Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution

Abstract

Physical unclonable functions (PUFs) are emerging as an alternative to information security by providing an advanced level of cryptographic keys with non‐replicable characteristics, yet the cryptographic keys of conventional PUFs are not reconfigurable from the ones assigned at the manufacturing stage and the overall authentication process slows down as the number of entities in the dataset or the length of cryptographic key increases. Herein, a supersaturated solution‐based PUF (S‐PUF) is presented that utilizes stochastic crystallization of a supersaturated sodium acetate solution to allow a time‐efficient, hierarchical authentication process together with on‐demand rewritability of cryptographic keys. By controlling the orientation and the average grain size of the sodium acetate crystals via a spatiotemporally programmed temperature profile, the S‐PUF now includes two global parameters, that is, angle of rotation and divergence of the diffracted beam, in addition to the speckle pattern to produce multilevel cryptographic keys, and these parameters function as prefixes for the classification of each entity for a fast authentication process. At the same time, the reversible phase change of sodium acetate enables repeated reconfiguration of the cryptographic key, which is expected to offer new possibilities for a next‐generation, recyclable anti‐counterfeiting platform.

Physical Unclonable Functions Based on Photothermal Effect of Gold Nanoparticles

“…An uneven ratio of "0" and "1" bits for a coding key can lead to bias that decreases the encoding capacity of PUFs. 24 A balanced ratio of "0" and "1" bits maximizes encoding capacity, with bit uniformity approaching 0.5. The bit uniformity of unoptimized PT−PUF, calculated using 25 independent coding keys, is illustrated in Figure 3g.…”

“…15−17 Optical PUFs have gained increased attention due to high contrast responses and encoding capacity since Pappu et al proposes the concept of PUF in 2002. 18−23 Scattering PUFs, such as laser scattering patterns 24,25 and localized surface plasmon resonance (LSPR) of metal nanoparticles 26,27 are modulated by the laser parameters and the geometry of nanoparticles. However, the scattering PUFs are unreliable due to the sensitivity to the fluctuation of excitation.…”

“…The reasonable choice of entropy source is crucial for the construction of high security level PUFs. According to the type of entropy source, PUFs are categorized into different types, such as electrical PUFs and optical PUFs. − Optical PUFs have gained increased attention due to high contrast responses and encoding capacity since Pappu et al proposes the concept of PUF in 2002. − Scattering PUFs, such as laser scattering patterns , and localized surface plasmon resonance (LSPR) of metal nanoparticles , are modulated by the laser parameters and the geometry of nanoparticles. However, the scattering PUFs are unreliable due to the sensitivity to the fluctuation of excitation .…”

Optical-Anisotropy-Exploited Irreproducible Functions Using Microwrinkles

“…A promising alternative in the field of information security is a physical unclonable function (PUF), which leverages the unique and unpredictable identifiers generated through the inherent physical variations of electronic devices. − PUF serves as a cryptographic primitive technology utilizing the imperfections in materials, manufacturing tolerances, and environmental conditions that occur during the production process. − Exploiting these distinctive variations, PUF generates a unique “fingerprint” for each device, making it challenging for attackers to replicate or reproduce PUF responses. PUF is widely utilized in various security-related applications, including security tokens, anticounterfeiting methods, and hardware-based encryption key generation and storage .…”

“…However, while semiconductor-based PUFs offer unique advantages in enhancing information security, the integration of these systems into practical implementations presents challenges such as complexity, compatibility between hardware and software, and inflated cost due to the use of semiconductor processes. Among the diverse types of PUFs, optical PUFs are recognized as a promising field for creating unique and unpredictable identifiers by utilizing inherent optical property changes. − Research is underway on optical PUFs utilizing a variety of materials, including surface-structure-based signals, ,− fluorescent molecules, , and DNA-like twisted structures. , When these materials are irradiated with light, the light travels through various pathways such as reflection, refraction, and scattering within the material . The optical interactions are determined by the unique microstructure or properties of the material; therefore, it is improbable that two optical patterns will have the same scattering pattern, even if they use the same material.…”