Exploring Hardware Vulnerabilities in Robotic Actuators: A Case of Man-in-the-Middle Attacks

One of the main vulnerabilities in robotic systems lies in the communication buses that enable low-level controllers to interact with the actuators responsible for the robot’s movements. In this context, hardware attacks represent a significant threat; however, the hardware version of the man-in-the-middle attack, implemented by Trojan hardware, has not yet been extensively studied. This article examines the impact of such threats on robotic control systems, focusing on vulnerabilities in an asynchronous communication bus used to transmit commands to a digital servomotor. To explore this, Trojan hardware was implemented on an FPGA device (XC7A100T, AMD: Santa Clara, CA, USA). Furthermore, the article proposes and implements detection methods to identify this type of attack, integrating them into an FPGA device as part of the actuator. The method is based on measuring the answer time detecting the presence of a strange module due to an increase in this time considering an AX-12 servomotor (Robotis: Seoul, Republic of Korea), with a Dynamixel protocol. This approach has been validated through a series of experiments involving a large number of transmitted messages, resulting in a high rate of true positives and a low rate of false negatives. The main conclusion is that response time can be used to detect foreign modules in the system, even if the module is kept waiting to attack, as long as the condition that the servomotors have a low variation in their latency is met.