An Encrypted On-Chip Power Supply With Random Parallel Power Injection and Charge Recycling Against Power/EM Side-Channel Attacks

Abstract

As hardware security becomes a crucial challenge for modern electronic devices to protect information privacy, this article presents an encrypted on-chip power supply to combat power and electromagnetic (EM) side-channel attacks (SCAs) for crypto cores. By splitting power and security into separate paths, random parallel power injection and charge recycling are realized to encrypt supply power activities for high SCA immunity while largely minimizing power and performance overheads. Despite of crypto core power variations, the proposed power supply can maintain uncorrelated input profile by adaptively modulating parallel noisy power injection. Moreover, its EM leakage is highly attenuated by spreading the spectrum energy to a wide frequency range and increasing noise floor. To achieve such, a recycled masking power stage with an encryption interface is designed to randomly inject power noise and recycle system charge with random <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -time modulation while still retaining nominal power delivery. A silicon IC prototype of this design is fabricated using a 65 nm CMOS process with an active die area of 0.19 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Measured input power profiles are fully encrypted to improve power SCA immunity. Operating at a nominal switching frequency of 10 MHz, random parallel power encryption reduces peak EM interference noise from 64.57 dBμV to 43.12 dBμV to meet EN55032 Class B standards and verify EM spectrum profile encryption. In response to a step-up load change from zero to full load current of 200 mA, the power supply achieves 1% settling time of 0.78 μs, with measured voltage droop of 54 mV with no other performance overhead. It achieves a peak efficiency of 90.5%, only suffering the maximum power overhead of 4.9%.