Optical PUF chip, reading system and coding capacity evaluation method

Abstract

The present invention provides an optical PUF chip, reader system, and encoding capacity evaluation method based on a plasmonic random structure. The optical PUF chip comprises a substrate on which a dense array of nanostructures is deposited using a porous nanofilm as a deposition-assisted template. Due to the randomness and localized defects of the template, as well as the varying gradients of angular deposition, the nanostructures exhibit random variations in size, dimension, and distribution, exhibiting distinct plasmon resonance effects. The nanostructures include densely packed granular structures with statistically distinct variations determined by the template pore size, and clustered island structures determined by random defects within the template. This invention significantly accelerates the mass production of plasmonic chips and can be integrated with devices such as personal smartphones without the need for additional equipment. It provides a simple and direct method for improving encoding capacity, security, and stability, meeting the demands for tag encoding capacity and information verification in diverse fields.

Description

Technical Field

[0001] The present invention relates to the fields of hardware security, product anti-counterfeiting and identity authentication, as well as optical chips and micro-nano manufacturing technologies, and in particular to an optical PUF chip based on a plasmon random structure, a reading system and a coding capacity evaluation method. Background Art

[0002] In recent years, with the implementation of domestic and international regulations such as the Data Security Law of the People's Republic of China and the EU's General Data Protection Regulation, the development of new information security equipment, architectures, and disposal strategies has become a hot topic in current competition among major powers and a strategic imperative for my country to safeguard its new development landscape with a new security framework. A "Physically Unclonable Function" (PUF), as a digital fingerprint, is inherently immune to reverse engineering and offers the highest level of security. In practical applications, PUFs often appear as physical objects with inherent and unique characteristics in the form of chips. Information within these objects is generated through a specific random and non-deterministic process, making them unclonable and resistant to physical attacks. Currently, commercially available PUF chips all utilize silicon-based integrated circuit PUF architectures, including memory-based PUFs such as SRAM and DRAM, as well as analog circuit-based PUFs. Their common characteristic is that they are based on mature integrated circuit process solutions and utilize the physical random fluctuations of hardware systems to achieve identity identification. Electrical PUF technology based on integrated circuits has been steadily improving over the past 20 years. However, counter-attack techniques have also evolved, leading to an increasingly fierce competition with PUF defenses. During this process, electrical PUFs have revealed significant shortcomings: first, there are inherent biases in the integrated circuit process, resulting in insufficient randomness in the PUF output; second, once the electrical PUF is fabricated, it is difficult to reconstruct. Even after an exhaustive attack, the hardware protected by the PUF may still face hardware security threats; finally, changes in the chip's environmental conditions (such as temperature, ambient noise, and electromagnetic interference) can easily cause changes in the RAM random values, resulting in insufficient stability.

[0003] Optical PUFs offer significant advantages over electrical PUFs, including increased security and practicality due to their susceptibility to modeling attacks, limited entropy sources, and resistance to aging and degradation. The first optical PUF was proposed by a team at MIT in 2002. It used laser speckle, generated by scattering in an inhomogeneous optical medium, as a source of optical information. Subsequently, the materials and structures used in the development of chip-scale optical PUFs have become increasingly diverse. Beyond graphic PUFs, which solely exploit the structural randomness and disorder that influence elastic scattering, there are also optical multimodal PUFs that exploit various light-matter interactions, such as luminescence, Raman scattering, and nonlinear processes. The range of materials is no longer limited to conventional semiconductors, but has expanded to include micron- and nanoscale photoluminescent materials, such as fluorescent proteins, quantum dots, perovskites, photoluminescent defect centers in diamond, and organic semiconductors.

[0004] The following are the major issues currently hindering the transition of many optical PUF technologies from the laboratory to practical application: 1) Optical PUFs based on complex luminescence and nonlinear processes typically require high-precision equipment such as pump sources, narrow-linewidth lasers, and spectrometers to read the PUF tag, resulting in high application costs and hindering miniaturized integration and packaging. For example, the prior art patent CN 116002689B proposes a silicon-based optical PUF scheme that utilizes seven different optical response signals from nanomaterials (blank background, surface morphology, luminescence intensity of the silicon nanomaterial, luminescence intensity of erbium ions, central luminescence wavelength of the silicon nanomaterial, luminescence lifetime of the silicon nanomaterial, and luminescence intensity ratio of the silicon nanomaterial and erbium ions). The need for precise measurement of luminescence wavelength and lifetime increases the complexity of the reading process. At the same time, this solution requires strict control of rare earth element doping parameters, such as etching components, etching component ratio, addition volume, etching time, temperature, cleaning, etc.; 2) The optical action process involved in PUF operation is not stable over long periods of time or in extreme environments, and phenomena such as luminescence may decrease, which greatly limits the working life of PUF.

[0005] Furthermore, for high-capacity random key generation applications, existing optical PUFs that achieve ultra-large challenge-response pair (CRP) capacities often rely on complex encoding schemes, involving information manipulation processes in the spatial, temporal, and frequency domains of the light field. Patent CN 107257285B, for example, proposes an authentication system based on single-photon excitation and an optical PUF to improve static encoding capabilities. However, this system's static encoding capability relies heavily on the manipulation of laser speckle by digital micromirrors (DMDs), rather than on the inherent device structure of the optical PUF. This overreliance on DMDs introduces numerous limitations and disadvantages, including increased complexity, the high cost of DMD integration, and calibration errors. DMD-related issues can lead to decreased optical PUF performance and limited encoding capacity scalability. If this external component is omitted from the system, the static encoding capability of the optical PUF often suffers from the same CRP capacity limitations as electrical PUFs.

[0006] To this end, the present invention proposes an optical PUF chip, encoding system, and encoding capacity evaluation method based on a plasmon random structure, which mainly achieves significant improvements in three aspects:

[0007] 1) The realization of low-cost, large-scale, and highly integrated optical PUF chip processing can significantly accelerate chip production. 2) A compact and portable random information query system proposes an efficient and convenient tag encoding and reading method that can be integrated with personal smartphones and portable devices without the need for additional equipment. 3) A low-cost, multi-dimensional information expansion solution for multiple purposes and scenarios improves encoding capacity and security in a simple and direct manner. This solution aims to meet the needs of different fields for tag encoding capacity and information verification. Summary of the Invention

[0008] The main purpose of the present invention is to provide an optical PUF chip, reading system, and coding capacity evaluation method based on a plasmon random structure. The aim is to realize an array-integrated optical PUF architecture on a transparent substrate. Based on the differences in the plasmon resonance process caused by the randomness of densely stacked nanostructures, unclonable information is constructed based on transmission imaging, and capacity expansion is achieved using efficient and simple coding strategies in both wavelength and polarization dimensions.

[0009] To achieve the above objectives, the present invention proposes an optical PUF chip based on a plasmon random structure, comprising: a substrate on which are deposited a plurality of densely arranged nanostructures using a porous nanofilm as a deposition-assisted template. Due to the randomness and local defects of the template and the different gradients of angular deposition, the nanostructures have random differences in size, dimension, and distribution, exhibiting different plasmon resonance effects. The nanostructures include: a dense particle structure with statistical differences determined by the template pore size, and a clustered island structure determined by random defects in the template.

[0010] A further technical solution of the present invention is that the substrate is a transparent material or a flexible film;

[0011] The transparent material includes quartz or glass;

[0012] The flexible membrane is based on PDMS, PMMA or hydrogel.

[0013] To achieve the above objectives, the present invention further proposes an optical PUF chip reading system based on a plasmon random structure. The optical PUF chip reading system based on a plasmon random structure is applied to the optical PUF chip based on a plasmon random structure as described above. The optical PUF chip reading system based on a plasmon random structure includes a broadband light source, a wavelength selection device, a polarizer, a half-wave plate, an objective lens, and an image sensor, which are arranged in sequence. The optical PUF chip is located between the half-wave plate and the objective lens.

[0014] To achieve the above objectives, the present invention also proposes an optical PUF chip reading system based on a plasmon random structure. The optical PUF chip reading system based on a plasmon random structure is applied to the optical PUF chip based on a plasmon random structure as described above. The optical PUF chip reading system based on a plasmon random structure includes a light source and an image sensor. The optical PUF chip is bonded to the image sensor, and light from the light source directly illuminates the optical PUF chip.

[0015] To achieve the above objectives, the present invention further proposes a method for evaluating the coding capacity of an optical PUF chip based on a plasmon random structure. The method is applied to the optical PUF chip based on a plasmon random structure as described above, and the method comprises the following steps:

[0016] Step S10, obtaining a PUF transmission image received by the image sensor;

[0017] Step S20, performing a hash algorithm on the PUF transmission image to generate a frequency coefficient matrix;

[0018] Step S30, extracting low-frequency information from the frequency coefficient matrix based on information features to form a two-dimensional pixel matrix with a resolution of M×M, where M is the number of pixels;

[0019] Step S40, binarizing the two-dimensional pixel matrix and comparing it with a preset frequency coefficient threshold, setting coefficients greater than 0 to 1 and coefficients less than 0 to 0, where the preset frequency coefficient threshold is 0;

[0020] Step S50, generate a single capacity of 2 M×M PUF key, M is an integer greater than 20 and less than P / 2, and P is the minimum image resolution.

[0021] A further technical solution of the present invention is that, before step S10, the following steps are included:

[0022] Step S00, setting the excitation light source wavelength channel 1-i and polarization channel 1-j, fixing a wavelength m and polarization n of the excitation light source (1≤m≤i, 1≤n≤j);

[0023] After step S50, the following steps are further included:

[0024] Step S60: Multiplexing is performed using multiple channel wavelengths and polarizations to obtain a maximum coding capacity of 2 M×M×i×j PUF key.

[0025] A further technical solution of the present invention is that, after step S60, the following steps are further included:

[0026] Step S70: Evaluate the uniformity of the PUF key.

[0027] A further technical solution of the present invention is that step S70 includes: selecting N PUF keys with the same parameters integrated on the same chip, and calculating the bit uniformity metric of the PUF keys using the following formula, where N is generally in the range of 5-100:

[0028] Among them, K i and n represents the i-th binary bit of the key and the key size.

[0029] A further technical solution of the present invention is that the step S70 includes:

[0030] Step S80 : Verify the randomness of the N PUF keys with the same parameters integrated on the same chip.

[0031] The beneficial effects of the optical PUF chip, reading system, and coding capacity evaluation method based on the plasmon random structure of the present invention are:

[0032] The present invention implements an array-integrated optical PUF architecture on a transparent substrate. Based on the randomness of the densely stacked nanostructures and the differences in the photoexcited plasmon resonance process, it constructs unclonable information based on transmission imaging and utilizes efficient and simple wavelength and polarization coding strategies to achieve capacity expansion. This can significantly reduce costs and accelerate the mass production of plasmon chips. It can be integrated with devices such as personal smartphones without the need for additional equipment, and can improve coding capacity and security in a simple and direct manner, meeting the needs of different fields for tag coding capacity and information verification. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the three-dimensional structure of the optical PUF chip based on the plasmon random structure of the present invention;

[0034] Figure 2 1 is a top view of the optical PUF chip based on the plasmon random structure of the present invention;

[0035] Figure 3 This is a top view of the optical PUF chip based on the plasmon random structure of the present invention in a microscopic state;

[0036] Figure 4 This is a side view of the optical PUF chip based on the plasmon random structure of the present invention in a microscopic state;

[0037] Figure 5 Schematic diagram of the preparation process of the optical PUF chip based on the plasmon random structure of the present invention;

[0038] Figure 6 Schematic diagram of an optical PUF chip reading system based on a plasmon random structure according to the present invention;

[0039] Figure 7 This is a schematic diagram of another solution of the optical PUF chip reading system based on the plasmon random structure of the present invention;

[0040] Figure 8 2 is a flow chart of a first embodiment of a method for evaluating coding capacity of an optical PUF chip based on a plasmon random structure according to the present invention;

[0041] Figure 9 2 is a flow chart of a second embodiment of a method for evaluating coding capacity of an optical PUF chip based on a plasmon random structure according to the present invention;

[0042] Figure 10 This is a schematic diagram of the structure of a PUF chip prepared using gold as a target material;

[0043] Figure 11This is a schematic diagram of imaging a sample using a scanning electron microscope at a 50 μm scale;

[0044] Figure 12 This is a schematic diagram of imaging a sample using a scanning electron microscope at a 5 μm scale;

[0045] Figure 13 is a schematic diagram of the extinction spectrum when the deposition angle 107 is 8° and 16°;

[0046] Figure 14 This is a schematic diagram of the original random two-dimensional scattering image captured by the CMOS camera for a PUF tag with a deposition angle of 8° under the conditions of a fixed wavelength of 580nm and an excitation light source with a polarization of 0°;

[0047] Figure 15 This is a schematic diagram of the frequency coefficient matrix distribution of the transmission image after the Phash algorithm;

[0048] Figure 16 This is a schematic diagram of the randomness test of 15 PUF keys with the same parameters on the same chip;

[0049] Figure 17 This figure shows the distribution of intra-chip and inter-chip Hamming distances among 15 PUF chips processed with the same parameters at a deposition angle of 8°. The inset graph shows the detailed information of the intra-chip Hamming distance.

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0051] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] This paper proposes an optical PUF chip based on a plasmonic random structure. This array-integrated optical PUF architecture is implemented on a transparent substrate. This architecture leverages the inherent randomness of densely packed nanostructures to generate variability in plasmon resonance, constructing unclonable information through transmission imaging, and ultimately, achieving capacity expansion through efficient and simple wavelength and polarization encoding strategies. This invention has applications in high-end product security and anti-counterfeiting labels, random key generation and storage, device identity verification, random number generation, and optical encryption communication and verification.

[0053] like Figures 1 to 5As shown, the optical PUF chip based on a plasmon random structure of the present invention includes: a substrate 101, on which a densely arranged nanostructure is obtained by evaporation using a porous nanofilm as a deposition auxiliary template. Due to the randomness and local defects of the template and the different gradients of angular deposition, the nanostructure has random differences in size, dimension and distribution, showing different plasmon resonance effects. The nanostructure includes: a dense particle structure 104 with statistical differences determined by the template pore size and a clustered island structure 105 determined by random defects in the template.

[0054] The substrate 101 is a transparent material or a flexible film. The transparent material includes quartz or glass. The flexible film is based on PDMS, PMMA or hydrogel.

[0055] The present invention uses a porous nanofilm as a deposition-assisted template, enabling the large-scale fabrication of densely packed nanostructures on a substrate 101. By patterning the quartz substrate, the location information of each PUF tag is defined, forming a PUF array. Due to the randomness and localized defects of the template, as well as the varying gradients of angular deposition, the size, shape, and distribution of the deposited nanoparticles vary significantly between each PUF tag. The on-chip deposited structures are primarily divided into two types: small particle structures 104 determined by the template pore size, and cluster structures 105 determined by random defects within the template. The localized surface plasmon resonance (LSPR) of gold nanostructures in the visible wavelength range and the resulting strong absorption, combined with their high-density arrangement and high signal intensity, allows the present invention to avoid the dark-field scattering imaging required for the traditional characterization of small quantities of nanoparticles. Spatial non-uniformity information can be easily extracted using simple, even portable, equipment. The image can be frequency-domain selected and binarized using the pHash algorithm to generate the corresponding PUF key. At the same time, by utilizing the ultra-high sensitivity of PUF keys to wavelength and polarization, randomness is ensured while facilitating the construction of low-cost and high-reliability coding schemes, thereby achieving the construction of a more secure key management system and the formation of a larger-capacity database.

[0056] Figure 1 and Figure 2 The overall architecture of the optical PUF chip based on a plasmon random structure of the present invention is shown. PUF chips are often centimeter-scale or even larger, facilitating large-scale, batch-scale production of hundreds or thousands of PUF tags. In subsequent applications, the chip can be further divided by cutting. Chip substrate 101 is preferably a transparent material, including common quartz, glass, and some organic polymer materials, including polystyrene. Substrate 101 can also be made of flexible films such as PDMS, PMMA, and hydrogel to adapt to the integration process for different products and scenarios, expanding its application range.

[0057] In addition to the heterogeneity within the unit, the on-chip nanostructure can also be designed with gradient differences between each unit, such as differences in extinction coefficients at specific working wavelengths. Nanostructure unit 102 has a smaller characteristic structure size than nanostructure unit 103, thus exhibiting plasmon resonance effects with different spatial and spectral responses. Figure 3 and Figure 4 As shown, from a microscopic perspective, the nanostructure has dense particle structures 104 with statistical differences on a scale of tens of nanometers, and there are also differences in clustered island structures 105 that exist in the form of random defects. The two together determine the final imaging information.

[0058] like Figure 5 As shown, the fabrication process for an optical PUF chip based on a random plasmon structure employs template-assisted evaporation on substrate 101. The target material 106 is not limited to gold; other precious metals that can produce plasmon resonance, such as silver, platinum, and aluminum, are also suitable. Furthermore, oxides that exhibit Mie resonance, such as silicon dioxide, titanium dioxide, and aluminum oxide, can also achieve the functionality of an optical PUF chip using similar principles. Evaporation methods include conventional physical deposition (thermal evaporation, magnetron sputtering, etc.) and chemical deposition. Evaporation can be performed in a conventional vertical direction or by shadow deposition. The angle 107 between the deposition direction and the substrate perpendicular can be controlled, preferably between 0° and 15°. The template is a porous nanofilm structure, preferably a treated anodized aluminum oxide film. The pore size is preferably tens to hundreds of nanometers, which determines the morphology of the small particle structure 104. The location of some template defects determines the morphology of the clustered island structure 105.

[0059] The present invention implements an array-integrated optical PUF architecture on a transparent substrate based on an optical PUF chip with a plasmon random structure. Based on the randomness of the densely stacked nanostructures and the variability of the photoexcited plasmon resonance process, the invention constructs unclonable information using transmission imaging, and utilizes efficient and simple wavelength and polarization coding strategies to achieve capacity expansion, significantly reducing costs and accelerating chip production. The invention can be integrated with devices such as personal smartphones without the need for additional equipment, and can improve coding capacity and security in a simple and direct manner, meeting the needs of different fields for tag coding capacity and information verification.

[0060] To achieve the above objectives, the present invention also proposes an optical PUF chip reading system based on a plasmon random structure, and the optical PUF chip reading system based on a plasmon random structure is applied to the above optical PUF chip based on a plasmon random structure.

[0061] like Figure 6As shown, the optical PUF chip reading system based on the plasmon random structure includes a broadband light source 201, a wavelength selection device 202, a polarizer 203, a half-wave plate 204, an objective lens 206 and an image sensor 207 arranged in sequence, and the optical PUF chip 205 is located between the half-wave plate 204 and the objective lens 206.

[0062] A broadband light source 201 passes through wavelength-selective devices 202, such as a monochromator and tunable filter, to generate narrowband excitation light at a specific central wavelength. Polarizers 203 and half-wave plates 204 are used to control the polarization state of the excitation light, which then enters an optical PUF chip 205. Imaging of a specific individual PUF tag is achieved through focusing using an objective lens 206, and the final image is captured by an image sensor 207, such as a CCD or CMOS sensor.

[0063] As another embodiment, Figure 7 As shown, the optical PUF chip reading system based on plasmon random structure is a handheld portable solution. The optical PUF chip reading system based on plasmon random structure includes a light source and an image sensor. The optical PUF chip is bonded to the image sensor, and the light from the light source directly illuminates the optical PUF chip.

[0064] This solution uses a miniaturized light source 208 such as LED, SLD, LD, etc. to directly illuminate the optical PUF chip 205, and the optical PUF chip 205 is attached to the image sensor 207 itself, so that imaging is completed without the need for an objective lens.

[0065] To achieve the above objectives, the present invention also proposes a coding capacity evaluation method for an optical PUF chip based on a plasmon random structure, which is applied to the optical PUF chip based on a plasmon random structure as described above. Figure 8 As shown, the first embodiment of the coding capacity evaluation method of the optical PUF chip based on the plasmon random structure of the present invention includes the following steps:

[0066] Step S10, obtaining a PUF transmission image received by the image sensor;

[0067] Step S20, performing a hash algorithm on the PUF transmission image to generate a frequency coefficient matrix;

[0068] Step S30, extracting low-frequency information from the frequency coefficient matrix based on the information features to obtain a two-dimensional pixel matrix with a resolution of M×M, where M is the number of pixels;

[0069] Step S40, binarizing the two-dimensional pixel matrix and comparing it with a preset frequency coefficient threshold, setting coefficients greater than 0 to 1 and coefficients less than 0 to 0, and the preset frequency coefficient threshold is 0;

[0070] Step S50, generate a single capacity of 2 M×M PUF key, M is an integer greater than 20 and less than P / 2, and P is the minimum image resolution.

[0071] Please refer to Figure 9 In this embodiment, the steps before step S10 include:

[0072] Step S00, setting the excitation light source wavelength channel 1-i and polarization channel 1-j, fixing a wavelength m and polarization n of the excitation light source (1≤m≤i, 1≤n≤j);

[0073] After step S50, the following steps are also included:

[0074] Step S60: Multiplexing is performed using multiple channel wavelengths and polarizations to obtain a maximum coding capacity of 2 M×M×i×j PUF key.

[0075] In this embodiment, after step S60, the following steps are further included:

[0076] Step S70: Evaluate the uniformity of the PUF key.

[0077] In this embodiment, step S70 includes: selecting N PUF keys with the same parameters integrated on the same chip, and calculating the bit uniformity metric of the PUF keys using the following formula, where N ranges from 5 to 100:

[0078]

[0079] Among them, K i and n represents the i-th binary bit of the key and the key size.

[0080] In this embodiment, the steps after step S70 include:

[0081] Step S80 : Verify the randomness of N PUF keys with the same parameters integrated on the same chip.

[0082] The following further describes the coding capacity evaluation method of the optical PUF chip based on the plasmon random structure of the present invention.

[0083] The coding capacity evaluation method of the optical PUF chip based on the plasmon random structure of the present invention uses the perceptual hash algorithm (Phash) based on the two-dimensional discrete cosine transform (DCT) of MATLAB to extract the PUF key. Figure 8The flowchart of the first embodiment of the coding capacity evaluation method of the optical PUF chip based on the plasmon random structure of the present invention is shown. The PUF transmission image received by the image sensor is processed by the perceptual hash algorithm (phash algorithm) to generate a frequency coefficient matrix. The matrix contains both low-frequency coefficients that store information and high-frequency coefficients that are related to minor details but do not affect the main changes in the image itself. In subsequent processing, these high-frequency coefficients will be ignored, while the information in the low-frequency range, such as local spots, wrinkle-like patterns, and non-uniform backgrounds, are retained in the form of a matrix. Based on the information features, low-frequency information can be extracted from the frequency coefficient matrix. The size is a two-dimensional pixel matrix with a resolution of M×M, where M is the number of pixels. By setting the frequency coefficient threshold to 0, the two-dimensional pixel matrix is ​​binarized, and the coefficients greater than 0 are set to 1, and those less than 0 are set to 0. The capacity corresponding to the generated PUF key is 2 M×M The value of M can be any integer, and its value is 20<M<P / 2, where P is the minimum image resolution.

[0084] also, Figure 9 This is a flow chart of the second embodiment of the coding capacity evaluation method for an optical PUF chip based on a plasmon random structure of the present invention. This flow chart demonstrates a multi-channel coding strategy.

[0085] Since the optical response of the plasmon chip to different wavelengths and polarizations of the excitation light source is different, for the same optical PUF chip, a new PUF key will be generated when the wavelength or polarization of the excitation light source changes, which provides new possibilities for expanding the coding capacity. Set the excitation light source wavelength channel 1-i and polarization channel 1-j, fix a certain wavelength m and polarization n of the excitation light source (1≤m≤i, 1≤n≤j), obtain the transmission image of the optical PUF chip under this condition through the optical system, and then use Figure 9 The Phash algorithm processing process obtains a single capacity of 2 M×M Key. Using multiple channels of wavelength and polarization for multiplexing, the maximum coding capacity that can be obtained by a single PUF is 2 M×M×i×j It should be noted that the coding capacity here only considers the binary frequency intensity distribution. To expand the coding capacity and prevent duplication, the present invention can encode the frequency intensity of each point (for example, octal, decimal, hexadecimal, etc.), thereby expanding the PUF key capacity.

[0086] The following is an example of a PUF array based on plasmonic gold nanoparticles.

[0087] Figure 10The demonstration showcased a PUF chip fabricated using a gold target. Laser direct writing was used to define pixelated PUF regions measuring ~10×10 mm with a pitch of ~200 μm, totaling 324 PUF regions. The porous nanofilm structure was an anodic aluminum oxide film with a thickness of ~200 nm and an average pore size of ~80 nm. Figures 11 to 12 Demonstrates imaging of samples using scanning electron microscopy at 50μm and 5μm scales. Figure 11 The white spots in the middle are caused by the defects in the porous nanofilm structure during the preparation process, which lead to the formation of clustered gold nanoparticles. Figure 12 The gold nanoparticle cluster area and the array area can be more clearly distinguished. Figure 13 The extinction spectra are shown when the deposition angle 107 is 8° and 16°. Changing the deposition angle 107 will cause the particle size of the gold nanoparticles to change. The total particle size statistics corresponding to the two typical deposition angles of 8° and 16° are 60±20nm and 25±20nm, respectively. Among them, a smaller deposition angle 107 will produce nanoparticles with a larger overall size. At this time, the corresponding plasmon resonance wavelength is at a relatively long-wave position, resulting in a relatively larger extinction ratio. On the contrary, a larger deposition angle can result in an overall smaller nanoparticle size, and the corresponding plasmon resonance wavelength is at a relatively short-wave position.

[0088] Figure 14 This is the original random two-dimensional scattering image captured by the CMOS camera under the conditions of a fixed wavelength of 580nm and an excitation light source with a polarization of 0°, for a PUF tag with a deposition angle of 8°. The intensity distribution of each pixel value is 0 to 255. Figure 15 The frequency coefficient matrix distribution of the transmission image after the Phash algorithm is applied is shown. The matrix threshold is set to 0, the M value is selected to be 30, and the size of the PUF key extracted from the transmission image is 30×30. To better evaluate the uniformity of the PUF key, 15 PUFs with identical parameters integrated on the same chip were selected. The bit uniformity metric is calculated using the following formula:

[0089]

[0090] where K i and n represents the i-th binary bit and key size of the key. The average value of the 15 PUF keys is 0.5122. This proves that the PUF keys generated by the plasmonic gold nanoparticle chip using the Phash algorithm have ideal uniformity (the ideal value is 0.5).

[0091] Figure 16The randomness test of 15 PUF keys with the same parameters on the same chip is demonstrated. The NIST (National Institute of Standards and Technology) SP 800-22 standard is used here to evaluate the randomness of the generated PUF keys. The 15 PUF keys are processed to form an encryption key sequence with a length of 13500 bits (15×30×30 bits). The first 12800 bits are selected and divided into 100 groups of 128 bits each. According to the required number of bits for calculation, the Figure 16 The P values ​​for the nine tests were calculated. Each set of data constituted a test round, and a pass was awarded if the P value was greater than 0.01. The success rate for all tests was above 92%, demonstrating the randomness and unpredictability of the PUF key.

[0092] In actual use, PUF tags need to be repeatedly verified, which requires good reproducibility between readings of the same tag and obvious differences between different tags. The present invention uses normalized Hamming distance to quantify the similarity between PUF keys. For PUFs prepared with the same process parameters, the calculated Hamming distance histogram statistics are calculated by Gaussian fitting. The mean μ and standard deviation σ of the fitted Gaussian curve are obtained. Since all pixels constituting the PUF key are not completely independent of each other, the present invention can also use independent bits (i.e. degrees of freedom, defined as To determine the encoding capability of the PUF key, the encoding capability of the PUF key is

[0093] Figure 17 The intra-chip and inter-chip Hamming distance distributions of 15 PUF chips fabricated with the same parameters at an 8° deposition angle are shown. The calculated coding capacity is 2^875. The intra-chip and inter-chip Hamming distance distributions are highly discriminative, allowing for differentiation in real-world authentication by setting an appropriate threshold (e.g., 0.03).

[0094] The present invention's method for evaluating the coding capacity of optical PUF chips based on plasmon random structures implements an array-integrated optical PUF architecture on a transparent substrate. This method, based on the randomness of densely stacked nanostructures and the variability of photoexcited plasmon resonance processes, constructs unclonable information using transmission imaging, and achieves capacity expansion using the efficient and simple coding degrees of freedom of wavelength and polarization. This significantly accelerates the mass production of plasmon chips and can be integrated with devices such as personal smartphones without the need for additional equipment. It improves coding capacity and security in a simple and direct manner, meeting the needs of different fields for tag coding capacity and information verification.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for evaluating the coding capacity of an optical PUF chip based on a plasmon random structure, characterized in that: The method is applied to an optical PUF chip based on a plasmon random structure. The optical PUF chip based on a plasmon random structure includes: a substrate, on which a plurality of densely arranged nanostructures are obtained by evaporation using a porous nanofilm as a deposition auxiliary template. Due to the randomness and local defects of the template and the different gradients of angular deposition, the nanostructures have random differences in size, dimension, and distribution, exhibiting different plasmon resonance effects. The nanostructures include: a dense particle structure with statistical differences determined by the template aperture and a clustered island structure determined by random defects in the template. The method includes the following steps: Step S10, obtaining a PUF transmission image received by the image sensor; Step S20, performing pHash algorithm processing on the PUF transmission image to generate a frequency coefficient matrix; Step S30, extracting low-frequency information from the frequency coefficient matrix based on information features to form a two-dimensional pixel matrix with a resolution of M×M, where M is the number of pixels; Step S40, binarizing the two-dimensional pixel matrix and comparing it with a preset frequency coefficient threshold, setting coefficients greater than 0 to 1 and coefficients less than 0 to 0, where the preset frequency coefficient threshold is 0; Step S50, generate a single capacity of 2 M×M PUF key, M is an integer ranging from 20 to P / 2, and P is the minimum image resolution; The step S10 includes: Step S00, setting the excitation light source wavelength channel 1-i and polarization channel 1-j, fixing a wavelength m and polarization n of the excitation light source, 1≤m≤i, 1≤n≤j; After step S50, the following steps are further included: Step S60: Multiplexing is performed using multiple channel wavelengths and polarizations to obtain a maximum coding capacity of 2 M×M×i×j PUF key; After step S60, the following steps are further included: Step S70: Evaluate the uniformity of the PUF key.

2. The coding capacity evaluation method of an optical PUF chip based on a plasmon random structure according to claim 1 is characterized in that: The step S70 includes: selecting N PUF keys with the same parameters integrated on the same chip, and calculating the bit uniformity of the PUF keys using the following formula:

3. The coding capacity evaluation method of the optical PUF chip based on the plasmon random structure according to claim 2 is characterized in that: The step S70 includes: Step S80 : Verify the randomness of the N PUF keys with the same parameters integrated on the same chip.

4. The coding capacity evaluation method of an optical PUF chip based on a plasmon random structure according to claim 1, characterized in that: The substrate is a transparent material or a flexible film; The transparent material includes quartz or glass; The flexible membrane is based on PDMS, PMMA or hydrogel.

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