Enhanced Detection Range for EM Side-channel Attack Probes utilizing Co-planar Capacitive Asymmetry Sensing

Electromagnetic (EM) side-channel analysis (SCA) attack, which breaks cryptographic implementations, has become a major concern in the design of circuits and systems. This paper focuses on EM SCA and proposes the detection of an approaching EM probe even before an attack is performed. The proposed method of co-planar capacitive asymmetry sensing consists of a grid of four metal plates of the same size and dimension. As an EM probe approaches the sensing metal plates, the symmetry of the sensing metal plate system breaks, and the capacitance between each pair diverge from their baseline capacitances. Using Ansys Maxwell Finite Element Method (FEM) simulations, we demonstrate that the co-planar capacitive asymmetry sensing has an enhanced detection range compared to other sensing methods. At a distance of 1 mm between the sensing metal plates and the approaching EM probe, it shows >17 % change in capacitance, leading to a > 10 × improvement in detection range over the existing inductive sensing methods. At a distance of 0.1 mm, a > 45% change in capacitance is observed, leading to a > 3 × and > 11 × sensitivity improvement over capacitive parallel sensing and inductive sensing respectively. Finally, we show that the co-planar capacitive asymmetry sensing is sensitive to both E-field and H-field probes, unlike inductive sensing which cannot detect an E-field probe.