a 40 % reduction in communication costs, a 58 % reduction in memory requirements, and a tripling of authentication time compared to state-of-the-art blockchain AKA solutions. These results confirm that SH5-AKA makes it a scalable and cost-effective solution for 5 G and future 6 G deployments.”