Crosstalk-Sensitive Loops and Reconstruction Algorithms to Eavesdrop Digital Signals Transmitted Along Differential Interconnects

Abstract

This study explores and theoretically assesses the possibility to eavesdrop information from differential interconnects by resorting to sensing loop(s) placed in proximity and suitable signal processing algorithms. Time-domain crosstalk in the terminations of the loops, operating as hardware Trojans, is the coupling phenomenon exploited to reconstruct the transmitted digital signals. This investigation proves that—even though geometrical and electric characteristics of the emitting interconnect are not perfectly known—the original digital signal can be successfully reconstructed. To this end, three different methods and related algorithms are proposed and compared in terms of 1) reconstruction accuracy, 2) involved computational burden, and 3) flexibility in the design of the sensing loop(s). Effectiveness of the proposed algorithms (whose fundamentals are derived in free space) in the practical case of inhomogeneous media (i.e., presence of dielectric substrate) is assessed by full-wave numerical simulation of a virtual setup, in which the emitting and receiving pairs are realized as microstrip printed circuit board lands.