Electromagnetic Equalizer: An Active Countermeasure Against EM Side-channel Attack

Electromagnetic (EM) analysis is to reveal the secret information by analyzing the EM emission from a cryptographic device. EM analysis (EMA) attack is emerging as a serious threat to hardware security. It has been noted that the on-chip power grid (PG) has a security implication on EMA attack by affecting the fluctuations of supply current. However, there is little study on exploiting this intrinsic property as an active countermeasure against EMA. In this paper, we investigate the effect of PG on EM emission and propose an active countermeasure against EMA, i.e. EM Equalizer (EME). By adjusting the PG impedance, the current waveform can be flattened, equalizing the EM profile. Therefore, the correlation between secret data and EM emission is significantly reduced. As a first attempt to the co-optimization for power and EM security, we extend the EME method by fixing the vulnerability of power analysis. To verify the EME method, several cryptographic designs are implemented. The measurement to disclose (MTD) is improved by 1138× with area and power overheads of 0.62% and 1.36%, respectively.