Author: Fernando de los Santos Prieto
Year: Since 2002
Journal Papers
Harvesting random telegraph noise for true random number generation F.J. Rubio-Barbero, F. de los Santos-Prieto, R. Castro-López, E. Roca and F.V. Fernández Journal Paper · AEU - International Journal of Electronics and Communications, vol. 196, June 2025 abstractdoi
At first glance, Random Telegraph Noise (RTN) in deeply scaled CMOS transistors may seem like a reliability nuisance. Yet, behind the discrete trapping-and-detrapping events lurks a potent source of hardware entropy. In this paper, we harness RTN to build a dual-purpose security module that serves as both a Physical Unclonable Function (PUF) and a True Random Number Generator (TRNG). By measuring the so-called Maximum Current Fluctuation (MCF) at carefully chosen observation windows, our design switches effortlessly between the stable outputs needed for a PUF and the maximally unpredictable bitstreams demanded by a TRNG. Although single-defect RTN has long been deemed ideal for randomness, we show that multi-defect RTN scenarios, much more prevalent in real-world manufacturing, can also yield high-quality random bits, especially when aided by lightweight post-processing. Simple statistical metrics guide the initial tuning, after which the final bitstreams pass the NIST SP 800-22 test suite to validate the statistical soundness of our proposal. In doing so, we address key challenges that arise when designing an RTN-based TRNG and compare our results against state-of-the-art solutions, highlighting advantages in circuit simplicity, bit-rate scalability, and dual-use capability.
A Comprehensive Approach to Improving the Thermal Reliability of RTN-Based PUFs F. de los Santos-Prieto, F.J. Rubio-Barbero, R. Castro-López, E. Roca and F.V. Fernández Journal Paper · IEEE Transactions on Circuits and Systems I: Regular Papers (Early Access), 2024 abstractdoi
Silicon Physical Unclonable Functions (PUFs) have emerged as a promising solution for generating cryptographic keys in low-cost resource-constrained devices. A PUF is expected to be reliable, meaning that its response bits should remain consistent each time the corresponding challenges are queried. Unfortunately, the stability of these challenge-response pairs (CRPs) can be seriously eroded by environmental factors like temperature variations and the aging of the integrated circuits implementing the PUF. Several approaches, including bit masking, bit selection techniques, and error-correcting codes, have been proposed to obtain a reliable PUF operation in the face of temperature variations. As for aging, a new kind of aging-resilient silicon PUF has been reported that uses the time-varying phenomenon known as Random Telegraph Noise (RTN) as the underlying entropy source. Although this type of PUF preserves its reliability well when aged, it is not immune to the impact of temperature variations. The work presented here shows that it is possible to improve the thermal reliability of RTN-based PUFs with a proper combination of (a) a novel optimization-based bit selection technique, that is also applicable to other types of PUFs based on differential measurements; and (b) a temperature-aware tuning of the entropy-harvesting function.
