Digitization Algorithms in Ring Oscillator Physically Unclonable Functions as a Main Factor Achieving Hardware Security

IEEE Open J. Ind. Electron. Soc.

Sánchez-Azqueta

et al. 2023

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In the last years, guaranteeing the security in IoT communications has become an essential task. In this paper, the bias of a wide set of oscillators has been studied to determine their suitability as both True Random Number Generators (TRNGs) and Physically Unclonable Functions (PUFs). For this purpose, a generic configurable structure has been proposed and implemented in an FPGA. With this implementation, by introducing some external signals it is possible to configure the system in different oscillator topologies. This way, we have managed to analyze 2730 oscillators composed by 7 Lookup Tables (LUTs) without having to resynthesize the code each time. The performed analysis has included conventional ring oscillators, Galois ring oscillators and newly proposed oscillator topologies. From this analysis we have concluded that none of these oscillators behave as an ideal TRNG but ring oscillators present the closest to an ideal behavior. Regarding their suitability as PUFs, some of the newly proposed oscillators in this paper present a high reproducibility, higher than that of conventional ring oscillator PUF (RO-PUF) and a high uniqueness. Furthermore, we have noticed that both their reproducibility and their uniqueness tend to improve when increasing the length of the oscillators, which opens the possibility of finding new oscillators with even better properties by studying oscillators of bigger lengths. Finally, by studying the spatial correlation of the bias of these oscillators, we have observed that they present a much lower spatial correlation compared to the ring oscillators, which opens the possibility of using these oscillators in PUF architectures that use more comparisons than typical RO-PUFs.

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Section: B Measured Parametersmentioning

confidence: 99%

Suitability of Generalized GAROs on FPGAs as PUFs or TRNGs Considering Spatial Correlations

IEEE Open J. Ind. Electron. Soc.

Sánchez-Azqueta

et al. 2023

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“…In fact, there are several RO-PUF architectures depending on the comparison pattern used. In this work, the 2-masking architecture has been used, which consists of comparing the oscillators in pairs so that any oscillator is repeated in each comparison [19].…”

Section: Architecture Of a Ro-pufmentioning

confidence: 99%

Oscillator Selection Strategies to Optimize a Physically Unclonable Function for IoT Systems Security

Aparicio-Téllez

et al. 2023

Sensors

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Physically unclonable functions avoid storing secret information in non-volatile memories and only generate a key when it is necessary for an application, rising as a promising solution for the authentication of resource-constrained IoT devices. However, the need to minimize the predictability of physically unclonable functions is evident. The main purpose of this work is to determine the optimal way to construct a physically unclonable function. To do this, a ring oscillator physically unclonable function based on comparing oscillators in pairs has been implemented in an FPGA. This analysis shows that the frequencies of the oscillators greatly vary depending on their position in the FPGA, especially between oscillators implemented in different types of slices. Furthermore, the influence of the chosen locations of the ring oscillators on the quality of the physically unclonable function has been analyzed and we propose five strategies to select the locations of the oscillators. Among the strategies proposed, two of them stand out for their high uniqueness, reproducibility, and identifiability, so they can be used for authentication purposes. Finally, we have analyzed the reproducibility for the best strategy facing voltage and temperature variations, showing that it remains stable in the studied range.

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An analysis of the behaviour of a PUF based on ring oscillators depending on their locations

Aparicio

2022 17th Conference on Ph.D Research in Microelectronics and Electronics (PRIME)

et al. 2022