Lightweight Security Protocol for ModBus RTU

Many operational technology systems rely on the Modbus remote terminal unit (RTU) standard to provide wired Internet of Things (IoT) networks.However, this standard lacks privacy, replay protection, data integrity, and authentication features, leaving devices vulnerable to attackers.To maintain backward compatibility, this study offers a simplified improvement to the Modbus RTU protocol that includes replay protection, integrity, confidentiality, and authentication while maintaining the original frame structure.The proposed protocol prevents spoofing, replay, and data injection attacks, and functions well with embedded devices that have limited resources.It was implemented and tested on an Arduino Mega2560.The additional security layer slightly increases latency and power consumption when compared to the previous protocol.The findings show that robust and practical security can be achieved while making a fair performance trade-off.Therefore, the proposed protocol facilitates secure communication between IoT devices utilizing Modbus RTU in industrial IoT environments.