A Security-Enhanced Scheme for ModBus TCP Protocol Based on Lightweight Cryptographic Algorithm

In modern industrial control systems (ICSs), communication protocols such as Modbus TCP remain widely used due to their simplicity, interoperability, and real-time performance. However, these communication protocols (e.g., Modbus TCP) were originally designed without security considerations, lacking essential features such as encryption, integrity protection, and authentication. This exposes ICS deployments to severe security threats, including eavesdropping, command injection, and replay attacks, especially when operating over unsecured networks. To address these critical vulnerabilities while preserving the lightweight nature of the protocol, we propose a Modbus TCP security enhancement scheme that integrates ASCON, an NIST-standardized authenticated encryption algorithm, with the CBOR Object Signing and Encryption (COSE) framework. Our design embeds COSE_Encrypt0 structures into Modbus application data, enabling end-to-end confidentiality, integrity, and replay protection without altering the protocol’s semantics or timing behavior. We implement the proposed scheme in C and evaluate it in a simulated embedded environment representative of typical ICS devices. Experimental results show that the solution incurs minimal computational and memory overhead, while providing robust cryptographic guarantees. This work demonstrates a practical pathway for retrofitting legacy ICS protocols with modern lightweight cryptography, enhancing system resilience without compromising compatibility or performance.