Improved EM Side-Channel Analysis Attack Probe Detection Range Utilizing Coplanar Capacitive Asymmetry Sensing

While cryptographic implementations provide computational security in circuits and systems, hardware attack techniques, e.g., electromagnetic (EM) side-channel analysis (SCA) attack can still break through. The commonplace countermeasures for EM SCA attack require significant overheads in terms of power consumption. This article explores an on-chip capacitive sensing technique for the purpose of detection of an approaching EM probe even before an attack is performed, thereby alleviating the overheads incurred by any countermeasure against such attacks. Different type of capacitive structures are considered in regards to sensitivity and area. The proposed method of coplanar capacitive asymmetry sensing (CEASE) consists of a grid of four metal plates of the same size and dimensions determined through design space exploration. A comparison between the capacitive and inductive sensing technique is also performed in terms of detection range through theoretical arguments and EM simulation. A $>$ 17% change in capacitance is shown at a distance of 1 mm, implying a $>10\times $ improvement in the detection range over inductive sensing methods. Furthermore, at 0.1-mm distance, a $>$ 45% change in capacitance is observed, leading to a $>3\times $ and $>11\times $ sensitivity improvement over capacitive parallel plate sensing and inductive sensing, respectively.