Photonic physically unclonable function for true random number generation and biometric id for hardware security applications

Abstract

Photonic Physically Unclonable Function (PPUF) devices which harvest the variability in optical performance in which electromagnetic waves are incident surface sensitive. Embodiments describe Photon-Trapping (PT) feature-equipped photosensitive devices (i.e., photodiodes) coupled to sense amplifiers, or similar, to generate a random bit(s), while an array of these devices generates a random bit array, or for assigning a unique identity to hardware toward preventing cloning. The PPUF devices can also generate true random numbers critical for cryptographic key creation, secure communication, and authentication protocols.

Description

PHOTONIC PHYSICALLY UNCLONABLE FUNCTION FOR TRUE RANDOM NUMBER GENERATION AND BIOMETRIC ID FOR HARDWARE SECURITY APPLICATIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and the benefit of, U.S. provisional patent application serial number 63 / 570,212 filed on March 26, 2024, incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with Government support under Grant No. 2329884, awarded by the National Science Foundation. The Government has certain rights in the invention.NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION

[0003] A portion of the material in this patent document may be subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does not hereby waive any of its rights to have this patent document maintained in secrecy, including without limitation its rights pursuant to 37 C. F. R. § 1 .14.BACKGROUND

[0004] 1. Technical Field

[0005] The technology of this disclosure pertains generally to photonic physically unclonable function (PPUFs), and more particularly to PPUFs mechanisms which enhance variability in light sensitivity.

[0006] 2. Background Discussion

[0007] In view of the dramatic increases in available computational devices, such as quantum computers, conventional mechanisms used for hardware security may no longer be sufficient to prevent phishing attacks. Physically Unclonable Functions (PLIFs) are often utilized in true random number generators being utilized toward providing unbreachable hardware ID enabling an on-system guard to protect the system from any data leak.

[0008] One class of promising PLIFs are uninitialized Static Random-Access Memory (SRAM)-based PLIFs. However, these are still vulnerable to environmental sensitivity, aging effects, side-channel attacks, predictability, clonability, and other issues which could lead to security breaches.

[0009] Accordingly, a need exists for enhanced PUF technologies which cannot be overcome with high power computations, or other attack forms. The present disclosure fulfills that need and provides additional benefits over existing systems.BRIEF SUMMARY

[0010] The present disclosure describes a Photonic PUF (PPUF) that harvests the variability in optical performance instead of electrical performance. The PPUF takes advantage of the fact that electromagnetic waves are incident surface sensitive.

[0011] By way of example, and not of limitation, this disclosure describes methods and apparatus that use variability in the electromagnetic wave interaction in Photon-Trapping (PT) feature-equipped photodiodes to define photonic physically unclonable functions (PPUFs). A pair of these PT- equipped photodiodes are used to generate one random bit. An array of this PT-equipped Photodiode pair is used to generate a random bit array. These bit arrays are qualified for their randomness using inter-Hamming and intraHamm ing distance tests. Further, the bit stream randomness is tested using NIST statistical randomness test. The generated random bit array has passed all the aforementioned tests. These random bit arrays are transformed into true random decimal numbers using binary to decimal conversion. These bit arrays can also be used to assign a unique identity tohardware and prevent cloning.

[0012] Further aspects of the technology described herein will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the technology without placing limitations thereon.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The technology described herein will be more fully understood by reference to the following drawings which are for illustrative purposes only:

[0014] FIG. 1 A through FIG. 1C are pictorial views and a rendered image of a flat photodiode and a Photon-Trapping (PT)-equipped photodiode, according to at least one embodiment of the present disclosure.

[0015] FIG. 1 D and 1 E are graphs of current variation under of the devices in dark and under illumination, according to at least one embodiment of the present disclosure.

[0016] FIG. 2A depicts a schematic of a unit bit generation circuitry having parallel unique diodes connected with a sense amplifier to read the current difference and interpret the output bit, according to at least one embodiment of the present disclosure.

[0017] FIG. 2B is a diagram of generating a 1 D identification array, according to at least one embodiment of the present disclosure.

[0018] FIG. 2C is a block diagram of a 2D identification array implementation, according to at least one embodiment of the present disclosure.

[0019] FIG. 3A and FIG. 3B are graphs of inter-Hamming and intra-Hamming distance for the random bit stream, according to at least one embodiment of the present disclosure.

[0020] FIG. 4A is a pictorial view of incident light Directions of Arrival (DOAs) received by a photodiode.

[0021] FIG. 4B is a graph of absorption efficiency in response to the Direction of Arrival (DOA) of incident photons, according to at least one embodiment of the present disclosure.

[0022] FIG. 5A is a graph of FDTD simulation DOA dependency, as determined for at least one embodiment of the present disclosure.

[0023] FIG. 5B is a heat map of incidence and azimuth angles for a wavelength of 850 nm, as determined for at least one embodiment of the present disclosure.

[0024] FIG. 6A is an incident light received by a photodiode. \

[0025] FIG. 6B through FIG. 6E are plane views of example asymmetric photodiode surface structures and shapes, according to at least one embodiment of the present disclosure.

[0026] FIG. 7A through FIG. 7D are cross sections and plan views of power absorption variation with respect to asymmetry, according to at least one embodiment of the present disclosure.

[0027] FIG. 7E through FIG. 7Q depict power absorption comparisons for four different directions of arrival, according to at least one embodiment of the present disclosure.

[0028] FIG. 8A through FIG. 8C are graphs demonstrating DOA dependency on absorption efficiency, according to at least one embodiment of the present disclosure.

[0029] FIG. 9A through FIG. 9C are growth cross-sections and graphs of different mechanisms for extending PD wavelength range, such as to 2500 nm, according to at least one embodiment of the present disclosure.

[0030] FIG. 10A and FIG. 10B are plan and pictorial views of a light concentrating dielectric structure external to the photodiode, according to at least one embodiment of the present disclosure.

[0031] FIG. 11 is a pictorial cross-section of plasmonic metal structures within a PD utilized for a PPLIF device according to at least one embodiment of the present disclosure.DETAILED DESCRIPTION

[0032] 1. Introduction

[0033] Severe, unpredictable, and untraceable cybercrime has emerged in response to vulnerable hardware security. In the age of advanced computational capabilities, such as quantum computers, the conventional methods of hardware security will no longer be able to prevent phishing attacks. Industries are transforming toward cloud-based storage ofconfidential databases, giving rise to numerous cloud-data security startups. Despite the advancement in cloud storage, global storage servers are not protected from hardware security breaches and IP cloning.

[0034] Physically Unclonable Function (PUF)-based true random number generators are being utilized to provide unbreachable hardware ID enabling an on-system guard to protect the system from any data leak. There exist numerous PUF generation methods, such as uninitialized Static Random- Access Memory (SRAM)-based PLIFs, stochastic oxide breakdown-based (one-time programmable, OTP memory) PLIFs, utilizing process variation in photodiodes to generate PLIFs, and other light-matter interaction driven PLIFs, and similar.

[0035] There are limitations of current technologies, for example current Static Random-Access Memory (SRAM) and One-Time Programmable (OTP) memory based PLIFs are vulnerable to: (i) environmental sensitivity, (ii) aging effects, (iii) side-channel attacks, (iv) predictability, (v) clonability, and have additional drawbacks, and are being rendered more vulnerable in view of the state of the art machine learning and quantum computing.

[0036] OTP-based PLIFs utilize two parallel capacitors, and the stochasticity in bit generation depends on the hard breakdown of one of the capacitors. Such hard breakdowns are easily scannable using advanced electron-beam scanning methods. The use of uninitialized SRAM-based PUF is seemingly unbreachable, however, the advancement in the study of process-induced variations, such as threshold voltage, which is a parameter that makes one transistor dominant over the other, can be modeled and the threshold voltage variability can be predicted. Withing this variety of PUF strategies the use of SRAM and OTP-based PUFs have shown potential for further implementation improvements to provide system-level protection.

[0037] 2. Technology of the Present Disclosure

[0038] 2.1. Introduction

[0039] The technology of this disclosure generally comprises a Photonic PUF (PPUF) that harvests the variability in optical performance instead of electrical performance. The PPUF takes advantage of the fact that electromagnetic waves are incidence surface sensitive.

[0040] It should be noted that the photonic device of the PPLIF may comprise any desired device that is sufficiently sensitive to illumination. One example is that of a photodiode, which is described herein for the sake of simplicity of illustration. However, the present disclosure can be implemented on other light sensitive devices or photoelectric technologies, such as phototransistors, light-dependent resistors (LDRs) or photo-conductor, light to frequency converters, and other technologies which generate an output in response to converting / sensing incoming light.

[0041] Various aspects and embodiments of the technology include, but are not limited to, the following.

[0042] (a) A photodiode is described which is configured with Photon-Trapping (PT) holes. The introduction of PT holes increases the variability in the Electromagnetic (EM) wave interaction to enable hardware security features.

[0043] (b) Allowing, and more preferably encouraging, process-induced variations, primarily edge and surface roughness in the PT holes which result in significantly increased EM wave interaction variations. The PT surface structures increase the surface-to-volume ratio of each device, facilitating light diffraction and enhancing light-material interactions. The additional surface areas introduce increased process-induced variations, which in turn contribute to improved PPUFs.

[0044] (c) Variability in PT hole dimensions (e.g., PT hole diameter; PT hole period, shape) leads to significant variation in the EM wave interaction; in particular when the dimensions of the PT holes are comparable to (on the same order of magnitude as) that of the illumination wavelength.

[0045] (d) The PT holes provide a unique dependence on EM wave interaction and create performance variations which are even more significant under proper illumination.

[0046] (e) The PT-equipped photodiodes exhibit greater than a ten fold (10x) increase in EM wave interaction variation as compared with flat photodiodes.

[0047] (f) The present disclosure was tested with 17 identical PT-equipped photodiodes which were located in different portions of a die to generate a random bit array and perform the PUF qualifying tests (Hamming distance testand National Institute of Standards and Technology (NIST) statistical test) on 272 randomly generated bit arrays.

[0048] (g) The physically unclonable functions based on the PT-holes photodiode array qualify as passing the Hamming distance tests (inter-HD and intra-HD) and the 11 NIST random number generator tests.

[0049] (h) These PT-equipped photodiodes are essential in generating true random numbers and generating unique identifiers (IDs) for hardware.

[0050] (i) Using the disclosed technology, fabless companies can activate the hardware ID by illuminating the PT-equipped photodiode array after receiving the chips from the foundries and thus preventing IP cloning.

[0051] 2.2. Example Embodiment

[0052] A range of flat photodiodes and PT-equipped photodiodes with fixed PT dimensions. By way of example and not limitation the PT-equipped photodiodes were fabricated with PT hole diameters of 1000 nm, and PT-hole periodicity of 2500 nm. The measurements were performed on devices with a fixed device diameter of 500 pm. It should be appreciated that the present disclosure is not limited to the shapes and dimensions as described above. It should be appreciated, however, that PT hole dimensions that approximate the wavelength of light being used and detected provides more pronounced variability. Otherwise, depending on the application the dimensions may span at least an order of magnitude.

[0053] FIG. 1 A and FIG. 1 B illustrate examples of a flat surface photodiode 10 in comparison with the presently disclosed Photon-Trapping (PT) photodiode.

[0054] In FIG. 1A is shown a flat conventional photodiode with base 12 (e.g., substrate), over which is fabricated a bottom mesa 14, over which is a bottom contact 18 along with the top mesa 16 over which is a top contact 20. Top contact 20 is connected to Coplanar Waveguide (CPW) electrode 22c, while bottom contact 18 is connected to a CPW electrode with ends 22a, 22b.

[0055] In FIG. 1 B is shown a PT-photodiode with base 32 (e.g., substrate), over which is fabricated a bottom mesa 34, over which is a bottom contact 38 along with the top mesa 36 over which is a top contact 40. Top contact 40 is connected to CPW electrode 42c, while bottom contact 38 is connected to a CPW electrode with ends 42a, 42b.

[0056] FIG. 1 C is an image rendition of a microscopic image of conventional flat photodiodes 10 as well as fabricated PT-equipped photodiodes 30 according to the present disclosure.

[0057] FIG. 1 D and FIG. 1 E show quantile plots 70, 90 of current captured at a reverse biased voltage of 1 V for both the flat and PT-equipped photodiodes.

[0058] It can be seen from the current quantile plots for dark and under illumination of white LED, 550 nm-laser, and 600 nm-laser, that introducing the PT holes increased the variability in the illumination current as against the under-illumination current variability in the flat photodiode. It was seen that this increased variability in the illumination current arises due to the variability in the electromagnetic (EM) wave interaction, while the dark current in the PT- equipped photodiodes remains negligible.

[0059] Table 1 presents a summary of device-to-device variability in flat and PT-equipped photodiodes. It was found that the dark state current has a low standard deviation both in flat and PT-equipped devices. The standard deviation increases significantly in the PT-equipped devices under illumination as against the flat devices. This increase in the variability in PT-equipped devices under illumination is due to the variation in the EM wave interaction.

[0060] The PT-hole dimensions (diameter = 1000 nm; period = 2500 nm) are on the order of the illumination wavelength (550 nm and 600 nm), therefore, the variability in the PT-holes is translated into the variability of EM wave interaction. Variation in the interaction results in variability in the absorption followed by variability in the illumination current. The absence of significant variability in the illumination current in flat devices and a ten-fold increase in the variability in PT-equipped devices reflect the increased EM wave interaction variation.

[0061] 3. Methodology to Demonstrate Random Bit Generation

[0062] FIG. 2A illustrates a generation 110 of one random bit. The circuitry involves two of these unique photodiodes 112a, 112b connected in parallel to a sense amplifier 114, or similar circuit, that outputs digital bit(s) in response to sensing the differences in the respective diode input currents.

[0063] FIG. 2B illustrates a 1 D bit array arrangement 130 of the bit generator seen in FIG. 2A to produce a 1 D QR code ID.

[0064] FIG. 2C illustrates a 2D bit array arrangement 150 of the bit generator seen in FIG. 2A, to produce the 2D QR code ID 154 (simulated). An example 2D array comprises 128 x 128 PUF 152, a portion of which is seen with rows 156 and column lines 158 across which the random bit unit from FIG. 2A are connected 160. As the diodes exhibit uncorrelated standby (dark) and under illumination (light) performance, this facilitates dual unique ID production using the same set of bit array arrangements.

[0065] A detailed Hamming Distance (HD) analysis is performed to test the uniqueness and reproducibility of the PUF ID. The inter-HD of the PUFs is greater than 50%, and the intra-HD is less than 5%, a key criterion for unique ID production.

[0066] It should be appreciated that the use of a pair of PT equipped photodiodes followed by the sense amplifier is given by way of example and not limitation; as any multiple of these unique photodiodes may be utilized, insofar as they are coupled to a detection circuit which determines differences in their respective diode currents and converts this to a digital output of one or more bits.

[0067] 4. Uniqueness, Repeatability and NIST Statistical Randomness

[0068] The uniqueness of the random bit array is characterized using interhamming distance (Inter-HD). The repeatability of the random bit array is characterized by intra-hamming distance (Intra-HD). The method to calculate the HD is as follows.

[0069] N = 4; % 4-bit sequence

[0070] A = 0101

[0071] B = 0011

[0072] XOR (A,B) = 0110

[0073] HDn = number of 1s in XOR(A,B) = 2

[0074] HD(%) = 100*HDn / N; %%% Hamming Distance

[0075] 4.1 Inter-HD

[0076] HD between two random bit arrays: the Mean Inter-HD must be greater than or equal to 50% to ensure uniqueness.

[0077] FIG. 3A illustrates the inter-HD distribution calculated for the bit array generated using the PT-equipped photodiodes is shown here to have a meaninter-HD of 50%.

[0078] 4.2 Intra-HD

[0079] The intra-HD is the HD calculated for a bit array with itself by introducing a single-bit challenge. This is a measure of the reproducibility of the randomly generated bit array. The perfectly reproducible bit array will have 0% intra-HD. In practice, intra-HD less than 5% is a measure of good reproducibility.

[0080] FIG. 3B illustrates the intra-HD distribution calculated for the bit array generated using the PT-equipped photodiodes, which is shown here having a mean intra-HD of approximately 1 %.

[0081] 4.3 NIST Statistical Test Suite for Random Number Generators

[0082] The NIST test suite comprises 15 tests that characterize the randomness in the bit array.

[0083] Table 2 indicates testing on the generated random bit stream using PT- equipped photodiodes for 11 out of 15 tests and the random bit array has passed all 11 tests as seen in this table. The table lists that each of these tests (S.N.) has Passed (Pass) as seen in the Status (Stat.) column.

[0084] 5. Supplemental Content

[0085] FIG. 4A and FIG. 4B illustrate absorption efficiency manipulation by Direction of Arrival (DOA) of incident photons. In FIG. 4A is seen a view 410 of a photodiode equipped with asymmetric surface structures, such as rectangular gratings, changing the DOA on the incident wavefront and path length travelled by the wavefront changes. The figure shows illumination arriving from a horizontal angle of and angle 0 from the vertical. In FIG. 4B is shown a graph 430 of responsivity (R) versus wavelength . The variation in the shape of the wavefront and the path length results in variation in the responsivity or absorption efficiency profile at a fixed incidence electromagnetic wavelength as illustrated in the figure,

[0086] FIG. 5A illustrates FDTD Simulation 510 based on Direction Of Arrival (DOA) dependency on photon absorption efficiency. It should be noted that the original graph was in vivid color allowing each of the 26 plots to be identified, however, this was rendered in black lines to aid reproduction. This simulated absorption efficiency profile is for a photodiode with a rectangularsurface gratings. The device is illuminated with electromagnetic waves for a range of wavelength varying from 450 nm to 1100 nm and at different directions of arrival. The direction of arrival is represented by normal angles of incidence, 0 and angle of azimuth, . as per FIG. 4A. The graph covers incidence 0 values of 20°, 30°, 45°, 60°, 70°, which are checked for each azimuth angle of 0°, 30°, 45°, 60°, and 90°. With the change in DOA, the absorption efficiency shows significant changes thus providing increased DOA sensitivity. This sensitivity data set is used to harvest the variability in the DOA and its impact on the photodiode’s performance.

[0087] FIG. 5B illustrates a heat map 530 of incidence and azimuth angles for a wavelength of 850 nm.

[0088] FIG. 6B through FIG. 6E depicts examples 630, 650, 670, and 690 of asymmetric photodiode surface structures and shapes. By increasing the asymmetry in the surface structure and the device shape DOA sensitivity is increased which leads to an increase of variability in the absorption performance.

[0089] In FIG. 6A is shown a view 610 of a photodiode equipped with asymmetric surface structures, such as rectangular gratings, changing the DOA on the incident wavefront and path length travelled by the wavefront changes, which is similar to that of FIG. 4A, and shows illumination arriving from a horizontal angle of and angle 6 from the vertical.

[0090] In FIG. 6B is shown 630 a partially asymmetric pattern with a straight parallel bar geometry having a complexity of 0.299. In FIG. 6C is shown 650 a partially asymmetric pattern with a tapered parallel bar geometry having a complexity of 0.312. In FIG. 6D is shown 670 a fully asymmetric pattern, exemplified with a lowercase ‘y’ pattern having a complexity of 0.422. In FIG. 6E is shown 690 a fully asymmetric pattern, exemplified with a complex imaged pattern having a complexity of 0.579.

[0091] FIG. 7A through FIG. 7D illustrate power absorption variation with respect to asymmetry. In FIG. 7A is seen a 2D cross-section 710 of a Partially Symmetric Tapered Gratings (PSRG) device, whose plan view is seen in FIG. 7B, and which has a structural complexity of 0.0706. In FIG. 7C is a 2D cross-section of a fully asymmetric mesa (FAM) device shown in thex-z plane, whose plan view is seen in FIG. 7D, and which has a structural complexity of 0.4236. In the above views the boundary outlines the domain of the simulation and the black dotted line indicates the z-depth at which the power absorption contours are extracted.

[0092] Power absorption comparisons are illustrated for four different directions of arrival, which in this example are shown as insets demonstrating the change in from the x-y plane.

[0093] FIG. 7E through FIG. 7G depicts one DOA, as seen in FIG. 7E with a DOA from 0 = 45°, = 45°, with FIG. 7F showing PSRG normalized power absorption with IQE at 52%, and FIG. 7G showing FAM normalized absorption with IQE at 68%.

[0094] FIG. 7H through FIG. 7J depicts one DOA, as seen in FIG. 7H with a DOA from 0 = 45°, = 135°, with FIG. 7I showing PSRG normalized power absorption with IQE at 52%, and FIG. 7J showing FAM normalized absorption with IQE at 70%.

[0095] FIG. 7K through FIG. 7M depicts one DOA, as seen in FIG. 7K with a DOA from 0 = 45°, = 225°, with FIG. 7L showing PSRG normalized power absorption with IQE at 52%, and FIG. 7M showing FAM normalized absorption with IQE at 69%.

[0096] FIG. 7N through FIG. 7Q depicts one DOA, as seen in FIG. 7N with a DOA from 0 = 45°, = 315°, with FIG. 7P (note there is no FIG. 70, to prevent confusion with the number 70) showing PSRG normalized power absorption with IQE at 52%, and FIG. 7Q showing FAM normalized absorption with IQE at 72%.

[0097] It should be noted that the power absorption contours are shown at the z-depth for PSRG and FAM devices. The power absorption contours for the PSRG device show symmetric absorption profiles and result in the same IQE. The FAM device exhibits four different absorption contours for all four directions and results in different IQEs.

[0098] FIG. 8A through FIG. 8C illustrate example tests of DOA dependency on absorption efficiency. FDTD simulation from Lumerical® provides a framework for calibration.

[0099] In FIG. 8A is shown 810 with an inset 812 of a microscopic image ofthe fabricated photodiode with azimuthal asymmetry in two quadrants. Inset 814 shows the zoom-in view of the measured current variations caused by different direction of arrival (DOA), while the principle graph of FIG. 8A depicts current-voltage characteristics measured under the illumination at a wavelength of 640 nm for two different angles of incidence (9) and three different angles of azimuth ((j>) to demonstrate the DOA dependency of the asymmetric photodiode.

[0100] In FIG. 8B is shown with inset 832 of a circular PT-photodiode, while the principle graph 834 depicts IQE percentage with respect to wavelength, for each of 6 different DOAs.

[0101] In FIG. 8C is shown a comparison of simulated quantum efficiency (QE) versus experimentally obtained QE values with 640 nm illumination at different (-45°, 0°, 45°) and 0 (30°, 45°). Both the experimental and simulated QE show a comparable range of variation.

[0102] FIG. 9A through FIG. 9C illustrate examples of select methods for extending wavelength to 2500 nm. Materials of different bandgap can be grown on top of each other using methods such as Solid Phase Epitaxy (SPE, FIG. 9A). Pure silicon can absorb photons up to 1100nm. Pure germanium can absorb up to 1800 nm of light. A mix of silicon and germanium can extend the wavelength depending on the ratio of Ge in Si (FIG. 9C). Multiple semiconductors can be grown with precise thickness to create Type I and Type II MQWs. This allows fine-tuning of band alignment, strain, and optical properties to extend the wavelengths beyond the cut-off wavelength (FIG. 9B). For example, Type II Si / Ge MQWs can absorb wavelengths longer than 1100 nm, with absorption tunable into 1 .3 - 1 .5 pm and even mid-IR (greater than 2 pm) range by adjusting the Ge composition, strain, and layer thickness.

[0103] FIG. 10A and FIG. 10B illustrate a light concentrating dielectric structure 1010 which is external to the photosensor (photodiode) 1018. The object of this structure is to enhance the efficiency of light-harvesting from the surroundings and to increase variations in the light material interactions.

[0104] Each photodiode 1018 is surrounded with a crosstalk blocking and reflecting metal structure 1012, within which is a dielectric film 1016, such as above underlying electronic layer(s), upon which are photon-trappingstructures 1014. In FIG. 10B is seen light 1024 interacting with the photontrapping structures directed to the photodiode. The diameter of the photodiode (PD / APD) is shown 1020, with each pixel having a pitch 1022. Using a small PD with High Efficiency (HE) in this structure results in increased bandwidth, lower noise (Id), lower cross-talk between pixels, and can provide a higher variation in responses.

[0105] In these PPUF devices it should be appreciated that different colors of light can create different kinds of responses for true random numbers and generating unique identifiers (IDs) for hardware and / or software. Ultraviolet (UV), visible, and infrared light interact differently with materials and impact quantum efficiency. Thus, in at least one embodiment the PPUF devices can be simultaneously illuminated with different colors (wavelengths) to enhance variability.

[0106] Light polarization affects the response of photon-trapping photodetectors. The response varies due to differences in absorption, resonance behavior, material anisotropy, and structural design. Optimizing polarization sensitivity can enhance performance for applications in polarization-sensitive imaging, optical communication, and biosensing. Thus, in at least one embodiment the PPUF devices can be illuminated with one or more polarized light sources to enhance variability.

[0107] Acoustic vibrations in the substrate can significantly impact photontrapping photodetectors by modulating optical properties, deforming nanostructures, influencing charge transport, and inducing acousto-optic effects. These interactions can lead to fluctuations in detection efficiency, spectral response, and signal stability, which may need to be accounted for in precision applications, such as high-speed optical communication, quantum sensing, and optomechanical devices. Thus, in at least one embodiment the PPUF devices can be simultaneously driven by acoustic vibrations to enhance variability.

[0108] FIG. 11 illustrates plasmonic metal structures within a PD 1110 utilized for a PPUF device. In like manner to the use of photon-trapping structures that enhance light interaction within a device, carefully designed metallic nanostructures, known as plasmonic structures, can achieve similar effects.These structures manipulate light at the nanoscale by leveraging plasmonic resonance, which enhances optical and electromagnetic interactions within the material. By incorporating plasmonic structures into a device, it is possible to improve the performance and uniqueness of PPUFs, making them effective for ID and cryptographic applications. The figure depicts base layers 1012, upper layer 1014 over which are plasmonic metal structures 1016 so that incident photons undergo enhanced interaction 1018. It will be noted that the base and upper layers are light absorbing layers, such as may simply comprise multiple doped layers such p-doped, n-doped, i-doped (which is undoped), such as creating a P-l-N structure that absorbs light.

[0109] 6. Conclusion

[0110] The technology of this disclosure has the potential to enable on-chip unique ID generation to facilitate multi-level hardware protection. Two photodiodes with identical PT structures are connected in parallel, followed by transimpedance amplifiers and a voltage comparator to detect current differences, producing a random bit. A number of such photodiode pairs can be expanded into 1 D or 2D arrays, to generate complex random bit streams or QR codes for unique hardware IDs. As can be seen, the electromagnetic wave interaction variation is harvested in response to the variability in the PT hole patterning. The variation in the PT holes are not sufficient to allow harvesting of the dark performance using the device. The dimensions of PT holes are preferably comparable to the illumination wavelengths used, therefore, a slight variation in the PT holes will result in significant variation in device response. The disclosed photonic physically unclonable function devices are exploiting this EM wave interaction to generate unique random ID for a system, which is a feature essential for hardware security. It also generates true random numbers critical for cryptographic key creation, secure communication, and authentication protocols. The optical nature of the devices makes them more resilient to attacks that target traditional electronic PUFs.

[0111] From the description herein, it will be appreciated that the present disclosure encompasses multiple implementations of the technology which include, but are not limited to, the following:

[0112] A photonic physically unclonable function (PPLIF) apparatus, comprising: (a) multiple photodiodes configured with photon-trapping (PT) holes which increase the variability in the electromagnetic (EM) wave interaction; (b) allowing process-induced variations to arise during the production of said multiple photodiodes; (c) wherein said process-induced variations comprise edge roughness in the PT holes which result in EM wave interaction variations; (d) a detection circuit is coupled to the output of said multiple photodiodes, said detection circuit is configured to detect current flow differences between said multiple photodiodes and generate an associated digital output; and (e) wherein variability in the electromagnetic wave interaction in photon-trapping (PT) feature-equipped photodiodes define photonic physically unclonable functions (PPUFs) which enable hardware security features.

[0113] The apparatus of any preceding or following implementation, wherein said detection circuit comprises a sense amplifier.

[0114] The apparatus of any preceding or following implementation, wherein said multiple photodiodes comprises a pair of said photodiodes.

[0115] The apparatus of any preceding or following implementation, wherein as the dimensions of the PT holes are comparable to that of the illumination wavelength, so that the variability in the PT hole dimensions causes significant variation in the EM wave interaction,

[0116] The apparatus of any preceding or following implementation, wherein said PT holes comprise a plurality of holes.

[0117] The apparatus of any preceding or following implementation, wherein said PT holes are spaced at a specified PT hole period, which itself may be variable.

[0118] The apparatus of any preceding or following implementation, wherein variability of PT hole dimensions comprise variabilities in PT hole diameter and edge roughness.

[0119] The apparatus of any preceding or following implementation, wherein said multiple PT-equipped photodiodes are used in combination to generate one bit, wherein an array of these bits create a random bit array.

[0120] The apparatus of any preceding or following implementation, whereinrandom bit arrays may be transformed into any desired number base using digital conversion.

[0121] The apparatus of any preceding or following implementation, wherein said PT-equipped photodiodes allow generating true random numbers and generating unique identifiers (IDs) for hardware.

[0122] The apparatus of any preceding or following implementation, wherein said random bit arrays provide a mechanism for assigning a unique identity to a hardware device to prevent cloning.

[0123] The apparatus of any preceding or following implementation, wherein the apparatus utilizes optical process variations, and thus does not rely on electronic hardware manufacturing process variation which are subject to being breached in response to sufficient levels of prediction.

[0124] 7. General Scope of Embodiments

[0125] Embodiments of the technology of this disclosure may be described herein with reference to flowchart illustrations of methods and systems according to embodiments of the technology. Embodiments of the technology of this disclosure may also be described with reference to procedures, algorithms, steps, operations, formulae, or other computational depictions, which may be included within the flowchart illustrations or otherwise described herein. It will be appreciated that any of the foregoing may also be implemented as computer program instructions. In this regard, each block or step of a flowchart, and combinations of blocks (and / or steps) in a flowchart, as well as any procedure, algorithm, step, operation, formula, or computational depiction can be implemented by various means, such as hardware, firmware, and / or software including one or more computer program instructions embodied in computer-readable program code. As will be appreciated, any such computer program instructions may be executed by one or more computer processors, including without limitation a general purpose computer or special purpose computer, or other programmable processing apparatus to produce a machine, such that the computer program instructions which execute on the computer processor(s) or other programmable processing apparatus create means for implementing the function(s) specified.

[0126] Accordingly, blocks of the flowcharts, and procedures, algorithms, steps, operations, formulae, or computational depictions described herein support combinations of means for performing the specified function(s), combinations of steps for performing the specified function(s), and computer program instructions, such as embodied in computer-readable program code logic means, for performing the specified function(s). It will also be understood that each block of the flowchart illustrations, as well as any procedures, algorithms, steps, operations, formulae, or computational depictions and combinations thereof described herein, can be implemented by special purpose hardware-based computer systems which perform the specified function(s) or step(s), or combinations of special purpose hardware and computer-readable program code.

[0127] Furthermore, these computer program instructions, such as embodied in computer-readable program code, may also be stored in one or more computer-readable memory or memory devices that can direct a computer processor or other programmable processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory or memory devices produce an article of manufacture including instruction means which implement the function specified in the block(s) of the flowchart(s). The computer program instructions may also be executed by a computer processor or other programmable processing apparatus to cause a series of operational steps to be performed on the computer processor or other programmable processing apparatus to produce a computer- implemented process such that the instructions which execute on the computer processor or other programmable processing apparatus provide steps for implementing the functions specified in the block(s) of the flowchart(s), procedure (s) algorithm(s), step(s), operation(s), formula(e), or computational depiction(s).

[0128] It will further be appreciated that the terms "programming" or "program executable" as used herein refer to one or more instructions that can be executed by one or more computer processors to perform one or more functions as described herein. The instructions can be embodied in software, in firmware, or in a combination of software and firmware. The instructionscan be stored locally to the device in non-transitory media, or can be stored remotely such as on a server, or all or a portion of the instructions can be stored locally and remotely. Instructions stored remotely can be downloaded (pushed) to the device by user initiation, or automatically based on one or more factors.

[0129] It will further be appreciated that as used herein, the terms controller, microcontroller, processor, microprocessor, hardware processor, computer processor, central processing unit (CPU), and computer are used synonymously to denote a device capable of executing the instructions and communicating with input / output interfaces and / or peripheral devices, and that the terms controller, microcontroller, processor, microprocessor, hardware processor, computer processor, CPU, and computer are intended to encompass single or multiple devices, single core and multicore devices, and variations thereof.

[0130] From the description herein, it will be appreciated that the present disclosure encompasses multiple implementations of the technology which include, but are not limited to, the following:

[0131] A photonic physically unclonable function (PPUF) apparatus, comprising: (a) multiple photodiodes in an array, each photodiode of said multiple photodiodes configured with photon-trapping (PT) holes which increase variability of electromagnetic (EM) wave interaction; (b) wherein process-induced variations are allowed to arise during the production of said multiple photodiodes; (c) wherein said process-induced variations comprise edge roughness in the PT holes which result in EM wave interaction variations; (d) a detection circuit is coupled to the output of said multiple photodiodes, said detection circuit is configured to detect current flow differences between said multiple photodiodes and generate an associated digital output, or outputs; and (e) wherein variability in the electromagnetic wave interaction in photon-trapping (PT) feature-equipped photodiodes define photonic physically unclonable functions (PPUFs) which enable hardware security features.

[0132] A photonic physically unclonable function (PPUF) apparatus, comprising: (a) multiple photodiodes in an array, each photodiode of saidmultiple photodiodes configured with a plurality of photon-trapping (PT) holes which increase variability of electromagnetic (EM) wave interaction; (b) wherein as the dimensions of the PT holes are comparable to that of the illumination wavelength, so that the variability in the PT hole dimensions causes significant variation in the EM wave interaction, and wherein said PT holes are spaced at a specified PT hole period; (c) wherein process-induced variations are allowed to arise during the production of said multiple photodiodes; (d) wherein said process-induced variations comprise edge roughness in the PT holes which result in EM wave interaction variations; (e) a detection circuit is coupled to the output of said multiple photodiodes, said detection circuit is configured to detect current flow differences between said multiple photodiodes and generate an associated digital output, or outputs; (f) wherein variability in the electromagnetic wave interaction in photon-trapping (PT) feature-equipped photodiodes define photonic physically unclonable functions (PPUFs) which enable hardware security features; and (g) wherein said multiple PT-equipped photodiodes are configured for being utilized in combination to generate one bit, wherein an array of these bits create a random bit array.

[0133] The apparatus of any preceding implementation, wherein said detection circuit comprises a sense amplifier.

[0134] The apparatus of any preceding implementation, wherein said multiple photodiodes comprises a pair of said photodiodes.

[0135] The apparatus of any preceding implementation, wherein as the dimensions of the PT holes are comparable to that of the illumination wavelength, so that the variability in the PT hole dimensions causes significant variation in the EM wave interaction.

[0136] The apparatus of any preceding implementation, wherein said PT holes comprise a plurality of holes.

[0137] The apparatus of any preceding implementation, wherein said PT holes are spaced at a specified PT hole period, which itself may be variable.

[0138] The apparatus of any preceding implementation, wherein variability of PT hole dimensions comprise variabilities in PT hole diameter and edge roughness.

[0139] The apparatus of any preceding implementation, wherein said multiple PT-equipped photodiodes are used in combination to generate one bit, wherein an array of these bits create a random bit array.

[0140] The apparatus of any preceding implementation, wherein random bit arrays may be transformed into any desired number base using digital conversion.

[0141] The apparatus of any preceding implementation, wherein said PT- equipped photodiodes allow generating true random numbers and generating unique identifiers (IDs) for hardware.

[0142] The apparatus of any preceding implementation, wherein said random bit arrays provide a mechanism for assigning a unique identity to a hardware device to prevent cloning.

[0143] The apparatus of any preceding implementation, wherein said random bit arrays generate true random numbers critical for cryptographic key creation, secure communication, and authentication protocols.

[0144] The apparatus of any preceding implementation, wherein the apparatus utilizes optical process variations, and thus does not rely on electronic hardware manufacturing process variation which are subject to being breached in response to sufficient levels of prediction.

[0145] The apparatus of any preceding implementation, further comprising introducing photon-trapping surface features toward increasing variability in sensitivity to illuminating light.

[0146] The apparatus of any preceding implementation, further comprising incorporating one or more direction of arrival sensitive asymmetric surface features toward increasing variability in sensitivity to illuminating light.

[0147] The apparatus of any preceding implementation, further comprising incorporating one or more polarization-sensitive meta-surfaces toward increasing variability in sensitivity to illuminating light.

[0148] The apparatus of any preceding implementation, further comprising incorporating one or more plasmonic surface features toward increasing variability in sensitivity to illuminating light.

[0149] The apparatus of any preceding implementation, further comprising incorporating one or more direction of arrival sensitive asymmetric plasmonicsurface features to capture the variation in the incidence direction and harvest the randomness.

[0150] The apparatus of any preceding implementation, wherein operational wavelength range is set in the range from 400 nm to 2500 nm in response to fabricating the PDs by selecting properties from group IV elemental semiconductors and group lll-V and group ll-VI compound semiconductors.

[0151] The apparatus of any preceding implementation, wherein said elemental semiconductors are selected from the group of material consisting of Si and Ge.

[0152] The apparatus of any preceding implementation, wherein said semiconductor composites selected from the group of materials consisting of SiGe, GeSn, and SiSn.

[0153] The apparatus of any preceding implementation, wherein illumination is provided using different wavelengths of light and / or light polarization toward enhancing a true random nature in generating unique identifiers (IDs).

[0154] The apparatus of any preceding implementation, further comprising providing acoustic excitations and / or mechanical vibration on said multiple photodiodes to enhance randomness in variability of electromagnetic (EM) wave interaction.

[0155] As used herein, the term "implementation" is intended to include, without limitation, embodiments, examples, or other forms of practicing the technology described herein.

[0156] As used herein, the singular terms "a," "an," and "the" may include plural referents unless the context clearly dictates otherwise. Reference to an object in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more."

[0157] Phrasing constructs, such as “A, B and / or C”, within the present disclosure describe where either A, B, or C can be present, or any combination of items A, B and C. Phrasing constructs indicating, such as “at least one of” followed by listing a group of elements, indicates that at least one of these groups of elements is present, which includes any possible combination of the listed elements as applicable.

[0158] References in this disclosure referring to “an embodiment”, “at leastone embodiment” or similar embodiment wording indicates that a particular feature, structure, or characteristic described in connection with a described embodiment is included in at least one embodiment of the present disclosure. Thus, these various embodiment phrases are not necessarily all referring to the same embodiment, or to a specific embodiment which differs from all the other embodiments being described. The embodiment phrasing should be construed to mean that the particular features, structures, or characteristics of a given embodiment may be combined in any suitable manner in one or more embodiments of the disclosed apparatus, system, or method.

[0159] As used herein, the term "set" refers to a collection of one or more objects. Thus, for example, a set of objects can include a single object or multiple objects.

[0160] Relational terms such as first and second, top and bottom, upper and lower, left and right, and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0161] The terms "comprises," "comprising," "has", "having," "includes", "including," "contains", "containing" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, apparatus, or system, that comprises, has, includes, or contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, apparatus, or system. An element proceeded by "comprises . . . a", "has . . . a", "includes . . . a", "contains . . . a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, apparatus, or system, that comprises, has, includes, contains the element.

[0162] As used herein, the terms "approximately", "approximate", "substantially", "substantial", "essentially", and "about", or any other version thereof, are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. When usedin conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ± 10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1 %, less than or equal to ±0.5%, less than or equal to ±0.1 %, or less than or equal to ±0.05%. For example, "substantially" aligned can refer to a range of angular variation of less than or equal to ±10°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1 °, less than or equal to ±0.5°, less than or equal to ±0.1 °, or less than or equal to ±0.05°.

[0163] Additionally, amounts, ratios, and other numerical values may sometimes be presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. For example, a ratio in the range of about 1 to about 200 should be understood to include the explicitly recited limits of about 1 and about 200, but also to include individual ratios such as about 2, about 3, and about 4, and sub-ranges such as about 10 to about 50, about 20 to about 100, and so forth.

[0164] The term "coupled" as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is "configured" in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[0165] Benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of the technology described herein or any or all the claims.

[0166] In addition, in the foregoing disclosure various features may be grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than areexpressly recited in each claim. Inventive subject matter can lie in less than all features of a single disclosed embodiment.

[0167] The abstract of the disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0168] It will be appreciated that the practice of some jurisdictions may require deletion of one or more portions of the disclosure after the application is filed. Accordingly, the reader should consult the application as filed for the original content of the disclosure. Any deletion of content of the disclosure should not be construed as a disclaimer, forfeiture, or dedication to the public of any subject matter of the application as originally filed.

[0169] All text in a drawing figure is hereby incorporated into the disclosure and is to be treated as part of the written description of the drawing figure.

[0170] The following claims are hereby incorporated into the disclosure, with each claim standing on its own as a separately claimed subject matter.

[0171] Although the description herein contains many details, these should not be construed as limiting the scope of the disclosure, but as merely providing illustrations of some of the presently preferred embodiments. Therefore, it will be appreciated that the scope of the disclosure fully encompasses other embodiments which may become obvious to those skilled in the art.

[0172] All structural and functional equivalents to the elements of the disclosed embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed as a "means plus function" element unless the element is expressly recited using the phrase "means for". No claim element herein is to be construed as a "step plus function" element unless the element is expressly recited using the phrase "step for".Table 1Current Quantile PlotTable 2NIST Statistical Test Suite for Random / Pseudorandom Number Generators

Claims

CLAIMSWhat is claimed is:1 . A photonic physically unclonable function (PPLIF) apparatus, comprising:(a) multiple photodiodes in an array, each photodiode of said multiple photodiodes configured with photon-trapping (PT) holes which increase variability of electromagnetic (EM) wave interaction;(b) wherein process-induced variations are allowed to arise during the production of said multiple photodiodes;(c) wherein said process-induced variations comprise edge roughness in the PT holes which result in EM wave interaction variations;(d) a detection circuit is coupled to the output of said multiple photodiodes, said detection circuit is configured to detect current flow differences between said multiple photodiodes and generate an associated digital output, or outputs; and(e) wherein variability in the electromagnetic wave interaction in photontrapping (PT) feature-equipped photodiodes define photonic physically unclonable functions (PPUFs) which enable hardware security features.

2. The apparatus of claim 1 , wherein said detection circuit comprises a sense amplifier.

3. The apparatus of claim 1 , wherein said multiple photodiodes comprises a pair of said photodiodes.

4. The apparatus of claim 1 , wherein as the dimensions of the PT holes are comparable to that of the illumination wavelength, so that the variability in the PT hole dimensions causes significant variation in the EM wave interaction.

5. The apparatus of claim 1 , wherein said PT holes comprise a plurality of holes.

6. The apparatus of claim 1 , wherein said PT holes are spaced at a specified PT hole period, which itself may be variable.

7. The apparatus of claim 1 , wherein variability of PT hole dimensions comprise variabilities in PT hole diameter and edge roughness.

8. The apparatus of claim 1 , wherein said multiple PT-equipped photodiodes are used in combination to generate one bit, wherein an array of these bits create a random bit array.

9. The apparatus of claim 1 , wherein random bit arrays may be transformed into any desired number base using digital conversion.

10. The apparatus of claim 1 , wherein said PT-equipped photodiodes allow generating true random numbers and generating unique identifiers (IDs) for hardware.11 . The apparatus of claim 1 , wherein said random bit arrays provide a mechanism for assigning a unique identity to a hardware device to prevent cloning.

12. The apparatus of claim 1 , wherein said random bit arrays generate true random numbers critical for cryptographic key creation, secure communication, and authentication protocols.

13. The apparatus of claim 1 , wherein the apparatus utilizes optical process variations, and thus does not rely on electronic hardware manufacturing process variation which are subject to being breached in response to sufficient levels of prediction.

14. The apparatus of claim 1 , further comprising introducing photontrapping surface features toward increasing variability in sensitivity to illuminating light.

15. The apparatus of claim 1 , further comprising incorporating one or more direction of arrival sensitive asymmetric surface features toward increasing variability in sensitivity to illuminating light.

16. The apparatus of claim 1 , further comprising incorporating one or more polarization-sensitive meta-surfaces toward increasing variability in sensitivity to illuminating light.

17. The apparatus of claim 1 , further comprising incorporating one or more plasmonic surface features toward increasing variability in sensitivity to illuminating light.

18. The apparatus of claim 1 , further comprising incorporating one or more direction of arrival sensitive asymmetric plasmonic surface features to capture the variation in the incidence direction and harvest the randomness.

19. The apparatus of claim 1 , wherein operational wavelength range is set in the range from 400 nm to 2500 nm in response to fabricating the PDs by selecting properties from group IV elemental semiconductors and group lll-V and group ll-VI compound semiconductors.

20. The apparatus of claim 19, wherein said elemental semiconductors are selected from the group of material consisting of Si and Ge.21 . The apparatus of claim 19, wherein said semiconductor composites selected from the group of materials consisting of SiGe, GeSn, and SiSn.

22. The apparatus of claim 1 , wherein illumination is provided using different wavelengths of light and / or light polarization toward enhancing a true random nature in generating unique identifiers (IDs).

23. The apparatus of claim 1 , further comprising providing acoustic excitations and / or mechanical vibration on said multiple photodiodes to enhancerandomness in variability of electromagnetic (EM) wave interaction.

24. A photonic physically unclonable function (PPLIF) apparatus, comprising:(a) multiple photodiodes in an array, each photodiode of said multiple photodiodes configured with a plurality of photon-trapping (PT) holes which increase variability of electromagnetic (EM) wave interaction;(b) wherein as the dimensions of the PT holes are comparable to that of the illumination wavelength, so that the variability in the PT hole dimensions causes significant variation in the EM wave interaction, and wherein said PT holes are spaced at a specified PT hole period;(c) wherein process-induced variations are allowed to arise during the production of said multiple photodiodes;(d) wherein said process-induced variations comprise edge roughness in the PT holes which result in EM wave interaction variations;(e) a detection circuit is coupled to the output of said multiple photodiodes, said detection circuit is configured to detect current flow differences between said multiple photodiodes and generate an associated digital output, or outputs;(f) wherein variability in the electromagnetic wave interaction in photontrapping (PT) feature-equipped photodiodes define photonic physically unclonable functions (PPUFs) which enable hardware security features; and(g) wherein said multiple PT-equipped photodiodes are configured for being utilized in combination to generate one bit, wherein an array of these bits create a random bit array.

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