Reconfigurable Switched Capacitor DC-DC Converter for Improved Security in IoT Devices

Abstract

With the ever increasing number of IoT devices, security and energy efficiency have become critical constraints in circuit design. To achieve small size and energy efficiency, devices need to be supplied by on-chip regulators. The power line generates the strongest signal in the circuit, and it is exploited for both, power and electromagnetic, side-channel attacks. In this work we propose to improve the security of the on-chip switched capacitor DC-DC converters by randomly switching between different converter topologies. Random ripple size and maximum supply voltage modulate the circuit current and power consumption, making the circuit more robust against side-channel attacks. We analyze the most common converter topologies and propose reconfigurable switched-capacitor cell for the efficient implementation in CMOS technology. The results show that power and time entropy of the proposed cell are increased significantly when compared to the commonly used DC-DC converter cell. There is around 6% variation in the DC-DC switching frequency for the constant load, and additional noise is observed in the frequency spectrum of the measured signal, thus, increasing the difficulty of the attack.