Impedance monitoring system

Abstract

Disclosed is an impedance monitoring system for detection of attacks on a secure system. The impedance monitoring system comprises a perturbation current generator (PCG), a voltage sensing ring oscillator (VSRO), and a controller. The PCG generates a perturbation current to excite a supply impedance of the secure system and the controller counts oscillations in the VSRO, resulting from voltage changes in the secure system, to detect an attack. In particular, the controller detects an attack by capturing a reference VSRO count, capturing a subsequent VSRO count for a non-zero perturbation current, and normalising the subsequent VSRO count based on the reference VSRO count.

Dependencies are inferred from the claim text.