FR3048106A1 - VISUAL AUTHENTICATION PROCESS - Google Patents

Abstract

The invention relates to a visual process for the authentication and/or integrity check of a subject, consisting in superimposing visually, optically or electronically: - on the one hand, at least one so-called authentication image of at least an authentication region of an authentic subject, the authentication image comprising at least one texture with a random component, - and, on the other hand, the authentication region itself of a candidate subject or at the at least one verification image of the authentication region of the candidate subject, for in the event of observation by an operator, on the image resulting from the superposition, of an optical phenomenon of the Glass pattern type at the region of concluding that the candidate subject is the authentic subject and/or at least partial integrity of the authentication region of the authentic subject.

Description

[1] The present invention relates to the technical field of authentication and integrity control of material subjects as well as the field of visual cryptography. In a preferred but not exclusive application, the invention relates to the field of unitary authentication of material subjects.

In the above field, it is known, in particular from US Pat. No. 4,423,415, to identify material subjects by extracting a signature from a so-called authentication region. comprising a substantially random intrinsic three dimensional intrinsic micro structure. This extraction is generally carried out with electronic computing means such as a computer and require for the verification of the authenticity of a subject to use such calculating means again. Thus, according to certain known methods, it is proceeded to a first extraction of the signature of the authentication region to proceed to the registration of an authentication signature. Then, during the verification of the authenticity, it is proceeded to the extraction of a second signature, called verification, of the same authentication region then there is a comparison of the authentication and verification signatures for determine the authenticity according to a threshold of similarity of the signatures. According to other known methods, a similarity or correlation coefficient is calculated between a previously recorded authentication image and a verification image acquired at the time of the verification of authenticity for, depending on the value of the coefficient of correlation or similarity, to conclude or not to the authenticity of the subject.

[3] Such methods, if they actually allow authentications presenting a very low risk of concluding the authenticity of a non-authentic subject, nevertheless have the disadvantage of requiring calculations and the corresponding resources both during the phase of registration only during the verification phase. In addition, the operator or human being is excluded from the authenticity validation process so that the operator must trust the calculation system with respect to the authenticity validation process. Moreover, there is always a risk that the computing system can be pirated or fraudulently modified so as to provide a conclusive result to authenticity when this is not the case.

[4] It is also known methods that have proposed, in a recording phase, to record an authentication image at a high magnification or magnification of an authentication region of the hardware subject to be authenticated so as to allow observing microscopic details of this authentication region. These methods then propose, in a verification phase, to make an image of verification of the authentication region on the subject to be authenticated by an operator at the same magnification or magnification so that the operator can make a visual comparison of the two juxtaposed images. to identify the identical regions or different regions and conclude or not to the authenticity of the subject to authenticate. If such a method or method allows an authentication that does not require calculation means since the authentication results from a visual comparison performed by an operator, this visual method has the major disadvantage of requiring a long training of the operator and / or a relatively long observation period for the operator to conclude authenticity or not with a satisfactory degree of self-confidence and certainty. In addition, these methods implement the explicit memory of the operator, which memory is very variable from one individual to another.

[5] It has therefore emerged the need for a new Visual Visual Authentication Method which, while not requiring little or no calculation means for the final decision phase as to authenticity by taking advantage of the performance of the human visual system of an operator, allows this operator to conclude the authenticity with a reduced observation time compared to known methods and offers the operator means to have confidence in his judgment.

[6] In order to achieve this objective, the invention relates to a visual method for authenticating and / or verifying the integrity of a subject with an authentication visual and / or integrity control of a subject. consisting of superimposing visually, optically or electronically: on the one hand, at least one so-called authentication image of at least one authentication region of an authentic subject, the authentication image comprising at least one random-component texture, and on the other hand, the authentication region itself of a candidate subject or at least one verification image of the authentication region of the candidate subject, in case of observation. by an operator, on the image resulting from the superposition, of a Glass pattern optical phenomenon at the level of the authentication region to conclude that the candidate subject is the authentic subject and / or the integrity of the less partial of the authentication region the authentic subject.

[7] With regard to the authentication region, according to the invention, its image or visual representation by the human visual system (abbreviated SVH) has a texture that an observer of average visual acuity can observe either at 'naked eye either after via a zoom performed optically and / or numerically. Thus the observation of structures of small dimensions or perceived as small by the SVH at observation magnification are perceived by the SVH as images containing a texture. This is the case for example sand grains: observed with the naked eye several tens of centimeters away, they are perceived as being of small dimensions whereas observed with the magnifying glass they are perceived as objects of average dimensions . In the same way, a meadow observed at several ten meters is perceived as being uniform or being constituted by a structure of very small indistinguishable elements whereas during an observation to about ten centimeters it is possible for an observer to perceive the strands grass. The same phenomenon is noticeable with regard to a pebble beach according to the observation distance.

[8] In the context of the invention the term texture refers to what is perceptible by the SVH as a signal or a homogeneous area in an image resulting from a direct observation or via an optical system or via a digital image system. image acquisition provided with at least display means while the term structure refers to the composition and organization of the constituent material of the subject itself. The texture of interest of the authentication region is referred to as a random component texture or a random component texture in that it comprises at least a portion or a certain proportion of randomness or irregularity. To illustrate, the image of a subject woven by means of threads consisting of fibers generally comprises a quasi-periodic or regular component corresponding to the weave of the fabric and a random component corresponding to the fibers and reflecting their variability. The combination of the two components corresponds to what is perceived by the SVH as a texture that is qualified in the context of the random-component texture invention. In the observation of a superimposition of an authentication image and a verification image of the same authentication region of a fiber yarn fabric, it is perceived by the VHS according to the method of the invention a Glass type pattern resulting from the random component of the texture combined with a regular moiré resulting from the regular component of the texture.

[9] In the context of the invention the term texture refers to what is visible or observable on an image or a subject or a sctandis that the term structure or microstructure refers to the material subject itself. Thus, a texture or microtexture of the authentication region corresponds to an image of the structure or microstructure of the authentication region.

[10] Within the scope of the invention and in certain configurations, a component texture may be described as continuous in that it results from the perception or is the image of a continuous structure, juxtaposition or overlap otic continuous structures, the juxtaposition or optical overlap of particles or elements perceived as small at magnification or scale of observation. For the purposes of the invention, a continuous or visually continuous microstructure or structure is either physically or physically continuous or consists of elements juxtaposed in such a way that visually two adjacent or consecutive elements are visually in contact or superimposed as opposed to a structure discrete in which two adjacent or consecutive elements are not visually in contact. It is also possible to define the continuous structures or microstructures within the meaning of the invention as being in particular environments without vacuum or particulate media for which the Knudsen number is small in front of 1 and still dense media on the scale of 'observation.

[11] In a preferred embodiment of the invention, each authentic subject belongs to the families of subjects comprising at least one authentication region whose material structure is not easily reproducible that is to say whose reproduction is difficult or impossible because it results in particular from a non-fully controlled training process involving randomness at the component level and / or the process itself. Imaging under similar observation conditions according to points of view adjacent to such an authentication region provides images each having a random component texture which is the noisy reflection of its material structure. Such a random component texture inherits its unpredictability and independence with respect to a random component texture resulting from a completely different authentication region, from randomness in the formation of their material structures. The authentication regions correspond to the physical nonclonal functions "Physical Unclonable Functions" (PUFs) as defined in particular by the publication in English Encyclopedia of Cryptography and Security edition 01/2011 pages 929 to 934 in the article by Jorge Guajardo . Preferably, the authentication region of a subject according to the invention corresponds to an intrinsic non-clonal physical function designated in English by "Intrinsic PUFs" in the aforementioned article.

[12] The inventors take advantage of the fact that the random nature of the three-dimensional structure of the authentication region is inherent or intrinsic to the very nature of the subject or the authentication region because resulting from its method of elaboration , development or growth so that it is not necessary to add to the authentication region a particular structure, including an impression, or an engraving, the sole function of which would be the generation of patterns of Glass by superposition of images of this particular structure. However, this does not exclude the use of natural or reported singularities to facilitate calibration and / or relative scaling for example.

Among the material subjects comprising an authentication region suitable for implementing the visual authentication method according to the invention, it is possible to mention in particular: paper and cardboard packaging, fibrous materials, sintered metal, plastic, ceramic or other materials, - cellular or cellular materials, - leathers including galuchats, - wood, - metals in particular machined, stamped, molded, injected or rolled, - glass, glass frosted, - plastics, - rubber, - woven or non-woven textiles (with possible tilting) - certain coats or plumages, - images of natural scenes such as: - landscape pictures, - foliage pictures, - pictures of skies cloudy, - images of pavement or sidewalk, - images of field or meadow, - images of stone or concrete wall, - skin and fingerprints, - the iris of an animal eye or to be human, - biometric fingerprints, - works of art, - powdered or granular products or materials stored in a transparent container or package, [14] without this list being either exhaustive or exhaustive.

[15] It should be noted that the multi-scale character of the subject in an authentication region can allow the observation of natural textures with several distinct magnifications, Glass motifs then being able to be perceived or generated at each of said magnifications. On the other hand, different parts of the same authentication region may have different optical behaviors and, for example, include a light-transmitting portion and a specular or diffusely reflective portion.

[16] With regard to so-called reasons for Glass, the present invention takes advantage of the demonstration by the inventors that reasons similar to those obtained by Léon GLASS in articles of the journal NATURE vol.223 August 9, 1969 pages 578-580 and Nature vol. 246 of December 7, 1973 pages 360 to 362, can appear by superposition of two images respectively comprising natural textures or random components resulting from the acquisition or even photography at a magnification or enlargement adapted to the same intrinsic three-dimensional material structure random multi-scale of the same subject. In this regard, it is also possible to refer to the publication of Léon GLASS entitled "Looking at dots" published in 2002 in Mathematics Intelligencer, 24, No. 4, pages 37 to 43 and the publication of Matthew SMITH et al. entitled "Glass pattern response in macaque V2 neurons" of the journal Journal of Vision of February 27, 2007 7.3.5 page 1 to 15. The inventors have shown that these patterns, of type Glass, appear only when there is superimposition random-component textures from the same material structure and essentially geometric residual transformations of each other and do not appear in practice when the random-component textures are not sufficiently correlated or do not result from the acquisition of the same hardware structure corresponding to an authentication region of a subject. The invention is therefore able to provide unit authentication.

[17] The method according to the invention is based on the observation of Glass motives by the operator, an observation which, according to Léon GLASS, implements the visual system which is widely shared by all human beings so that the method according to the invention can be implemented by an operator having average visual acuity with or without correction and, if necessary, after undergoing a small training to teach him to recognize a pattern of Glass. Indeed, the visual authentication according to the invention is based on the Glass pattern visualization whose formation is a reduction of entropy vis-à-vis the textures (images of the subject) involved -and their recognition, when the superposition of images perceived by the human brain. According to C. von der Malsburg's "The Correlation Theory of Brain Function" (Springer New York, 1994), a figure is decomposed by the human visual system, into parts formed according to their close correlation values, in the preliminary phase of pre-emptive vision. (B. Juliesz, Nature, 290, 1981) before actual recognition. In other words, the method according to the invention uses in particular the ability of the zones VI and V2 of the visual cortex to detect local self-correlations in the image forming in the eye on the one hand and secondly , the ability to integrate these auto-correlations of the upper parts of the brain to form a global percept and identify a pattern where appropriate. This operation implements, if necessary, deeper layers of the visual cortex and other areas of the brain than those strictly dedicated to the SVH such as the memory and / or learning areas and possibly mobilizes the mechanisms of the 'intuition. Thus, past experience, whether conscious or not, of the operator concerning the perception of Glass motifs is an aid in the effective targeted search for this type of motif. The addressing of his visual memory allows an almost instantaneous perception and a quasi-immediate decision-making guided by his own intuition. The observation of Glass's motives by the future auditor during a learning phase, which may consist of the observation of a single Glass motif, allows his visual memory to be enriched in order to increase his ability to Visual recognition of Glass motifs.

[18] The visualization perception of a Glass type pattern also allows, in an immediate manner, within the scope of the invention, to secure or comfort the operator in his decision making to validate or not the authenticity of the subject candidate. In this respect, it should be emphasized that the invention makes it possible to remove the doubt as to the authenticity of the candidate subject insofar as if a Glass type pattern is observed then there is certainty about the authenticity under the conditions of implementation of data (if the implementation conditions are well respected) of the subject remaining in view and / or accessible to manipulation by the operator, without image processing denaturing the random component texture resulting from the structure hardware of the authentication region. On the other hand, in case of non-observation of a Glass motif, it is not possible to conclude with certainty the non-authenticity.

[19] In addition, the inventors have demonstrated that, in the case of hardware subject authentication, said material subject has sufficient material stability over time, images made at different times can be separated by several days, months, or years allow by their superposition to engender such motifs of Glass. Moreover, according to the invention, the authentic subject may undergo modifications after the registration of the authentication image while remaining authenticatable insofar as part of the authentication region has not been deeply affected by these voluntary modifications or not.

[20] The inventors have also demonstrated that it is not necessary to proceed with the synthesis and / or construction and / or the manufacture of a specific structure (quasi-Jaleéatoire or not to generate a pattern of Glass and in particular that it is not necessary to print or generate a cloud of random or quasi-random distribution points on a support to obtain the appearance of a Glass pattern by the superposition of images of this cloud. inventors have also demonstrated that Glass patterns obtained after superposition of images, are likely to authenticate a subject based on its non-reproducible nature and on an acquisition, under similar conditions of observation, of its texture to a random component at two different instants and not only to appear in response to a synthesis of dot images, typically for the purpose of authenticating or studying the ability of human vision to identify such a phenomenon. tif.

The invention has the advantage of implementing simple processes which do not require a large computing power and / or a fine scan / comparison as is the case for the prior systems, since the The invention is based on, on the one hand, the properties of uniqueness, non-reproducibility and unpredictability of the material structure and, on the other hand, the human visual system, namely the ability of the latter to perform naturally. an identification of the presence of a Glass motif as demonstrated by Leon Glass himself.

[22] According to a first embodiment, the Visual Visual Authentication method of a subject using Glass type patterns comprises the following steps: selecting an authentic subject from three-dimensional or material subjects presenting each at least one so-called authentication region presenting, under given observation conditions, an intrinsic material micro structure that is not easily reproducible and observable, where appropriate via an ad hoc device, by an observer having a mean visual acuity; recording: - acquisition of at least one optical image called authentication of the authentic subject comprising at least the authentication region, the acquisition being performed at a given acquisition magnification or magnification and / or under given conditions of such that for an observer with average visual acuity the image of the authentication region present e at least one random component texture, - registration of the authentication image, - in a visual verification phase performed by an operator: - at least partial superimposition of each authentication image and of a candidate subject, for : - in case of observation by the operator of the appearance of a glass pattern optical phenomenon conclude that the candidate subject is the authentic subject, - and in case of non observation of a Glass motif, realize an at least local geometric transformation of the authentication image and / or a relative displacement of the authentication image with respect to the candidate subject for observation by the operator of the appearance of an optical phenomenon of type Glass type conclude that the subject candidate is the authentic subject, [23] According to a feature of the first embodiment, the authentication image is projected on the subject to authenticate or candidate.

[24] According to another characteristic of the first embodiment, the acquisition of the authentication image is performed at a magnification or acquisition magnification allowing the superimposition of the authentication image and the subject candidate.

[25] According to yet another feature of the first embodiment, the authentication region of the authentic subject is at least translucent and the verification phase is performed in transvision.

[26] According to a feature of the first embodiment, the verification phase is performed by means of an electronic device comprising at least display means adapted to display or project the authentication image and to enable the superposition of the candidate subject and the authentication image substantially on the scale of the candidate subject.

[27] According to the first embodiment of the Visual Authentication Method according to the invention, the authentication image is superimposed in any appropriate manner directly with the candidate subject. However, such a procedure is not strictly necessary for the implementation of the invention.

[28] According to a second embodiment, a visual method for visually authenticating a subject by means of Glass patterns comprising the steps of: selecting an authentic subject from three-dimensional subjects or material each comprising at least one subject; least one so-called authentication region presenting, under given observation conditions, an intrinsic material micro structure that is not easily reproducible and observable by an observer with average visual acuity, - in a recording phase: - acquisition of at least an authentic authentication image of the authentic subject comprising at least the authentication region, the acquisition being adapted to allow perception of a random component texture at the image of the authentication region, the authentication image, - in a visual verification phase carried out by an operator: - acquisition of at least one image verification of a candidate subject comprising at least a part of the authentication region, the acquisition being carried out at a magnification or magnification allowing a visualization of the authentication and verification images at close or similar scales, - superposition to the less partial authentication and verification images, for: - in case of observation by the operator of the appearance of a glass pattern optical phenomenon conclude that the candidate subject is the authentic subject, - and in non-observation of a Glass pattern, performing at least one geometric transformation of at least one image of the superimposed images and / or a relative displacement of the superimposed images for observation by the operator of the appearance of a glass pattern optical phenomenon conclude that the candidate subject is the authentic subject.

[29] In a preferred form, if no Glass pattern is observed at the simple superimposition then the verification phase is continued to search for a glass pattern by first realizing a relative registration of the verification images and authentication then realizing relative scaling or scaling type transformations and / or rotational and / or translational type displacements or combinations of these displacements.

[30] In another preferred form, the authentication and verification images are made under similar conditions.

[31] Preferably, but not strictly necessary, during the visual verification phase, the candidate subject is physically present in front of the operator who can observe it directly or even touch it and even move it or move around the optical system or acquisition associated with a display system. Thus, the candidate subject is in the sensory environment of confidence of the operator which contributes to the reliability of the authentication operation.

[32] Likewise and in a preferred but not strictly necessary manner, the image quality corrections made on the verification image and / or on the authentication image are carried out in real time under the visual control of the image. so that it can ensure that there is no denaturation of the random component texture in the image and / or image substitution, these modifications preferably being reversible so that it is possible to return to the original image.

[33] In the context of the invention, the superposition realized can be static, that is to say without there being relative movement of the superimposed elements, or dynamic that is to say during a relative movement of superimposed elements, as far as possible decidable by the operator. Similarly, according to the invention it is possible to superimpose two images or an image and a video stream or two video streams being understood that a video stream corresponds to a sequence of images. Thus, in the context of the invention, what is explained in relation to a static image overlay applies mutatis mutandis to a superimposition of an image with a sequence of images or a superposition of image sequences synchronously or not synchronized .

[34] It should be noted that the two embodiments of the invention seek the appearance of a Glass type pattern. Now, such a motif of Glass appears only in the case of an authentic subject and if there exists a nonzero light geometric transformation said in the sense of the invention residual geometrical transformation between the candidate subject and the image of authentication or between verification and authentication images, acquired under the given conditions. In the theoretical case of a perfect superposition of strictly identical elements / images, there is no appearance of a Glass motif even in the presence of an authentic subject, hence the need for presence of this residual geometrical transformation and the general interest of the implementation of a movement or a relative displacement or a deformation induced by a difference of angle of view or point of view between the acquisitions of the authentication image and verification image. This property of the Glass patterns offers great robustness to the process according to the invention insofar as it is not necessary for the acquisition conditions of the verification image to be strictly identical to the conditions for acquiring the image. authentication. Thus, the resolutions of the authentication and verification images may in particular be different.

[35] It should be noted that according to the invention and in the context of the first embodiment, the authentication image is an optical image whose acquisition chain comprises an optical part and which results from the soliciting the authentication region by light radiation visible or perceptible to the human eye or the human visual system.

[36] In the context of the second form of implementation, the term image must be understood in the broad sense and not limited to the only meaning of an optical image resulting in particular from the solicitation of the authentication region by radiation. visible light. Thus, in the context of the second form of implementation, the authentication and verification images can be obtained by any type of solicitation of the authentication region in association with a suitable acquisition chain, it being understood that the same type or the same nature of solicitation is implemented for the acquisition of authentication and verification images. Among the types of solicitations or acquisition modes that can be envisaged, it is possible to mention: ultrasound, X or gamma radiation, X-ray or laser tomography, X-ray, magnetic resonance, without this list being exhaustive or comprehensive.

[37] According to a preferred but not strictly necessary characteristic of the second embodiment of the invention, the verification phase is performed by means of an electronic device comprising at least: acquisition means adapted to acquire at least one verification image; display means adapted to display the verification image on a display screen and to allow the superimposition of the verification and authentication images substantially on the same scale.

[38] Preferably but not strictly necessary, the electronic device is adapted to allow modulating or adjusting the level of transparency or absolute or relative opacity of the superimposed images. This level of transparency or opacity is also called a channel. Thus, the electronic device is preferably adapted to allow adjustment of the channel a.

[39] According to a variant of the invention, the electronic device is adapted to ensure a display of a sequence or series of verification images resulting from a relative displacement of the acquisition means and the candidate subject and to enable the superimposing verification images with the authentication image. This variant makes it possible, in particular, to easily implement the method according to the invention when the exact location of the authentication region on the candidate subject is not perfectly known or spotted on the latter.

[40] According to another variant of the invention, during the recording step the acquisition of an authentication image sequence is performed and the electronic device, used during the verification phase, is adapted to acquire a sequence of verification images and to allow visualization of the superimposition of the authentication image sequence with the verification image sequence.

[41] According to another variant of the invention, the electronic device comprises processing means adapted to perform an at least local geometric transformation of at least one image of the superimposed images and / or a relative displacement of the superimposed images. This variant can notably facilitate the task of the operator, who can then trigger the acquisition of only one verification image, the electronic device then making it possible to carry out the relative displacement or the relative geometrical transformation necessary for the appearance of a Glass type pattern in the case of an authentic subject.

[42] According to yet another variant of the invention, minus a verification image is recorded in digital form. Such registration in digital form substantially facilitates subsequent processing by the electronic device.

[43] It should be noted that for the purposes of the invention the term "registration" without precision is understood in the broad sense subject of course to be compatible with the corresponding implementation of the invention. Thus, the term "recording" is intended, in the sense of the invention, to be a recording in any appropriate manner in digital or analog form. Among the recording modes compatible with the invention, it is possible to mention in particular: a recording in any computer and / or electronic format, a recording in printed form on a support adapted to the implementation of the invention as for example a transparent support, a photographic recording on a support such as a positive or negative photographic film, color or black and white, a recording in a holographic form, a recording in engraved form including laser, without this list does not either limiting or exhaustive.

[44] According to another variant of the invention, the verification image is displayed and / or recorded in a binarized form, in gray level or in semitones or in color. In the same way, according to yet another characteristic of the invention, the authentication image is visualized and / or recorded in a binarized form, in gray level or in semitones or in color.

[45] According to one characteristic of the invention, the electronic device is adapted to record at least one image resulting from the superposition.

[46] According to another characteristic of the invention, the authentication method further comprises an automatic verification phase which is performed in part at least by the electronic device. The part of the automatic verification phase performed by the electronic device can then simply include the acquisition of the verification image and the sending of this verification image to an external processing unit. Of course, the electronic device can also perform all the steps of the automatic verification phase.

[47] According to one characteristic of the invention, the automatic verification phase comprises a step of calculating a similarity coefficient between a verification image and the authentication image for, if the similarity coefficient is greater than threshold given, to conclude to a high probability of authenticity even to an authenticity and in the opposite case not to conclude to the authenticity (not thrown of doubt).

[48] According to a variant of this characteristic, the calculation of the similarity coefficient is, for example, made from signatures extracted from a verification image and the authentication image. It can thus be used a vector "from the decomposition" of the image to be analyzed on a predefined basis, typically Gabor functions or wavelets in adequacy with the characterization of the receptive fields of the primary visual cortex (see JG Daugman, Computational Neuroscience, ed. Schwartz E., 403-423, MIT Press, Cambridge, MA, 1990), or a learned base on a family - typically to which the image of the subject belongs - in adequacy with the characteristics of this family, by factorization non-negative matrix (NMF) or principal component analysis (PCA). Atypical use (i.e. predefined basis other than Gabor, and family other than that to which the subject's image belongs) is possible.

[49] The signature can be directly the decomposition vector and the measure of similarity the Euclidean distance for example in the case of the NMF. The signature can be the vector formed by the signs of the components of the decomposition vector and the measure of similarity the Hamming distance: the case of the "iriscode" of Daugman that can easily be transposed to other types of subjects to be authenticated. .

[50] The automatic verification phase may include a step of transmitting or communicating the result of the automatic check to a third party or to the operator. Third party means any person other than the operator such as a manufacturer, seller or owner of the candidate subject, a certification or authentication authority, a governmental or supranational authority or agency, the public authorities , a supplier or service provider, a trusted third party without this list being exhaustive or exhaustive. The result of the automatic verification can also be associated, before sending, with other data such as geolocation data, timestamp, profile or identity of the operator without this list being exhaustive. Such data may be used as part of the customer relationship management designated by CRM for "Customer Relationship Management" see "Enhanced Customer Experience" applications. This data may also be used by the producer or a distributor of an authenticated subject, in particular to know if this subject is in a catchment area for which it was intended in particular in order to control the distribution networks and prevent parallel distribution. .

[51] It should be noted that the visual authentication phase performed by the operator can also, and independently of any automatic verification, be followed by a phase of sending information to a third party initiated by the operator. The information sent may in particular indicate whether or not there has been a doubt.

[52] According to a characteristic that can be used in both embodiments of the invention, the authentication image is recorded by applying on the latter a matrix or grid of cells with thick edges independent of the authentication image whose interior is formed by the corresponding part of the authentication image after having subjected it if necessary a transformation at least geometric selected from a collection of transformations. Such a mode of registration of the authentication image may in some applications facilitate control or verification performed by the operator. It should be noted that not all cells in a grid necessarily have the same shape. Moreover, the size or the surface of each cell is chosen so as to be sufficient to allow the total or partial display of a Glass pattern, if necessary, in the corresponding cell. The thickness of the cell edges must be at least equal to the correlation length of the authentication image at the location of the cells in question, so as to act as a separation surface between the cells and not to allow the prediction of the inverse transformation to that applied, if necessary, to a given cell (independence between the interiors of two disjunct cells). . By correlation length is meant a value proportional to the width at mid-height of the auto-correlation peak of the image considered.

[53] [54] According to a variant of this characteristic, the cells undergoing a transformation are chosen so as to form a message or pattern during the superposition with a verification image. This variant embodiment of the invention can be considered as a two image shared visual cryptography method, one of the images being the authentication image while the other image is either the candidate subject itself or a verification image.

[55] Note that according to a variant of the invention, the grid of cells and the choice of a transformation to be made or not per cell can be applied in the latter case only or also to the verification image. In addition to the revelation of a secret message-image, the visualization of a message-image in the case of an authentic subject facilitates and reinforces the decision-making and the confidence of the operator.

[56] According to one characteristic applicable to the two embodiments of the invention, the geometrical transformation consists of at least one residual geometrical transformation to be applied locally to the image or to the images, chosen of rigid type or not, of a nature linear or nonlinear, at least one fixed or quasi-fixed point. Among the applicable geometric transformations, it is thus possible to implement the transformations described by Léon Glass in his articles of 1973 and 2002 cited above and incorporated herein by reference. By quasi-fixed point it is necessary to hear a point undergoing after residual geometrical transformation a displacement of small amplitude with respect to the maximum displacement caused by the residual geometrical transformation.

[57] According to another characteristic applicable to both embodiments of the invention, the geometric transformation induces a reduced small amplitude modification of the modified image portion of the image of the authentication region before modification.

[58] According to yet another characteristic applicable to both embodiments of the invention, the relative displacement is a translation, a rotation or the combination of one or more rotation and / or translation.

[59] According to a characteristic applicable to the two embodiments of the invention, the relative displacement distance is reduced by small amplitude.

[60] According to a feature of the invention, the authentication image is recorded in analog form on an analog photographic film-type medium or printed on a transparent medium.

[61] According to another characteristic of the invention, the authentication image is recorded in gray level or semitones. Of course, the authentication image can also be recorded in color.

[62] According to yet another characteristic of the invention, the authentication image is recorded in digital form and may have undergone a compression phase so as to optimize the storage space of the authentication images for example.

[63] According to a variant of this characteristic, the authentic subject is associated with an identifier and the corresponding authentication image is stored in a database while being indexed at least by the identifier of the authentic subject or the image. authentication can carry the identifier (tattoo watermark, ...). The identifier can then be registered or stored or worn on the authentic subject according to various known methods and ideally partly hidden from an average user.

[64] According to another variant of this characteristic, an identifier of the candidate subject is a signature extracted or calculated from the authentication region. Thus, the verification phase may comprise, prior to the superposition step, a step of determining the signature of the candidate subject followed by a sending of the determined signature to a server which in response to this sending and on the basis of the signature sends to the electronic verification device one or more authentication images to be used for the superposition step. The server will then include a database of authentication images indexed on the basis of a signature and possibly an identifier of the authentic subjects. The verification can then consist in quantitatively comparing the signature extracted from the candidate subject to the signature pointed to by reference in the database (one-on-one authentication) or to a subset of n signatures identified in the database (n small , typically of the order of 1 to 10) as the closest signatures and / or the most likely authentic subjects (identification 1 against n), the corresponding authentication images can then be subjected to the visual recognition of the operator or transmitted as such for execution by the operator of the method object of the invention.

[65] According to one characteristic of the invention, the authentication and / or verification images are the subject of at least one descreening and / or filtering before superposition. This characteristic makes it possible to eliminate any periodic patterns that may interfere with or hinder the perception of the Glass type patterns in case of an authentic subject.

[66] According to a preferred characteristic of the invention, the authentication and verification images undergo, for the purpose of the superposition, for the verification phase no transformation other than operations for improving or modifying the contrast, brightness, transformation into halftone, change of color space such as changing to grayscale or black and white, operations to change the saturation in certain shades, inversion of levels or changes in relative opacity via the channel a. Thus, according to this preferred characteristic, the images generally undergo so-called enhancement transformations which do not affect the possibility of visually recognizing the nature of the subject. Preferably, the applied transformations do not denature the images, in particular the random component textures that they contain. This also applies to the parts of the images located in the cells of the cryptographic variant of the invention. It should be noted that the improvement operations may concern only one of the two images and that moreover these improvement operations are not always necessary for the implementation of the invention. According to one characteristic of the invention, at least one of the two images is not subjected to transformation by sampling it by means of arbitrary grids, thick or not, regular, periodic or random.

[67] According to another characteristic of the invention, the position of the authentication region on the authentic subject is recorded. Such registration allows, although it is not absolutely necessary, to facilitate the verification phase.

[68] According to yet another feature of the invention, the position of the authentication region is marked on the authentic subject. This identification makes it possible, although it is not absolutely necessary, to also facilitate the verification phase.

[69] According to a characteristic of the invention, the authentic subject belongs to at least one of the following categories of document, subject, or object: fiduciary document, security document, bank note, contractual document, coin, official document , document or piece of identification, luxury product, work of art, art product, regulated product, packaging, medication in particular compressed, mechanical safety or other part, mechanical wear part, optically variable components, holograms of protection and in general any object, product or subject that may be necessary to control authenticity and / or integrity.

[70] The invention also relates to an electronic device that can be used for one or other of the forms of implementation of the visual authentication method according to the invention in particular for the verification phase. This device makes it possible to carry out on its display screen the superposition of the current verification and authentication images via the alpha channel by giving the possibility of performing in a relative manner, if necessary numerically, a rotation, a change of scale according to the horizontal, respectively the vertical, a translation or a correction of distortions including optical. Preferably, but not strictly necessary, the electronic device comprises a tactile display screen and is adapted to allow a modification of the magnification of the display of the authentication image and / or the verification image by the displacement of two points. contact on the touch screen. X4 magnification can typically be investigated. The touch screen can also be used to control the relative displacement of superimposed images, typically a rotation with a non-zero angle of less than 10 °. This device makes it possible to efficiently perform a glass pattern search. In particular, the device makes it possible to perform, according to a preferred search, first of all the registration of the verification and authentication images and then a residual geometric transformation in order to reveal a Glass type pattern. An alternative is to overlay the verification and authentication images in the state until a Glass pattern or image registration is obtained.

[71] Of course, the various features, variants and forms of implementation of the method according to the invention can be associated with each other in various combinations to the extent that they are not incompatible or exclusive of each other.

[72] Furthermore, various other features of the invention appear from the attached description made with reference to the drawings which illustrate non-limiting forms of implementation of the method according to the invention. FIG. 1 is an authentic subject, to be authenticated by means of the method according to the invention, formed by a banknote and on which the authentication region is framed. FIG. 2 illustrates a flowchart of an exemplary implementation of FIG. process of the invention. FIG. 3 is an authentication image of the authentication region of the authentic subject of FIG. 1. FIG. 4 is a verification image of the authentication region of a candidate subject analogous to the authentic subject of the FIG. 1 - FIG. 5 shows an example of step of acquisition of the verification phase of the method according to the invention. FIG. 6 is an image of the superposition of the images of FIGS. 3 and 4 which makes it possible to visualize a Glass pattern. FIG. 7 non-exhaustively shows various possible forms of Glass patterns that can be viewed in the context of the implementation of the invention. FIG. 8 is an image of an authentic subject, to be authenticated by means of the method according to the invention, formed by a sheet of paper on which the authentication region is marked by a printed frame. FIG. 9 is an authentication image, here a slide, of the authentication region of the authentic subject of FIG. 5. FIG. 10 is an image of the superposition of the images of FIGS. 5 and 7 which makes it possible to visualize a Glass motif. FIG. 11 is an image of a candidate subject formed by a sheet of paper which is different from that of FIG. 5 and on which the authentication region is marked by a printed frame. FIG. 12 is an image of the superimposition of the images of FIGS. 6 and 8 which does not make it possible to visualize a Glass pattern. FIG. 13 is an authentication image of an authentic subject to be authenticated by means of the method according to the invention, formed by a palm of the hand. FIG. 14 is a verification image of a candidate subject similar to that of FIG. 13. FIG. 15 is an image of the superimposition of the images of FIGS. 13 and 14 which makes it possible to visualize a Glass pattern showing as well as the candidate subject and the authentic subject. FIG. 16 is an authentication image of an authentic subject formed by a natural scene. FIG. 17 is a verification image of the authentic subject of FIG. 16 with an angle of view slightly different from that of FIG. 16. FIG. 18 is an image of the superimposition of the images of FIGS. allows you to view a Glass pattern. - Figure 19 is an authentic image of an authentic subject, formed by granular products stored in a transparent container. FIG. 20 is a verification image of the authentic subject of FIG. 19. FIG. 21 is an image of the superposition of the images of FIGS. 19 and 20 which makes it possible to visualize a pattern of Glass. FIG. authentication of an authentic subject formed by a stretch of sand. Fig. 23 is a verification image of the authentic subject of Fig. 22 which differs from Fig. 22 in that a portion of the sand extent has been disturbed and a shadow is present therein. FIG. 24 is an image of the superposition of the images of FIGS. 21 and 22 which makes it possible to visualize a Glass pattern.

It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[73] In the context of a first example of implementation of the method according to the invention, it is chosen as subjects to authenticate S bank notes printed on watermarked paper as illustrated in FIG. Indeed, it is chosen as an authentication region R a partially watermarked region at least translucent. Such a watermarked region R has the advantage of presenting the watermark pattern which provides a means of easily identifying the authentication region at which the Glass pattern should appear during a verification phase. In addition, the filigree region makes it possible to easily observe the fibrous structure of the paper, which constitutes an intrinsic structure comparable to the observation scale to an essentially random continuous medium that is not easily reproducible or even non-reproducible. In the case of paper, it is possible to speak of essentially random, non-reproducible continuous microstructure in the sense that this microstructure diffuses the light illuminating it in all directions and is in essence random and different from one region to another. a single sheet of paper or sheets of paper from the same machine or sheets of paper from different machines.

[74] As is apparent from Figure 2, it is first carried out a recording phase E which is for example carried out after manufacture of the banknotes and before their circulation. For example, the registration phase can take place immediately after printing the serial number of each ticket.

During this recording, for each ticket, forming an authentic subject, the acquisition E1 of a so-called authentication image iA represented in FIG. 2 comprising at least the authentication region is carried out. To achieve the acquisition, it is implemented a system for placing each ticket next to an acquisition camera connected to an electronic system for recording and storing data. The lighting of the notes is preferably provided opposite the acquisition camera so that the acquisition region is observed in transmission. In general, the lighting of the subject, here the ticket, is adapted to the optical behavior of the authentication region in reflection and / or transmission.

[76] The acquisition of each authentication image iA is performed at a given acquisition magnification or magnification and adapted to the nature of the microstructure of the paper in this case. According to this embodiment of the method according to the invention, the acquisition magnification is chosen at an initial value which coincides with a visual observation without intermediate optics.

[77] Each authentication image iA, as illustrated in FIG. 3, is, after its acquisition, recorded E2, if necessary in compressed form, in a database Bd while being indexed on the basis of a identifier of the corresponding ticket, for example its serial number.

[78] In a verification phase V, when an operator wishes to verify the authenticity of a banknote belonging to the series of banknotes that have been the subject of the registration phase, the operator proceeds with the acquisition VI of a verification image iV of the authentication region. The verification image iV may for example comprise an image of the entire watermark acquired at a magnification by means of an electronic device D, such as for example a smartphone, comprising a camera and a touch screen display or not . Preferably, the electronic device comprises image acquisition means, calculation and image processing means, means of communication with an extended communication network, means for viewing an image, means for acquiring images, and is adapted to put at least some step of the method according to the invention. Among the electronic devices that can be implemented, it is possible to cite in particular in addition to smartphones, tablets, computers associated with acquisition and viewing systems such as a screen, a pair of glasses with a system of integrated projection, a video projector without this list being exhaustive or exhaustive.

[79] The verification image, as illustrated in FIG. 4, is for example made by placing the candidate subject S on a pane 1 so that it is illuminated by the rear during the acquisition such as the FIG. 5 shows a diagram. Preferably, the acquisition conditions of the authentication and verification images are close without necessarily being identical. It should be noted that, in the present case, the operator has in his possession the candidate subject S at the time of acquisition of the verification image which contributes to reinforcing the confidence of the operator in the operation of the control that he drives.

[80] Next, a suitable application is implemented which has been previously installed by the operator on the electronic device D. This application interrogates on the basis of the serial number of the candidate subject previously entered by the operator a database of remote data so that the database sends the application the authentication image iA corresponding to the serial number. The application then ensures, step V2, the superposition of the verification image and the authentication image, which makes it possible to display the image represented in FIG. 6. If the verification and authentication images are not substantially the operator moves relative to the verification and authentication images in order to recalibrate them with the help of the watermark pattern by means of the keys of the Smartphone or by moving his finger on the screen if last is tactile. This action of the operator then makes it possible to shift one of the two images with respect to the other if they were initially in coincidence and to highlight in a progressive way their similarities through the formation of a glass pattern at neighborhood of their registration / coincidence. If during this relative movement of the authentication image with respect to the verification image, step V3, the operator observes a Glass pattern, as visible in FIG. 6, then he can conclude that the candidate subject is the authentic subject, here the bank note in his possession.

[81] If the operator does not observe Glass's pattern during this registration operation and until he has placed the authentication and verification images in coincidence, he may from there order, step V4, a slight relative displacement of the two images for example a slight rotation, typically 2 ° or 5. This slight displacement may then result from a command similar to that used for the registration operation. The slight displacement can also result from a function of the application which automatically ensures the relative displacement of the two images whose parameters have been pre-recorded. If following this slight displacement, the operator observes, step V5, a pattern of Glass then he can conclude that the candidate subject is the authentic subject. On the other hand, if the operator does not observe Glass's motives then he can not conclude to the identity between the candidate subject and the authentic subject, he can not remove the doubt.

[82] The fact that the resetting or moving of one of the two images is initiated and decided by the operator confirms to the operator that he is well master of the operation and thus to reinforce the confidence in the control operation performed. Indeed, the last steps of the visual authentication are provided by the operator so that he does not have to worry about being provided with erroneous information since it is the operator who in the context of authentication Visual decides whether or not there is authentication.

[83] The visual authentication method according to the invention thus makes it possible to ensure in a simple manner a verification of the authenticity of a candidate subject or to authenticate by an operator, the final decision as to the authenticity of the candidate subject remaining of the operator.

[84] Furthermore, it should be noted that the Glass motif appears, as is apparent from Figure 6, in the light and dark areas of the watermark with a continuity or trace, resulting from the displacement or transformation applied, which extends in the light and dark areas. Thus, the inventors have demonstrated that the appearance of the Glass pattern does not require an evenly clear or dark background and point clouds as implemented by Leon Glass in his aforementioned publications.

[85] Furthermore, it should be noted that the other security elements integrated in the banknote remain accessible and visible to the operator who can use them to reinforce the authentication that he has carried out.

[86] The method according to the invention is particularly robust insofar as the iA and / or iV verification images or the authentic subject S can undergo changes over time without this being an obstacle to the implementation. process of the method provided that the modifications remain minor in the sense that the authentication and verification images are substantially geometric transformations of each other, for example a relative geometric transformation G having at least one fixed or quasi-fixed point or that these images result from an essentially projective transformation of the subject according to neighboring points of view and poses during their acquisition under similar conditions.

[87] Among the transformations or modifications which do not hinder the implementation of the invention, it is possible to cite: a small displacement (rotation-translation) or a small geometrical transformation whose parameters change over time according to a motion not predefined and not known a priori, driven by the observer to further strengthen the confidence associated with its observation (and rule out the assumption of being in the presence of a "Yes machine"), - minor treatments of image enhancement (signal level transformations, scalar or vector quantization, contrast enhancement, interpolations, ...), - minor optical distortions (seen through optically transparent components), - minor distortions of the resulting image dynamic or static variations of the angle of view between the authentication image and the verification image, resulting for example from a slight inclination of the image Spositive as indicated by the arrows Fl to F3 of Figure 5, - the effects of acquisition noise (implicit in any acquisition / re-acquisition)), - a minor damage suffered by the authentication region because of the use (aging, wear, localized damage, ...), - minor surface treatments such as varnishing, film coating, - without this list being neither exhaustive nor exhaustive.

[88] The motifs of Glass visualized in the context of the invention are all the more visually perceptible than the correlation between the authentication and verification images or between the authentication image and the candidate subject or to be authenticated. , is important and varies since at least one fixed or quasi-fixed point. This variation is all the greater as the details of the intermediate frequency domain (the high frequencies are cut off by the SVH, the low frequencies provide small variations) are preserved and their contrast is high. Optical and / or digital image enhancement pretreatments can thus be applied to it for a better visual perception. Thus an optical zoom (variable focus devices) and / or digital to better select the observation scale, a deconvolution of the image to remove a focus defect or a shake, bandpass filtering to select Favoring the details of intermediate frequencies or a contrast enhancement to accentuate the contrast may for example be applied. Thus, in order to facilitate the visualization of the possible Glass pattern, the authentication and verification images as well as the image of the superposition can, before their display or even their recording, undergo one or more improvement processes such as, for example a contrast enhancement in particular by histogram equalization of grayscale or decomposition color channels or by inversion of grayscale scales or decay color so as to form a negative image of the other (the positive ) in order to perceive an anti-correlation [89] Furthermore, the electronic device D can be adapted to allow the real-time superimposition of the authentication image with a verification video stream, that is to say a sequence of verification images, of the authentication region. Thus, the relative movements of the electronic device with the candidate subject induce a variation of the angle of view or more generally from the point of view of the verification images with respect to the angle of view, respectively from the point of view the authentication image. This variation induces the appearance of Glass patterns when superimposing images of the authentication region. In this respect it should be noted that the Glass patterns likely to appear do not necessarily have a spiral or circular conformation to a single center as shown in Figure 6. Thus, Figure 7 shows other shapes. it is understood that this is not an exhaustive or limiting presentation of the forms of Glass patterns that may appear in the context of the invention.

[90] According to another alternative embodiment of the invention, for example to authenticate a sheet of paper as shown in Figure 8 forming the authentic subject, the authentication image is recorded on a photographic film type invertible to form a slide, illustrated in Figure 9, at a substantially increase of 1 of an authentication region R of the subject that can be marked or marked on the sheet to be authenticated.

[91] In the verification phase, the operator superimposes the slide to the authentication region of the sheet and observes the result of this superposition in transvision by illuminating the assembly from the rear as shown in Figure 10. If the operator observes a Glass pattern then he can conclude to authenticity. On the other hand, if the observer does not observe a Glass pattern, he makes a slight relative displacement of the slide and the sheet of paper to proceed with their registration. If during the registration the observer perceives a Glass motif, he concludes the authenticity of the sheet, otherwise the observer can not validate the authenticity of the subject. It should be noted that unless there is a perfect superposition, difficult enough to obtain manually, there is at least one beginning of the Glass pattern at the superposition, this pattern being accentuated by the displacement.

[92] When superimposing the authentication image of a sheet of paper as shown in Figure 11 which does not correspond to the authentication image of Figure 6, no Glass pattern is visible as shown in Figure 12.

[93] It should be emphasized that the implementation of the method according to the invention with an authentication image consisting of a slide superimposed on a sheet of paper conclusively demonstrates that the Glass patterns can be perceived by the superimposition two natural textures from an acquisition of the same authentication region of the same material subject. It may further be noted that the textures of the superimposed images result from structures observed with the naked eye or with a magnification generally less than x10, preferably between x2 and x5. It is therefore not necessary to use images of submicron structures to reveal Glass type patterns.

[94] In the implementation examples described above in relation with FIGS. 1 to 12, the acquisition of the authentication and verification images is carried out in transmission of light through the subject. However, the method according to the invention can be implemented with authentication and verification images whose acquisition is carried out in reflection.

[95] Thus, the method according to the invention can be implemented to proceed to the authentication of a palm of which an authentication image will first have been recorded as illustrated in FIG. 13. Subsequent to this recording, an authenticity check or an identification is carried out for which a verification image is acquired as shown in Figure 14. the superposition of the two images as illustrated in FIG. 15. Since a Glass pattern can be observed in FIG. 15, it can be concluded that the palm of the authentication image of FIG. palm of the verification image of Figure 14.

[96] The invention is likely to find applications in different fields, for example in a process of traceability of a logistic chain in which the various parties involved: producer, distributor, reseller, consumer are all interested in the control of authenticity with financial and technical means to their different provisions to ensure this control. Thus, the invention is particularly advantageous in that it offers the possibility of the producer to the downstream part of the distribution and consumption chain the possibility of carrying out the control with simple tools and without risk of disclosure of secrecy. implemented as it exists in the case of the use of digital signature extracted from the material with complex algorithms whose secret must be preserved. On the other hand, a producer with intellectual property rights may also be interested in knowing whether a controlled product is in the right place in the supply chain (parallel market control) while a consumer is primarily concerned about whether the product in question is very authentic or is interested in services that can be accessed via an authentic product. All this can be implemented as previously indicated with recourse to a means of automatic unit authentication (signature and identifier) and a means of visual authentication object of this invention. An access control can thus be realized with or without the extraction of a signature but with the help of the human visual system. The approach is valid for the consumer.

[97] The invention can be implemented in the context of various authentication, identification, serialization, integrity control and visual cryptography applications. In this respect, it should be considered that in the context of the invention, the terms "authentication", "identification" and "integrity control" may be equivalent depending on the intended application.

[98] The invention can be implemented to identify a natural scene or a landscape as shown in Figures 16 to 18. Figure 16 is an image of a plain scene with a foreground and a background in the foreground. a mountain. Figure 17 is an image of the same scene with a slightly different angle of view.

[99] Figure 18 is the result of the superimposition of the two images with a slight relative rotation which makes it possible to reveal a Glass pattern at the bottom left of the image. The appearance of this pattern makes it possible to demonstrate the robustness of the method according to the invention to the differences in acquisition conditions. In addition, the appearance of the Glass pattern makes it possible to conclude that the two images correspond to the same natural scene. Thus, it is possible to identify the scene of the image of FIG. 17 from the image of FIG. 16. This would also have been possible if, for example, the image of FIG. part of the meadow without the characteristic mountain background. The superimposition of the two images would have allowed to deduce that the image 17 corresponded to a part of the meadow of the image 16. The same principle can be used to control the integrity of images or sequences of images of a movie or video. Moreover, by the implementation of a prairie image, the inventors further demonstrate that it is not necessary to implement structures of microscopic size or very small sizes to reveal Glass patterns from of the material.

[100] Figures 19 to 21 illustrate an implementation of the invention to provide integrity control of granular products stored in transparent containers. The image of Fig. 18 was taken at a time T0 while the image of Fig. 20 was taken at a time Ti with a shooting angle slightly different from that of Fig. 19. Superimposition of the images 19 and with a slight relative rotation a Glass pattern appears as shown in Fig. 21. The appearance of this Glass pattern makes it possible to conclude that they are indeed the same containers. In addition, the appearance of the Glass pattern makes it possible to conclude that the content of the containers on which the Glass pattern is visible has not been moved or mechanically affected, which also allows to conclude the integrity of this content.

[101] Figures 22 to 24 illustrate an implementation of the invention to provide authentication or identification of a sand surface displayed at two different times and having been partially modified. Thus, FIG. 22 is an image of the sand surface in an initial state while FIG. 23 is an image of the same surface acquired after alteration of this surface by a mark 2 made with a stick. The image of Figure 23 differs from that of Figure 22 by the presence of a shadow 3 and a slight difference in shooting angle. The superimposition of these two images with a slight relative rotation shows a pattern of Glass M as shown in Figure 24. The visualization of this pattern of Glass can be concluded that this is the same surface of sand so from the same place. Moreover, observation of the Glass pattern demonstrates that the method according to the invention is resistant to partial alterations of the authentic and robust subject with regard to the variations of the acquisition conditions of the authentication and verification images.

[102] It may further be noted that Glass patterns are not observable in the area of the image corresponding to the altered portion of the surface or authentication region. Thus, the invention can be implemented to control the integrity of the authentication region insofar as; where the Glass pattern is visible; it is possible to conclude the authentication region is intact or has not been tampered with since the acquisition of the authentication image.

[103] Thus, the method according to the invention makes it possible to control the integrity of the surface of a subject. For this purpose, a series of authentication images is carried out so as to cover the surface whose integrity must be verified. The series of authentication images is recorded as part of the registration phase. During the authentication phase, corresponding in this case to an integrity check, a series of surface verification images are performed whose integrity must be verified in order to cover it. Then, each authentication image of a region of the surface is superimposed with a verification image of the same region of the surface in case of visualization of a pattern of Glass conclude to the integrity of the corresponding region, the doubt about the integrity remaining in the regions where the pattern does not appear.

[104] According to another variant of the invention, the Visual Authentication Method uses visual cryptography. It should be noted that this variant may according to its implementation be assimilated to a method of pure visual cryptography. Typically the choice of a rotation to be applied locally within a thick edge grid on the authentication image can be done as a residual geometric transformation, accompanied by a gray level inversion to improve the contrast of the message during the overlay.

[105] In this context, it is an authentication image of a sheet of paper which is recorded after having masked it according to a matrix or grid of cells whose inner surface is formed by the corresponding part of the image of authentication and which are separated by an independent thick edges intended to break the continuity of the image to avoid any detection of the geometric transformation applied within each cell whose choice depends on a random bit and, if appropriate, on the bit corresponding to the image-message here supposed to be binary to transmit, as is apparent from Figure 25. In this case the transformed cells are rotated a few degrees around their center or isobarycentre. The authentication image as illustrated in Figure 25 is then registered. It is possible to notice that no message is visible in FIG. 25. When a reading of the message hidden in FIG. 25 is desired, a verification image, as illustrated in FIG. image of the same authentication region as that used for the realization of the authentication image.

[106] The verification image (FIG. 26) is then superimposed on the authentication image (FIG. 28) and the image of FIG. 27 is thus obtained where it is possible to read the message Elc. In order to facilitate the reading, the image of the superposition can undergo an improvement processing such as a histogram transformation which makes it possible to obtain the image illustrated in FIG. 28 on which the message is more contrasted. [107] Of course Various other variants of the process according to the invention may be envisaged within the scope of the appended claims.

Claims (29)

1. Visual process for authenticating and / or checking the integrity of a subject consisting of superimposing visually, optically or electronically: on the one hand, at least one so-called authentication image of at least one region; authentication of an authentic subject, the authentication image comprising at least one random component texture, and, secondly, the authentication region in itself of a candidate subject or at least one image of verification of the authentication region of the candidate subject, in case of observation by an operator, on the image resulting from the superposition, of a glass pattern optical phenomenon at the level of the authentication region conclude that the candidate subject is the authentic subject and / or the at least partial integrity of the authentication region of the authentic subject. 2. The visual authentication and / or integrity control method as claimed in claim 1, comprising the following steps: selecting an authentic subject from three-dimensional or hardware subjects each having at least one authentication region having, in given observation conditions, an intrinsic material structure not easily reproducible and observable by an observer having a mean visual acuity, - in a recording phase: - acquisition of at least one optical image called authentication of the authentic subject including at minus the authentication region, the acquisition being performed at a given acquisition magnification or magnification in given conditions such that for an observer having a mean visual acuity the image of the authentication region has at least one texture with random component, - registration of the authentication image, - dan s a phase of visual verification carried out by an operator: - at least partial superimposition of each authentication image and a candidate subject, for: - in case of observation by the operator of the appearance of an optical phenomenon of the Glass motif type conclude that the candidate subject is the authentic subject, - and in case of non observation of a Glass pattern, perform at least a geometric transformation of the authentication image and / or a relative displacement of the authentication image with respect to the candidate subject for, in case of observation by the operator of the appearance of a glass pattern optical phenomenon, to conclude that the candidate subject is the authentic subject. Visual visual authentication method according to claim 2, characterized in that the authentication image is projected onto the candidate subject. 4. Visual authentication method according to one of the preceding claims, characterized in that the acquisition of the authentication image is performed at a magnification or acquisition magnification for superimposition of the acquisition image. and the candidate subject. 5. Visual authentication method according to one of the preceding claims, characterized in that the authentication region is at least translucent and in that the verification phase is performed in transvision. 6. Visual authentication method according to one of the preceding claims, characterized in that the verification phase is performed by means of an electronic device comprising at least display means adapted to display or project the image of authentication and to allow the superposition of the candidate subject and the authentication image substantially on the scale of the candidate subject. 7. Visual authentication and / or integrity control method according to claim 1, comprising the following steps: selection of an authentic subject among three-dimensional or material subjects each comprising at least one so-called authentication region having, in given observation conditions, an intrinsic micro structure not easily reproducible and observable by an observer having a mean visual acuity, - in a recording phase: - acquisition of at least one so-called authentication image of the authentic subject including at minus the authentication region, the acquisition being carried out at a magnification or magnification of acquisition such that for an observer having a mean visual acuity the image of the authentication region has a random component texture, - recording of the authentication image, - in a visual verification phase carried out by an operator: acquisition of at least one verification image of a candidate subject comprising at least a part of the authentication region, the acquisition being performed at a magnification or magnification allowing a visualization of the authentication and verification images at a same scale, - at least partial superimposition of the authentication and verification images substantially on the same scale, for: - in case of observation by the operator of the appearance of a glass pattern optical phenomenon conclude that the candidate subject is the authentic subject, - and in case of non-observation of a Glass pattern, perform at least one geometric transformation of at least one image of the superimposed images and / or a relative displacement of the superimposed images for: in case of observation by the operator of the appearance of a glass pattern optical phenomenon conclude that the candidate subject is the authentic subject. 8. Visual authentication method according to the preceding claim characterized in that the verification phase is performed by means of an electronic device comprising at least: acquisition means adapted to acquire at least one verification image, display means adapted to display on a display screen the verification image and to allow the superimposition of the verification and authentication images substantially on the same scale. 9. Visual authentication method according to the preceding claim characterized in that the electronic device is adapted to ensure a display of a sequence or series of verification images resulting from a relative displacement of the acquisition means and the candidate subject and to allow the superimposition of the verification images with the authentication image. 10. Visual authentication method according to claim 8 or 9, characterized in that the electronic device comprises processing means adapted to perform a geometric transformation at least local at least one image of the superimposed images and / or a relative displacement superimposed images. 11. Method according to one of claims 8 to 10, characterized in that at least one verification image is recorded in digital form. 12. Method according to one of claims 8 to 11, characterized in that the verification image is displayed and / or recorded in gray level or semitones. 13. Visual authentication method according to one of claims 8 to 12, characterized in that it further comprises an automatic verification phase which is carried out in part at least by the electronic device and which comprises a calculation step of a similarity coefficient between a verification image and the authentication image for si, the similarity coefficient is greater than a given threshold, conclude that there is a high probability of authenticity, and even an authenticity, and if not, do not conclude with authenticity. 14. Visual authentication method according to the preceding claim, characterized in that the calculation of the similarity coefficient is performed from signatures extracted from a verification image and the authentication image. 15. Visual authentication method according to claim 13 or 14, characterized in that the automatic verification phase comprises a step of transmitting or communicating the result of the automatic verification to a third party or to the user. 16. Visual authentication method according to one of the preceding claims, characterized in that the authentication image is recorded by applying on the latter a matrix or a grid of cells whose inner surface is formed by the corresponding part of the authentication image and which are separated by a surface unrelated to the authentication image and in that prior to registration of the authentication image, at least some of the cells undergo a geometric transformation of the image contained in the corresponding cell. 17. Method according to the preceding claim, characterized in that the cells undergoing a transformation are chosen so as to form a message or pattern during the superposition with a verification image. 18. Method according to one of the preceding claims, characterized in that the geometric transformation consists of at least one locally applied geometric transformation chosen from affine or rigid transformations or combinations of affine and / or rigid transformations. 19. Method according to one of the preceding claims, characterized in that the geometric transformation induces a reduced or small or very small amplitude modification of the modified image portion and preferably less than the correlation length of the image of the image. authentication region before modification. 20. Method according to one of the preceding claims, characterized in that the relative displacement is a translation, a rotation or the combination of one or more rotation and / or translation. 21. Method according to one of the preceding claims, characterized in that the relative displacement distance is reduced or small or very small amplitude and preferably less than the correlation length of the image of the authentication region. 22. Visual visual authentication method according to one of the preceding claims, characterized in that the authentication image is recorded in an analog form on a photographic film type analog medium or printed on a transparent medium. 23. Visual authentication method according to one of the preceding claims, characterized in that the authentication image is recorded in gray level or semitones. 24. Visual authentication method according to one of the preceding claims, characterized in that the authentication image is recorded in digital form. 25. Visual authentication method according to the preceding claim, characterized in that the authentic subject is associated with an identifier and in that the corresponding authentication image is stored in a database being indexed at least by the identifier of the authentic subject. 26. Method according to one of the preceding claims, characterized in that the authentication and verification images are subjected to at least one descreening and / or filtering before superposition. 27. Method according to one of the preceding claims, characterized in that the position of the authentication region on the authentic subject is recorded. 28. Method according to one of the preceding claims, characterized in that the position of the authentication region on the authentic subject is marked on the subject to authentic. 29. Method according to one of the preceding claims, characterized in that the subject to be identified belongs to at least one of the following categories of subject: fiduciary document, security document, bank note, contract document, coin, official document , document or piece of identity, fingerprint or biometric, natural scene.