HALC: A Real-time In-sensor Defense against the Magnetic Spoofing Attack on Hall Sensors

Abstract

Several papers have been published over the last ten years to provide a defense against intentional spoofing to sensors. However, these defenses would only work against those spoofing signals, which have a separate frequency from the original signal being measured. These defenses would not work if the spoofing attack signal (i) has a frequency equal to the frequency of original signals, (ii) has zero frequency, and (iii) is strong enough to drive the sensor output close to its saturation region. More specifically, these defenses are not designed for a magnetic spoofing attack on passive Hall sensors. Our work begins to fill this gap by providing a defense against the magnetic spoofing attack on passive Hall sensors. Our proposed defense HALC can detect and contain all types of strong and weak magnetic spoofing, such as constant, sinusoidal, and pulsating magnetic fields, in real-time. HALC works up to ∼9000 G of external magnetic spoofing within a frequency range of 0-150 kHz, whereas existing defenses work only when the spoofing signals have a separate frequency from the original signal being measured. HALC utilizes the analog and digital cores to achieve a constant computational complexity O(1). Moreover, it is low-power (∼1.9 mW), low-cost (∼$12), and can be implemented in the sensor hardware. We have tested HALC on ten different industry-used Hall sensors from four different manufacturers to prove its efficacy and found that the correlation coefficient between the signals before and after the attack is greater than 0.91 in every test case. Moreover, we demonstrate its efficacy in two practical systems: a grid-tied solar inverter and a rotation-per-minute measurement system. We find through experiments that HALC is a robust real-time defense against a magnetic spoofing attack on passive Hall sensors.