SECURE DOCUMENT, PROCESS AND DEVICE FOR SECURE DOCUMENT AUTHENTICATION

Abstract

The invention relates to a method and device for authenticating a document, as well as a secure document (1), equipped with personalization data (5) inscribed on its support (3), characterized in that it comprises a non-clonable diffractive element (7) incorporated in said support, said diffractive element (7) being configured to display a personalized pattern (9) whose chromaticity varies according to the viewing angle, said personalized pattern being created from a unique cryptographic signature derived from at least one personalization data of interest among said personalization data. Figure 1.

Description

Title of the invention: SECURE DOCUMENT, METHOD AND DEVICE FOR AUTHORIZING THE SECURE DOCUMENT technical field

[0001] The present invention relates to the field of secure documents and more particularly, the authentication of secure documents. PREVIOUS STATE OF THE ART

[0002] In the current context, the demand for highly secure identity documents is increasing. It is imperative that these documents be easily verifiable while also being effectively resistant to counterfeiting. This requirement applies to a wide range of supporting documents, including but not limited to national identity cards, passports, secure access badges, and driver's licenses. These documents take various forms, such as laminated cards, booklets, or other alternatives, each requiring reliable authentication.

[0003] Over time, a range of secure documents incorporating images has been developed to ensure reliable identification of individuals. In this era of heightened vigilance, a majority of official documents such as passports and identity cards now incorporate security features that allow for document authentication and limit the risks of fraud, falsification, or counterfeiting. In response to these challenges, electronic identity documents, particularly those with embedded chips such as biometric passports, have seen remarkable growth in recent years.

[0004] Despite the proven effectiveness of current security methods, there remains significant room for improvement, particularly with the aim of achieving near-total invulnerability to falsification of secure documents, while simplifying their authentication process.

[0005] The object of the present invention is to provide a highly secure and virtually tamper-proof document, accompanied by an authentication method that is simple, efficient and extremely robust. Description of the invention

[0006] This objective is achieved with a secure document, equipped with personalization data inscribed on its medium, comprising a non-clonable diffractive element incorporated in said medium, said diffractive element being configured to display a personalized pattern whose chromaticity varies according to the viewing angle, said personalized pattern being created from a unique cryptographic signature derived from at least one relevant personalization data among said personalization data.

[0007] This document, as designed by the invention, achieves such a high level of security that it becomes almost impossible to counterfeit. Indeed, the personalized diffractive pattern, closely linked to the signature, is extremely difficult to reproduce, both in terms of digital design and manufacturing. The combination of these two aspects, design and manufacturing, guarantees the authenticity of the document, even if the personalized pattern and the personalization data are both visually accessible on the same document.

[0008] According to a first embodiment, the personalized pattern is a geometric structure in the form of a fractal, the configuration of which is derived from random sequences generated from an initial value corresponding to said signature.

[0009] A fractal is a complex geometric structure whose reproduction requires knowledge of several critical parameters: the number of iterations required, the starting point, the specific area to be observed and the underlying pattern that guides its construction.

[0010] According to a second embodiment, the personalized pattern is a geometric structure in the form of a Q-code (monochrome or colour) generated from said signature.

[0011] The exact reproduction of the Q-code proves complex, as it requires knowledge of a unique cryptographic signature, which is itself derived from the personalization data.

[0012] Advantageously, the cryptographic signature is determined by means of a cryptographic hash function applied to said personalization data.

[0013] The cryptographic hash function makes it possible to convert text of any length into a fixed-size string, thus facilitating the comparison of the original texts in a simplified manner without requiring direct access to them.

[0014] Advantageously, said cryptographic function is a secure hash function of type SHA-512.

[0015] According to one aspect of the present invention, the diffractive element comprises a metallic holographic layer forming an arrangement of pixels configured to create the custom pattern.

[0016] Advantageously, the diffractive element comprises an opaque layer surmounted by the metallic holographic layer, the metallic holographic layer comprising perforations locally revealing dark areas in the pixel arrangement caused by underlying regions of the opaque layer, thus enabling the creation of the customized pattern by the combination of pixels and dark areas.

[0017] The diffractive element dynamically adjusts the color of the custom pattern according to the angle from which it is viewed. This makes it possible to form a custom pattern, in color or black and white, that is of good quality, easy to authenticate, and robust against the risks of fraud, falsification, or counterfeiting.

[0018] Advantageously, the diffractive element further comprises calibration zones located at predetermined locations, each of the calibration zones having a predefined reference color.

[0019] This facilitates the straightening of the customized pattern, regardless of the viewing angle.

[0020] Advantageously, said visible personalization data is at least one of the following data: photo, MRZ auto-reading zone, first name, last name, date of birth.

[0021] The invention also relates to a method for authenticating a secure document according to any one of the preceding characteristics, comprising the following steps:

[0022] - optical acquisition of the personalization data of interest recorded on the document,

[0023] - optical acquisition of the representation of the personalized pattern projected by the element diffractive,

[0024] - rectification of said representation of the personalized pattern to obtain an image straightened from the custom pattern,

[0025] - calculation of a cryptographic signature by applying the function cryptographic information on said personalization data of interest,

[0026] - generation of an expected reference image of the personalized pattern from the cryptographic signature obtained, and

[0027] - verification of the document's authenticity by comparing the rectified image of its personalized pattern with the expected reference image, validating the document in case of a match between the two images.

[0028] This process allows for the authentication of a document by correcting the personalized pattern present on it and comparing it to a reference pattern. The latter is created by respecting all the steps of the original design, based on the document's personalized data, given that the correction operation and the design steps remain confidential, known only to authorized entities.

[0029] Advantageously, the rectification of said representation of the personalized pattern comprises the following steps:

[0030] - measurement of observable colours in the calibration zones of the diffractive element, under the usual acquisition conditions;

[0031] - spatial interpolation, using observable colors measured in the areas calibration and their predefined positions, to estimate the theoretically observable color of each color within data areas encoding the custom pattern; and

[0032] - identification of the actual colors assigned to the data areas encoding the pattern customized from the results of spatial interpolation, allowing the representation of the customized pattern to be corrected.

[0033] This ensures a reliable and accurate reading of the personalized pattern, whether in color or black and white, regardless of the acquisition conditions under which the reading is carried out.

[0034] The invention also relates to a device for authenticating a secure document according to any one of the preceding characteristics, comprising:

[0035] - a camera configured to acquire the personalization data of interest recorded on the document as well as the representation of the custom pattern projected by the diffractive element,

[0036] - a processor configured for:

[0037] to straighten said representation of the custom pattern to obtain a straightened image of the custom pattern,

[0038] - calculate a cryptographic signature by applying the function cryptographic information on said personalization data of interest,

[0039] - generate an expected reference image of the custom pattern from the cryptographic signature obtained, and

[0040] - verify the authenticity of the document by comparing the rectified image of its A customized pattern with the expected reference image, validating the document if the two images match.

[0041] Advantageously, the authentication device includes an optical character recognition module for recognition.

[0042] Advantageously, the cryptographic function and the algorithm for generating a calculated image of the custom geometric pattern are obtained securely from a centralized server.

[0043] According to one embodiment, the authentication device is a mobile phone equipped with an application dedicated to the authentication of secure documents, implementing the authentication process according to the preceding characteristics. Brief description of the drawings

[0044] The present invention will be better understood upon reading the description of exemplary embodiments given by way of illustration only and in no way limiting, with reference to the accompanying drawings in which:

[0045] [Fig.1] schematically illustrates a secure document, according to one embodiment of the invention;

[0046] Figure 2 schematically illustrates a diffractive element according to one embodiment of the invention;

[0047] Figure [Fig. 3] illustrates an example of the Julia set fractal with different parameters;

[0048] Fig. 4 schematically represents a system for creating a personalized pattern in the shape of a fractal, according to one embodiment of the invention;

[0049] Figure 5 illustrates a simple example of generating a tree-type fractal from an initial data point of interest; and

[0050] Figure 6 schematically illustrates a secure document authentication device according to one embodiment of the invention.

[0051] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0052] The concept behind the invention consists of associating personalized data from a document with a unique diffractive pattern.

[0053] [Fig.1] schematically illustrates a secure document, according to one embodiment of the invention.

[0054] The secure document 1 (or security document) comprises a body, designated as a medium 3, on which personalization data 5 are legibly inscribed. This data may include, among other things, a photograph, an MRZ (Machine-Readable Zone), a first name, a last name, a date of birth, a document number, and a date of issue.

[0055] Furthermore, the secure document 1 is equipped with a non-clonable diffractive element 7, visibly integrated into the support 3. This diffractive element 7 is designed to display a personalized pattern 9 whose color varies depending on the viewing angle. The principles and implementation of the diffractive element 7 are described in patent application FR3103736 filed by the applicant.

[0056] [Fig.2] schematically illustrates a diffractive element, according to one embodiment of the invention.

[0057] By way of example, the diffractive element 7 comprises a first layer 11 which, where appropriate, can be superimposed on a second layer 13. The first layer 11 is a holographic layer comprising a metallic holographic structure. This structure forms an arrangement 15 of pixels, each composed of a plurality of sub-pixels that may be of different colors. The metallic holographic layer 11 has laser perforations 17.

[0058] Advantageously, the second layer 13 is opaque at least in the visible wavelength spectrum. Certain perforations 17, created by laser in the metallic holographic layer 11, reveal, by transparency through the structure holographic 11, dark areas 18 within the sub-pixels, due to the corresponding regions of the opaque layer 13 located just below the perforations 17.

[0059] The combination of this pixel arrangement 15, the perforations 17, and, where applicable, the dark areas, allows for the creation of data areas 19. These data areas encode a custom pattern in the desired colors. The holographic structure 11 generates this pixel arrangement 15 in the form of a hologram through the diffraction and / or refraction and / or reflection of incident light. This makes it possible to display the custom pattern 9, the colors of which vary depending on the viewing angle. When the diffractive element 7 is viewed from the correct angle, the custom pattern 9 appears in its true colors. From other angles, the pattern 9 does not display its true colors. Consequently, the custom pattern 9 cannot be cloned to reproduce this specific visual effect. It should be noted that the custom pattern 9 can be engraved with high precision, given that a pixel measures approximately 30 µm.

[0060] Furthermore, the diffractive element 7 incorporates calibration zones 21 in addition to the data zones 19 that form the custom pattern 9. The calibration zones 21 are arranged in predetermined locations, and each has a predefined reference color. Thanks to these calibration zones 21, it is possible to extrapolate the actual colors of the custom pattern 9, regardless of the viewing angle. The principles relating to the calibration zones 21 and color correction are described in patent application EP3945451 filed by the applicant.

[0061] According to the invention, the personalized pattern 9 is generated from a unique cryptographic signature which is derived from at least one relevant personalization data within the personalization data 5.

[0062] Advantageously, the cryptographic signature is obtained by using a cryptographic hash function applied to this personalization data. For example, the hash function used could be of the SHA-512 (Secure Hash Algorithm 512) type. SHA-512 is a hash function designed to transform text, such as the document number, the holder's name, or the issue date, regardless of its length, into a fixed-size cryptographic fingerprint. In the case of SHA-512, this fingerprint, or cryptographic signature, is 512 bits long, or 64 bytes. This type of operation ensures that two similar pieces of information produce distinctly different results, thus preventing two slightly different textual pieces of information from resulting in two similar personalized patterns.

[0063] The personalized pattern 9, created from this unique cryptographic signature, takes the form of an extremely complex and distinct design element or geometric structure.

[0064] In a first embodiment, the personalized pattern 9 takes the form of a fractal geometric structure, characterized by a repetition of similar patterns at different scales. The fractal configuration is derived from random sequences generated from an initial value that corresponds to the unique cryptographic signature.

[0065] Indeed, starting from a basic element, this element is reproduced at various locations on the structure. Several parameters can be modified, such as the number of iterations of the fractal, the starting point, the specific area to be examined, as well as the underlying basic element that guides its construction.

[0066] There are many types of fractals, each with varying degrees of complexity, and depending on the parameters chosen, the resulting structure is unique. Famous examples of fractals include the Koch snowflake fractal, the Julia set fractal, and the Mandelbrot fractal. An example of the Julia set fractal is shown with different parameters in [Fig. 3].

[0067] Fractals can be considered in two dimensions or in three dimensions. In particular, a three-dimensional fractal is in colors.

[0068] Figure 4 schematically represents a pattern creation system customized in the form of a fractal, according to one embodiment of the invention.

[0069] This system comprises a computer or calculator 25, which is equipped with all standard components, including a processor 27, a memory 29, and input and output interfaces 31. The calculator 25 is designed to execute a custom pattern formation process algorithm, which proceeds according to the steps E1 to E4 described below.

[0070] At step El, the processor 27 is configured to retrieve the data of interest "D" of the bearer, such as his first name, last name, date of birth, or the machine read zone (MRZ).

[0071] In step E2, the processor 27 is configured to calculate the cryptographic signature "S", which serves as a unique identifier for the data of interest "D". This operation can be carried out using a hash function "HASH", resulting in a unique identifier that can be converted into an integer.

[0072] In step E3, the processor 27 is configured to use the integer from the signature "S" as a seed to generate random numbers that determine the characteristics of the fractal. Depending on the type of fractal chosen, various parameters may be involved. These parameters are generated randomly and specifically linked to the bearer of document 1 by means of the seed defined previously.

[0073] The resulting fractal is then etched onto the diffractive element 7 by laser radiation, creating perforations 17 in the metallic holographic layer 11, in accordance with the manufacturing process described, for example, in the applicant's patent application FR3103736. This ensures the uniqueness of the secure document 1 and allows for dual authentication, both on the diffractive element 7 and on the fractal.

[0074] It is also possible to simply print the main lines of the fractal in black on secure document 1. For this purpose, the use of a greyscale level can allow for a more detailed representation of the figure.

[0075] Figure 5 illustrates a simple example of generating a Tree-type fractal from an initial data point of interest.

[0076] This Tree fractal 91 is constructed using the first name "Coralie" as the data of interest. Applying a hash function, based on the MD5 algorithm, converts this first name into a hexadecimal signature designated by "S":

[0077] S=Hash(Coralie)=d72c67fa36117fd005882fl977efead6.

[0078] Converting the hexadecimal signature S into an integer gives the following result:

[0079] Integer(S) = 23218171280447847264756436398764620393266989875962.

[0080] Processor 27 uses this integer as a seed to generate random numbers which then define parameters such as the angle of the right branch, the angle of the left branch, the length of the right branch, and the length of the left branch. The fractal 91 thus created is subsequently engraved onto secure document 1.

[0081] It should also be noted that other random variables, calculated from the same seed, can be used to determine other characteristics, such as the color of each branch.

[0082] Of course, this example is not limited to the Tree fractal 91; it is also applicable to other types of fractals.

[0083] During a check of document 1, the process described above is repeated in order to regenerate the fractal 91. This is then compared to the fractal present on document 1, as will be explained in more detail in relation to [Fig.6].

[0084] Thus, from a photograph of identity document 1, it is possible to recalculate the parameters of fractal 91 using the textual elements and to reconstruct it. The theoretically recalculated fractal 91 can then be compared to the original fractal present on document 1 by image processing.

[0085] In this way, the textual elements are protected against falsification in the event of document theft. As for counterfeit documents, it will not be possible to reproduce the appropriate fractal.

[0086] According to a second embodiment, the personalized pattern 9 takes the form of a geometric structure which can be a barcode or a QR code (2D barcode) Generated from the S signature, which can be monochrome or in color. The QR code is a fairly complex type of graphic code, made up of small black squares and white areas that allow a large amount of information to be concentrated.

[0087] Figure 6 schematically illustrates a document authentication device secured, according to an embodiment of the invention.

[0088] This authentication device 125 specifically comprises a processor 127, a camera 129, and an optical character recognition (OCR) module 131. During document verification, the authentication device 125 is designed to capture an image or video stream of the document 1 in order to verify its authenticity, following the steps Eli to E16 below.

[0089] In step El 1, the camera 129 is configured to acquire an image or video of the personalization data recorded on document 1, and in particular, the personalization data of interest "D". The optical recognition module 131 is then configured to extract the personalization data of interest by performing optical character recognition (OCR) on the image captured by the camera 129.

[0090] In addition, during step El2, the camera 129 is configured to also acquire images or a video stream of the custom pattern 7 as it is projected by the diffractive element 9. The acquisition of this video representation makes it possible to observe variations in the angle of incident light on the diffractive surface 7.

[0091] It is important to specify that the authentication device 125 can produce a single video of document 1 which will be used both for the acquisition of personalization data and for that of the representation of the personalized pattern 9. Thus, the video obtained in step E12 can be identical to that used to capture the personalization data D.

[0092] In step E13, the processor 127 is configured to apply an image processing method to rectify the representation of the custom pattern 9, in order to obtain a rectified IM image that faithfully reflects its original colorimetric nuances.

[0093] More specifically, the rectification of the representation of the personalized pattern is carried out by the processor by following a sequence of substeps E131 to E133 below.

[0094] At step E131, the processor 127 measures the colors observable in the calibration areas 21 of the diffractive element 7, under the usual acquisition conditions.

[0095] At step E132, the processor 127 performs a spatial interpolation using the observable colors measured in the calibration zones 21, as well as their predefined positions, in order to estimate the theoretically observable color for each of the 19 data areas that encode the custom pattern 9.

[0096] In step E133, the processor 127 determines the actual colors assigned to the data areas 19 that encode the custom pattern 9, based on the results of the spatial interpolation. This allows the representation of the custom pattern 19 to be rectified to display its true colors on the rectified image IM.

[0097] Advantageously, the authentication device 125 securely acquires the rectification application and the necessary parameters from a centralized server 41 where the application and its parameters are stored.

[0098] Furthermore, the processor 127 is configured to reproduce the steps of the process described in [Fig.4] in order to regenerate a reference image of the custom pattern 9. This reference image will then be used for comparison with the one appearing on the document.

[0099] Indeed, during step E14, the processor 127 is configured to calculate a cryptographic signature S by applying the cryptographic function to the personalization data of interest D previously identified by the module 131 OCR.

[0100] Advantageously, the authentication device 125 securely acquires the cryptographic function from the server 41 which stores this function.

[0101] Next, during step E15, the processor 127 is configured to generate the expected IR reference image of the custom pattern 9 from the cryptographic signature S obtained.

[0102] Finally, in step E16, the processor 127 is configured to verify the authenticity of document 1 by comparing the rectified IM image of the custom pattern 9 with the expected IR reference image. It should be noted that this comparison would not be possible if the acquired image of the custom pattern 9 had not been rectified beforehand. The authenticity of document 1 is confirmed only if the expected IR reference image corresponds to the rectified IM image.

[0103] This authentication process allows the diffractive element 7 and the personalized pattern 9 to be authenticated simultaneously in a single acquisition operation, since all the elements to be verified are visible on the same document 1. The authentication of the diffractive element 7 ensures the authenticity of the pre-personalized document support, while the verification of the personalized pattern 9 guarantees that of the personal data.

[0104] By way of example, the authentication device 125 may be a mobile phone equipped with an application dedicated to the authentication of secure documents, implementing the authentication process described above.

Claims

Demands

1. Secure document (1), equipped with personalization data (5) written on its medium (3), characterized in that it includes a non-clonable diffractive element (7) incorporated in said medium, said diffractive element (7) being configured to display a personalized pattern (9) whose chromaticity varies according to the viewing angle, said personalized pattern being created from a unique cryptographic signature derived from at least one personalization data of interest among said personalization data.

2. Secure document according to claim 1, characterized in that the personalized pattern (9) is a fractal-shaped geometric structure (91), the configuration of which is derived from random sequences generated from an initial value corresponding to said signature.

3. Secure document according to claim 1, characterized in that the personalized pattern (9) is a geometric structure in the form of a Q-code generated from said signature.

4. Secure document according to any one of the preceding claims, characterized in that the cryptographic signature is determined by means of a cryptographic hash function applied to said personalization data.

5. Secure document according to claim 4, characterized in that said cryptographic function is a SHA-512 type secure hash function.

6. Secure document according to any one of the preceding claims, characterized in that the diffractive element (7) comprises a metallic holographic layer (11) forming a pixel arrangement configured to create the custom pattern (9).

7. Secure document according to claim 6, characterized in that the diffractive element (7) comprises an opaque layer (13) surmounted by the metallic holographic layer (11), the metallic holographic layer (11) comprising perforations (17) locally revealing dark areas (18) in the pixel arrangement caused by underlying regions of the opaque layer (13), thus enabling the creation of the personalized pattern (9) by the combination of pixels and dark areas.

8. Secure document according to claim 6 or 7, characterized in that the diffractive element (7) further comprises calibration zones (21) located at predetermined locations, each of the calibration zones having a predefined reference color.

9. Secure document according to any one of the preceding claims, characterized in that said personalization data of interest is at least one of the following data: photo, MRZ auto-read area, first name, last name, date of birth.

10. A method for authenticating a secure document according to any one of the preceding claims, characterized in that it comprises the following steps: - optical acquisition of the personalization data of interest (D) inscribed on the document, - optical acquisition of the representation of the personalized pattern (9) projected by the diffractive element, - rectification of said representation of the personalized pattern (9) to obtain a rectified image (IM) of the personalized pattern, - calculation of a cryptographic signature by applying the cryptographic function to said personalization data of interest, - generation of an expected reference image (IR) of the personalized pattern from the cryptographic signature obtained, and - verification of the authenticity of the document (1) by comparing the rectified image (IM) of its personalized pattern with the expected reference image (IR), validating the document in the event of a match between the two images.

11. A method according to claim 10, characterized in that the rectification of said representation of the personalized pattern comprises the following steps: - measurement of the observable colors in the calibration zones (21) of the diffractive element (7), under normal acquisition conditions; - spatial interpolation, using the observable colors measured in the calibration zones and their predefined positions, to estimate the theoretically observable color of each color within data zones (19) encoding the personalized pattern (9); and - identification of the actual colors assigned to the data areas (19) encoding the custom pattern from the results of the spatial interpolation, allowing the representation of the custom pattern to be corrected.

12. A device for authenticating a secure document according to any one of claims 1 to 9, characterized in that it comprises: - a camera (129) configured to acquire the personalization data of interest inscribed on the document (1) as well as the representation of the personalized pattern (9) projected by the diffractive element (7), - a processor (127) configured to: - rectify said representation of the personalized pattern to obtain a rectified image (MI) of the personalized pattern, - calculate a cryptographic signature by applying the cryptographic function to said personalization data of interest, - generate an expected reference image (RI) of the personalized pattern from the cryptographic signature obtained, and - verify the authenticity of the document (1) by comparing the rectified image (MI) of its personalized pattern with the expected reference image (RI), validating the document in case of concordance between the two images.

13. Authentication device according to claim 12, characterized in that it comprises an optical character recognition module (131) for recognizing.

14. Authentication device according to claim 12 or 13, characterized in that the cryptographic function and the algorithm for generating a calculated image of the personalized geometric pattern are obtained securely from a centralized server (41).

15. Authentication device according to claim 12 or 13, characterized in that the authentication device (125) is a mobile phone equipped with an application dedicated to the authentication of secure documents, implementing the authentication method according to claims 10 and 11.

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