Evaluation and Monitoring of Free Running Oscillators Serving as Source of Randomness

  • Elie Noumon Allini Hubert Curien Laboratory, University of Lyon
  • Maciej Skórski Institute of Science and Technology (IST), Klosterneuburg
  • Oto Petura Hubert Curien Laboratory, University of Lyon
  • Florent Bernard Hubert Curien Laboratory, University of Lyon
  • Marek Laban Department of Electronics and Multimedia Communications, Technical University of Košice; Micronic A. S., Bratislava
  • Viktor Fischer Hubert Curien Laboratory, University of Lyon
Keywords: Physical source of randomness, physical RNG, stochastic model, entropy

Abstract

In this paper, we evaluate clock signals generated in ring oscillators and self-timed rings and the way their jitter can be transformed into random numbers. We show that counting the periods of the jittery clock signal produces random numbers of significantly better quality than the methods in which the jittery signal is simply sampled (the case in almost all current methods). Moreover, we use the counter values to characterize and continuously monitor the source of randomness. However, instead of using the widely used statistical variance, we propose to use Allan variance to do so. There are two main advantages: Allan variance is insensitive to low frequency noises such as flicker noise that are known to be autocorrelated and significantly less circuitry is required for its computation than that used to compute commonly used variance. We also show that it is essential to use a differential principle of randomness extraction from the jitter based on the use of two identical oscillators to avoid autocorrelations originating from external and internal global jitter sources and that this fact is valid for both kinds of rings. Last but not least, we propose a method of statistical testing based on high order Markov model to show the reduced dependencies when the proposed randomness extraction is applied.

Published
2018-08-14
How to Cite
Noumon Allini, E., Skórski, M., Petura, O., Bernard, F., Laban, M., & Fischer, V. (2018). Evaluation and Monitoring of Free Running Oscillators Serving as Source of Randomness. IACR Transactions on Cryptographic Hardware and Embedded Systems, 2018(3), 214-242. https://doi.org/10.13154/tches.v2018.i3.214-242
Section
Articles