Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution

Nanoseed-based physically unclonable function for on-demand encryption

A physically unclonable function (PUF) is a promising hardware-based cryptographic primitive to prevent confidential information leakage. However, conventional techniques, such as weak and strong PUFs, have limitations in overcoming the trade-off between security and storage volume. This study introduces nanoseed-based PUFs that overcome the drawbacks of conventional PUFs using optical and electrical randomness originated from nanoseeds and a unique on-demand cryptographic algorithm. Ideally mixed PbS quantum dots and Ag nanocrystals in the same medium are exploited as nanoseeds to simultaneously promote independent optical and electrical randomness. The number of secured keys that can be generated on-demand by combining the optical and electrical features in parallel using shuffling method is almost infinite (>1058741 per square millimeter). The proposed PUF achieves a near-ideal Hamming distance in uniqueness and randomness tests, validating its cryptographic efficacy. Last, storage-free and on-demand PUF with the shuffling method are demonstrated using smartphones, realizing manufacturer-/user-friendly cryptography system.

Statistical evaluation for enhancing the robustness of optical PUF-based authentication systems

Optical physical unclonable function (PUF)-based authentication systems are gaining significant attention in the field of hardware security. However, their susceptibility to external factors (especially PUF misalignment) leads to a relatively low robustness, which severely hinders its practical applications. To address this, we propose a highly robust authentication scheme by integrating the strengths of multiple speckle-comparison methods. The speckle recognition performance of conventional metrics and the newly introduced KAZE method is extensively analyzed and quantitatively assessed, utilizing a wide range of statistical measures, including false rejection rate (FRR), false acceptance rate (FAR), and receiver operating characteristic (ROC) curve. Notably, even when traditional methods underperform, our solution still achieves ultrahigh robustness with a FRR as low as 10-320 on the premise of ensuring security. Our results provide a comprehensive and in-depth understanding for optical PUF-based authentication systems, advancing their practical application in the field of hardware security.

Disturbance-Triggered Instant Crystallization Activating Bioinspired Emissive Gels

Many marine organisms feature sensitive sensory-perceptual systems to sense the surrounding environment and respond to disturbance with intense bioluminescence. However, it remains a great challenge to develop artificial materials that can sense external disturbance and simultaneously activate intense luminescence, although such materials are attractive for visual sensing and intelligent displays. Herein, we present a new class of bioinspired smart gels constructed by integrating hydrophilic polymeric networks, metastable supersaturated salt and fluorophores containing heterogenic atoms. Upon external disturbance, the composite gels undergo an instant and reversible soft-rigid state transition, simultaneously turning on intense fluorescence and activating ultralong afterglow emission with a maximum lifetime of 877.15 ms. The experimental results and molecular dynamics simulations reveal that the disturbance-induced luminescence mainly results from the geometrical confinement of aggregated fluorophores and enhanced molecular interactions to immensely suppress the non-radiative dissipation. Given their versatile and sensitive disturbance-responsiveness, dynamic interactive painting and 3D smart optical displays are demonstrated. This study paves a new avenue to achieve disturbance-sensing soft materials and promotes the development of smart visual sensors and interactive optical displays.

Chiroptical Synaptic Perovskite Memristor as Reconfigurable Physical Unclonable Functions

Physical unclonable functions (PUFs), often referred to as digital fingerprints, are emerging as critical elements in enhancing hardware security and encryption. While significant progress has been made in developing optical and memory-based PUFs, integrating reconfigurability with sensitivity to circularly polarized light (CPL) remains largely unexplored. Here, we present a chiroptical synaptic memristor (CSM) as a reconfigurable PUF, leveraging a two-dimensional organic-inorganic halide chiral perovskite. The device combines CPL sensitivity with photoresponsive electrical behavior, enabling its application in optoneuromorphic systems, as demonstrated by its ability to perform image categorization tasks within neuromorphic computing. Furthermore, by leveraging a 10 × 10 crossbar array of the CSMs, we develop a PUF capable of generating reconfigurable cryptographic keys based on the combination of neuromorphic potentiation and polarized light conditions. This work demonstrates an integrated approach to optoneuromorphic functionality, data storage, and encryption, providing an alternative approach for reconfigurable memristor-based PUFs.

Robust and Versatile Biodegradable Unclonable Anti-Counterfeiting Labels with Multi-Mode Optical Encoding Using Protein-Mediated Luminescent Calcite Signatures

Physical unclonable functions (PUFs) are emerging as a cutting-edge technology for enhancing information security by providing robust security authentication and non-reproducible cryptographic keys. Incorporating renewable and biocompatible materials into PUFs ensures safety for handling, compatibility with biological systems, and reduced environmental impact. However, existing PUF platforms struggle to balance high encoding capacity, diversified encryption signatures, and versatile functionalities with sustainability and biocompatibility. Here, all-biomaterial-based unclonable anti-counterfeiting labels featuring multi-mode encoding, multi-level cryptographic keys, and multiple authentication operations are developed by imprinting biomimetic-grown calcites on versatile silk protein films. In this label, the inherent non-clonability comes from the randomized characteristics of calcites, mediated by silk protein during crystal growth. The successful embedding of photoluminescent molecules into calcite lattices, assisted by silk protein, allows the resulting platform to utilize fluorescence patterns alongside birefringence for high-capacity encoding. This design facilitates easy and rapid authentication through Hamming distance and convolutional neural networks using standard cameras and portable microscopes. Moreover, angle-dependent polarization patterns enable multi-level key generation, while multi-spectral fluorescence signals offer multi-channel keys. The developed anti-counterfeiting labels combine biodegradability, green manufacture, easy authentication, high-level complexity, low cost, robustness, patternability, and versatility, offering a practical and high-security solution to combat counterfeiting across various applications.

Self-assembly by anti-repellent structures for programming particles with momentum

Self-assembled configurations are versatile for applications in which liquid-mediated phenomena are employed to ensure that static or mild physical interactions between assembling blocks take advantage of local energy minima. For granular materials, however, a particle's momentum in air leads to random collisions and the formation of disordered phases, eventually producing jammed configurations when densely packed. Therefore, unlike fluidic self-assembly, the self-assembly of dry particles typically lacks programmability based on density and ordering symmetry and has thus been limited in applications. Here, we present the self-assembly of particles with momentum, yielding regular arrays with programmable density and symmetry. The key is to embed anti-repellent structures, i.e. traps, that can capture kinetic particles individually and then robustly hold them against collisions with other momentum granules during a dynamic assembly procedure. By using anti-repellent traps, physical interactions between neighbouring particles can be inhibited, resolving many phenomena related to the uncertainty of space-sharing events in granular packing. With our self-assembly strategy, highly dense yet unjammed configurations are demonstrated, which conserve the inherent randomness in the location information of each granule in the trap and are useful for robust multilevel authentication systems as unique applications.

Multilevel Stimuli-Responsive Smart "Sandwich" Label with Physical Unclonable Functions Bionic Wrinkles and Space-Selective Fluorescence Patterns

With the increasing popularity of the internet, it brings convenience to lives while also increases security risks. Physical Unclonable Functions (PUFs) can generate random, unclonable, and unique identifiers using their inherent physical characteristics, which have broad prospects in anti-counterfeiting. Herein, inspired by the irregular tree bark fissures and random skin wrinkles found in nature, a method for creating complex micro-wrinkles with unclonable random patterns is proposed by simply stretching hydrogels. The random texture information contained in the micro-wrinkles is digitized into binary codes using an adaptive threshold algorithm. Additionally, a novel "sandwich" label with a multilevel intelligent anti-counterfeiting system is proposed. The first-level involves photoluminescence encryption with adjustable luminescence within visible light range and modulated luminescence at different excitation wavelengths; the second-level includes strain-related mechanical encryption, and the third-level consists of highly random and unclonable micro-wrinkles. The certification difficulty increases as the anti-counterfeiting grade increases, thereby enhancing label security. Furthermore, space-selective doping of rare earth metal-organic framework (RE-MOF) fluorescent materials in hydrogels is achieved through the use of screen-printing technology. The concept of novel multilevel smart anti-counterfeiting PUF labels will further enhance current levels of counterfeiting prevention.

Amorphous Photonic Structure Patterns with Thin Film Interference Effects for Multilevel Anticounterfeiting

Colloidal photonic structures with the ability to control and manipulate light propagation offer long-term color stability, low optical loss, and angle-dependent color properties, while combinations of different photonic structures across multiple scales provide an extensive color range and enhanced optical functionalities, presenting significant potential for advanced anticounterfeiting applications. However, the proper design or manufacture of such complex structures is still challenging. In this study, amorphous photonic structures (APSs) with thin film interference (TFI) effects were fabricated for multilevel anticounterfeiting. The APSs inherit the isotropic resonant scattering and render partial TFI effects, resulting in unprecedented dynamic specular and diffuse color-shifting features as the viewing or incident direction shifts. Additionally, incorporating a certain concentration of fluorescent microspheres into the colloidal ink adds a third layer of fluorescent anticounterfeiting mode to the APSs. Enabled by infiltration-assisted (IFAST) colloidal assembly technologies, the sophisticated color distributions and randomly arranged fluorescent microspheres on the microscale of APSs grant unique and inherent fingerprint features. The unique and unpredictable optical and structural characteristics of APSs provide physical unclonable functions (PUFs) to prevent replication and tampering, demonstrating their potential as optical PUF security labels for anticounterfeiting applications through artificial intelligence (AI) reading and authentication.

Scalable Photo-Responsive Physical Unclonable Functions via Particle Kinetics

The increasing menace of counterfeiting and information theft underscores the urgent need for security platforms compatible with both micro- and nanoelectronics. Existing methods for anticounterfeiting labeling and cryptographic systems rely on unclonable patterns derived from the unpredictable variability of physical phenomena. However, these approaches impose limitations on the scalability of security components. Here we present a scalable platform for photoresponsive physically unclonable functions based on oxide particle kinetics in polymer solutions. The stochastic agglomeration process occurring during the formation of polymer films with dispersed oxide particles yields random patterns, with pixel sizes scalable from micro to nanoscales. We produce mechanically flexible and self-destructible optical unclonable function patterns utilizing oxide aggregates on a polymer film. Moreover, we establish a strategy for generating electrical unclonable patterns on a conducting polymer film. This involves covering the polymer film with an aggregate pattern mask, which serves as an ultraviolet-blocking layer for randomly exposing the film to ultraviolet ozone treatment. These unclonable patterns constitute robust and compact security systems, exhibiting effective resilience against machine-learning attacks (∼50% prediction error for training data sets of 1000). The developed scalable platforms for physically unclonable functions provide a hardware solution for robust cryptographic applications.

Physical Unclonable Functions with Hyperspectral Imaging System for Ultrafast Storage and Authentication Enabled by Random Structural Color Domains

Physical unclonable function (PUF) is attractive in modern encryption technologies. Addressing the disadvantage of slow data storage/authentication in optical PUF is paramount for practical applications but remains an on-going challenge. Here, a highly efficient PUF strategy based on random structural color domains (SCDs) of cellulose nanocrystal (CNC) is proposed for the first time, combing with hyperspectral imaging system (HIS) for ultrafast storage and authentication. By controlling the growth and fusion behavior of the tactoids of CNC, the SCDs display an irregular and random distribution of colors, shapes, sizes, and reflectance spectra, which grant unique and inherent fingerprint-like characteristics that are non-duplicated. Based on images and spectra, these fingerprint features are used to develop two sets of PUF key generation methods, which can be respectively authenticated at the user-end and the manufacturer-front-end that achieving a high coding capacity of at least 22304. Notably, the use of HIS greatly shortens the time of key reading and generation (≈5 s for recording, 0.5-0.7 s for authentication). This new optical PUF labels can not only solve slow data storage and complicated authentication in optical PUF, but also impulse the development of CNC in industrial applications by reducing color uniformity requirement.

Silicon Vacancies Diamond/Silk/PVA Hierarchical Physical Unclonable Functions for Multi-Level Encryption

Physical unclonable functions (PUFs) have emerged as a promising encryption technology, utilizing intrinsic physical identifiers that offer enhanced security and tamper resistance. Multi-level PUFs boost system complexity, thereby improving system reliability and fault tolerance. However, crosstalk-free multi-level PUFs remain a persistent challenge. In this study, a hierarchical PUF system that harnesses the spontaneous phase separation of silk fibroin /PVA blend and the random distribution of silicon-vacancy diamonds within the blend is presented. The thermodynamic instability of phase separation and inherent unpredictability of diamond dispersion gives rise to intricate random patterns at two distinct scales, enabling time-efficient hierarchical authentication for cryptographic keys. These patterns are complementary yet independent, inherently resistant to replication and damage thus affording robust security and reliability to the proposed system. Furthermore, customized authentication algorithms are constructed: visual PUFs authentication utilizes neural network combined structural similarity index measure, while spectral PUFs authentication employs Hamming distance and cross-correlation bit operation. This hierarchical PUF system attains a high recognition rate without interscale crosstalk. Additionally, the coding capacity is exponentially enhanced using M-ary encoding to reinforce multi-level encryption. Hierarchical PUFs hold significant potential for immediate application, offering unprecedented data protection and cryptographic key authentication capabilities.

Robust Optical Physical Unclonable Function Based on Total Internal Reflection for Portable Authentication

Physical unclonable functions (PUFs) utilize uncontrollable manufacturing randomness to yield cryptographic primitives. Currently, the fabrication of the most generally employed optical PUFs mainly depends on fluorescent, Raman, or plasmonic materials, which suffer inherent robustness issues. Herein, we construct an optical PUF with high environmental stability via total internal reflection (TIR-PUF) perturbed by randomly distributed polymer microspheres. The response image is transformed into encoded keys via an iterative binning procedure. The concentration of the polymer solution is optimized to debias the bit nonuniformity and maximize encoding capacity. The constructed TIR-PUF shows significantly high encoding capacity (2370) and markedly low total authentication error probability (1.614 × 10-23). The intra-Hamming distance is as low as 0.068, indicating the excellent readout reliability of TIR-PUF. The environmental stability of TIR-PUF has demonstrated promising results under a range of challenging conditions such as ultrasonic washing, high temperature, ultraviolet irradiation, and severe chemical environments. Moreover, the challenge-response pairs of our TIR-PUFs are demonstrated on an authentication system with low-power dissipation, lightweight components, and wireless imaging capture, rendering the possibility of portable authentication for practical applications.

Four-Dimensional Physical Unclonable Functions and Cryptographic Applications Based on Time-Varying Chaotic Phosphorescent Patterns

Physical unclonable functions (PUFs) have attracted interest in demonstrating authentication and cryptographic processes for Internet of Things (IoT) devices. We demonstrated four-dimensional PUFs (4D PUFs) to realize time-varying chaotic phosphorescent randomness on MoS2 atomic seeds. By forming hybrid states involving more than one emitter with distinct lifetimes in 4D PUFs, irregular lifetime distribution throughout patterns functions as a time-varying disorder that is impossible to replicate. Moreover, we established a bit extraction process incorporating multiple 64 bit-stream challenges and experimentally obtained physical features of 4D PUFs, producing countless random 896 bit-stream responses. Furthermore, the weak and strong PUF models were conceptualized and demonstrated based on 4D PUFs, exhibiting superior cryptological performances, including randomness, uniqueness, degree of freedom, and independent bit ratio. Finally, the data encryption and decryption in pictures were performed by a single 4D PUF. Therefore, 4D PUFs could enhance the counterfeiting deterrent of existing optical PUFs and be used as an anticounterfeiting security strategy for advanced authentication and cryptographic processes of IoT devices.

Dual Challenge-Response Systems of a Three-Dimensional "Bionic" Fluorescent Physically Unclonable Function Label

Inspired by the light and dark variations observed in natural cloud clusters under sunlight, we propose a three-dimensional (3D) "bionic" fluorescent physically unclonable function (PUF) label. The minimalist preparation process eliminates the need for expensive traditional instruments, thus offering new insight into the widespread adoption of 3D PUF labels. The Eu(CCA)3(H2O)2 powder, which is the first to propose its secondary building unit, was chosen as the fluorescent material. Its 3D morphology is preserved in the resin to mimic cloud-like structures. Furthermore, the luminescent properties are elucidated through experimental tests and first-principles calculations. To overcome the coding capacity limitation of traditional two-dimensional (2D) fluorescent PUF labels, a dual challenge-response system model is proposed. The shallow and deep models provide anticounterfeiting information from macro and micro perspectives, respectively. This successfully increases the encoding capacity from 210×10 to 2100×10000 for a 10 × 10 pixel binary code. Therefore, 3D "bionic" fluorescent PUF labels strike a balance between the simple usage of PUF labels and enhanced label security.

Physical Unclonable Functions Based on Photothermal Effect of Gold Nanoparticles

Physical unclonable functions (PUFs) based on uncontrollable fabrication randomness are promising candidates for anticounterfeiting applications. Currently, the most popular optical PUFs are generally constructed from the scattering, fluorescent, or Raman phenomenon of nanomaterials. To further improve the security level of optical PUFs, advanced functions transparent to the above optical phenomenon have always been perused by researchers. Herein, we propose a new type of PUF based on the photothermal effect of gold nanoparticles, which shows negligible scattering, fluorescent, or Raman responses. The gold nanoparticles are randomly dispersed onto the surface of fused silica, which can enhance the photothermal effect and facilitate high contrast responses. By tuning the areal density of the gold nanoparticles, the optimized encoding capacity (2319) and the total authentication error probability (3.6428 × 10-24) are achieved from our PUF due to excellent bit uniformity (0.519) and inter Hamming distances (0.503). Moreover, the intra-Hamming distance (0.044) indicates the desired reliability. This advanced PUF with invisible features and high contrast responses provides a promising opportunity to implement authentication and identification with high security.

All-optical multilevel physical unclonable functions

Disordered photonic structures are promising for the realization of physical unclonable functions-physical objects that can overcome the limitations of conventional digital security and can enable cryptographic protocols immune against attacks by future quantum computers. The physical configuration of traditional physical unclonable functions is either fixed or can only be permanently modified, allowing one token per device and limiting their practicality. Here we overcome this limitation by creating reconfigurable structures made by light-transformable polymers in which the physical structure of the unclonable function can be reconfigured reversibly. Our approach allows the simultaneous coexistence of multiple physical unclonable functions within one device. The physical transformation is done all-optically in a reversible and spatially controlled fashion, allowing the generation of more complex keys. At the same time, as a set of switchable individual physical unclonable functions, it enables the authentication of multiple clients and allows for the practical implementations of quantum secure authentication and nonlinear generators of cryptographic keys.

Voxelated opto-physically unclonable functions via irreplicable wrinkles

The increased prevalence of the Internet of Things (IoT) and the integration of digital technology into our daily lives have given rise to heightened security risks and the need for more robust security measures. In response to these challenges, physical unclonable functions (PUFs) have emerged as promising solution, offering a highly secure method to generate unpredictable and unique random digital values by leveraging inherent physical characteristics. However, traditional PUFs implementations often require complex hardware and circuitry, which can add to the cost and complexity of the system. We present a novel approach using a random wrinkles PUF (rw-PUF) based on an optically anisotropic, facile, simple, and cost-effective material. These wrinkles contain randomly oriented liquid crystal molecules, resulting in a two-dimensional retardation map corresponding to a complex birefringence pattern. Additionally, our proposed technique allows for customization based on specific requirements using a spatial light modulator, enabling fast fabrication. The random wrinkles PUF has the capability to store multiple data sets within a single PUF without the need for physical alterations. Furthermore, we introduce a concept called 'polyhedron authentication,' which utilizes three-dimensional information storage in a voxelated random wrinkles PUF. This approach demonstrates the feasibility of implementing high-level security technology by leveraging the unique properties of the rw-PUF.