Protection of Oscillator-Based PUFs against Side Channel Analyses by Random Interruption

Oscillation-based physical unclonable functions (PUFs) are known to be sensitive to power trace side channel analyses (SCAs). Although previous work investigated on countermeasures, these required significant additional amount of hardware or were just able to obscure sign information of a frequency comparison, while the magnitude information remains available to the attacker. As recent innovation on oscillation-based PUFs also require the magnitude-information beside the sign, e.g., to increase the reliability, the need arises to protect both. We present a new protection approach to hide both sign and magnitude information of oscillation-based PUF from an attacker. By introducing random interruptions in the oscillation, the power spectrum is blurred while the quality of the PUF is maintained. In addition to concept simulations and the discussion of different implementations, we use the example of a loop-PUF to show that the presented countermeasure can withstand several attack scenarios.