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Impact of the Flicker Noise on the Ring Oscillator-based TRNGs

Authors:
Licinius Benea , Univ. Grenoble Alpes, CEA, LETI MINATEC Campus, F-38054 Grenoble, France
Mikael Carmona , Univ. Grenoble Alpes, CEA, LETI MINATEC Campus, F-38054 Grenoble, France
Viktor Fischer , Hubert Curien Laboratory, Jean Monnet University, Saint-Etienne, France; Faculty of Information Technologies, Czech Technical University, Prague, Czech Republic
Florian Pebay-Peyroula , Univ. Grenoble Alpes, CEA, LETI MINATEC Campus, F-38054 Grenoble, France
Romain Wacquez , Univ. Grenoble Alpes, CEA, LETI MINATEC Campus, F-38054 Grenoble, France; CEA-Leti, Mines Saint-√Čtienne, Equipe Commune, F-13541 Gardanne, France
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DOI: 10.46586/tches.v2024.i2.870-889
URL: https://tches.iacr.org/index.php/TCHES/article/view/11450
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Abstract: Ring Oscillators (RO) are often used in true random number generators (TRNG). Their jittered clock signal, used as randomness source, originates from thermal and flicker noises. While thermal noise jitter is generally used as the main source of randomness, flicker noise jitter is not due to its autocorrelation. This work aims at qualitatively settling the issue of the influence of flicker noise in TRNGs, as its impact increases in newer technology nodes. For this, we built a RO behavioural model, which generates time series equivalent to a jittered RO signal. It is then used to generate the output of an elementary RO-TRNG. Despite general expectations, the autocorrelation inside the output bit stream is reduced when the amplitude of flicker noise increases. The model shows that this effect is caused by the sampling of the jittered signal by the second oscillator, which hides the behaviour of the absolute jitter, causes resetting of the perceived phase, and suppresses any memory effect. The inclusion of flicker noise as a legitimate noise source can increase the TRNG output bit rate by a factor of four for the same output entropy rate. This observation opens new perspectives towards more efficient stochastic models of the RO-TRNGs.
BibTeX
@article{tches-2024-34073,
  title={Impact of the Flicker Noise on the Ring Oscillator-based TRNGs},
  journal={IACR Transactions on Cryptographic Hardware and Embedded Systems},
  publisher={Ruhr-Universität Bochum},
  volume={024 No. 2},
  pages={870-889},
  url={https://tches.iacr.org/index.php/TCHES/article/view/11450},
  doi={10.46586/tches.v2024.i2.870-889},
  author={Licinius Benea and Mikael Carmona and Viktor Fischer and Florian Pebay-Peyroula and Romain Wacquez},
  year=2024
}