Optical Physical Unclonable Functions Research Articles

Traceable Optical Physical Unclonable Functions Based on Germanium Vacancy in Diamonds.

Physical unclonable functions (PUFs) have emerged as an unprecedented solution for modern information security and anticounterfeiting by virtue of their inherent unclonable nature derived from distinctive, randomly generated physical patterns that defy replication. However, the creation of traceable optical PUF tags remains a formidable challenge. Here, we demonstrate a traceable PUF system whose unclonability arises from the random distribution of diamonds and the random intensity of the narrow emission from germanium vacancies (GeV) within the diamonds. Tamper-resistant PUF labels can be manufactured on diverse and intricate structural surfaces by blending diamond particles into polydimethylsiloxane (PDMS) and strategically depositing them onto the surface of objects. The resulting PUF codes exhibit essentially perfect uniformity, uniqueness, reproducibility, and substantial encoding capacity, making them applicable as a private key to fulfill the customization demands of circulating commodities. Through integration of a digitized "challenge-response" protocol, a traceable and highly secure PUF system can be established, which is seamlessly compatible with contemporary digital information technology. Thus, the GeV-PUF system holds significant promise for applications in data security and blockchain anticounterfeiting, providing robust and adaptive solutions to address the dynamic demands of these domains.

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 (≈5s for recording, 0.5-0.7s 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.

Electrospray deposition of physical unclonable functions for drug anti-counterfeiting

In recent years, pharmaceutical counterfeiting has become an increasingly dangerous situation. A patient who unknowingly consumes a counterfeit drug is at a serious health risk. To address this problem, a low-cost and robust approach for authentication that can be administered at the point-of-care is required. Our proposed solution uses Optical Physical Unclonable Functions (PUFs); patterns formed by a stochastic process that can be used for authentication. We create edible PUFs (ePUFs) using electrospray deposition, which utilizes strong electric fields to atomize a liquid suspension into a plume of micro-scale droplets that are delivered to the target. The ePUFs are electrospray-deposited from an edible ink directly onto the surface of the drug tablets. The process parameters (flow rate, translation speed, and suspension concentration) govern the characteristics of the ePUF to provide highly stochastic patterns. To evaluate our approach, 200 ePUFs were deposited onto tablets at various conditions, followed by imaging and storage of the patterns in a database. For ePUF authentication, a machine vision approach was created using the open source SIFT pattern matching algorithm. Using optimized pattern-matching constraints, our algorithm was shown to be 100% successful in authenticating the cellphone images of the ePUFs to the database. Additionally, the algorithm was found to be robust against changes in illumination and orientation of the cellphone images.

Near-Infrared Circularly Polarized Luminescent Physical Unclonable Functions.

Distinguished from traditional physical unclonable functions (PUFs), optical PUFs derive their encoded information from the optical properties of materials, offering distinct advantages, including solution processability, material versatility, and tunable luminescence performance. However, existing research on optical PUFs has predominantly centered on visible photoluminescence, while advanced optical PUFs based on higher-level covert light remain unexplored. In this study, we present optical PUFs based on the utilization of the covert light of near-infrared circularly polarized luminescence (NIR-CPL). This interesting property is achieved by incorporating Yb-doped metal halide perovskite nanocrystals (Yb-PeNCs) possessing NIR emission property into chiral imprinted photonic (CIP) films. By employing a solvent immersion method, we successfully integrated Yb-PeNCs into these CIP films, thereby creating an optically unclonable surface. The resulting NIR-CPL emission adds a layer of advanced security to the optical PUF systems. These findings underscore the potential of solution-processable chiral films to play a pivotal role in advancing the next generation of PUFs.

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.

All-silicon multidimensionally-encoded optical physical unclonable functions for integrated circuit anti-counterfeiting

Integrated circuit anti-counterfeiting based on optical physical unclonable functions (PUFs) plays a crucial role in guaranteeing secure identification and authentication for Internet of Things (IoT) devices. While considerable efforts have been devoted to exploring optical PUFs, two critical challenges remain: incompatibility with the complementary metal-oxide-semiconductor (CMOS) technology and limited information entropy. Here, we demonstrate all-silicon multidimensionally-encoded optical PUFs fabricated by integrating silicon (Si) metasurface and erbium-doped Si quantum dots (Er-Si QDs) with a CMOS-compatible procedure. Five in-situ optical responses have been manifested within a single pixel, rendering an ultrahigh information entropy of 2.32 bits/pixel. The position-dependent optical responses originate from the position-dependent radiation field and Purcell effect. Our evaluation highlights their potential in IoT security through advanced metrics like bit uniformity, similarity, intra- and inter-Hamming distance, false-acceptance and rejection rates, and encoding capacity. We finally demonstrate the implementation of efficient lightweight mutual authentication protocols for IoT applications by using the all-Si multidimensionally-encoded optical PUFs.

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.

Advances in Physical Unclonable Functions Based on New Technologies: A Comprehensive Review

A physical unclonable function (PUF) is a technology designed to safeguard sensitive information and ensure data security. PUFs generate unique responses for each challenge by leveraging random deviations in the physical microstructures of integrated circuits (ICs), making it incredibly difficult to replicate them. However, traditional silicon PUFs are now susceptible to various attacks, such as modeling attacks using conventional machine learning techniques and reverse engineering strategies. As a result, PUFs based on new materials or methods are being developed to enhance their security. However, in the realm of survey papers, it has come to our attention that there is a notable scarcity of comprehensive summaries and introductions concerning these emerging PUFs. To fill this gap, this article surveys PUFs based on novel technologies in the literature. In particular, we first provide an insightful overview of four types of PUFs that are rooted in advanced technologies: bionic optical PUF, biological PUF, PUF based on printed electronics (PE), and PUF based on memristors. Based on the overview, we further discuss the evaluation results of their performance based on specific metrics and conduct a comparative analysis of their performance. Despite significant progress in areas such as limited entry and regional expertise, it is worth noting that these PUFs still have room for improvement. Therefore, we have identified their potential shortcomings and areas that require further development. Moreover, we outline various applications of PUFs and propose our own future prospects for this technology. To sum up, this article contributes to the understanding of PUFs based on novel technologies by providing an in-depth analysis of their characteristics, performance evaluation, and potential improvements. It also sheds light on the wide range of applications for PUFs and presents enticing prospects for future advancements in this field.

Physically Unclonable Functions Based on Self‐Oriented Nanowires

AbstractAs scaling down to the nanoscale, the dramatically increased morphological deviation between nanostructures becomes a major challenge in implementing large‐scale nanodevices. On the other side of the coin, the often‐undesirable rich non‐repeatable randomness introduced during nanostructure growth and subsequent device fabrication is of great value in the implementation of physically unclonable functions (PUF), a booming innovative security primitive. Herein, it is shown that the self‐oriented organic nanowires grown on a faceted surface through a vapor transport process are advanced building blocks for the implementation of two novel PUFs. An optical PUF is first demonstrated by exploiting the unclonable morphological randomness of the self‐oriented nanowires (e.g., length, thickness, density, and location), which can provide an entity‐specific primary encryption for nanowire devices. Next, these nanowires are integrated into photodetector arrays directly on their growth substrate and accordingly enable an electrical PUF based on the inherent resistance variation between detector cells. Furthermore, by combining these two PUFs, a secondary encryption with higher security is proposed for information communication. The implementation of nanowire‐based PUFs not only opens a new device direction to exploit the annoying unclonable randomness of bottom‐up nanowires, but also provides innovative label‐free security primitives for emerging nanowire‐based devices and systems.

Oxide Breakdown Spot Spatial Patterns as Fingerprints for Optical Physical Unclonable Functions

Oxide Breakdown Spot Spatial Patterns as Fingerprints for Optical Physical Unclonable Functions

Optical identification using physical unclonable functions

In this work, the concept of optical identification (OI) based on physical unclonable functions is introduced for the first time, to our knowledge, in optical communication systems and networks. The OI assigns an optical fingerprint and the corresponding digital representation to each sub-system of the network and estimates its reliability in different measures. We highlight the large potential applications of OI as a physical layer approach for security, identification, authentication, and monitoring purposes. To identify most of the sub-systems of a network, we propose to use the Rayleigh backscattering pattern, which is an optical physical unclonable function and allows OI to be achieved with a simple procedure and without additional devices. The applications of OI to fiber and path identification in a network and to the authentication of users in a quantum key distribution system are described.

Planar Spin Glass with TopologicallyProtected Mazes in the Liquid Crystal Targeting for Reconfigurable Micro Security Media.

The planar spin glass pattern is widely known for its inherent randomness, resulting from the geometrical frustration. As such, developing physical unclonable functions (PUFs)-which operate with device randomness-with planar spin glass patterns is a promising candidate for an advanced security systems in the upcoming digitalized society. Despite their inherent randomness, traditional magnetic spin glass patterns pose considerable obstacles in detection, making it challenging to achieve authentication in security systems. This necessitates the development of facilely observable mimetic patterns with similar randomness to overcome these challenges. Here, a straightforward approach is introduced using a topologicallyprotected maze pattern in the chiral liquid crystals (LCs). This maze exhibits a comparable level of randomness to magnetic spin glass and can be reliably identified through the combination of optical microscopy with machine learning-based object detection techniques. The "information" embedded in the maze can be reconstructed through thermal phase transitions of the LCs in tens of seconds. Furthermore, incorporating various elements can enhance the optical PUF, resulting in a multi-factor security medium. It is expected that this security medium, based on microscopically controlled and macroscopically uncontrolled topologicallyprotected structures, may be utilized as a next-generation security system.

Randomized whispering-gallery-mode microdisk laser arrays via cavity deformations for anti-counterfeiting labels

Optical physical unclonable functions (PUFs) have emerged as a promising strategy for effective and unbreakable anti-counterfeiting. However, the unpredictable spatial distribution and broadband spectra of most optical PUFs complicate efficient and accurate verification in practical anti-counterfeiting applications. Here, we propose an optical PUF-based anti-counterfeiting label from perovskite microlaser arrays, where randomness is introduced through vapor-induced microcavity deformation. The initial perovskite microdisk laser arrays with regular positions and uniform sizes are fabricated by femtosecond laser direct ablation. By introducing vapor fumigation to induce random deformations in each microlaser cavity, a laser array with completely uneven excitation thresholds and narrow-linewidth lasing signals is obtained. As a proof of concept, we demonstrated that the post-treated laser array can provide fixed-point and random lasing signals to facilitate information encoding. Furthermore, different emission states of the lasing signal can be achieved by altering the pump energy density to reflect higher capacity information. A threefold PUF (excited under three pump power densities) with a resolution of 5×5 pixels exhibits a high encoding capacity (1.43×1045), making it a promising candidate to achieve efficient authentication and high security with anti-counterfeiting labels.

Optical Systems Identification through Rayleigh Backscattering.

We introduce a technique to generate and read the digital signature of the networks, channels, and optical devices that possess the fiber-optic pigtails to enhance physical layer security (PLS). Attributing a signature to the networks or devices eases the identification and authentication of networks and systems thus reducing their vulnerability to physical and digital attacks. The signatures are generated using an optical physical unclonable function (OPUF). Considering that OPUFs are established as the most potent anti-counterfeiting tool, the created signatures are robust against malicious attacks such as tampering and cyber attacks. We investigate Rayleigh backscattering signal (RBS) as a strong OPUF to generate reliable signatures. Contrary to other OPUFs that must be fabricated, the RBS-based OPUF is an inherent feature of fibers and can be easily obtained using optical frequency domain reflectometry (OFDR). We evaluate the security of the generated signatures in terms of their robustness against prediction and cloning. We demonstrate the robustness of signatures against digital and physical attacks confirming the unpredictability and unclonability features of the generated signatures. We explore signature cyber security by considering the random structure of the produced signatures. To demonstrate signature reproducibility through repeated measurements, we simulate the signature of a system by adding a random Gaussian white noise to the signal. This model is proposed to address services including security, authentication, identification, and monitoring.

Tunable Key-Size Physical Unclonable Functions Based on Phase Segregation in Mixed Halide Perovskites.

Optical physical unclonable functions (PUFs) have been considered as an effective tool for anti-counterfeiting owing to the uncontrollable manufacturing process and excellent resistance to machine-learning attacks. However, most optical PUFs exhibit fixed challenge-response pairs and static encoding structures after they are manufactured, which significantly impedes the actual development. Herein, we propose a tunable key-size PUF based on reversible phase segregation in mixed halide perovskites with uncontrollable Br/I ratios under variable power densities. The basic performance of encryption keys of low and high power density was evaluated and indicated a high degree of uniformity, uniqueness, and readout repeatability. Merging the binary keys of low and high power density, tunable key-size PUF is realized with higher security. The proposed tunable key-size PUF offers new insights into the development of dynamic-structure PUFs and demonstrates a novel scheme for achieving higher security of anti-counterfeiting and authentication.

Analysis of entropy source for random number generation based on optical PUFs

In this paper, we present an in-depth analysis for entropy source based on optical physical unclonable functions (PUFs). The randomness of speckle patterns is elaborated essentially according to its statistical characteristics. Various factors affecting the source of entropy have been analyzed in detail, including wavefront modulation, sensitivity, and universality of the optical PUF, and bit-depth settings of captured speckle patterns. In view of the above considerations, we demonstrate that the entropy source can achieve an ultra-high min-entropy (>0.985 bits/bit) while maintaining a high extraction rate of 75% and also verify its independent and identically distributed nature. These results provide an in-depth and comprehensive understanding of the developed entropy source and offer a firm foundation for its practical use.

Reconfigurable Multilevel Optical PUF by Spatiotemporally Programmed Crystallization of Supersaturated Solution.

Physical unclonable functions (PUFs) areemerging 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.

On-Chip Silicon Optical Scattering Physical Unclonable Function Towards Hardware Security

Physical Unclonable Function (PUF) serves as a physical security primitive that cannot be feasibly duplicated and has diversified applications in the field of hardware security. Although optical PUF is regarded as one of the most promising PUF due to high information capacity, conventional image-based optical PUF generally suffers from notorious sensitivity to mechanical alignment and difficulty in integrating with electronic circuits. Here we propose a novel silicon optical scattering PUF (SOSPUF) with its optical components integrated on Silicon on Insulator (SOI) platform, yielding easy-to-integrate and easy-to-use merits over conventional optical PUF. In the disordered scattering region, the randomly distributed holes are introduced to enhance security of SOSPUF. The uniqueness, unpredictability and reliability properties of SOSPUF are demonstrated via numerical simulations. This work provides a solid basis for the design and implementation of SOSPUF.

Visually Hidden, Self-Assembled Porous Polymers for Optical Physically Unclonable Functions

Owing to the advancement of security technologies, several encryption methods have been proposed. Despite such efforts, forging artifices is financially and somatically becoming a constraint for individuals and society (e.g., imprinting replicas of luxury goods or directly life-connected medicines). Physically unclonable functions (PUFs) are one of the promising solutions to address these personal and social issues. The unreplicability of PUFs is a crucial factor for high security levels. Here, this study proposes a visually hidden and self-assembled porous polymer (VSPP) as a tag for optical PUF systems. The VSPP has virtues in terms of wavelength dependency, lens-free compact PUF system, and simple/affordable fabrication processes (i.e., spin coating and annealing). The VSPP consists of an external saturated surface, which covers the inner structures, and an internally abundant porous layer, which triggers stochastic multiple Mie scattering with wavelength dependency. We theoretically and experimentally validate the unobservability of the VSPP and the uniqueness of optical responses by image sensors. Finally, we establish a wavelength-dependent PUF system by using the following three components: solid-state light sources, a VSPP tag, and an image sensor. The captured raw images by the sensor serve as "seed" for unique bit sequences. The robustness of our system is successfully confirmed in terms of bit uniformity (∼0.5), intra/interdevice Hamming distances (∼0.04/∼0.5), and randomness (using NIST test).