Fault injection, also known as glitching, is a technique where some form of interference or invalid state is intentionally introduced into a system in order to alter the behavior of that system. In the context of embedded hardware and electronics generally, there are a number of forms this interference might take. Common methods for fault injection in electronics include:
Clock glitching (errant clock edges are forced onto the input clock line of an IC)
Voltage fault injection (applying voltages higher or lower than the expected voltage to IC power lines)
Electromagnetic glitching (Introducing EM interference)
This article will focus on voltage fault injection, specifically, the introduction of momentary voltages outside of normal operating conditions on the target device’s power rails. These momentary pulses or drops in input voltage (glitches) can affect device operation and are directed with the intention of achieving a particular effect. Commonly desired effects include “corrupting” instructions or memory in the processor and skipping instructions.