Paper 2019/810

Refutation and Redesign of a Physical Model of TERO-based TRNGs and PUFs

Jeroen Delvaux


In an article from CHES 2015, which appears in extended form in the Journal of Cryptology in 2019, Bernard, Haddad, Fischer, and Nicolai modeled the physical behavior of a transient effect ring oscillator (TERO), thereby providing a means to certify its operation as a true random number generator (TRNG). In this work, we disprove the physical assumption on which the whole model is based. Moreover, we show that the convenient use of tractable, closed-form equations stems from a mathematical error. On a more constructive note, we are the first to point out that TEROs and Bistable Ring physically unclonable functions (PUFs) are closely related, thereby not only laying the foundations of a more accurate physical model but also revealing a new design trade-off between throughput, entropy, and reliability. Furthermore, we demonstrate that most TERO implementations in the literature are prone to counter value corruptions, and propose a solution to this problem. Measurements performed on a field-programmable gate array (FPGA) substantiate our claims.

Available format(s)
Publication info
Preprint. Minor revision.
transient effect ring oscillatortrue random number generatorphysically unclonable functionstochastic model
Contact author(s)
jeroen delvaux @ osr-tech com
2019-07-14: received
Short URL
Creative Commons Attribution


      author = {Jeroen Delvaux},
      title = {Refutation and Redesign of a Physical Model of TERO-based TRNGs and PUFs},
      howpublished = {Cryptology ePrint Archive, Paper 2019/810},
      year = {2019},
      note = {\url{}},
      url = {}
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