ROPAD: A Fully Digital Highly Predictive Ring Oscillator Probing Attempt Detector

Abstract

Microprobing is an invasive attack technique to intercept data from on-chip signals. As a countermeasure, we propose a new probing detector for an industrial sub-40 nm advanced process node. It is based on ring oscillators incorporating bus lines. The oscillation frequency caused by the capacity of bus lines is differentially measured to detect attached probes. This concept reduces calibration effort and required protected nonvolatile memory in comparison to state of the art. Furthermore, the protected bus line capacitance is increased up to four times. This work is the first analyzing the detector behavior considering cross coupling between the protected bus lines.