Printed physical unclonable function pattern
Patent Information
- Application Number
- JP2022036251
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-04-12
- Filing Date
- 2022-03-09
- Publication Date
- 2025-03-18
- Estimated Expiration
- 2042-03-09
AI Technical Summary
Current methods for producing Physical Uncloneable Functions (PUFs) are expensive and require specialized equipment, making them economically unviable for widespread use, and their detection is not accessible to distributors and end users.
A method involving applying a clearcoat layer to a substrate, forming random microstructures through drying, and dispensing a printing fluid to fill these structures, creating a high-resolution PUF pattern that can be authenticated using widely available devices like cell phone cameras.
The method produces low-cost, high-resolution PUFs that are difficult to replicate and can be authenticated with common equipment, enhancing security and accessibility.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure generally relates to anti-counterfeiting, and more specifically, to methods and apparatuses for printing physical unclonable function patterns.
Background Art
[0002] A physical unclonable function (PUF) is a unique random physical pattern that can be used for anti-counterfeiting. A PUF can be very difficult and costly to clone and can be manufactured by a probabilistic process that yields a large number of robust tags. The PUF pattern can be designed to be readable with appropriate analysis tools. The PUF pattern can be recorded and stored for verification. A PUF can be used to prevent counterfeiting, prevent replacement of parts within an assembly, ensure proper management, and function as an uncopyable digital signature.
[0003] Current methods for generating PUFs can be costly to manufacture and may not be cost-effective for widespread use. Some examples of these expensive methods can include PUFs integrated with unique markers that include special optical signatures (e.g., absorption or emission at specific wavelengths or combinations of wavelengths), or the creation of random distributions of nanostructures (e.g., nanoparticles, quantum dots, or self-assembling molecules). Further, the detection of these types of PUFs may require special analytical equipment that is not readily available to vendors and end-users.
Summary of the Invention
[0004] A method for printing physically hard-to-replicate functions (PUFs) and a non-temporary computer-readable medium are provided according to embodiments illustrated herein. One disclosed feature of an embodiment is a method comprising: applying a clear coat layer to a substrate; drying the clear coat layer to form random microstructures on the clear coat layer; dispensing a printing fluid to print a graphic pattern onto the clear coat layer; and generating a physically hard-to-replicate function (PUF) pattern by drying the printing fluid that fills the random microstructures formed on the clear coat layer.
[0005] Another disclosed feature of the embodiment is a non-temporary computer-readable medium storing a plurality of instructions, which, when executed by a processor, causes the processor to perform the following actions: applying a clear coat layer to a substrate; drying the clear coat layer to form random microstructures on the clear coat layer; dispensing a printing fluid to print a graphic pattern onto the clear coat layer; and generating a physically hard-to-replicate function (PUF) pattern by drying the printing fluid that fills the random microstructures formed on the clear coat layer.
[0006] Another disclosed feature is a method for authenticating a printed PUF. This method includes capturing an image of a printed physically hard-to-replicate function (PUF) on a substrate with a camera on a mobile device, wherein the PUF is formed on the substrate using a printing fluid dispensed into a clear coat, and the clear coat is dried to form a random microstructure filled with the printing fluid; comparing the image with an image stored on a server; and authenticating the substrate when the image of the PUF matches an image stored on the server. [Brief explanation of the drawing]
[0007] The teachings of this disclosure can be easily understood by considering the embodiments for carrying out the following invention in conjunction with the following accompanying drawings.
[0008] [Figure 1]An exemplary block diagram of a PUF in this disclosure is shown.
[0009] [Figure 2] This disclosure shows a close-up of the PUF.
[0010] [Figure 3] A block diagram of an exemplary apparatus for generating the PUF of this disclosure is shown.
[0011] [Figure 4] A block diagram of an exemplary system for authenticating the PUF of this disclosure is shown.
[0012] [Figure 5] A flowchart of the method for printing the PUF of this disclosure is shown.
[0013] [Figure 6] A flowchart of the method for authenticating the printed PUF in this disclosure is shown.
[0014] [Figure 7] This specification shows an exemplary high-level block diagram of a computer suitable for use when performing the functions described herein.
[0015] To facilitate understanding, whenever possible, the same reference number is used to indicate the same element common to the drawings. [Modes for carrying out the invention]
[0016] This disclosure broadly discloses methods and apparatus for printing physically hard-to-replicate function (PUF) patterns. As described above, current methods for generating PUFs are expensive to manufacture and may not be economically viable for widespread use. Some examples of these expensive methods may involve PUFs integrated with unique markers containing special optical signatures (e.g., absorption or emission at specific wavelengths or combinations of wavelengths), or the creation of random distributions of nanostructures (e.g., nanoparticles, quantum dots, or self-assembled molecules). Furthermore, detection of these types of PUFs may require specialized analytical instruments that are not readily available to vendors and end-users.
[0017] Several low-cost methods using printing are available. For example, an ink-edge anti-counterfeiting method has been developed that uses blowing and pressing after printing to create a random structure on the ink edge. However, printing using ink alone results in a lower resolution that is easier to duplicate, reducing the security of the PUF.
[0018] Embodiments of this disclosure provide a low-cost printable PUF while offering high resolution that makes duplication difficult. In one embodiment, a primary clear coat may be applied to a substrate. The clear coat can be dried to form random cracks in the coat on the substrate. Ink can be dispensed onto the dried primary clear coat. The ink can fill the random cracks formed in the coat to produce a PUF.
[0019] The Printed Printed Forms (PUFs) of this Disclosure can also be authenticated using widely available equipment. For example, an image of the PUF can be captured for authentication using a camera on a mobile phone or mobile device. Therefore, no special equipment is required to authenticate the printed PUFs of this Disclosure.
[0020] Figure 1 shows an exemplary document 100 that includes a Physically Unclonable Function (PUF) 108 generated via the printing process of the present disclosure. In one embodiment, the PUF 108 is shown as being printed on the document 100, although the PUF 108 can be printed on any surface including, for example, the surface of a package, component, device, or housing.
[0021] In one embodiment, the document 100 can include a substrate 102. The substrate 102 can be any other type of surface capable of receiving a printing fluid used to print the clear coat layer 104 and the pattern 106, such as paper, cardboard, plastic, or the like. In one embodiment, the clear coat layer 104 can include a colloidal mixture of fluid and solid particles. For example, the fluid can be a solvent or water. The solid particles can include silica or other types of polymers. In one embodiment, the clear coat layer 104 can also use a nanoparticle colloidal mixture, sol-gel solution, polymer solution, polymer blend, or the like.
[0022] In one embodiment, the clear coat layer 104 can be a commercially available colloidal mixture of water and silica containing 30 weight percent to 50 weight percent silica. In one embodiment, the clear coat layer 104 can include 34 weight percent silica. In one embodiment, the clear coat layer 104 can include 50 weight percent silica.
[0023] In one embodiment, the printing fluid is dispensed onto the clear coat layer 104 to form the pattern 106 of the PUF(s) 1081 - 108 (hereinafter also individually referred to as PUF 108 or collectively referred to as PUF 108). The pattern 106 of the PUF 108 is shown as a series of dots, but note that any pattern 106 can be printed. For example, the pattern 106 can be a barcode, a Quick Response (QR) code, or a pattern of different shapes (e.g., square, rectangle, ellipse, irregular shape, etc.). n
[0024] In one embodiment, any type of clear coat layer 104 that can adhere to the substrate 102 can be used. In one embodiment, any type of printing fluid compatible with the clear coat layer 104 can be used. In other words, the printing fluid should be able to adhere to the clear coat layer 104 and dry to produce a pattern 106.
[0025] In one embodiment, PUF108 can be printed to have a small width of about 50 micrometers or a diameter of 110. Therefore, the method can be used to print relatively small PUF108 using commercially available compounds. Furthermore, PUF108 can be analyzed or authenticated using widely available equipment (e.g., a mobile phone camera). Thus, the method of the present disclosure provides PUF108 that is difficult to counterfeit while maintaining a relatively low cost for printing PUF108.
[0026] Figure 2 shows an enlarged view of an exemplary PUF108. In one embodiment, the clear coat layer 104 is dispensed and dried to form random microstructures 1101-110 11 These can form (hereinafter referred to individually as random microstructures 110, or collectively as microstructures 110). Random microstructures 110 may be cracks formed in the clear coat layer 104 due to drying.
[0027] In one embodiment, the resolution of the cracks or random microstructures 110 can be controlled by the thickness of the clear coat layer 104. For example, if the resolution is too high (e.g., fewer large microstructures 110), the random microstructures 110 may be too easily copied through the printing process alone. If the resolution is too low (e.g., many smaller microstructures 110), the random microstructures 110 may be too small to be analyzed using images captured by a standard red, green, and blue (RGB) camera on a mobile device (e.g., a mobile phone camera).
[0028] In one embodiment, the thickness of the clear coat layer 104 can be controlled by the amount of clear coat layer 104 dispensed through the printer's print head. In one embodiment, the thickness of the clear coat layer 104 can be controlled by the spin rate of the spin coating process. For example, the clear coat layer 104 can be spun on the substrate 102 at 100 revolutions per minute (RPM) to 5000 RPM. In one embodiment, the clear coat layer 104 can be spun on the substrate 102 at 500 RPM to 3000 RPM.
[0029] While the spin coating process is described above, it should be noted that other coating methods may be used. For example, the clear coat layer 104 may be applied using methods such as drawdown coating or aerosol spraying.
[0030] In one embodiment, the resolution of the random microstructure 110 may be such that the random microstructure 110 has a length 112 and a width 114 of several hundred micrometers. In one embodiment, the random microstructure 100 may have a length 112 of 20 to 70 micrometers and a width 114 of 3 to 9 micrometers. In one embodiment, the thickness of the clear coat layer 104 to achieve the desired resolution of the random microstructure 110 may be about 5 nanometers (nm) to 100 nm for the nanoparticle colloid coating. The thickness may vary depending on the type of other material. For example, the thickness of the clear coat layer 104 may be 5 nm to 10 micrometers for a polymer coating.
[0031] In one embodiment, the printing fluid can be dispensed onto the clear coat layer 104 as described above. The printing fluid can fill random microstructures 110 formed within the clear coat layer 104. The image formed by the combination of the printing fluid in the random microstructures 110 and the printing fluid at specific locations on the clear coat layer 104 can form a PUF 108. In other words, in the example shown in Figure 2, the PUF 1081 may include printing dots and random microstructures 1101 and 1102 filled with printing fluid.
[0032] The arrangement and size of random microstructures 1103 and 1104 may differ from the arrangement and size of random microstructures 1101 and 1102 of PUF1081, so PUF1082 may differ from PUF1081. PUF1083 and PUF1084 may also differ from random microstructures 1105-1108 and 1109-110, respectively. 11 They may have their own unique arrangement, number, and size. In other words, each PUF 108 in pattern 106 may be unique or different due to random microstructures 110 generated at different positions along the surface of the clear coat layer 104.
[0033] Figure 3 shows an exemplary apparatus 300 that may be used to print the PUF 108 of the present disclosure. In one embodiment, the apparatus 300 may be a printer including a plurality of print heads 304 and 306. The print heads 304 and 306 may be used to dispense different fluids. For example, a storage container 308 may store the clear coat dispensed via the print head 304. A storage container 310 may store the printing fluid dispensed via the print head 306.
[0034] In one embodiment, the processor 302 is communicatively coupled to the print heads 304 and 306 to control the dispensing of the clear coat and printing fluid. In one embodiment, the substrate 102 may pass under the print heads 304 and 306, or the print heads 304 and 306 may move over the substrate 102.
[0035] In one embodiment, the processor 302 can control the print head 304 to dispense the clear coat and form a clear coat layer 104 on the substrate 102. As described above, the clear coat can be dispensed to form a clear coat layer 104 of a desired thickness. The print head 304 can dispense the clear coat by passing over the substrate 102 multiple times.
[0036] The substrate 102 having the clear coat layer 104 can be dried by moving it to a drying device, an oven, or by air drying to dry the clear coat layer 104. Drying the clear coat layer 104 can generate random microstructures 110 within the clear coat layer 104.
[0037] After the clear coat layer 104 has dried, the substrate 102 can be placed under the print heads 304 and 306. The processor 302 can then control the print heads 306 to dispense the printing fluid and print the pattern 106 onto the clear coat layer 104. The printing fluid can fill the area around where the printing fluid is dispensed with random microstructures 110. The printing fluid can then be dried to form a PUF 108.
[0038] It should be noted that the apparatus 300 has been simplified for the sake of clarity and may include additional components not shown. For example, the apparatus 300 may include motors for moving the print heads 304 and 306, memory for storing instructions, a power supply, and other electrical components.
[0039] Figure 3 shows printing the PUF 108 with a single printer or device 300, but it should be noted that the PUF 108 can be printed using different devices. For example, the clear coat layer 104 can be spin-coated onto the substrate 102 via a spin coater. In addition, an oven can be used to dry the dispensed clear coat layer 104 and the printing fluid.
[0040] Examples 1 to 3 below provide examples having process parameters for printing the PUF108 of the present disclosure.
[0041] Example 1:
[0042] A 34 wt percent colloidal silica solution was obtained by suspension in deionized water, and a clear coat layer 104 was formed. The colloidal silica solution was applied to a cardboard substrate by spin-coating at 500 RPM for 1 minute. The clear coat layer 104 was dried in an oven at 60 degrees Celsius (°C) for 1 hour. A pattern was printed on the dried clear coat layer 104 using aqueous graphic ink. A Dimatix DMP2800 printer was used to dispense the ink and produce a 600 × 600 dots / inch (dpi) pattern under the following conditions: droplet mass = 4.5–4.8 nanograms (ng), droplet velocity = 6–7 meters / second, frequency = 5 kilohertz, print head temperature = ambient temperature ~40°C, and voltage = 16–20 volts. The ink was dried in an oven at 120°C or higher for 10 minutes.
[0043] Example 2:
[0044] A 34 wt percent colloidal silica solution was obtained by suspension in deionized water, and a clear coat layer 104 was formed. The colloidal silica solution was applied to a cardboard substrate by spin coating at 3000 RPM for 1 minute. The clear coat layer 104 was dried in an oven at 60 degrees Celsius (°C) for 1 hour. A pattern was printed on the dried clear coat layer 104 using aqueous graphic ink. A Dimatix DMP2800 printer was used to dispense the ink and generate a 600 × 600 dots / inch (dpi) pattern under the following conditions: droplet mass = 4.5–4.8 nanograms (ng), droplet velocity = 6–7 meters / second, frequency = 5 kilohertz, print head temperature = ambient temperature ~40°C, and voltage = 16–20 volts. The ink was dried in an oven at 120°C or higher for 10 minutes.
[0045] Example 3:
[0046] A 50 wt percent colloidal silica solution was obtained by suspension in deionized water, and a clear coat layer 104 was formed. The colloidal silica solution was applied to a cardboard substrate by spin-coating at 500 RPM for 1 minute. The clear coat layer 104 was dried in an oven at 60 degrees Celsius (°C) for 1 hour. A pattern was printed on the dried clear coat layer 104 using aqueous graphic ink. A Dimatix DMP2800 printer was used to dispense the ink and produce a 600 × 600 dots / inch (dpi) pattern under the following conditions: droplet mass = 4.5–4.8 nanograms (ng), droplet velocity = 6–7 meters / second, frequency = 5 kilohertz, print head temperature = ambient temperature ~40°C, and voltage = 16–20 volts. The ink was dried in an oven at 120°C for 10 minutes.
[0047] The above embodiment was found to form PUF108 with the desired resolution. The random microstructure 110 in the clear coat layer 104 was measured to obtain a width of 3 to 9 micrometers and a length of 20 to 70 micrometers.
[0048] Figure 4 shows a block diagram of the system 400 used to authenticate the PUF108 of this disclosure. As described above, the printed PUF108 can be made available devices to be used to authenticate the PUF108. In other words, expensive specialized equipment is not required to authenticate the PUF108 of this disclosure.
[0049] In one embodiment, the system 400 may include a mobile device 420 including a camera 422. The mobile device 420 may be a cellphone, mobile telephone, smartphone, tablet, notebook PC, etc. In other words, images can be captured using any device having an image capture device.
[0050] An end user may receive a document printed on substrate 402 and wish to authenticate the document. The end user can capture an image 424 of the PUF 408 printed on substrate 402. The PUF 408 can be printed or formed in the same manner as the PUF 108 can be printed or formed, as described above.
[0051] In Figure 4, PUF408 is shown as a barcode. As described above, PUF408 can be any pattern (e.g., a barcode, QR code, or a pattern of shapes). PUF408 may contain various random microstructures 410 located at different positions and on different lines of the barcode. PUF408 can be formed by dispensing a printing fluid or ink onto a dry clear coat layer 404 and filling the random microstructures 410 with the printing fluid.
[0052] In one embodiment, the image of the PUF 408 may be captured after it has been printed during manufacturing. The image may be stored as a stored image 430 in a database (DB) 428 on network 432. Network 432 may be an Internet Protocol (IP) network.
[0053] To authenticate a document printed on a substrate 402, a mobile device 420 can transmit the captured image 424 to an application server (AS) 426 via a network 432. The AS 426 can access the stored image 430 in a database 428. The AS 426 can compare the captured image 424 with the stored image 430. If a match is found, the AS 426 can send a notification to the mobile device 420 that the document has been authenticated. If no match is found, the AS 426 can send a notification to the mobile device 420 that the document is not authentic. Thus, the printed PUF 408 may enable relatively inexpensive and widely available equipment to be used to authenticate the printed PUF 408 of this disclosure.
[0054] Figure 5 shows a flowchart of an exemplary method 500 for printing the PUF of the present disclosure. In one embodiment, method 500 may be performed by apparatus 300 or by apparatus such as apparatus 700, which is illustrated in Figure 7 and discussed below.
[0055] In one embodiment, Method 500 begins in block 502. In block 504, Method 500 applies a clear coat layer onto the substrate. The clear coat layer may be any type of colloidal suspension of solid fine particles compatible with the substrate. For example, the colloidal suspension must be able to adhere to the substrate. An example of a colloidal suspension is silica particles suspended in deionized water.
[0056] In one embodiment, the clear coat layer may be applied via a spin coating process, a drawdown coating method, aerosol spraying, or the like. In one embodiment, the clear coat layer may be applied via a printer. The clear coat layer may be applied to a desired thickness to obtain a desired resolution of the microstructure formed in the clear coat layer, as described below.
[0057] In block 506, method 500 dries a clear coat layer to form a random microstructure in the clear coat layer. The random microstructure may include microcracks formed in the clear coat layer when it is dried. The random microstructure may have different shapes, arrangements, and sizes. An exemplary desired resolution of the random microstructure may include microstructures having a width of 3 to 9 micrometers and a length of 20 to 70 micrometers.
[0058] In block 508, method 500 involves dispensing a printing fluid to print a graphic pattern onto a clear coat layer. The printing fluid may be an aqueous graphic ink. Any type of ink can be used that is compatible with the clear coat layer and can adhere to the clear coat layer to print the desired pattern on the PUF. The printing fluid may be filled into random microstructures around the locations where the printing fluid is dispensed onto the clear coat layer.
[0059] In block 510, method 500 generates a physically difficult-to-replicate function (PUF) pattern by drying a printing fluid that fills random microstructures formed within a clear coat layer. For example, the printing fluid may be dried, and the resulting image of the dispensed printing fluid and the printing fluid within the random microstructures may form a PUF pattern. In block 512, method 500 concludes.
[0060] Figure 6 shows a flowchart of an exemplary method 600 for authenticating a printed PUF of the present disclosure. In one embodiment, method 600 may be performed by system 400 or by an apparatus such as apparatus 700 illustrated in Figure 7 and discussed below.
[0061] In one embodiment, Method 600 begins in block 602. In block 604, Method 600 captures an image of a print-physically hard-to-replicate function (PUF) on a substrate using the camera of a mobile device, the PUF being formed on the substrate using a printing fluid dispensed into a clear coat, the clear coat drying to form a random microstructure filled with the printing fluid. In one embodiment, the mobile device may be a cell phone, mobile phone, smartphone, tablet computer, notebook PC, etc. In other words, any type of device with a camera can be used to capture an image of the PUF for authentication.
[0062] Printed PUFs can be formed via random microstructures formed in a clear coat layer dispensed onto a substrate. A printing fluid can be dispensed onto the clear coat, filling the clear coat layer with random microstructures. The resolution of the PUF can be controlled via the material used for the clear coat and the thickness of the clear coat layer, as described above.
[0063] In block 606, method 600 compares the image with an image stored on a server. For example, when a PUF is formed, an image of a printed PUF can be captured. The image may be stored in a database on the network. The database may be managed by an authentication service or the company that printed the PUF. The image captured by the mobile device can be compared with the image stored in the database to determine if a match is found.
[0064] In block 608, method 600 authenticates the substrate when the image of the PUF matches an image stored on the server. If a match is found, the substrate can be authenticated. For example, a mobile device that has captured an image of the printed PUF may receive a message or notification that the substrate has been authenticated. In block 610, method 600 terminates.
[0065] Figure 7 depicts a high-level block diagram of a computer dedicated to performing the functions described herein. As depicted in Figure 7, the computer 700 comprises one or more hardware processor elements 702 (e.g., a central processing unit (CPU), a microprocessor, or a multicore processor), memory 704 (e.g., random access memory (RAM) and / or read-only memory (ROM)), a module 705 for printing a PUF, and various input / output devices 706 (e.g., storage devices including, but not limited to, tape drives, floppy drives, hard disk drives, or compact disk drives, receivers, transmitters, speakers, displays, speech synthesizers, output ports, input ports, and user input devices (keyboards, keypads, mice, microphones, etc.)). Note that although only one processor element is shown, a computer may employ multiple processor elements.
[0066] It should be noted that this disclosure may be implemented in software and / or in combination of software and hardware, for example, using computer-readable instructions that may be used to configure a hardware processor to perform the steps, functions, and / or operations of the disclosed method, including, for example, application-specific integrated circuits (ASICs), programmable logic arrays (PLAs) including field-programmable gate arrays (FPGAs), or state machines, computers, or any other hardware equivalents deployed on hardware devices. In one embodiment, instructions and data for the module or process 705 for printing a PUF (e.g., a software program including computer-executable instructions) are loaded into memory 704 and executed by a hardware processor element 702 to implement the steps, functions, or operations discussed above. Furthermore, when a hardware processor executes instructions and performs an "action," this may include the hardware processor performing the action directly and / or facilitating, directing, or cooperating with another hardware device or component (such as a coprocessor) to perform an action.
[0067] A processor that executes computer-readable instructions or software instructions related to the above method may be recognized as a programmed processor or a specialized processor. Thus, the module 705 (including the corresponding data structure) for printing the PUF of the present disclosure may be stored in a tangible or physical (broadly speaking, non-temporary) computer-readable storage device or medium, such as volatile memory, non-volatile memory, ROM memory, RAM memory, magnetic or optical drives, devices, or diskettes. More specifically, the computer-readable storage device may comprise any physical device that provides the ability to store information such as data and / or instructions accessed by a processor or computing device such as a computer or application server.
[0068] It will be understood that variations of those disclosed above, as well as other features and functions, or substitutes thereof, may be combined into many other different systems or applications. Various currently unforeseen or unprecedented substitutes, modifications, variations, or improvements may subsequently be made by those skilled in the art, and these are also intended to be covered by the following claims.
Claims
1. 1. A method comprising: applying a clear coat layer onto the substrate; drying the clearcoat layer to form a random microstructure in the clearcoat layer; dispensing a printing fluid to print a graphic pattern on the clear coat layer, the graphic pattern comprising a bar code, a quick response code, or a pattern of shapes; and generating a physically unclonable function (PUF) pattern by drying the printing fluid filling the random microstructures formed in the clearcoat layer.
2. The method of claim 1 , wherein the clearcoat layer comprises a colloidal mixture of water and solid particulates.
3. The method of claim 2, wherein the solid particulate comprises silica in the range of 30 weight percent to 50 weight percent.
4. The coating step comprises: The method of claim 1 , comprising dispensing the clearcoat using a print head of a printing device that also dispenses the printing fluid.
5. The method of claim 1 , wherein the applying is performed via a spin coating procedure at between 100 revolutions per minute (RPM) and 5000 RPM.
6. The method of claim 1 , wherein the clearcoat layer is applied to a desired thickness to form the random microstructures at a desired resolution.
7. The method of claim 6 , wherein the desired thickness comprises between 5 nanometers (nm) and 100 nm.
8. The method of claim 1 , wherein the printing fluid comprises a water-based graphic ink.
9. A non-transitory computer-readable medium storing a plurality of instructions, the plurality of instructions, when executed by a processor, causing the processor to: applying a clear coat layer onto the substrate; drying the clearcoat layer to form a random microstructure in the clearcoat layer; dispensing a printing fluid to print a graphic pattern on the clear coat layer, the graphic pattern comprising a bar code, a quick response code, or a pattern of shapes; and generating a physically unclonable function (PUF) pattern by drying the printing fluid that fills the random microstructures formed in the clearcoat layer.
10. 10. The non-transitory computer readable medium of claim 9, wherein the clearcoat layer comprises a colloidal mixture of water and solid particulates.
11. 11. The non-transitory computer readable medium of claim 10, wherein the solid particulate comprises silica in the range of 30 weight percent to 50 weight percent.
12. The coating step comprises:
10. The non-transitory computer-readable medium of claim 9, comprising dispensing the clearcoat layer using a print head of a printing device that also dispenses the printing fluid.
13. 10. The non-transitory computer readable medium of claim 9, wherein the applying is performed via a spin coating procedure at between 100 revolutions per minute (RPM) and 5000 RPM.
14. 10. The non-transitory computer readable medium of claim 9, wherein the clear coat layer is applied to a desired thickness to form the random microstructures at a desired resolution.
15. 15. The non-transitory computer-readable medium of claim 14, wherein the desired thickness comprises between 5 nanometers (nm) and 100 nm.
16. The non-transitory computer-readable medium of claim 9 , wherein the printing fluid comprises a water-based graphic ink.
17. 1. A method comprising: capturing an image of a printed physically unclonable function (PUF) on a substrate with a camera of a mobile device, the PUF being formed on the substrate using a printing fluid dispensed into a clear coat, the clear coat being dried to form random microstructures filled with the printing fluid, the clear coat comprising a colloidal mixture of water and silica in the range of 30 weight percent to 50 weight percent; comparing the image of the printed PUF with an image stored on a server; authenticating the substrate when the image of the printed PUF matches the image stored on the server.