On Code Execution Tracking Via Power Side-Channel

With the proliferation of Internet of Things, there is a growing interest in embedded system attacks, e.g., key extraction attacks and firmware modification attacks. Code execution tracking, as the first step to locate vulnerable instruction pieces for key extraction attacks and to conduct control-flow integrity checking against firmware modification attacks, is therefore of great value. Because embedded systems, especially legacy embedded systems, have limited resources and may not support software or hardware update, it is important to design low-cost code execution tracking methods that require as little system modification as possible. In this work, we propose a non-intrusive code execution tracking solution via power-side channel, wherein we represent the code execution and its power consumption with a revised hidden Markov model and recover the most likely executed instruction sequence with a revised Viterbi algorithm. By observing the power consumption of the microcontroller unit during execution, we are able to recover the program execution flow with a high accuracy and detect abnormal code execution behavior even when only a single instruction is modified.