PUF device based on integrated optical microcavity and encryption method thereof

Abstract

The invention discloses a PUF (Physical Unclonable Function) device based on an integrated optical microcavity and an encryption method thereof. The PUF device comprises a chip substrate; the chip lower cladding covers the surface of the chip substrate, and the input coupling grating, the trunk input waveguide and the optical microcavity at least comprise one form are arranged on the surface of the chip lower cladding; the nano scatterer is arranged in the optical microcavity; and a light excitation and acquisition assembly. According to the encryption method, two feature extraction schemes are provided based on scattering imaging, so that the secret key is convenient to expand. One method is a spectrum method obtained by extracting information based on a scattered spectrum excited by a device in a certain wave band range; one method is an image method for extracting information based on a specific wave band microcavity vertical surface scattering image. According to the image method, information extracted from a two-dimensional area of a light field serves as an additional multiplexing means to enrich a random source of a device, and the safety of the system can be improved. The invention provides the PUF device which is reliable, low in cost and capable of being manufactured in a large scale and the encryption method of the PUF device.

Description

Technical Field

[0001] The present invention belongs to the field of hardware security devices and encryption technology, and in particular relates to a PUF device based on an integrated optical microcavity and an encryption method thereof using scattering imaging. Background Art

[0002] In the era of the Internet of Things (IoT), a large number of sensors have been installed in various hardware facilities in production and life; while making objects intelligent, they also provide opportunities for potential attackers. At the same time, counterfeit chips or hardware devices provide attackers with an attack platform for the Internet of Things, thereby causing losses. The previous encryption design concept based on software has been difficult to provide comprehensive protection. Physical Unclonable Function (PUF), as a hardware security technology analogous to digital fingerprints, is essentially not affected by reverse engineering and has the highest level of security. Its development has received great attention in recent years.

[0003] Commercial PUF solutions mainly include memory PUFs such as SRAM and DRAM, and analog circuit PUFs. They are all based on mature integrated circuit process solutions and rely on the random differences brought by integrated circuit devices during the production process. These solutions can be collectively referred to as electrical PUF solutions. In the past development of electrical PUF, its corresponding attack technology has also been developed. In a study in 2012, researchers used machine learning to successfully implement an attack on one of the classic electrical PUF design solutions: Arbiter PUF, and the prediction accuracy of PUF can reach more than 90%, which brings huge challenges to electrical PUF. In general, electrical PUF is gradually exposing the following shortcomings: First, it relies on random errors in production and usually has a certain inherent bias, resulting in imperfect key randomness; second, some structural independence of electrical PUF is poor, and it is easy to be attacked by complex modeling under machine learning and other means, which leads to high accuracy. Break; finally, the random values ​​of RAM of some electrical PUFs are easily affected by environmental disturbances, resulting in poor stability.

[0004] Unlike electrical PUF, optical PUF technology was proposed as the initial prototype concept of PUF by Ravikanth Pappu et al. of MIT in 2002. It relies on the interaction between visible light and random microstructures, and uses physical methods to reduce the microstructure of the medium to a string of binary digits of fixed length, thereby generating a unique identifier for allocating and verifying. Optical PUF is also the only form that has been proven to be mathematically unclonable so far, and it guarantees absolute security at both the basic mechanism and engineering technology levels. In the past decade, innovations in the hardware form and encryption scheme of optical PUF have emerged in an endless stream. Some achievements use new materials as PUF elements, such as the authorized patent CN 113758956 A, which introduces a lead halide perovskite material. Some achievements focus on the dimension in the spectrum as the original signal source of PUF, such as Yuqing Gu et al.'s 2020 work "Gap-enhanced Raman tags for physically unclonable anticounterfeiting labels", which introduces a confocal method to read random source information. However, this random source requires a highly complex Raman spectroscopy system, and its complexity greatly increases the difficulty of practical application, so it is still far from commercialization. As described in the authorized patent CN 110166248A, a chaotic signal with a higher degree of randomness is introduced at one end of the excitation source. Its random source emphasizes the third-order nonlinear effect of its excitation end, so the source of randomness is more dependent on the random signal generator, which brings great limitations to the convenience of the system.

[0005] In addition to the complexity of the system, the PUF device materials may also be complex in production and manufacturing. For example, the authorized patent CN113758956A introduces laser into the microcavity as an excitation source, uses silicon-based materials as a substrate and randomly generates some semiconductor microspheres on top to change the gain and resonance characteristics of the entire device. These non-standard processes greatly increase the preparation cost of the device.

[0006] In recent years, based on the silicon-based platform and the mature CMOS process technology of the microelectronics industry, the concept of developing optical integrated PUF under the fusion of light and electricity has attracted attention. Researchers at Johns Hopkins University in the United States proposed an optical PUF based on ultrafast nonlinear optical interaction of silicon materials in microcavities, and the relevant patent US10860746 was authorized in 2020. This optical PUF is based on the interaction between the excitation pulse and the on-chip microcavity, which produces a highly complex and unpredictable ultrafast response, forming a unique "fingerprint" of the microcavity. In addition, within two days after the experimental device was disassembled, it can still be reconstructed with a fidelity of about 0.1 Hamming distance. However, the excitation and reading of this type of system requires complex external modulated excitation light sources and high-speed reading equipment, which greatly increases the cost. Therefore, how to promote practical application based on this silicon-based optoelectronic chip PUF and compress the cost of the solution is the key to truly commercialize optical PUF.

[0007] In summary, the current optical PUF solution has not yet been truly commercialized. The major problems that hinder many optical PUF technologies from moving from the laboratory to practical applications are as follows: 1) A large number of non-silicon-based optical PUFs rely on new materials and new non-standard processes. The design lacks process-based tools such as EDA for electrical PUFs, and it is difficult to produce and process them in large quantities and at low cost. 2) The working system required by most PUFs involves light emission and nonlinear processes, so high-precision equipment such as pump sources, narrow linewidth lasers, and spectrometers are usually involved to read PUF tags. The application cost is high and is not conducive to miniaturization integration and product packaging; 3) For high-capacity random key generation applications, it is still difficult to achieve ultra-large "Challenge-Response Pairs" (C RPs) capacity. They are often based on complex encoding schemes (such as information control in the spatial, temporal, and frequency domains of light fields). Once these schemes cancel the reading method that relies on complex external equipment, the static encoding capability of their optical PUFs often has the same problems as electrical PUFs, such as limited CRPs capacity. Summary of the invention

[0008] In view of the above problems, the present invention provides a PUF device based on an integrated optical microcavity and an encryption method thereof, aiming to provide a PUF device and an encryption method thereof that are both reliable, low-cost and can be mass-manufactured.

[0009] According to a first aspect of an embodiment of the present disclosure, a PUF device based on an integrated optical microcavity is provided, comprising:

[0010] Chip substrate;

[0011] A chip lower cladding layer covering the surface of the chip substrate;

[0012] An input coupling grating, a trunk input waveguide and an optical microcavity of at least one form arranged on the surface of the lower cladding layer of the chip;

[0013] A nano-scatterer disposed in the optical microcavity; and

[0014] An optical excitation and collection component for providing external excitation light and collecting out-of-plane scattered light;

[0015] The input coupling grating is used to couple external excitation light to the trunk input waveguide, and the trunk input waveguide couples the received excitation light to the optical microcavity.

[0016] A further technical solution of the present invention is: the light collection component includes an external excitation light source and an external imaging element, and the external imaging element completes far-field scattering signal collection under single exposure imaging.

[0017] Further preferably, the light collection component includes an external excitation light source, an external imaging element and an objective lens, the objective lens has a magnification range of 5 times to 100 times, and the external imaging element completes far-field scattering signal collection under single exposure imaging.

[0018] A further technical solution of the present invention is: an output waveguide and an output coupling grating are also provided on the surface of the lower cladding of the chip, and the output waveguide couples out part of the light field in the optical microcavity, and spectral information is obtained by collecting the change of the light field intensity with the scanning wavelength at the output coupling grating.

[0019] A further technical solution of the present invention is that the average distribution density of the nanoscatterers in the optical microcavity is not greater than 10 / micrometer 2 .

[0020] A further technical solution of the present invention is: the chip substrate material is any one of silicon, glass, and III-V semiconductors, the chip lower cladding is a corresponding low-refractive index material such as silicon oxide, and the on-chip waveguide optical structure material arranged on the surface of the chip lower cladding is any one of silicon, silicon nitride, and silicon carbide.

[0021] A further technical solution of the present invention is: the external excitation light source is a laser or a light emitting diode, and the corresponding working wavelength is between the visible light range and the near / mid-infrared band of several microns. Preferably, the working wavelength range is 400-1000nm.

[0022] A further technical solution of the present invention is: the external imaging element is a CMOS or CCD camera.

[0023] A further technical solution of the present invention is: the optical microcavity has a shape of any one or more of a racetrack shape, a peanut shape, a snail shape and a "D" shape.

[0024] A further technical solution of the present invention is: the design method of the optical microcavity and the external imaging element, the input coupling grating, and the trunk input waveguide includes any one or more of single waveguide evanescent wave coupling, double waveguide evanescent wave coupling, single waveguide edge intrusive coupling, and single waveguide center intrusive coupling.

[0025] In a second aspect of the present invention, a PUF device encryption method based on an integrated optical microcavity is provided. The method utilizes the above-mentioned PUF device based on an integrated optical microcavity and is implemented by the following steps:

[0026] Loading the chip containing the PUF device into the working system, scanning the PUF device using the optical excitation and collection components, and capturing the optical scattering information of the surface of the optical microcavity during the scanning process;

[0027] After filtering based on the optical scattering information, a spectrum containing scattering information characteristics is obtained;

[0028] Using a peak detection algorithm to extract indexed features from the spectrum, obtaining N indices, performing a logical multiplication operation on the N indices, and obtaining a PUF pool of size S;

[0029] Any K bit sequences in the PUF pool are selected as original keys, and the length of the bit sequences of the original keys is expanded to R times of the original length through an expansion algorithm to generate a key with a length of R×K bits.

[0030] In a third aspect, the present invention provides another encryption method for a PUF device based on an integrated optical microcavity, wherein the method comprises the following steps:

[0031] The PUF device is loaded onto a platform, an optical excitation component is used to externally excite the PUF device, and scattered light is imaged in an out-of-plane vertical direction to obtain a scattering image;

[0032] Selecting an optical microcavity region in the scattering image and rectangularizing the optical microcavity region;

[0033] The rectangularized image is processed in the frequency domain using the perceptual hashing algorithm to obtain the frequency coefficient matrix;

[0034] The key size M is determined, an M×M area in the frequency coefficient matrix is ​​selected, and this area is binarized with 0 as a threshold to obtain a key with a size of M×M bits.

[0035] Since the coding and variability of the stimulus are directly related to the reliability and capacity of the PUF, multiple modulations in the spatial domain, time domain, frequency domain, etc. are required, thereby increasing the complexity of the PUF device and the precision requirements of the external acquisition device. The embodiment of the present disclosure provides a PUF device based on an integrated optical microcavity and an encryption method thereof, and its beneficial effects include:

[0036] 1) Improvement in PUF processing. Many existing optical PUF chip solutions are non-silicon-based architectures, often involving a variety of non-standardized micro-nano processing technologies, and are difficult to produce and process in large quantities and at low cost. The PUF device architecture proposed in the present invention is mature, based on silicon wafers and CMOS processes compatible with current commercial foundries, does not involve non-standard materials other than Group IV semiconductors, and is compatible with the foundry process design kit (PDK), so it is low-cost and suitable for large-scale manufacturing. Compared with previous inventions, the PUF device of the present invention effectively solves the difficult problem of "reliability" and "low-cost, large-scale manufacturing feasibility" at the design level.

[0037] 2) Improvements at the PUF working system level. Most PUFs require working systems involving luminescence and nonlinear processes, so they usually involve high-precision equipment such as pump sources, narrow linewidth lasers, and spectrometers to read PUF tags. The application cost is high, which is not conducive to miniaturization integration and product packaging. The input signal of the present invention is simple, and there is no requirement for the line width and modulation of the light source. Ordinary low-cost laser diodes (LD) or superluminescent diodes (SLD) can meet the requirements. In addition, wavelength scanning lasers can also be used to read spectral information. By selecting materials such as silicon nitride and utilizing a large transparent window, the working window can be transferred from the near-infrared communication band of traditional communications to the visible or sub-micron band compatible with the CMOS / CCD cameras equipped in mobile smart devices, and the overall cost is greatly reduced. The overall working scheme does not require nonlinear processes and complex luminescence processes, so it is not sensitive to the intensity of the input light source, which improves the stability of the device while increasing the reliability of the device.

[0038] 3) Improvements in PUF reading schemes. In the past, optical PUF chips often required the design of various complex modulation methods to achieve "excitation-response pairs". The present invention provides two feature extraction schemes based on scattering imaging, which makes it easy to expand the key. One is a spectral method based on the scattering spectrum of the device stimulated by a certain band range, and the other is an image method based on the vertical surface scattering image of the microcavity in a specific band to extract information. The image method generates keys from the light field detail information, and has a low correlation with the one-dimensional spectral information obtained by integration. Therefore, it can be used as an additional multiplexing method to enrich the key source of the device and complement each other to improve the security of the entire system.

[0039] In summary, the mass production potential of the PUF device of the present invention can greatly improve the portability of on-demand anti-counterfeiting, data encryption and identity authentication technologies, and is a highly competitive solution for practical industrial applications.

[0040] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0042] Figure 1 Schematic diagram of the overall structure of a PUF device based on an integrated optical microcavity in an embodiment of the present invention;

[0043] Figure 2 4 typical shapes of the optical microcavity 108 in the embodiment of the present invention, 2(a) is a racetrack shape; 2(b) is a peanut shape; 2(c) is a snail shape; 2(d) is a D shape;

[0044] Figure 3 These are four typical coupling modes of the waveguide integrated microcavity in the embodiments of the present invention, 3(a) is single waveguide evanescent wave coupling; 3(b) is double waveguide evanescent wave coupling; 3(c) is single waveguide edge intrusive coupling; 3(d) is single waveguide center intrusive coupling;

[0045] Figure 4 is an actual optical microscopic image of a PUF device in an embodiment of the present invention;

[0046] Figure 5 is a flow chart of a spectrum reading method according to an embodiment of the present invention;

[0047] Figure 6 is a light field distribution diagram obtained based on electromagnetic field simulation in an embodiment of the present invention;

[0048] Figure 7 is the field intensity spectrum inside the optical cavity obtained based on electromagnetic field simulation in an embodiment of the present invention;

[0049] Figure 8 is a key sequence diagram obtained based on spectroscopy for simulation data in an embodiment of the present invention;

[0050] Fig. 9 is a scattered light field imaging diagram collected and measured in the verification of the embodiment of the present invention;

[0051] Fig.10 is a scattering spectrum graph collected in the verification of the embodiment of the present invention;

[0052] Fig.11 is the encryption key obtained based on the spectral reading method in the verification of the embodiment of the present invention;

[0053] Fig.12 is the NIST test result of the key obtained based on the spectral reading method in the verification of the embodiment of the present invention;

[0054] Fig.13 is the inter-chip Hamming distance matrix of the key obtained based on the spectral reading method in the verification of the embodiment of the present invention;

[0055] Fig.14 It is a Hamming distance statistical histogram of the key obtained based on the spectrum reading method in the verification of the embodiment of the present invention, and the curve is a Gaussian distribution obtained by fitting;

[0056] Fig.15 is a flow chart of an image reading method in an embodiment of the present invention;

[0057] Fig.16 It is the frequency domain matrix data based on the image reading method in the verification of the embodiment of the present invention;

[0058] Fig.17 is the encryption key obtained based on the image reading method in the verification of the embodiment of the present invention;

[0059] Fig.18 This is a NIST test effect diagram of obtaining a key based on an image reading method in the verification of an embodiment of the present invention;

[0060] Fig.19 is the inter-chip Hamming distance matrix obtained based on the image reading method in the verification of the embodiment of the present invention;

[0061] Fig. 20 It is a Hamming distance statistical histogram of the key obtained based on the image reading method in the verification of the embodiment of the present invention, and the curve is a Gaussian distribution obtained by fitting.

[0062] Description of reference numerals:

[0063] 101. Chip substrate; 102. Chip lower cladding; 103. External excitation light source; 104. External imaging element; 105. Objective lens; 106. Input coupling grating; 107. Input trunk waveguide; 108. Optical microcavity; 109. Nanoscatterer; 110. Output waveguide; 111. Output coupling grating. DETAILED DESCRIPTION

[0064] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0065] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0066] It should be mentioned before discussing the exemplary embodiments in more detail that some exemplary embodiments are described as processes or methods depicted as flow charts. Although the flow charts describe the steps as sequential processes, many of the steps therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of the steps can be rearranged. The process can be terminated when its operation is completed, but can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0067] The embodiment of the present invention is aimed at the development needs of key registration and user identity authentication in hardware encryption. Based on silicon-based photonic chip technology, a PUF chip with an on-chip integrated optical microcavity as the main body is proposed. Based on the convenient, efficient, and streamlined working mechanism of out-of-plane scattering imaging, two key generation schemes are proposed to construct a communication mechanism between the response image and the scalable and reconfigurable key.

[0068] Specifically, the core of the embodiment is to propose a deformable optical microcavity based on waveguide coupling under a silicon-based platform as the core response unit of the PUF device. The disordered optical behavior of the chaotic light field in the microcavity is fully utilized, and the disordered random out-of-plane scattering generated by the nano-random body is superimposed. The scattered light signal in the vertical direction is obtained by the top camera. The light signal reflects the response after the superposition of the internal chaotic light field and the random defects, and the features are extracted and encoded into a random key that can be used for encryption.

[0069] There are two schemes for generating keys based on out-of-plane scattering images: 1) Spectral method, which is based on the mapping relationship between the scanning wavelength and the changing output transmission or scattered light intensity; 2) Image method, which is based on the fine position information of the microcavity scattered light field image at a fixed wavelength. Further:

[0070] 1. Spectral reading method: This method focuses on the chaotic behavior of light in the microcavity, which causes the "whispering-gallery" mode with clear resonance characteristics to fade away, and manifests as a disordered chaotic spectral response. After scanning the wavelength of the input light source in a certain band, the "region of interest" (ROI) of the microcavity in the image is defined, and the corresponding spectrum is obtained by associating the wavelength with the corresponding value, and the random information is extracted for feature extraction; and the information is encoded and expanded based on the existing encryption standard to obtain the PUF key sequence.

[0071] Due to the manufacturing error of the scatterer in the cavity during production, the scattering or transmission spectrum of each device after scanning in the same wavelength range has significant characteristics and uniqueness. The spectral information can be obtained by filtering to obtain a stable component, and then the characteristic information can be extracted. Then the key is expanded using existing encryption methods to obtain a PUF key sequence with sufficient length.

[0072] 2. Image reading method: Under the disordered optical behavior of the chaotic light field in the microcavity, at any wavelength, a small part of the light field in the cavity is scattered above the microcavity, and is captured by the image sensor after being focused. A specific algorithm is used to crop and select the microcavity area information of the image. Subsequently, feature extraction is implemented based on the frequency domain information extraction algorithm to obtain low-frequency information. After binary encoding, PUF keys for encryption and anti-counterfeiting can be directly generated. Compared with the spectral reading method, this solution is suitable for a more streamlined reading system. It does not require a wavelength scanning process. Any fixed-band light source can be directly selected as an excitation to obtain a scattered image, which is directly used for PUF key generation.

[0073] The first aspect of the embodiment relates to the overall excitation and reading system of the PUF, and the design of on-chip optical waveguide and waveguide-coupled optical deformation microcavity. Figure 1 The overall structure of the PUF device is shown. It includes a chip substrate 101; a chip lower cladding 102 covering the surface of the chip substrate 101; an input coupling grating 106, a trunk input waveguide 107 and an optical microcavity 108 arranged on the surface of the chip lower cladding 102; and a nanoscatterer 109 arranged in the optical microcavity 108; wherein the input coupling grating 106 is used to couple an external excitation signal to the trunk input waveguide 107, and the trunk input waveguide 107 couples the received excitation light to the optical microcavity 108 in the form of evanescent wave coupling or direct coupling.

[0074] Specifically, the chip substrate 101 is preferably silicon, and a glass substrate or a III-V semiconductor material substrate may also be selected. The chip lower cladding 102 is a corresponding low refractive index material, preferably silicon oxide in a silicon-based platform. The on-chip waveguide optical structure is preferably silicon or common high refractive index materials such as silicon nitride and silicon carbide.

[0075] Specifically, the PUF device also includes three additional off-chip components, namely, an external excitation light source 103, an imaging element 104, and an objective lens 105. The objective lens 105 has a magnification range of 5 to 100 times, and the external imaging element 104 completes the far-field scattering signal acquisition under single-exposure imaging. Another optional solution is to omit the objective lens, bring the external imaging element 104 into close contact with the PUF device, and directly image the far-field scattering in a "lensless" form.

[0076] The light source 103 is preferably a laser or light-emitting diode with a narrow linewidth, and the corresponding operating wavelength is between the visible light range and the near / mid-infrared band of several microns. Considering the operating range of silicon-based photodetectors, the preferred operating wavelength is between 400-1000nm. Another optional solution is an on-chip integrated light source. Correspondingly, the imaging element 104 is preferably a low-cost, high-sensitivity CMOS, CCD camera, and the PUF chip includes an on-chip grating input coupler structure 106 to achieve the coupling of the external excitation signal of the light source 103 and the coupling of the external input optical signal to the trunk input waveguide 107. Subsequently, the excitation light in the trunk waveguide is coupled to the optical microcavity 108 by evanescent wave coupling or direct coupling.

[0077] Random scattering in the optical microcavity is caused by a variety of reasons, including the inevitable rough shape of the side walls caused by processes such as photolithography exposure and etching, and the introduction of embedded nanoscatterers 109 in the microcavity. The introduced embedded nanoscatterers 109 can adopt a uniform size at the design level, but due to the unavoidable random errors in the processing technology, the scatterers inside each chip will be different after production. The nanoscatterers can be circular, square, etc., and the characteristic size is preferably not more than one wavelength, and is generally not less than the processing accuracy, such as about 150nm under deep ultraviolet lithography conditions. The number can range from tens to thousands or even tens of thousands. The average density of nanoscatterers must be guaranteed to be no more than 10 / micron. 2 , otherwise it will greatly increase the optical loss and reduce the chaotic light field effect.

[0078] In actual operation, scatter imaging is mainly for the collection of scattered light in the "out-of-plane" direction, which can be based on a conventional optical objective lens solution, where the objective lens 105 can have a magnification of 5 to 100 times. After determining the appropriate objective lens and image sensor size, ensure that the field of view (FOV) completely covers the PUF unit, and ensure that single exposure imaging uses camera 104 to collect far-field scattering signals to complete the measurement.

[0079] An output waveguide 110 and an output coupling grating 111 are also provided on the surface of the chip lower cladding 102 . The output waveguide 110 couples out a part of the light field in the optical microcavity 108 , and the spectrum information is obtained by collecting the light field intensity at the output coupling grating 111 .

[0080] Specifically, another operation scheme is to couple part of the light field in the microcavity through the output waveguide 110, and collect the light field intensity at the on-chip grating output coupler structure 111 to evaluate the overall resonance in the cavity. This scheme can only extract spectral information and is therefore only applicable to spectral reading methods.

[0081] like Figure 2 As shown, various optional forms of the PUF core optical microcavity 108 deformation structure are shown. Typical deformation microcavity forms include racetrack type ( Figure 2 a) Peanut type ( Figure 2 b) Limacon type ( Figure 2 c) Type "D" ( Figure 2 d).

[0082] The runway shape is composed of a central rectangle and two semicircular arcs on the left and right, and the diameter of the semicircle is equal to the length of the short side of the rectangle. Its shape is controlled by the parameters: radius R and length L.

[0083] The contour parameter equation of the peanut-shaped microcavity is:

[0084]

[0085] The contour parameter equation of the spiral microcavity is:

[0086]

[0087] Where R represents the radius of the device; θ represents the angle formed by the point in the counterclockwise direction to the positive semi-axis of the horizontal coordinate of the coordinate system; ε represents the eccentricity, which is the control parameter of the parametric equation. In order to avoid waveguide bending loss, the preferred device radius R is 10 microns to hundreds of microns.

[0088] Type D is obtained by cutting off the arc-shaped part of a perfect circular microcavity, and its shape is controlled by the parameters: device radius R and chord length L.

[0089] The design of the optical microcavity 108 and the external imaging element 104, the input coupling grating 106, and the trunk input waveguide 107 includes any one of single waveguide evanescent wave coupling, double waveguide evanescent wave coupling, single waveguide edge intrusive coupling, and single waveguide center intrusive coupling.

[0090] Specifically, Figure 3As shown in the figure, four design methods of microcavity and input and output waveguides are demonstrated, including single waveguide evanescent wave coupling ( Figure 3 a) Dual-waveguide evanescent wave coupling ( Figure 3 b) Single waveguide edge intrusive coupling ( Figure 3 c) Single waveguide center intrusive coupling ( Figure 3 d) In the preferred embodiment, a single-sided intrusive coupling is selected.

[0091] like Figure 4 As shown, an optical microscopic image of a processed on-chip PUF device of a specific instantiation is shown. The main body of the device is made of silicon nitride with a large transparent window in the 400-4000nm band and is manufactured at the Swiss wafer foundry Ligentec. This instantiation scheme uses a peanut-shaped microcavity, and the central area is an embedded scatterer structure with a diameter of 600nm. At the same time, a local phase shifter is integrated in the upper edge of the microcavity. Through the metal plate connected to the surface of the chip through the lead, a weak perturbation current can be applied to the metal area on the left and right sides through the probe or the bonded metal lead to test the robustness of the device.

[0092] Based on the PUF device in the above specific example, the embodiment provides a PUF device encryption method based on an integrated optical microcavity, such as Figure 5 As shown, the overall steps can be divided into two steps: spectrum acquisition and key generation. The implementation includes the following steps:

[0093] First, the PUF device is loaded onto the test platform, and an external laser source is introduced to scan the device. During the scanning process, the camera above the device and other acquisition devices will capture the optical scattering information on the microcavity surface during the entire scanning process. The scanning range is defined by a preset program, and the optical pixel intensity is calculated to obtain the corresponding spectrum of the device. After the spectrum passes through a certain filtering algorithm, a spectrum that highlights the characteristics of the scattering information can be obtained. This embodiment uses wavelet transform to complete the filtering operation.

[0094] After the spectrum is processed, the features are extracted through indexing. This embodiment uses a peak detection algorithm to extract features from the spectrum to obtain N indicators. There is no limit on the length of each indicator, but short bit sequences are preferred. Performing a logical multiplication operation on the obtained N indicators, a PUF pool of size S can be obtained. Any K bit sequences selected from the PUF pool can be used as the original key. After the expansion algorithm, the bit sequence length of the original key can be expanded to R times the original; then a PUF key with a length of R×K bits is generated, which can be directly used for system verification.

[0095] Before actual application, the feasibility of the scheme can be investigated based on electromagnetic field simulation tools. The specific steps of the scheme are shown below in combination with the simulation results. The numerical simulation is completed based on the commercial software COMSOL Multiphysics for two-dimensional finite element analysis. The simulated light field in the cavity is as follows Figure 6 As shown in the figure. Due to the introduction of deformation features, the light field distribution in the cavity is completely different from the conventional whispering gallery mode reflected along the inner boundary. In the simulation, since there is no out-of-plane scattered light field, the light field in the cavity is used instead. Within a certain wavelength range (taking 767nm to 772nm as an example), the light field intensity in the selected microcavity ROI is integrated, and the obtained value is Figure 7 The resonance spectrum is displayed. The spectrum is feature extracted to obtain an initial key of a certain length. In this embodiment, the initial key length K is selected as 128 bits. The sequence is expanded by the encryption algorithm to obtain the encryption key. This example uses the Advanced Encryption Standard (AES) to expand the key to 10×K, that is, after expanding by 10 times, the following is obtained: Figure 8 The key length is 1280 bits. As part of the Advanced Encryption Standard, the AES extended algorithm has been maturely applied and practiced in various industries, such as financial systems, the Internet of Things industry, and single-chip microcomputer systems. UltraScale+ TM In order to protect the electrical PUF device from side channel attacks, the AES algorithm is introduced as the protection part of its PUF.

[0096] After verifying the basic process at the simulation level, the present invention directly migrates to the instantiated device for experimental verification. A variable wavelength, stable power laser source (Newport TLB-6712) with an operating wavelength of around 770nm is used to complete the input of different bands. The scattering imaging effect of the randomly selected test is as follows: Fig. 9 After completing the image acquisition of a fixed wavelength range (taking 767nm to 772nm as an example), the computer automatically performs intensity integration to complete the scattering spectrum measurement. The result is shown in Fig.10 After obtaining the spectrum, feature extraction is used to obtain an initial key of 128 bits in length, and after expanding it to 1280 bits, the result is as follows Fig.11 shown.

[0097] Fig.12The randomness test of the randomly selected PUF key based on the above scheme is demonstrated. The National Institute of Standards and Technology (NIST) SP 800-22 standard is used here to evaluate the randomness of the generated PUF key. This test standard calculates the number of bits required for calculation. Fig.12 The results of 8 tests in the verification results are shown in Figure 2. Each test divides the key into multiple groups and calculates the P value (a measure of randomness) for each group. For each round of testing, if the P value is greater than 0.01, it is awarded the randomness test specified in the standard. The success rate of all tests in the verification results is above 97%, proving that the PUF key has good randomness.

[0098] To test the non-clonability of PUF components, this example verification selected 7 chips with the same design from the same fab and the same batch of multi-project wafer (MPW) process flow, and used normalized Hamming distance to quantify the similarity. The inter-chip Hamming distance matrix is ​​as follows: Fig.13 As shown in the figure, based on the same steps, the Hamming distance between the keys generated by different devices is measured. It can be seen that the Hamming distance between different keys is around 0.5, which means that the keys generated by different chips can be completely distinguished.

[0099] Fig.14 The Hamming distance histogram statistics obtained based on example verification are shown, in which the distribution of intra-chip and inter-chip Hamming distances is very distinct. In addition, the Gaussian fitting The mean μ and standard deviation σ of the curve are obtained. Since all pixels constituting the PUF key are not completely independent of each other, the present invention adopts independent bits (i.e., degrees of freedom, defined as ) to estimate the PUF key encoding capacity, i.e. 2 Nc . Fig.14 The distribution of intra-chip and inter-chip Hamming distances among 7 PUF chips is shown, and the coding capacity is calculated to be 2 995 .

[0100] like Fig.15 As shown, based on the PUF device in the above specific example, another PUF device encryption method based on integrated optical microcavity is provided, and the implementation includes the following steps:

[0101] The PUF device is loaded onto a platform, the PUF device is scanned by a light collection component, and scattered light is imaged in an out-of-plane vertical direction to obtain a scattered image;

[0102] Selecting the optical microcavity region in the scattering image. Since the microcavity region is often the outline of a deformed cavity, an algorithm is required to rectangularize the microcavity region before it can be further used to generate a key. The optical microcavity region is rectangularized.

[0103] The rectangularized image is processed in the frequency domain using the perceptual hashing algorithm to extract the frequency domain information of the image and obtain the frequency coefficient matrix;

[0104] Determine the key size M, select an M×M area in the frequency coefficient matrix, binarize the area with a threshold of 0, and obtain a key of M×M bits. Specifically, the value of M cannot exceed the image size. Select an M×M area in the upper left corner of the hash matrix, binarize the area with a threshold of 0, and obtain a key of M×M bits.

[0105] In the verification embodiment, for a single scattering image under a single wavelength input, the following is obtained after the perceptual hashing (Phash) algorithm: Fig.16 The frequency coefficient matrix distribution is shown. Set the matrix threshold to 0 and select the key size M value to 30. Fig.17 The PUF key of size 30×30 extracted from the microcavity scattering image is demonstrated.

[0106] Fig.18 The randomness test using the NIST-SP 800-22 standard is demonstrated. 10 PUF keys are processed to form an encryption key sequence of length 9000 bits (10×30×30 bits). The first 8960 bits of the sequence are selected and divided into 70 groups of 128 bits each. The P value of the test is calculated based on the number of bits required for calculation. For each round of testing, if the P value is greater than 0.01, it is granted a pass. The success rate of all tests is above 97%, proving the randomness of the PUF key.

[0107] As with the spectroscopy method, the verification of unclonability is also based on the images of the microcavity elements of the same design on the 7 chips under the same input conditions, generating keys of the same length. Fig.19 The inter-chip Hamming distance matrix can be used to determine that the keys generated by different chips can be well distinguished.

[0108] Fig. 20 The Hamming distance histogram statistics obtained based on the image method are shown, in which the distribution of the Hamming distance between chips is very distinct. According to the same Gaussian fitting scheme in the spectral method, the coding capacity is calculated to be 2 632 Although this value is smaller than the data obtained using the spectral reading method, compared with the spectral method, the imaging method has the advantages of being simple to work with and requiring very little external equipment.

[0109] In summary, the technical solutions provided in the above embodiments provide a PUF device based on an integrated optical microcavity and an encryption method thereof, and its beneficial effects include:

[0110] 1) Improvement in PUF processing. Many existing optical PUF chip solutions are non-silicon-based architectures, often involving a variety of non-standardized micro-nano processing technologies, and are difficult to produce and process in large quantities and at low cost. The PUF device architecture proposed in the present invention is mature, based on silicon wafers and CMOS processes compatible with current commercial foundries, does not involve non-standard materials other than Group IV semiconductors, and is compatible with the foundry process design kit (PDK), so it is low-cost and suitable for large-scale manufacturing. Compared with previous inventions, the PUF device of the present invention effectively solves the difficult problem of "reliability" and "low-cost, large-scale manufacturing feasibility" at the design level.

[0111] 2) Improvements at the PUF working system level. Most PUFs require working systems involving luminescence and nonlinear processes, so they usually involve high-precision equipment such as pump sources, narrow linewidth lasers, and spectrometers to read PUF tags. The application cost is high, which is not conducive to miniaturization integration and product packaging. The input signal of the present invention is simple, and there is no requirement for the line width and modulation of the light source. Ordinary low-cost laser diodes (LD) or superluminescent diodes (SLD) can meet the requirements. In addition, wavelength scanning lasers can also be used to read spectral information. By selecting materials such as silicon nitride and utilizing a large transparent window, the working window can be transferred from the near-infrared communication band of traditional communications to the visible or sub-micron band compatible with the CMOS / CCD cameras equipped in mobile smart devices, and the overall cost is greatly reduced. The overall working scheme does not require nonlinear processes and complex luminescence processes, so it is not sensitive to the intensity of the input light source, which improves the stability of the device while increasing the reliability of the device.

[0112] 3) Improvements in PUF reading schemes. In the past, optical PUF chips often required the design of various complex modulation methods to achieve "excitation-response pairs". The present invention provides two feature extraction schemes based on scattering imaging, which makes it easy to expand the key. One is a spectral method based on the scattering spectrum of the device stimulated by a certain band range, and the other is an image method based on the vertical surface scattering image of the microcavity in a specific band to extract information. The image method generates keys from the light field detail information, and has a low correlation with the one-dimensional spectral information obtained by integration. Therefore, it can be used as an additional multiplexing method to enrich the key source of the device and complement each other to improve the security of the entire system.

[0113] In summary, the mass production potential of the PUF device of the present invention can greatly improve the portability of on-demand anti-counterfeiting, data encryption and identity authentication technologies, and is a highly competitive solution for practical industrial applications.

[0114] In this document, the terms "comprises," "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, such that a step or method that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such step or method.

[0115] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A PUF device based on an integrated optical microcavity, characterized in that: include: Chip substrate; A chip lower cladding layer covering the surface of the chip substrate; An input coupling grating, a trunk input waveguide and an optical microcavity of at least one form arranged on the surface of the lower cladding layer of the chip; A nano-scatterer disposed in the optical microcavity; as well as Optical excitation and collection components for assisting external excitation and collecting out-of-plane scattered light; The input coupling grating is used to couple external excitation light to the trunk input waveguide, and the trunk input waveguide couples the received excitation light to the optical microcavity.

2. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: The light excitation and collection component includes an external excitation light source and an external imaging element, and the external imaging element completes far-field scattering signal collection under single exposure imaging.

3. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: An output waveguide and an output coupling grating are also provided on the surface of the lower cladding layer of the chip. The output waveguide couples out part of the light field in the optical microcavity, and spectrum information is obtained by collecting the change of the light field intensity with the scanning wavelength at the output coupling grating.

4. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: The average distribution density of the nanoscatterers in the optical microcavity is no more than 10 / micrometer 2 .

5. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: The chip substrate material is any one of silicon, glass, and III-V semiconductors, and the waveguide optical structure material arranged on the chip is any one of silicon, silicon nitride, and silicon carbide.

6. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: The external excitation light source is a laser or a light emitting diode.

7. The PUF device based on integrated optical microcavity according to claim 1, characterized in that: The optical microcavity morphology is any one or more of a racetrack shape, a peanut shape, a snail shape, and a "D" shape.

8. The PUF device based on integrated optical microcavity according to claim 2, characterized in that: The design of the optical microcavity, the external imaging element, the input coupling grating, and the trunk input waveguide includes any one of single waveguide evanescent wave coupling, double waveguide evanescent wave coupling, single waveguide edge intrusive coupling, and single waveguide center intrusive coupling.

9. A PUF device encryption method based on integrated optical microcavity, characterized in that: The method uses the PUF device based on the integrated optical microcavity according to any one of claims 1 to 8 to implement the following steps: Loading the chip containing the PUF device into the working system, scanning the PUF device using the optical excitation and collection components, and capturing the optical scattering information of the surface of the optical microcavity during the scanning process; After filtering based on the optical scattering information, a spectrum containing scattering information characteristics is obtained; Using a peak detection algorithm to extract indexed features from the spectrum, obtaining N indices, performing a logical multiplication operation on the N indices, and obtaining a PUF pool of size S; Any K bit sequences in the PUF pool are selected as original keys, and the length of the bit sequences of the original keys is expanded to R times of the original length through an expansion algorithm to generate a key with a length of R×K bits.

10. A PUF device encryption method based on integrated optical microcavity, characterized in that: The method uses the PUF device based on the integrated optical microcavity according to any one of claims 1 to 8 to implement the following steps: The PUF device is loaded onto a platform, externally excited by a light excitation and acquisition component, and scattered light is imaged in an out-of-plane vertical direction to obtain a scattering image; Selecting an optical microcavity region in the scattering image and rectangularizing the optical microcavity region; The rectangularized image is processed in the frequency domain using the perceptual hashing algorithm to obtain the frequency coefficient matrix; The key size M is determined, an M×M area in the frequency coefficient matrix is ​​selected, and this area is binarized with 0 as a threshold to obtain a key with a size of M×M bits.

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