Securing Bidirectional Wireless Control of DC Motors Against MQTT-Based Cyber Attacks Using Chaos-Based Encryption

This paper presents a comprehensive study on the security of wireless control systems by modeling a practical cyber-attack scenario that combines eavesdropping and man-in-the-middle (MITM) techniques over the MQTT protocol. The analysis highlights how traditional wireless control architectures remain vulnerable to interception at the network level. To improve data confidentiality and preserve control robustness under such conditions, the paper proposes a chaos-based encryption framework for securing bidirectional signal transmission in direct-current (DC) motor control systems. Two distinct Liu chaotic systems are employed—one for encrypting the PWM control signal and another for the motor speed feedback—operating in a master–slave configuration with different initial conditions. Synchronization is maintained via a sliding mode controller, while an adaptive disturbance observer (DOB) enhances robustness against external disturbances. Experimental validation on a physical setup with ESP32 microcontrollers and a separately excited DC motor demonstrates that, although the proposed scheme cannot prevent packet interception itself, it protects the payload from eavesdroppers and enables the system to maintain bounded synchronization errors and acceptable motor response even under MITM-induced delay and packet loss.