Security element, corresponding intaglio printing plate, and method and apparatus for creating, decoding and authenticating the security marking of said security element - Patents.com

Abstract

The present invention relates to a security marking printed via an intaglio process, a corresponding engraved intaglio printing plate, as well as a method and an apparatus for creating, encoding / decoding and authenticating said security marking. The security marking comprises a multi-tone 2D intaglio pattern of intaglio modules containing encoded data with a specific encoding symbol, the decoding of which, together with the measured tone values ​​of small shifts around their position in the decoding stage on a digital image of said intaglio pattern that correlates with said symbol, provides a robust and accurate estimation of the registration error between the modules of separate tones, thus allowing to easily detect any fake marking obtained via offset printing, even with a smartphone.

Description

[Technical field]

[0001]

[0001] The present invention relates to the technical field of two-dimensional multi-colour patterns printed by the intaglio process intaglio on security documents (e.g. banknotes, passports), stamps or tickets via intaglio printing with multi-tone intaglio inks (see for example EP 2 956 514) to provide protection against counterfeiting or unauthorized copying. The present invention further relates to the technical field of coding / decoding and authentication methods of two-dimensional coding patterns (see for example EP 2 619 714 or EP 2 780 865). BACKGROUND OF THEINVENTION

[0002]

[0002] Security markings comprising two-dimensional patterns printed by an intaglio process having thin recessed lines which may be of different colours or different tones of the same colour (e.g. half-tone intaglio patterns) are widely used as protection against their unauthorized duplication as it is extremely difficult to produce copies without misregistration.

[0003]

[0003] Intaglio printing results in the most consistent and high quality printing of fine lines. It can be considered the printing technique of choice to produce fine designs in the field of security documents, especially banknotes and stamps. One of the distinguishing features of the intaglio printing process is that the intaglio relief can be varied from a few micrometers to tens of micrometers by using corresponding shallow or respectively deep recesses of the intaglio printing plate. The intaglio relief, resulting from the thickness of the intaglio ink layer, is accentuated by the embossing of the substrate, said embossing being created by the pressure during the ink transfer. The tactility resulting from intaglio printing gives banknotes their typical and recognizable tactile feel.

[0004]

[0004] It is known in the art that intaglio inks can be used to create multi-tone designs, i.e. by printing a single intaglio ink in a single-step process, it is possible to create a printed design containing several different shades as a result of different printing ink thicknesses resulting from the engraving depth of different intaglio plates. EP 2956514 discloses an intaglio ink composition suitable for printing multi-characteristic intaglio printed designs in a predictable manner. The intaglio ink composition disclosed in EP 2956514 comprises two components which are pigment particles with different modal particle sizes.

[0005]

[0005] When the intaglio printing of a pattern (i.e. the "intaglio pattern") is realized in only one color, the technique commonly used to reproduce said pattern is the offset printing technique. In this case, it is true that a typical high-quality copy will not be free of misregistration errors whose visual appearance would be misleading, but of course the particular tactile perception provided by the relief features of the intaglio printed pattern is lost. This is one of the reasons why many banknotes around the world contain intaglio security features.

[0006]

[0006] In the case of multi-tone or multi-color intaglio patterns, the offset printing technique cannot provide copies without registration errors (due to the multiple offset steps and printing plates), the more colorful the worse. However, if the offset printing is performed with sufficient care, these registration errors can be hardly noticeable to the human eye or to a person on the street, and require specific analysis tools (e.g. magnifying lenses, microscopes) that are not generally available.

[0007]

[0007] There is therefore a need for a security intaglio pattern which can be easily detected as a counterfeit or unauthorized copy by commonly available means capable of taking a simple digital image of the pattern, for example a smartphone equipped with a camera, even when the smartphone camera has very low resolution, and even when advanced offset printing techniques are used. Summary of the Invention

[0008]

[0008] In order to overcome the above-mentioned drawbacks and limitations of the prior art, a security marking has been developed in accordance with the present invention which comprises both multi-tone intaglio printing of a pattern and encoding of said pattern by a highly secure encoding scheme, for example as specified in the above-cited EP Patent No. 2 619 714 or EP Patent No. 2 780 865.

[0009]

[0009] In particular, EP 2 780 865 discloses a pattern for encoding a numerical information item on a surface, comprising a particular arrangement of a plurality of symbols belonging to a set of symbols, each symbol in the arrangement intended to encode a part of said numerical information item, each symbol consisting of at least one differential pair of elements arranged in a particular way, each element comprising a parameter, the parameter of a first element of each differential pair having a first value and the parameter of a second element of each differential pair having a second value different from the first value, said particular arrangement corresponding to a predetermined arrangement of said symbols constituting a reference pattern.

[0010]

[0010] Furthermore, corresponding methods and apparatus for creating, encoding or decoding, and authenticating said security markings (through commonly available means) have also been developed in accordance with the present invention, so that counterfeit copies can be easily detected by anyone.

[0011]

[0011] In alternative printing processes, such as offset, silk screen, gravure or inkjet, the use of inks of different colors is essential to create designs containing three or more colors. However, these printing processes are not suitable to provide the required resolution and / or registration for the different colors of the security marking of the present invention. Therefore, these printing processes cannot be used to create multi-tone security features, including multi-tone security patterns as disclosed herein. If these alternative printing processes are used to attempt to replicate security markings of value documents as disclosed herein, the authentication according to the present invention of the copy will fail and the corresponding printed security document will be identified as a counterfeit.

[0012]

[0012] A security element according to a first aspect of the present invention comprises a substrate and a security marking, the security marking comprising a two-dimensional intaglio pattern printed on a surface of the substrate by intaglio printing with intaglio inks, the two-dimensional intaglio pattern comprising at least one base intaglio pattern having related colours and comprising a plurality of intaglio modules, each base intaglio pattern comprising only intaglio modules whose tones belong to corresponding sets of two different admissible tones, each intaglio module having one tone of said related colour, the tones of the intaglio modules being selected from a tone palette of a plurality of different reference tones of the related colours, and the CIE colour difference ΔE* between the tones is 2.0 or more, the width ε of the intaglio modules being greater than 20 μm and less than or equal to 50 μm, the two-dimensional intaglio pattern being created on the basis of an associated two-dimensional coding pattern comprising at least one reference pattern, each of the at least one base intaglio pattern being based on an associated reference pattern of the at least one reference pattern, each base intaglio pattern and the associated reference pattern encoding the same information portion specifying a unique identification number of the associated reference pattern, each reference pattern comprising a specific arrangement of a plurality of symbols, each symbol within the arrangement allowing to encode data according to a state of said symbol, the state of each symbol consisting of a specific arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 within the symbol, each element E having a corresponding parameter value p(E), the parameter of the first element E1 being dependent on the parameter of the second element E2. a positive value of the parameter p different from the zero value, each reference pattern only comprises dark and light symbols, the parameter value of the first element of the dark symbol corresponds to the dark tone of the pair of allowed tones of the associated base intaglio pattern and the parameter value of the first element of the light symbol corresponds to the light tone of said pair of allowed tones, and each intaglio module of each base intaglio pattern of the two-dimensional intaglio pattern is printed either as a separate intaglio module corresponding to the first element of a symbol of the associated reference pattern of the two-dimensional coding pattern and its position in the reference pattern, or as part of a concave line having the same parameter value p and connecting two first elements belonging respectively to two separate adjacent symbols of the associated reference pattern of the two-dimensional coding pattern and corresponding to the position of that line in the reference pattern.

[0013]

[0013] An intaglio module may be printed separately from other adjacent intaglio modules or may be part of a (thin) recessed line which may be connected to other parts of the recessed lines of adjacent intaglio modules to form a continuous path.

[0014]

[0014] The security marking described above may include a plurality of two-dimensional intaglio patterns, each having a corresponding associated color from a color palette, any color in the color palette being different from the background color of the substrate.

[0015]

[0015] Preferably, the security element comprises a plurality of two-dimensional intaglio patterns, each two-dimensional intaglio pattern having a corresponding associated colour which is different from the background colour of the substrate.

[0016]

[0016] Preferably, the two-dimensional intaglio pattern of the above-mentioned security marking is contained in a cell having a boundary formed by a concave line higher than the height of any of the intaglio modules of said two-dimensional intaglio pattern, and the distance between the edge of the two-dimensional intaglio pattern and the boundary of the cell is 40 μm or more.

[0017]

[0017] More preferably, the CIE colour difference ΔE* between the tones is 2.5 or greater.

[0018]

[0018] According to a second aspect, the present invention relates to an engraving surface for an intaglio printing press, comprising grooves of variable engraving depth adapted to receive intaglio ink and print a two-dimensional intaglio pattern of a security marking of a security element as specified above on the surface of a substrate.

[0019]

[0019] Thus, the above-mentioned engraved surface makes it possible to print an intaglio pattern on the surface of a substrate comprising a plurality of intaglio modules having the colour of an intaglio ink and forming a particular pattern of intaglio lines, each intaglio module having a tone of said colour, the tones of the intaglio modules of a plurality of different reference tones of said colour ranging from dark to light tones, and the CIE colour difference ΔE* between the tones being 2.0 or more, and the width ε of the intaglio lines being greater than 20 μm and less than 50 μm.

[0020] In fact, the variable engraving depth of the engraved plate surface is determined by the fact that the intaglio modules of the two-dimensional intaglio pattern are - the first element of a symbol of a reference pattern of a two-dimensional coding pattern, or - constitute a part of a concave line corresponding to a line connecting two elements having the same positive parameter value p, each of which belongs to two distinct adjacent symbols of a reference pattern of a two-dimensional coding pattern; The intaglio module is adapted to produce an intaglio module corresponding to any one of the following:

[0021]

[0021] According to a third aspect, the invention also relates to a corresponding method for producing a security element comprising a security marking comprising a two-dimensional intaglio pattern according to any one of claims 1 to 4, comprising: (i) generating a two-dimensional coding pattern comprising at least one reference pattern by encoding an information portion in each of said at least one reference pattern forming the two-dimensional coding pattern, said information portion assigning to each reference pattern its unique identification number, each reference pattern comprising a particular arrangement of a plurality of symbols, each symbol in the arrangement being capable of encoding data according to a state of said symbol, each symbol state consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 in the symbol, each element E having a corresponding parameter value p(E), a zero value of the parameter of the first element E1 being equal to a zero value of the parameter of the second element E2; a first element of the dark symbol corresponds to a dark tone of a pair of associated permissible tones selected from a tone palette of a plurality of distinct reference tones of a color associated with the two-dimensional coding pattern, and a first element of the light symbol corresponds to a light tone of said pair of associated permissible tones; a two-dimensional intaglio pattern to be created based on the generated two-dimensional coding pattern comprises at least one base intaglio pattern comprising a plurality of intaglio modules, each intaglio module having one tone of said associated color, the tones of the intaglio modules being selected from a tone palette, each of the at least one base intaglio pattern is based on an associated reference pattern of the at least one reference pattern, each base intaglio pattern encoding the same information portion as the associated reference pattern; each base Intaglio pattern contains only Intaglio modules whose tones belong to the pair of allowed tones of the associated reference pattern; and Each intaglio module of each base intaglio pattern of the two-dimensional intaglio pattern is as a first element of the symbol of an associated reference pattern of the two-dimensional coding pattern and a separate intaglio module corresponding to its position within the reference pattern, or as a part of a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of an associated reference pattern of the two-dimensional coding pattern, and a concave line corresponding to the position of that line in the reference pattern; The step to be printed is either (ii) engraving an intaglio printing machine plate having a variable engraving depth adapted to receive an intaglio ink of said color and to reproduce the intaglio modules of the two-dimensional intaglio pattern according to the generated two-dimensional coding pattern; (iii) inking the plate with an intaglio ink and using the inked plate to print a corresponding two-dimensional intaglio pattern onto the surface of the substrate using an intaglio printing press; The present invention relates to a method comprising the steps of:

[0022]

[0022] According to a corresponding fourth aspect, the invention relates to a method for decoding information encoded in a two-dimensional intaglio pattern of a security marking of a security element, the two-dimensional intaglio pattern comprising at least one base intaglio pattern comprising a plurality of intaglio modules, imaging the two-dimensional intaglio pattern; - detecting an arbitrary reference pattern of at least one reference pattern forming a two-dimensional coding pattern from an imaged intaglio module of the imaged two-dimensional intaglio pattern, on the basis of which a corresponding authentic two-dimensional intaglio pattern of an authentic security marking of an authentic security element according to any one of claims 1 to 4 is generated; - decoding each detected reference pattern and retrieving corresponding decoded information of the two-dimensional coded pattern; - verifying each decoded reference pattern and its corresponding base intaglio pattern; The present invention relates to a method comprising the steps of:

[0023]

[0023] Preferably, the above-mentioned method for decoding information comprises the steps of: a) imaging the two-dimensional intaglio pattern of the security marking using a camera equipped with a processor and a memory and whose optical sensor is adapted to detect the colours of the intaglio modules forming the authentic intaglio pattern and the different tones of a tone palette of said colours to obtain a digital image of the two-dimensional intaglio pattern and to store the obtained digital image in a memory, the memory storing a set of associated reference patterns and storing for each stored reference pattern an information portion specifying a corresponding reference pattern identification number, each stored reference pattern comprises a particular arrangement of a plurality of symbols, each symbol within the arrangement being capable of encoding data according to a state of said symbol, each symbol state consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 within the symbol, each element E having a corresponding parameter value p(E), the parameter of the first element E1 having a positive value different from the zero value of the parameter of the second element E2, - each pair of permitted tones of an Intaglio module of each base Intaglio pattern is stored in a memory in association with a corresponding base Intaglio pattern and in association with a reference pattern identification number of a reference pattern associated with said base Intaglio pattern; - each stored reference pattern comprises only dark and light symbols, the parameter value of a first element of a dark symbol corresponds to the dark tone of the pair of permitted tones of the associated base Intaglio pattern, and the parameter value of a first element of a light symbol corresponds to the light tone of the pair of permitted tones of said associated base Intaglio pattern; b) detecting, in the stored digital image, an Intaglio module within the window through image processing of the pixels of the digital image scanned by a processor through a movable window of the size of the reference pattern; - b1) for a candidate reference pattern selected from a set of stored reference patterns, each of said detected intaglio modules is a separate intaglio module corresponding to a first element of the symbol of the candidate reference pattern and its position within the candidate reference pattern; or represents a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of the candidate reference pattern, and a portion of the concave line corresponding to the position of the line in the candidate reference pattern and checking whether the - b2) if a detected intaglio module corresponds to a respective element of a symbol of a candidate reference pattern, decoding the candidate reference pattern to obtain its candidate reference pattern identification number and thereby decoding the associated base intaglio pattern, verifying the decoded candidate reference pattern and the decoded associated base intaglio pattern to obtain a corresponding associated verified reference pattern and a verified base intaglio pattern, and storing in a memory corresponding position data indicating the position on the digital image of the verified base intaglio pattern; - b3) if the detected intaglio modules do not correspond to the respective elements of the symbol of the candidate reference pattern, selecting a new candidate reference pattern from the set of stored reference patterns and carrying out steps b1) to b2) with said new candidate reference pattern; - b4) if the detected intaglio module does not correspond to a respective element of one of the symbols of the candidate reference patterns, moving a window with respect to the digital image to scan another area of ​​the digital image and detecting an intaglio module through the moved window and performing steps b1) to b3) until the entire digital image has been scanned through the window; c) delivering a signal indicating failure of decoding of the two-dimensional intaglio pattern if the entire digital image is scanned through the window and the detected intaglio modules do not correspond to the respective elements of the symbols of any of the candidate reference patterns; Includes.

[0024]

[0024] According to a fifth aspect of the invention, corresponding to the above-mentioned fourth aspect, the invention further relates to an apparatus for decoding information coded in a two-dimensional intaglio pattern of a security marking of a security element, the two-dimensional intaglio pattern comprising at least one base intaglio pattern comprising a plurality of intaglio modules, the apparatus comprising a camera equipped with a processor, a memory and a light sensor adapted to detect colours of the authentic intaglio pattern and tones that differ from a tone palette of said colours, the authentic two-dimensional intaglio pattern of the authentic security marking of the authentic security element is as defined in any one of claims 1 to 4, the processor is adapted to perform image processing of a digital image of the authentic two-dimensional intaglio pattern captured by the camera and stored in the memory and to perform a decoding operation of the coded information detected on the digital image, the memory stores at least one reference pattern forming the two-dimensional coding pattern, on the basis of which the authentic two-dimensional intaglio pattern has been created, the apparatus comprising: - imaging a two-dimensional intaglio pattern; - detecting an arbitrary reference pattern of at least one reference pattern of the two-dimensional coding pattern from an imaged intaglio module of the imaged two-dimensional intaglio pattern, on the basis of which an associated real two-dimensional intaglio pattern is created; - decoding each detected reference pattern and searching for corresponding decoded information in the two-dimensional coded pattern; - verifying each decoded reference pattern and its corresponding base intaglio pattern; The method is adapted to perform the following steps:

[0025] In a preferred mode of the above described device for decoding information, Each stored reference pattern comprises a particular arrangement of a plurality of symbols, each symbol in the arrangement enabling data to be encoded according to a state of said symbol, each state of the symbol consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 in the symbol, each element E having a corresponding parameter value p(E), the parameter of the first element E1 having a positive value different from the zero value of the parameter of the second element E2; each pair of permitted tones of the intaglio modules of each base intaglio pattern is associated with the base intaglio pattern and is stored in a memory in association with a reference pattern identification number of a reference pattern associated with said base intaglio pattern; each stored reference pattern comprises only dark and light symbols, the parameter value of a first element of a dark symbol corresponds to the dark tone of a pair of allowed tones of an associated base intaglio pattern, and the parameter value of a first element of a light symbol corresponds to the light tone of said associated pair of allowed tones, The device is a) imaging a two-dimensional intaglio pattern of a security marking using a camera to obtain a digital image of the two-dimensional intaglio pattern and storing the obtained digital image in a memory; b) detecting stored digital image intaglio modules within a movable window of the size of the accepted reference pattern through image processing of pixels of the digital image scanned by a processor through the window; b1) each of said detected intaglio modules is a distinct intaglio module which corresponds, for a candidate reference pattern selected from a set of reference patterns, to a first element of a symbol of the candidate reference pattern and its position within the candidate reference pattern; or represents a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of the candidate reference pattern, and a portion of the concave line corresponding to the position of the line in the candidate reference pattern and b2) if the detected intaglio module corresponds to a respective element of a symbol of the candidate reference pattern, decoding the candidate reference pattern to obtain its candidate reference pattern identification number and thereby decoding the associated base intaglio pattern, verifying the decoded candidate reference pattern and the decoded associated base intaglio pattern to obtain a corresponding associated verified reference pattern and a verified base intaglio pattern and storing in a memory corresponding position data indicating the position on the digital image of the verified base intaglio pattern; b3) selecting a new candidate reference pattern from the set of stored reference patterns if the detected intaglio modules do not correspond to the respective elements of the symbol of the candidate reference pattern, and performing steps b1) to b2) using said new candidate reference pattern; b4) if the detected intaglio module does not correspond to an element of any one of the symbols of the candidate reference patterns, shifting a window with respect to the digital image to scan another area of ​​the digital image and detecting the intaglio module through the shifted window and performing steps b1) to b3) until the entire digital image has been scanned through the window; c) delivering a signal indicating failure of decoding of the two-dimensional intaglio pattern if the entire digital image is scanned through the window and the detected intaglio modules do not correspond to the respective elements of the symbols of any of the candidate reference patterns; The method is adapted to perform the following steps:

[0026]

[0026] The device for decoding information may be a smartphone equipped with a camera and a processor programmed to decode data and perform digital image processing operations on a digital image captured by the camera according to the steps of the above-mentioned method for decoding information, the camera having a simple RGB (i.e., "red, green, blue") light sensor adapted to detect the intaglio modules and their tones of the two-dimensional intaglio pattern according to the present invention.

[0027]

[0027] According to a sixth aspect, the invention also relates to a method for authenticating a two-dimensional intaglio pattern of a security marking of a security element, comprising: - performing an operation of decoding the information encoded in the two-dimensional intaglio pattern according to the above-mentioned method for decoding information to obtain, from the imaged two-dimensional intaglio pattern, each base intaglio pattern and its corresponding verified reference pattern; - shifting, for each verified base Intaglio pattern, an intaglio module, which corresponds respectively to a tone of a pair of permitted tones from the color tone palette of the authentic two-dimensional Intaglio pattern, along a number of different directions relative to an initial position corresponding to the respective position of the detected intaglio module of each verified base Intaglio pattern on the photographed image of the two-dimensional Intaglio pattern upon decoding, to obtain corresponding shifted images of said intaglio modules; - determining, for each verified Intaglio pattern, for each corresponding symbol of the associated reference pattern, a pair of shift values ​​respectively for the Intaglio modules corresponding to each tone of said pair of allowed tones from the difference between the measured tone value at an initial position of the shifted Intaglio module on the respective shifted image and the measured tone value at the same initial position of said intaglio module on the image of the two-dimensional Intaglio pattern when decoded, and providing the maximum tone value of the verified base Intaglio pattern for all intaglio modules respectively corresponding to each tone of said pair of allowed tones; determining that each intaglio module of the two-dimensional intaglio pattern is in register only if, for a pair of permissible tones, the average norm value of the pairs of determined shift values ​​over all the verified base intaglio patterns of the two-dimensional intaglio pattern is less than or equal to 10 μm, preferably less than or equal to 5 μm; The present invention relates to a method comprising the steps of:

[0028]

[0028] Preferably, the above-mentioned method for authenticating a two-dimensional intaglio pattern according to the invention comprises the steps of: A) performing the operations a), b), b1), b2), b3), b4) and c) of the method for decoding information encoded in a two-dimensional intaglio pattern described above on the two-dimensional intaglio pattern to be authenticated, B) if the decoding of the two-dimensional intaglio pattern fails in step A), delivering information indicating that the decoding of the two-dimensional intaglio pattern has failed; C) if step A) provides for each stored location on the digital image of the verified base Intaglio pattern, information encoded in the two-dimensional Intaglio pattern indicating the reference pattern identification number of the associated verified reference pattern, determining the multi-tone aspect of the verified base Intaglio pattern by: determining their distinct allowed tone pairs Ta, Tb from their respective associated verified reference pattern identification numbers; measuring the printed tone value of each intaglio module of the verified base intaglio pattern on the digital image and determining a dynamic range of the digital image from the measured tone values; calculating an average printed tone value Ta of the intaglio modules of the verified base intaglio pattern corresponding to the tolerance tones Ta as the average of the measured printed tone values ​​of the intaglio modules corresponding to the tolerance tones Ta, and calculating an average printed tone value Tb of the intaglio modules of the verified base intaglio pattern corresponding to the tolerance tones Tb as the average of the measured printed tone values ​​of the intaglio modules corresponding to the tolerance tones Tb, For each acceptable tone pair Ta, Tb, check whether a multi-tone criterion is met that the difference between the calculated average printed tone values ​​Ta and Tb is greater than 1% of the dynamic range; and determining that the two-dimensional intaglio pattern has said multi-tone aspect if a multi-tone criterion is satisfied for each pair of allowed tones; or If the multi-tone criteria are not met for the pair of allowed tones Ta, Tb, then the two-dimensional intaglio pattern does not have the multi-tone aspect and is deemed to be inauthentic. and verifying by D) for each verified base Intaglio pattern having a corresponding pair of allowed tones Ta, Tb, whose location in the digital image is stored in memory, if the two-dimensional Intaglio pattern has a multi-tone aspect, using a processor: D1) measuring, within a window arranged at said position on the digital image, printed tone values ​​of the intaglio modules of the verified base Intaglio pattern from pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, via a sampling grid having an arrangement of symbols with respective sites of their two-dimensional elements E1 and E2 corresponding to symbols of a verified reference pattern associated with said verified base Intaglio pattern, to obtain corresponding initial tone values ​​attributable to each element E1 and E2 of the symbols of the verified reference pattern associated with the verified base Intaglio pattern, calculating for each symbol of the sampling grid the difference between the initial tone value attributable to element E1 and the initial tone value attributable to element E2 to obtain an initial differential symbol tone value, and storing in a memory the obtained initial differential symbol tone values ​​attributable to elements of the symbols of the verified reference pattern, wherein for each of two allowed tones Ta, Tb of the verified reference pattern a corresponding zero-shift sum is obtained by summing up the initial differential symbol tone values ​​of all symbols of the verified reference pattern corresponding to tones Ta and Tb, respectively, and the obtained zero-shift sum for the allowed tone Ta and the obtained zero-shift sum for the allowed tone Tb are stored in the memory, D2) shifting pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to an allowed tone Ta, backwards and forwards relative to the digital image along each of the plurality of different directions by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to each element E1 and E2 of the symbol of the sampling grid, the first element of which corresponds to the allowable tone Ta, for backward and forward shifts along each direction, respectively, through the sampling grid from shifted pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowable tone Ta, and storing the obtained shifted tone values ​​in a memory; For each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Ta, calculate a difference between the shifted tone value due to element E1 and the shifted tone value due to element E2 to obtain a corresponding shifted differential symbol tone value, and store in a memory the obtained shifted differential symbol tone value due to an element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Ta; For each shift, summing the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Ta to obtain a corresponding verified reference pattern shift sum for the allowed tone Ta; and selecting a best shift for the allowed tone Ta corresponding to a maximum calculated shift sum among the calculated shift sums and the zero shift sums for the verified reference pattern; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all selected best shifts for the tolerance tone Ta over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of tolerance tones Ta, Tb; a The operation of calculating D3) shifting pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to an allowed tone Tb, backwards and forwards along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to each element E1 and E2 of the symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, for backward and forward shifts along each direction, respectively, through the sampling grid, from shifted pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, and storing the obtained shifted tone values ​​in a memory; For each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Tb, calculate the difference between the shifted tone value due to element E1 and the shifted tone value due to element E2 to obtain a corresponding shifted differential symbol tone value, and store in a memory the obtained shifted differential symbol tone value due to an element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Tb; For each shift, sum the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Tb to obtain a corresponding verified reference pattern shift sum for the allowed tone Tb; and selecting a best shift for the allowed tone Tb corresponding to a maximum calculated shift sum among the calculated shift sums and the zero shift sums for the verified reference pattern; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all selected best shifts for the tolerance tones Tb over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of tolerance tones Ta, Tb; b The operation of calculating D4) For each remaining pair of tones Ta', Tb' from the pairs of tones of the stored verified base intaglio patterns of the two-dimensional intaglio pattern, perform the above-described operation D) to obtain the corresponding pair of global shifts (Δ a ',Δ b ') and storing said pair of global shifts in memory. and (E) The misregistration value r(a,b) of the intaglio module corresponding to any pair of allowable tones Ta, Tb of all verified base intaglio patterns of the two-dimensional intaglio pattern is expressed as r(a,b)=λ / f(Δ a 2 +Δ b 2 ) 1 / 2 where λ is the pixel size of the digital image in μm (i.e., 10 -6 determining that the two-dimensional intaglio pattern is genuine if the size of the two-dimensional intaglio pattern in units of m, f is the magnification of the digital image, and each misregistration value r(a,b) of each acceptable tone pair Ta, Tb of the verified base intaglio pattern of each of the two-dimensional intaglio patterns is less than or equal to 10 μm, preferably less than or equal to 5 μm; may include:

[0029]

[0029] According to a seventh aspect, corresponding to the above-mentioned authentication method, the invention further provides an apparatus for authenticating a two-dimensional intaglio pattern of a security marking of a security element, wherein the authentic two-dimensional intaglio pattern of the authentic security marking of an authentic security element is as defined in any one of claims 1 to 4, the apparatus comprising a camera equipped with a processor, a memory and a light sensor adapted to detect the colours of the authentic intaglio pattern and the different tones of a tone palette of said colours, the processor being adapted to perform image processing of a digital image of the authentic two-dimensional intaglio pattern taken by the camera and stored in the memory and to perform a decoding operation on the coded information detected on the digital image, the memory stores at least one reference pattern forming the two-dimensional coded pattern, on the basis of which the authentic two-dimensional intaglio pattern has been created, and the apparatus - decoding the information encoded in the two-dimensional intaglio pattern according to the above-mentioned decoding method to obtain, from an image of the two-dimensional intaglio pattern captured by the camera, each verified base intaglio pattern and its corresponding verified reference pattern; - shifting, for each verified base intaglio pattern, an intaglio module, which corresponds respectively to a tone of a pair of permissible tones from the color tone palette of the genuine two-dimensional intaglio pattern, along a number of different directions relative to an initial position corresponding to a respective position of the detected intaglio module of each verified base intaglio pattern on the photographed image of the two-dimensional intaglio pattern, to obtain corresponding shifted images of said intaglio modules; - determining, for each verified Intaglio pattern, for each corresponding symbol of the associated reference pattern, a pair of shift values, respectively for the Intaglio modules corresponding to each tone of said pair of allowed tones, from the difference between the measured tone value at an initial position of the shifted Intaglio module on the respective shifted image and the measured tone value at the same initial position of said intaglio module on the image of the two-dimensional Intaglio pattern when decoded, and providing the maximum tone value of the verified base Intaglio pattern for all intaglio modules corresponding respectively to each tone of said pair of allowed tones; determining that each intaglio module of the two-dimensional intaglio pattern is in register only if, for that pair of tolerance tones, the average norm value of the pairs of determined shift values ​​over all the verified base intaglio patterns of the two-dimensional intaglio pattern is equal to or smaller than 10 μm, preferably equal to or smaller than 5 μm; The present invention relates to an apparatus adapted to perform the steps of:

[0030]

[0030] Preferably, the above-mentioned device comprises: A) performing the operations a), b), b1), b2), b3), b4) and c) of the method for decoding information encoded in a two-dimensional intaglio pattern using a processor as described above for the two-dimensional intaglio pattern to be authenticated, such that the memory further stores pairs of allowed tones of the authentic two-dimensional intaglio pattern, B) if the decoding of the two-dimensional intaglio pattern in step A) fails, transmitting information indicating that the decoding of the two-dimensional intaglio pattern has failed; C) if step A) provides for each stored location on the digital image of the verified base Intaglio pattern, information encoded in the two-dimensional Intaglio pattern indicating the reference pattern identification number of the associated verified reference pattern, determining the multi-tone aspect of the verified base Intaglio pattern by: determining their distinct allowed tone pairs Ta, Tb from their respective associated verified reference pattern identification numbers; measuring the printed tone value of each intaglio module of the verified base intaglio pattern on the digital image and determining a dynamic range of the digital image from the measured tone values; calculating an average printed tone value Ta of the intaglio modules of the verified base intaglio pattern corresponding to the tolerance tones Ta as the average of the measured printed tone values ​​of the intaglio modules corresponding to the tolerance tones Ta, and calculating an average printed tone value Tb of the intaglio modules of the verified base intaglio pattern corresponding to the tolerance tones Tb as the average of the measured printed tone values ​​of the intaglio modules corresponding to the tolerance tones Tb, For each acceptable tone pair Ta, Tb, check whether a multi-tone criterion is met that the difference between the calculated average printed tone values ​​Ta and Tb is greater than 1% of the dynamic range; and determining that the two-dimensional intaglio pattern has said multi-tone aspect if a multi-tone criterion is satisfied for each pair of allowed tones; or If the multi-tone criteria are not met for the pair of allowed tones Ta, Tb, then the two-dimensional intaglio pattern is determined to not have the multi-tone aspect and is not genuine. As confirmed by D) for each verified base Intaglio pattern having a corresponding pair of allowed tones Ta, Tb, whose location in the digital image is stored in memory, if the two-dimensional Intaglio pattern has a multi-tone aspect, using a processor: D1) measuring, within a window arranged at said position on the digital image, printed tone values ​​of the intaglio modules of the verified base Intaglio pattern from pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, via a sampling grid having an arrangement of symbols with respective sites of their two-dimensional elements E1 and E2 corresponding to symbols of a verified reference pattern associated with said verified base Intaglio pattern, to obtain corresponding initial tone values ​​attributable to each element E1 and E2 of the symbols of the verified reference pattern associated with the verified base Intaglio pattern, calculating for each symbol of the sampling grid the difference between the initial tone value attributable to element E1 and the initial tone value attributable to element E2 to obtain an initial differential symbol tone value, and storing in a memory the obtained initial differential symbol tone values ​​attributable to elements of the symbols of the verified reference pattern, wherein for each of two allowed tones Ta, Tb of the verified reference pattern a corresponding zero-shift sum is obtained by summing up the initial differential symbol tone values ​​of all symbols of the verified reference pattern corresponding to tones Ta and Tb, respectively, and the obtained zero-shift sum for the allowed tone Ta and the obtained zero-shift sum for the allowed tone Tb are stored in the memory, D2) shifting pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to an allowed tone Ta, backwards and forwards relative to the digital image along each of the plurality of different directions by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to each element E1 and E2 of the symbol of the sampling grid, the first element of which corresponds to the allowable tone Ta, for backward and forward shifts along each direction, respectively, through the sampling grid from shifted pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowable tone Ta, and storing the obtained shifted tone values ​​in a memory; For each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Ta, calculate a difference between the shifted tone value due to element E1 and the shifted tone value due to element E2 to obtain a corresponding shifted differential symbol tone value, and store in a memory the obtained shifted differential symbol tone value due to an element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Ta; For each shift, summing the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Ta to obtain a corresponding verified reference pattern shift sum for the allowed tone Ta; and selecting a best shift for the allowed tone Ta corresponding to a maximum calculated shift sum among the calculated shift sums and the zero shift sums for the verified reference pattern; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all selected best shifts for the tolerance tone Ta over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of tolerance tones Ta, Tb; a The operation of calculating D3) shifting pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to an allowed tone Tb, backwards and forwards along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to each element E1 and E2 of the symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, for backward and forward shifts along each direction, respectively, through the sampling grid, from shifted pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, and storing the obtained shifted tone values ​​in a memory; For each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Tb, calculate the difference between the shifted tone value due to element E1 and the shifted tone value due to element E2 to obtain a corresponding shifted differential symbol tone value, and store in a memory the obtained shifted differential symbol tone value due to an element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Tb; For each shift, sum the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Tb to obtain a corresponding verified reference pattern shift sum for the allowed tone Tb; and selecting a best shift for the allowed tone Tb corresponding to a maximum calculated shift sum among the calculated shift sums and the zero shift sums for the verified reference pattern; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all selected best shifts for the tolerance tones Tb over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of tolerance tones Ta, Tb; b The operation of calculating D4) For each remaining pair of tones {Ta', Tb'} from the pairs of tones of the stored verified base intaglio patterns of the 2D intaglio pattern, perform the above operation D) to obtain the corresponding pair of global shifts (Δ a ',Δ b ') and storing said pair of global shifts in memory. To execute E) The misregistration value r(a,b) of the intaglio module corresponding to any pair of allowable tones Ta, Tb of all verified base intaglio patterns of the two-dimensional intaglio pattern is calculated as r(a,b)=λ / f(Δ a 2 +Δ b 2 ) 1 / 2 where λ is the size in μm of a pixel of the digital image, f is the magnification of the digital image, and the two-dimensional intaglio pattern is judged to be genuine if each misregistration value r(a,b) of each acceptable tone pair Ta, Tb of each verified base intaglio pattern of the two-dimensional intaglio pattern is 10 μm or less, preferably 5 μm or less. It may be adapted.

[0031]

[0031] More preferably, the above-mentioned device for authentication is a smartphone, the light sensor is an RGB light sensor, the camera has a resolution of at least 20 μm, and the measurement of the tone of the intaglio modules of the two-dimensional intaglio pattern illuminated with illumination light is performed by summing the respective red, green and blue light intensity components detected by the RBG light sensor from the received light reflected by said intaglio modules. The illumination can be provided by the flash of the smartphone or simply daylight (if the light intensity is sufficient).

[0032]

[0032] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which prominent aspects and features of the invention are shown. [Brief description of the drawings]

[0033] [Figure 1] 1 shows a photograph of a portion of a sample banknote including a security marking according to the present invention comprising a plurality of two-dimensional intaglio patterns printed on an industrial intaglio printing press. [Figure 2A] 1 shows a photograph of an enlarged reproduction of a detail of a two-dimensional intaglio pattern of a security marking according to the invention, printed with a laser printer on A4 standard printing paper. [Figure 2B]1 shows a photograph of an enlarged reproduction of a detail of a two-dimensional intaglio pattern of a security marking according to the invention, printed with a laser printer on A4 standard printing paper. [Figure 2C] 1 shows a photograph of an enlarged reproduction of a detail of a two-dimensional intaglio pattern of a security marking according to the invention, printed with a laser printer on A4 standard printing paper. [Figure 2D] 1 shows a photograph of an enlarged reproduction of a detail of a two-dimensional intaglio pattern of a security marking according to the invention, printed with a laser printer on A4 standard printing paper. [Figure 3A] 2 shows an example of a reference pattern with an arrangement of symbols and the states of these symbols according to the prior art disclosed in EP 2 619 714 B1 and EP 2 780 865 B1. [Figure 3B] 2 shows an example of a reference pattern with an arrangement of symbols and the states of these symbols according to the prior art disclosed in EP 2 619 714 B1 and EP 2 780 865 B1. [Figure 4A] 1 shows an example of a coded reference pattern adapted in one-to-one correspondence with an example of a base Intaglio pattern obtained by the Intaglio printing process of the present invention; [Figure 4B] 1 shows an example of a coded reference pattern adapted in one-to-one correspondence with an example of a base Intaglio pattern obtained by the Intaglio printing process of the present invention; [Figure 4C] 1 shows an example of a coded reference pattern adapted in one-to-one correspondence with an example of a base Intaglio pattern obtained by the Intaglio printing process of the present invention; [Figure 4D] 1 shows an example of a coded reference pattern adapted in one-to-one correspondence with an example of a base Intaglio pattern obtained by the Intaglio printing process of the present invention; [Diagram 5] 1 is a flowchart showing an example of decoding of a two-dimensional intaglio pattern by a smartphone. [Figure 6A] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6B]1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6C] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6D] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6E] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6F] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. [Figure 6G] 1 shows a schematic diagram of the operation of an example of a method for authenticating a two-dimensional intaglio pattern. Detailed Description

[0034] Example The invention will now be described in more detail with reference to non-limiting examples.

[0035] Example E1 Banknote sample FIG. 1 shows a photograph of a portion of a sample banknote comprising a security mark (100) according to an embodiment of the present invention. The sample banknote was printed under industrial conditions on an industrial intaglio printing machine using cyan intaglio printing ink. The two-dimensional intaglio pattern of the security marking (100) is embedded in the intaglio design, in particular in the lapel of the right jacket. As shown in FIG. 1, the two-dimensional intaglio pattern is not detectable by the naked eye and is fully integrated into the intaglio design. A first example of a two-dimensional intaglio pattern of a security marking Ex1 shown in FIG. 1 was printed on a banknote paper substrate (reference paper from Louisenthal) on an intaglio printing machine (Super Orloff SOI II) under banknote industrial printing conditions using an oxidative drying intaglio ink comprising an alkyl-based oxidative varnish, mineral fillers, mineral oil, wax, oxidative drying agent and 4.3 wt. % of a blue pigment (copper phthalocyanine blue (6CI) (CAS Nr 147-14-8) from Synthesia). The security marking was printed using an intaglio plate surface containing engravings with depths of 8 μm (L area), 16 μm (M area), and 22 μm (D area), creating a complete two-dimensional intaglio pattern (201) in the lapel of the jacket, as shown in Figure 2A.

[0036]

[0035] The security marking (100) in Fig. 1 corresponds to a portrait of a person and his / her clothing. The complete two-dimensional intaglio pattern (201) in Fig. 2A is placed on the lapel of the jacket of the person shown in Fig. 1 and contains a number of cells, each cell containing its own (small) two-dimensional intaglio pattern (220). The two-dimensional intaglio pattern (201) was authenticated as authentic according to the present invention using a Samsung Galaxy S10 or S21 smartphone (with a 12 megapixel camera sensor) at a distance of about 10 cm from the banknote specimen surface.

[0037]

[0036] Examples Ex2 to Ex4 and Comparative Examples CEx1 to CEx2 2A-2D show photographs of enlarged reproductions of details of two-dimensional intaglio patterns of security markings, with the two-dimensional intaglio patterns corresponding to Examples 2-4 (Ex2-Ex4) according to the invention, respectively, printed with a laser printer on A4 standard printing paper. The two-dimensional intaglio patterns of security markings of Examples Ex2-Ex4 and Comparative Examples CEx1-CEx2 (see Figs. 2B-2D) were printed on a conventional white printer paper substrate (A4 format). The printed two-dimensional intaglio patterns of security markings have a length of about 26.5 cm and a width of about 14.5 cm, corresponding to an enlargement of about 3.5 times compared to the security marking printed on the banknote specimen of Example Ex1 of Fig. 1 (the rectangular frame in Fig. 2A corresponds to the A4 paper substrate edge) using the design vector file used to create the intaglio plate surface used in Example Ex1. The same-tone parts of the multi-tone intaglio lines forming the two-dimensional intaglio pattern (201) correspond to different intaglio modules (205) (shown in Fig. 2D) of the two-dimensional intaglio pattern.

[0038]

[0037] Figure 2A shows the two-dimensional intaglio pattern (201) disclosed herein and the multi-tone intaglio printed reference areas ("RA"): L (light tone area), M (medium tone area), D (dark tone area). The multi-tone reference areas were printed with the three tones of the (small) multi-tone two-dimensional intaglio pattern (220 in Figure 2C) contained in the security marking. Using the multi-tone reference areas (RA-L, RA-M and RA-D), the ΔE* of the three tones of the multi-tone security pattern was determined by a spectrometer. The intaglio modules (205L, 205M, 205D) correspond to the same tones L, M and D parts of the multi-tone intaglio lines forming the two-dimensional intaglio pattern (220), respectively.

[0039]

[0038] Figure 2B shows an enlarged photograph of a part of the intaglio pattern reproduction of Figure 2A. As shown in Figure 2B, the concave lines (210) (see Figures 2C-2D) surrounding the (small) two-dimensional intaglio pattern (220) and forming the boundaries of the cells containing said two-dimensional intaglio pattern (220) are clearly visible in this enlarged view. As shown in Figure 2B, in this example, the concave lines (210) are printed with a thick intaglio layer (dark tone) and surround the two-dimensional intaglio pattern (220) like a wall with a height higher than any height of the intaglio modules of the two-dimensional intaglio pattern, thus providing protection of the (small) two-dimensional intaglio pattern (220) and the complete two-dimensional intaglio pattern (201) against mechanical wear.

[0040]

[0039] Figure 2C shows the photograph of Figure 2B viewed under a magnifying glass with a magnified 2D intaglio pattern (220) as disclosed herein. Even under a magnifying glass, the multi-tone characteristic of the 2D intaglio pattern is barely discernible to the naked eye, but a reading and authentication device according to the invention, in particular a smartphone, is able to distinguish the different tones and decode and authenticate the 2D intaglio pattern (201).

[0041]

[0040] To mimic the multi-tone characteristics of intaglio printed security markings, the file layers corresponding to the three file layers corresponding to the light / medium / dark tones (i.e., L / M / D tones) of the two-dimensional intaglio pattern and the reference areas (RA-L, RA-M and RA-D) were assigned gray levels (Ex2-Ex3 and CEx1) or cyan levels (Ex4 and CEx2) using Adobe Illustrator (AI). The reference areas (RA-L, RA-M and RA-D) were printed as squares with the following dimensions: 1.3 cm x 1.3 cm.

[0042]

[0041] Two-dimensional intaglio patterns of security markings corresponding to Ex2-Ex4 and comparative examples CEx1-CEx2 were printed using a laser printer (Konica Minolta bizhub C558; quality printer parameters: resolution: 600 dpi, pattern: fine, image compression: highest quality, edge enhancement: none) (Figure 2A).

[0043]

[0042] Using a spectrophotometer DC45 manufactured by Datacolor, the CIE color difference ΔE* values ​​between the three reference squares (RA-L, RA-M and RA-D) were measured, i.e. the ΔE* value LM between the light (RA-L) and the medium (RA-M) reference squares, and the ΔE* value MD between the medium (RA-M) and the dark (RA-D) reference squares (see Table 1 below). The ΔE* values ​​are calculated according to known formulas, for example as detailed in paragraph 102 of the cited patent EP 2 956 514.

[0044]

[0043] The 2D intaglio patterns of Examples Ex2-Ex4 and Comparative Examples CEx1-CEx2 were analysed using a Samsung Galaxy S10 or S21 smartphone placed at a distance of approximately 35 cm from the prints of Ex2-Ex4 and CEx1-CEx2 (i.e. at a distance approximately 3.5 times greater than the detection distance used to authenticate the security marking of the banknote sample in Ex1, see Figure 1).

[0045]

[0044] As shown in Table 1 below, the two-dimensional intaglio patterns of the examples Ex2 to Ex4 with ΔE*≧2.0, especially ΔE*≧3.13, are authenticated by a smartphone (see corresponding Y "Yes" in the "Authentication" column of Table 1). In contrast to the two-dimensional intaglio patterns of the examples Ex2 to Ex4, the comparative example CEx1 with ΔE* values ​​of 0.19 and 1.58 could not be authenticated by a smartphone, as indicated by the negative and zero Y values ​​(see corresponding N "No" in the "Authentication" column of Table 1). The comparative example CEx2 with ΔE* values ​​of 1.6 and 2.9 was slightly below the authentication threshold of the smartphone, as indicated by the zero Y value. The tone values ​​(or color values) were measured as luminance Y values ​​according to the well-known YUV color encoding scheme. The YUV color format describes colors using the color components luminance and chromaticity. The luminance component (Y) represents the information of the brightness of the color, while the chromaticity components (U and V) contain the color difference. [Table 1] Where: 1)L means light, M means medium, D means dark, 2) LM corresponds to the ΔE* between two consecutive light and mid tones, MD corresponds to the ΔE* between two consecutive mid and dark tones, 3) the value in % set in Adobe Illustrator (for example, in the gray example, 0% corresponds to white and 100% corresponds to black), and 4) The luminance difference Y value corresponds to the average value of the entire print pattern in any unit. CIE Tone Difference (or CIE Color Difference) was introduced by the International Commission on Illumination (CIE) in 1976. Given any two colors (or tones of colors) in the CIEL*a*b* color space, i.e. (L1,a1,b1) and (L2,a2,b2), the ΔE* formula is defined as follows:

number

[0046]

[0045] Intaglio inks as disclosed herein may be machine readable inks such as, for example, magnetic inks, luminescent inks, IR absorbing inks, and forensic inks, and are widely used in the field of security documents, particularly banknote printing, to impart additional covert security features to security documents. The protection of security documents against counterfeiting and unauthorized duplication offered by covert security features relies on the notion that such features usually require special equipment and knowledge for their detection.

[0047]

[0046] The intaglio inks described herein may comprise one or more machine-readable materials selected from the group consisting of luminescent materials known in the art, magnetic materials known in the art, IR-absorbing materials known in the art, forensic markers or taggants known in the art, and mixtures thereof, said one or more machine-readable materials providing a security marking with enhanced counterfeit resistance, so long as said one or more machine-readable materials do not adversely affect the authentication method described herein. As used herein, the term "machine-readable material" refers to a material that exhibits at least one distinctive property detectable by a device or machine, such as, for example, a magnetic detector (if the machine-readable material has magnetic properties) or an IR camera (if the machine-readable material has IR-absorbing properties), or a spectrophotometer (if the machine-readable material has luminescent properties), and that provides a method of authenticating said security marking by the use of specific equipment for its detection and / or authentication.

[0048]

[0047] When the two-dimensional intaglio pattern of the security marking described herein is produced using an intaglio ink comprising one or more machine-readable materials described herein, said security marking may be further authenticated using special equipment, said equipment being different from the devices for authentication described herein, e.g. smartphones. Moreover, these machine-readable materials may also be used to authenticate the two-dimensional intaglio pattern of the present invention (as an additional level of security).

[0049]

[0048] Luminescent materials may be detected by the naked eye as long as they emit light in the visible range upon appropriate excitation. Luminescent materials may be inorganic (inorganic host crystals or glasses doped with luminescent ions), organic or organometallic (complexes of luminescent ions with organic ligand substances). Luminescent materials in pigment form are widely used in inks (see, for example, U.S. Pat. No. 6,565,770, WO 2008 / 033059 and WO 2008 / 092522). Examples of luminescent materials include, inter alia, sulfides, oxysulfides, phosphates, vanadates, etc. of non-luminescent cations doped with at least one luminescent cation selected from the group consisting of transition metals and rare earth ions; rare earth oxysulfides and rare earth metal complexes, such as those described in WO 2009 / 005733, EP 0985007, US 6,180,029, US 6,153,123 or US 7108742. Examples of inorganic materials include, but are not limited to, La202S:Eu, ZnSi04:Mn, and YV04:Nd. Other examples include those disclosed in WO 2014 / 083145, WO 2012 / 160182, WO 2013 / 068275, WO 2013 / 079521, WO 1998 / 036888, US 2006 / 0083694, WO 2011 / 002960, WO 2011 / 041657. IR absorbing materials include organic compounds, inorganic materials, and glasses that contain significant amounts of IR absorbing atoms or ions.Typical examples of IR absorbing compounds include, inter alia, carbon black, quinone-diimmonium or ammonium salts, polymethines (e.g., cyanines, squaraines, croconines), phthalocyanine or naphthalocyanine types (IR absorbing pi-systems), dithiolenes, quaterylenediimides, metal (such as, for example, transition metal or lanthanide) salts (such as, for example, fluorides, chlorides, bromides, iodides, nitrates, nitrites, sulfites, sulfates, phosphates, carbonates, borates, benzoates, acetates, chromates, hexaborides, molybdates, manganates, ferrates, organosulfates, organosulfonates, organophosphonates, organophosphates and phosphono-tungstates), metal oxides (such as, for example, indium tin oxide, antimony tin oxide in nanoparticle form, and doped tin(IV) oxide), metal nitrides. Examples may be found, for example, in WO 2007 / 060133, WO 2007 / 132214, WO 2019 / 219250, EP 3068728 and WO 2018 / 178021. According to one embodiment, the security marking described herein comprises a first portion of an IR-absorbing machine-readable security feature and a second portion of a security marking comprising one or more compounds that absorb in another region of the electromagnetic spectrum (UV or Vis) to form a combined security marking. The first and second portions of the combined security marking described herein may be adjacent, overlapping, or spaced apart. Magnetic materials include magnetic substances such as high or medium coercivity materials (e.g., iron oxide, barium ferrite, strontium ferrite, or black iron oxide, etc.), and core-shell magnetic pigment particles. Examples of suitable magnetic materials include magnetic core-shell pigment particles comprising a magnetic core (preferably made from nickel, cobalt, iron and iron-containing alloys and oxides) surrounded by one or more additional layers of one or more materials selected from the group of organic materials and the group of inorganic materials, such as those described in WO 2010 / 115986 and WO 2016 / 005158.The organic materials described herein are preferably selected from the group consisting of polyacrylates, polystyrenes, parylenes, alkoxysilanes and mixtures thereof. The inorganic materials described herein are preferably selected from the group consisting of metals (preferably selected from the group consisting of silver, aluminum and gold), metal oxides (preferably selected from the group consisting of MgO and ZnO, Al2O3, Y2O3, Ln2O3 (wherein Ln is a lanthanide), SiO2, TiO2, ZrO2, CeO2 and mixtures thereof) and metal sulfides (preferably selected from the group consisting of ZnS, CaS and mixtures thereof).

[0050]

[0049] Figure 3A shows an example of a prior art two-dimensional reference pattern (300) that includes a particular arrangement of 32 symbols (310, 320, 330, 340), each having a more or less elliptical shape. Figure 3B shows an example of two-dimensional elements E1 (black dots) and E2 (unprinted elements, or "white" dots) that specify the state of some of the symbols of the reference pattern (300). The reference pattern (300) with its symbols and their states can encode 32 bits of data.

[0051]

[0050] Figure 4A is an example of an arrangement of symbols of a reference pattern (400) of a two-dimensional coding pattern used in one embodiment of the invention. The two-dimensional coding pattern may contain only one reference pattern, but more often it contains several reference patterns arranged according to a given arrangement, each reference pattern encoding an information portion contained in the two-dimensional coding pattern. According to the invention, a (two-dimensional) reference pattern encodes its corresponding (unique) identification number. In this example, the reference pattern (400) contains 18 symbols (S1, S2, ..., S18) arranged according to a specific arrangement. The symbols may have any shape, but in this example, for simplicity, only two shapes are possible: oval. These symbols are used to encode bits of data of the information portion encoded in the reference pattern. The symbols belong to a finite set of symbols, each symbol in the arrangement allows encoding data according to the state of said symbol. Figure 4B shows an example of a reference pattern in which the state of the symbols is assigned. In this example, a state of the symbol S consists of a specific arrangement of only two two-dimensional elements in the symbol S, namely E1 and E2, each element E having a corresponding parameter value p(E). The parameter of element E1 of each state of the symbol has a positive value p(E1) that is different from the zero value of the parameter of the other element E2 of said symbol. Elements E2 with parameter value p(E2)=0 are not shown in the symbol S in FIG. 4B (although they occupy the corresponding site in S) since they correspond to non-printed or "neutral" elements (or "white" elements, such as white dots, if represented on a white surface). Alternatively, elements E2 can be represented, for example, by cross dots. The reference pattern used in the present invention may have only two types of elements with distinct positive parameter values, here elements corresponding to black dots and elements corresponding to gray dots. Of course, the allowed parameter values ​​of distinct elements must in general only have distinct values, but it is always possible to assign distinct positive values ​​to distinct elements of type E1 and a value of 0 to neutral elements E2 via a simple one-to-one mapping, and this is merely a convention (non-limiting).The (two-dimensional) elements E1 of a symbol may have any shape, but in this example, for simplicity, they all have the same dot shape with the same size. For example, the element E1 of the symbol S1 is shown as a black dot ("black element"), while the element E1 of the adjacent symbol S2 is shown as a gray dot ("gray element"), and their respective parameter values ​​are different (and positive), such that, for example, p(black dot E1)>p(gray dot E1)>p(E2)=0. Thus, there are only two types of symbols in the reference pattern: a symbol with a black dot corresponding to a "black symbol" (or "dark symbol"), and a symbol with a gray dot corresponding to a "gray symbol" (or "light symbol"). In the example shown in FIG. 4B, the reference pattern (400) has 18 symbols of two elements (E1, E2), and therefore can encode 18 bits of data.

[0052]

[0051] For a two-dimensional intaglio pattern of a given color, its intaglio modules have tones from a given tone palette of that color and can form a specific pattern of recessed lines. According to the invention, a two-dimensional intaglio pattern has a one-to-one correspondence with an associated two-dimensional coding pattern, both of which code the same information. A two-dimensional intaglio pattern may contain only one base intaglio pattern, but more often it contains several base intaglio patterns, each base intaglio pattern coding a portion of the information contained in the two-dimensional coding pattern (and thus in the two-dimensional intaglio pattern). The several base intaglio patterns are arranged in the two-dimensional intaglio pattern so as to form a specific pattern of recessed lines corresponding to said two-dimensional intaglio pattern. According to the invention, each base intaglio pattern of a two-dimensional intaglio pattern has a one-to-one correspondence with an associated reference pattern of the two-dimensional coding pattern, which two-dimensional coding pattern is associated with said two-dimensional intaglio pattern, and both the base intaglio pattern and its associated reference pattern code the same portion of information coded in the two-dimensional intaglio pattern. This portion of information corresponds to a unique identification number attributed to this reference pattern. Furthermore, due to the one-to-one correspondence mentioned above, each base intaglio pattern belongs to a finite set of base intaglio patterns (necessary for encoding the information), so that the encoded information of each base intaglio pattern of the two-dimensional intaglio pattern specifies the reference pattern identification number of the associated reference pattern.

[0053] According to the invention, an intaglio module of a two-dimensional intaglio pattern corresponds to one of the following: - a two-dimensional element (E1) of a symbol of a reference pattern of a two-dimensional coding pattern having a positive parameter value (p(E1)>0), or - the portion of the concave line corresponding to the line connecting two elements (E1) having the same positive parameter value (p(E1)), respectively belonging to two distinct adjacent symbols Si and Sj (i ≠ j) of the reference pattern of the two-dimensional coding pattern associated with the two-dimensional intaglio pattern. For example, if a two-dimensional Intaglio pattern has the colour blue and the base Intaglio pattern of this two-dimensional Intaglio pattern has Intaglio modules of the two permissible tones "dark blue" and "light blue" (from the blue tone palette), then the associated reference pattern of the base Intaglio pattern (belonging to the two-dimensional coding pattern associated with the two-dimensional Intaglio pattern) will have symbols that either include a black dot as element E1 (corresponding for example to the dark blue tone) or a grey dot as element E1 (corresponding in that case to the light blue tone).

[0054]

[0053] Figure 4C shows details of intermediate steps of the construction of the base Intaglio pattern (430), shown alone on the right side of Figure 4C, starting from the reference pattern (400) of Figure 4A (shown on the left side of Figure 4C). In this example, for simplicity, the respective tones of the intaglio modules of the base Intaglio pattern and of the elements E1 of its associated reference pattern are the same, namely black and grey. Indeed, Figure 4C shows the reference pattern (400) superimposed on the base Intaglio pattern (430) (and together with the respective symbols of the reference patterns and their states) in order to clearly show the one-to-one correspondence between them. For example, the black-toned intaglio module (431) corresponds to the black element E1 of the symbol S1, the gray-toned intaglio module (432) corresponds to a concave line corresponding to a line connecting two gray elements E1 (having the same positive parameter value) belonging to two distinct adjacent symbols S2 and S15 of the reference pattern (400), the black-toned intaglio module (433) corresponds to a concave line corresponding to a line connecting two black elements E1 belonging to two distinct adjacent symbols S11 and S18 of the reference pattern (400), this line having the shape of an inverted Y, and the gray-toned intaglio module (434) is part of a concave line corresponding to a single gray element E1 of the symbol S8 of the reference pattern (400). The intaglio modules (431) and (432) form two parts of a continuous concave line. Thus, from the above mentioned rules for connecting the modules, it is possible to construct for each permissible reference pattern an associated base intaglio pattern, the correspondence between their identification numbers (in fact, they have the same identification number, i.e. the identification number of the associated reference pattern) unambiguously determines their one-to-one correspondence.

[0055]

[0054] In the upper part of Fig. 4D, a partial view of an example of a two-dimensional intaglio pattern (450) is shown, showing only two base intaglio patterns (430) and (440) that correspond (one-to-one) to the two reference patterns (400) and (410) of the related two-dimensional coding pattern (420) shown in the lower part of Fig. 4D. In the example shown in Fig. 1, the security marking (100) contains about 1400 two-dimensional intaglio patterns in the same number of cells, each two-dimensional intaglio pattern containing 16 reference patterns, each reference pattern containing 18 symbols of two elements of two possible tones. As can be clearly seen from the two-dimensional intaglio pattern (450), its intaglio modules form a specific pattern of concave lines (like interconnected branches of a graph forming a continuous path). In a variant of the above example (not shown), the two-dimensional intaglio pattern may also contain discrete intaglio modules (i.e. not connected with other intaglio modules to form a continuous concave line).

[0056]

[0055] A two-dimensional intaglio pattern, such as the one shown diagrammatically in Figure 4D, or one of the security markings (100) shown in Figure 1, is obtained by using an engraving surface for an intaglio printing machine (not shown), said engraving surface comprising grooves of variable depth adapted to receive intaglio ink and print said two-dimensional intaglio pattern onto the surface of a substrate. The variations in depth provide printed recessed lines of corresponding variable height, providing a multi-tone aspect of the lines.

[0057]

[0056] The variable engraving depth of the engraved plate surface and the particular arrangement of the engraved grooves of variable engraving depth make it possible to print on the surface of the substrate a two-dimensional intaglio pattern comprising a plurality of intaglio modules which, when appropriately inked with an intaglio ink, have the color of the intaglio ink and form a particular pattern of recessed lines corresponding to the inked grooves, each intaglio module having a tone of said color, which tone belongs to a tone palette (ranging from dark to light tones) of a plurality of distinct reference tones of colors corresponding to distinct engraving depths of the grooves on the intaglio plate surface. The choice of the intaglio ink and the variation of the depth of the grooves is such that the CIE color index difference ΔE* between any two consecutive tones of the tone palette is equal to or greater than 2.0 (this can be detected by a simple smartphone), making it possible to print on the surface a two-dimensional intaglio pattern with a width ε of the recessed lines greater than 20 μm and less than or equal to 50 μm.

[0058]

[0057] The engraving surface described above can be used in an intaglio printing machine for printing two-dimensional intaglio prints according to the invention. Thus, an example of the creation of a two-dimensional intaglio pattern of a security marking to be marked on the surface of a substrate involves the following operations: - generating a two-dimensional coding pattern (420) comprising 16 reference patterns, in particular said two reference patterns (400) and (410), by encoding corresponding parts of the received information (i.e. the respective identification numbers) in two reference patterns (400, 410) belonging to a finite set of 16 reference patterns forming a two-dimensional coding pattern, each reference pattern comprising a specific arrangement of a plurality of symbols belonging to a finite set of symbols, each symbol in the arrangement enabling to code data according to the state of said symbol, - the state of the symbol consists of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 within the symbol, each element E having a corresponding parameter value p(E), the parameter of the first element E1 having a positive value different from the zero value of the parameter of the second element E2, - each reference pattern comprises only dark symbols (e.g. reference pattern (400) has dark symbols S1, S3, S5, S7, S9, S11, S13, S15 and S18) and light symbols (S2, S4, S6, S8, S10, S12, S14, S16 and S17), the parameter value of the first element of the dark symbols corresponds to the dark tone of a pair of associated permissible tones (e.g. this parameter value specifies the first element E1 which is a black dot) selected from a tone palette of a plurality of distinct reference tones of a color associated with the two-dimensional coding pattern (i.e. the color of the two-dimensional intaglio pattern to be printed) and the parameter value of the first element of the light symbols corresponds to the light tone of said pair of associated permissible tones (e.g. this parameter value specifies the first element E1 which is a grey dot), - the two-dimensional intaglio pattern (450) created has a one-to-one correspondence with the generated two-dimensional coding pattern (420), encodes the same information and comprises a plurality of intaglio modules, each intaglio module having a tone of said associated color, the tones of the intaglio modules being selected from a tone palette, - the two-dimensional Intaglio pattern comprises two base Intaglio patterns (430) and (440), each base Intaglio pattern encoding a portion of said information and having a one-to-one correspondence with an associated reference pattern (400 and 410, respectively) of the two-dimensional coding pattern (420); each base Intaglio pattern contains only those Intaglio modules whose tones belong to the pair of allowed tones of the associated reference pattern (in this example of FIG. 4, the two allowed tones are black and grey, i.e. the same tones as in the reference pattern), the intaglio module of the two-dimensional intaglio pattern (450) associated with the generated two-dimensional coding pattern (420) a first element of a symbol of a reference pattern of the two-dimensional coding pattern (for example the dark element E1 of the symbol S1 of the reference pattern 400), or a concave portion corresponding to a line connecting two elements having the same positive parameter value p, each belonging to two distinct adjacent symbols of a reference pattern of a two-dimensional coding pattern (e.g., a concave portion (432) of the base intaglio pattern (430) connecting the gray elements E1 of adjacent symbols S2 and S15 of the reference pattern (400)) An action corresponding to one of the following: (ii) engraving an intaglio printing plate having a variable engraving depth adapted to receive intaglio ink in the color of the two-dimensional intaglio pattern (450) and to reproduce the intaglio modules according to the generated two-dimensional coding pattern (420); (iii) inking the plate surface with intaglio ink and using the inked plate surface to print a corresponding two-dimensional intaglio pattern (450) onto the surface of the substrate using an intaglio printing press.

[0059]

[0058] Figure 5 is a flow chart showing an example of a method for decoding a two-dimensional intaglio pattern of the present invention on a smartphone equipped with a camera, a processor, a memory and an RGB ("red, green, blue") light sensor. The processor is adapted (i.e. specifically programmed) to perform image processing and decoding operations on a digital image of the real two-dimensional intaglio pattern to extract the information encoded in the two-dimensional intaglio pattern. The real two-dimensional intaglio pattern considered to illustrate the decoding operation is that of Figure 4D. This real two-dimensional intaglio pattern (450) comprises only two base intaglio patterns (430, 440), each of which comprises a number of intaglio modules forming a (known) pattern of concave lines specific to the two-dimensional intaglio pattern (450). Each base intaglio pattern (430, 440) comprises only intaglio modules of two distinct allowed tones (dark and grey) corresponding to the pair of allowed tones {dark, grey}, namely a dark module (black) and a grey module. These dark and gray tones of the reference pattern in fact generally represent two separate tones of a given color, for example the dark blue and mid-blue tones respectively in a two-dimensional intaglio pattern whose color is blue. As an example, the CIE color difference ΔE* between these two tones for all intaglio modules confirms that ΔE*≧2.5. The width ε of the intaglio lines of the two-dimensional intaglio pattern is about 30 μm (±2 μm).

[0060]

[0059] The RGB light sensor of the camera is adapted to detect the colors of the intaglio modules forming the real intaglio pattern and the above-mentioned two different tones of the tone palette, for example blue {dark blue, mid blue}, in order to obtain a digital image of the two-dimensional intaglio pattern. The two-dimensional intaglio pattern (450) is in one-to-one correspondence with the corresponding two-dimensional coding pattern (420) and each base intaglio pattern (430, 440) is in one-to-one correspondence, respectively, with each reference pattern (400, 410) forming said two-dimensional coding pattern (420). The identification number of the base intaglio pattern is the same as the identification number of the corresponding (associated) reference pattern (it is respectively coded in these reference patterns). According to the invention, in order to decode the information coded in the two-dimensional intaglio pattern, it is necessary to first detect the intaglio modules forming the two-dimensional intaglio pattern on the digital image of the two-dimensional intaglio pattern taken by the camera and then to verify that the detected intaglio modules correspond one-to-one with the dark and gray elements of the arrangement of the symbols of the associated two-dimensional coding pattern. According to the invention, the mapping rule for establishing a one-to-one correspondence between the detected intaglio modules and the states of the symbols of the two-dimensional coding pattern is such that the intaglio modules of a genuine two-dimensional intaglio pattern: elements of the symbols of the reference pattern of the two-dimensional coding pattern having a positive parameter value (here corresponding to dark or gray elements), or - a part of a concave line corresponding to a line connecting two elements having the same positive parameter value p (here connecting two dark elements or two gray elements), each belonging to two distinct adjacent symbols of a reference pattern of a two-dimensional coding pattern It can only correspond to one of the above. The smartphone's memory stores a finite set of allowed reference patterns that form a known two-dimensional coding pattern related to a known genuine two-dimensional intaglio pattern.

[0061]

[0060] In order to detect the intaglio modules forming the two-dimensional intaglio pattern on the digital image of the two-dimensional intaglio pattern, the processor performs an image processing operation on the acquired digital image consisting of using a movable window having the size of the base intaglio pattern, which is shifted relative to the digital image and successively scans the entire digital image (see also cited document EP 2780865 and, for example, its claim 12 "Analysis window"). At each position of the window on the digital image, the RGB intensities of the pixels within the window are analyzed (here, only the intensities of the respective red, green and blue components are summed) to detect the presence of groups of different pixels of two different tones, these detected groups of pixels corresponding to the respective digital images of the set of intaglio modules of two different tones. In practice, the dynamic range of the digital image is determined from the tone values ​​measured by the RGB sensor and a check is performed to control that the difference between the measured tone values ​​of any two intaglio modules is actually greater than at least 1% of the determined dynamic range. These intaglio modules (actually their corresponding groups of pixels) detected through the window are therefore of two different tones, namely a dark tone and a light tone.

[0062]

[0061] Each time a set of intaglio modules is detected through the window, the processor checks whether these groups of pixels can be mapped in one-to-one correspondence, respectively, onto one of the allowed reference patterns stored in the memory and corresponding to the base intaglio pattern of the genuine two-dimensional intaglio pattern, and the groups of pixels are tentatively mapped according to the above-mentioned mapping rules onto the two-dimensional elements E1 of the symbol of the candidate reference pattern selected from the set of stored reference patterns forming the two-dimensional coding pattern. If such a mapping is possible, the corresponding candidate reference pattern is decoded and its identification number is extracted (the identification number of the associated candidate base intaglio pattern is also given). The candidate reference pattern and the corresponding base intaglio pattern are then verified and these verifications are stored in the memory in association with the decoded identification number of the candidate reference pattern. If the tentative mapping fails, the candidate reference pattern is rejected and a new candidate reference pattern is considered for a corresponding new tentative mapping (and new further checks) until all the allowed reference patterns stored in the memory have been tested. If none of the possible candidate reference patterns can be verified, the window is moved (shifted) towards a new position relative to the digital image and the above operations are repeated by the processor until the entire digital image has been scanned through the window.

[0063]

[0062] Obviously, if the candidate reference pattern cannot be verified after scanning the entire digital image, the imaged 2D intaglio pattern corresponds either to a (strongly) damaged genuine 2D intaglio pattern or to a fake 2D intaglio pattern. The above operations are summarized in the flow chart of FIG. 5 for an example of an embodiment of the decoding according to the invention: In step 500, a decoding is started for a given two-dimensional intaglio pattern (for example printed on the surface of a substrate such as a security document), - in step 510, the two-dimensional intaglio pattern is imaged with the smartphone camera and the acquired digital image is stored in memory; In step 520, a candidate reference pattern is selected from the set of stored reference patterns. in step 530, a group of pixels is tentatively mapped, according to a mapping rule, to a black element of the symbol of the candidate reference pattern and to a grey element of the symbol of the candidate reference pattern, respectively; if such a mapping is possible (Y), the following step 540 is executed, if the mapping is not possible (N), step 560 is executed; - in step 540, the corresponding candidate reference pattern is decoded and its identification number is extracted (the identification number of the corresponding candidate base intaglio pattern is also given), - in step 550, the candidate reference pattern and the corresponding base intaglio pattern are verified, these verifications being stored in a memory in association with the decoded identification number of the candidate reference pattern; - in step 560, if all possible candidate reference patterns from the allowed reference patterns stored in the memory have not been tested ("Y"), the candidate reference pattern is rejected and in step 520, a new candidate reference pattern is considered for a corresponding new tentative mapping (and a new further check), and conversely, if all possible candidate reference patterns from the allowed reference patterns stored in the memory have been tested ("N"), step 570 is executed; - in step 570, if the entire digital image has been scanned, step 580 is executed ("Y"), otherwise ("N"), the window is moved (shifted) to a new position relative to the digital image and the above-described operations from step 520 are repeated by the processor; - In step 580, the operation stops.

[0064]

[0063] There may be many possibilities for checking the one-to-one correspondence between the (pixels of) the intaglio modules in the window and the two-dimensional elements of the symbols of the (candidate) reference pattern according to the mapping rules. For example, it is possible to use a sampling grid corresponding to the arrangement of the symbols of the (candidate) reference pattern, including the sites occupied by their corresponding two-dimensional elements E1, arranged in the window (through image processing by a processor). Then, it is possible to find through the grid the pixels for each intaglio module that are included in the sites of the two-dimensional elements E1 of the respective symbols of the (candidate) reference pattern. As shown in FIG. 4A, the sampling grid in the window is in fact a "grid" formed by the respective boundaries of the symbols corresponding to the (candidate) reference pattern, so that when the reference pattern is scaled to the size of the window, the groups of pixels for the intaglio modules can be located (provisionally) directly in the symbol, and it is easy to check by image processing whether said groups of pixels are located completely or only partially in the symbol in the positions corresponding to the positions of the elements E1 of the symbol. A criterion may be used if a group of pixels is partially located within the symbol, for example if more than a quarter of said pixels are within the boundary of the symbol but outside the site in the symbol corresponding to that of element E1, then this group of pixels (and therefore the corresponding detected intaglio module) is considered not to correspond to element E1 of the symbol.

[0065]

[0064] According to the invention, a two-dimensional intaglio pattern of a security marking, when decoded, for example by a smartphone used for decoding (see above), can be authenticated both by ascertaining the multi-tone aspect of said two-dimensional intaglio pattern and by determining that the misregistration between its various intaglio modules interconnected to form a pattern of intaglio lines is below a given small value (for example 10 μm, preferably 5 μm), even if the typical width of the intaglio lines of said two-dimensional intaglio pattern is more than 20 μm (and not more than 50 μm). A distinctive feature of the authentication of a two-dimensional intaglio pattern according to the invention is the synergy that exists between the operations of decoding the two-dimensional intaglio pattern, ascertaining its multi-tone aspect and determining whether the misregistration between the various parts of that particular pattern of intaglio lines is below a given threshold value. Indeed, the decoding of the intaglio modules of a base intaglio pattern, together with small shifts carried out around their position during the decoding stage on the digital image of said base intaglio pattern with respect to a sampling "grid" formed by the arrangement of the symbols of the associated reference pattern in order to maximize (on average) the difference in tone values ​​between the elements E1 and E2 of the symbol of said grid, provides a robust and accurate estimation of the registration errors between intaglio modules of different tones, thus making it possible to easily detect any fake markings, in particular those obtained via multi-tone offset printing, even with a mere smartphone.

[0066]

[0065] Figure 6A shows an example of a base Intaglio pattern (600) of a two-dimensional Intaglio pattern (not shown) comprising a number of base Intaglio patterns and its associated reference pattern (610) of a two-dimensional coding pattern (not shown) associated with the two-dimensional Intaglio pattern according to the invention. Thus, in the decoding stage of the base Intaglio pattern (600), a mapping is (approximately) established between the detected groups of pixels corresponding to the Intaglio modules (typically there are at least three pixels per module) and the states of the symbols belonging to the reference pattern. However, this mapping is not necessarily "perfect" and, as shown in Figure 6C, the detected groups of pixels on the digital image of the base Intaglio pattern, when superimposed on the arrangement of symbols (the sites of their elements E1 and E2 are shown in dotted lines) of the sampling grid (615) (corresponding to the reference pattern of Figure 4A) corresponding to the reference pattern (610) shown in Figure 6B, may, once scaled, partially overlap the boundaries of the symbols shown. Obviously, certain groups of pixels are not completely superimposed on the sites of the two-dimensional elements (dark or grey) of the reference pattern. For example, some of the pixels relating to the dark Intaglio module corresponding to the dark element E1 of the symbol S7 in FIG. 6C are shifted out of the symbol S7 (nevertheless, the correct state of the symbol S7 can be retrieved from the pixels located in the site of the element E1). This means that for a symbol (e.g. S7) of the sampling grid, the measured tone difference between the pixels of the digital image in the window corresponding to the element E1 of the symbol and the neutral element E2, i.e. between the pixels located in the sites corresponding to the elements E1 and E2 of the symbol, respectively, does not reach its standard value (some light intensity is lost due to the pixels shifted out of the symbol). It reaches the standard value when the group of pixels corresponding to E1 is located sufficiently ("completely") within the symbol. Nevertheless, the mapping can still be obtained, since there are still some pixels in the site of the element E1 in the symbol (and therefore the difference in the parameter values ​​between the elements E1 and E2 of the symbol still exists), and the base Intaglio pattern can be decoded.

[0067]

[0066] Fig. 6C shows the case where the base Intaglio pattern has been decoded, but its detected intaglio modules are not completely superimposed on the symbols of the associated reference pattern. The corresponding positions of the intaglio modules are in fact the positions of the groups of pixels detected through image processing on the digital image, which correspond to the intaglio modules. They are located within the symbols. As explained above, it is certainly possible to be able to decode the base Intaglio pattern even if its intaglio modules are misregistered, for example some pixels may be beyond the boundaries of the sites of the elements of the symbol, but the majority of the pixels of each group of pixels corresponding to the respective intaglio module are correctly located within the sites of the elements of the corresponding symbol of the associated reference pattern (the state is correctly identified) and therefore decoding of the base Intaglio pattern is still possible. In the following, these decoded positions are considered to constitute the initial positions of the groups of pixels on the digital image, or for short the initial positions of the detected intaglio modules.

[0068]

[0067] In order to verify the multi-tone aspect of the decoded base intaglio pattern, i.e. the verified base intaglio pattern as described above, the following operations are performed on the smartphone, in which the locations on the digital image of the verified base intaglio patterns and their corresponding associated verified reference pattern identification numbers are stored in the smartphone memory: - determining, from the associated verified reference pattern identification number (obtained upon decoding), its distinct allowed tone pair {Ta, Tb} (stored in memory); - measuring, on the digital image, the printed tone values ​​of each intaglio module of the verified base intaglio pattern, for example by measuring, with an RGB light sensor of the smartphone, the RGB components of the corresponding pixels detected via the aforementioned sampling grid corresponding to the associated verified reference pattern, at the sites of the elements E1 of the symbol, - determining from the measured tone values, for pairs of acceptable tones, the dynamic range of the digital image of the verified base intaglio pattern, where the dynamic range is the difference between the highest measured tone value and the lowest measured tone value, - checking whether the condition is met that the difference in the measured mean tone values ​​of the intaglio modules is at least greater than 1% of the dynamic range; - determining that the verified base intaglio pattern has said multi-tone aspect if the condition is met, - if the condition is not met, determine that the verified base intaglio pattern does not have said multi-tone aspect and is not authentic. Works. More precisely, the above difference is calculated as follows: - first, the average printed tone value of the intaglio modules of the verified base intaglio pattern corresponding to the tolerable tone Ta <ta>is calculated as the average of the measured printed tone values ​​of the intaglio modules corresponding to the tolerance tones Ta and the average printed tone value of the intaglio modules of the verified base intaglio pattern corresponding to the tolerance tones Tb. <tb>is calculated as the average of the measured print tone values ​​of the intaglio modules corresponding to the tolerable tones Tb. Then: - Calculated average print tone value <ta>and <tb>Calculate the difference between - for each allowed tone pair {Ta, Tb}, the calculated average printed tone value <ta>and <tb>It is checked whether the multi-tone criterion is met: the difference between and is greater than 1% of the dynamic range. Therefore, any verified base intaglio pattern that does not have the multi-tone aspect is rejected and the two-dimensional intaglio pattern is considered to be inauthentic.

[0069]

[0068] Once the multi-tone aspects of the verified base intaglio patterns have been established, it is possible to start determining the registration errors based on these verified base intaglio patterns (their positions on the digital image are stored in the smartphone memory). For example, considering a (verified) base intaglio pattern as shown in Fig. 6C, decoded and clearly having a multi-tone aspect, this verified base intaglio pattern with the corresponding pair of allowed tones {Ta, Tb} (here dark and grey) is observed at a position in the digital image (stored in the memory) of said verified base intaglio pattern through the sampling grid (615) of the corresponding related verified reference pattern (see Fig. 6B) placed in a window (and scaled in the window), the smartphone processor performs the following operations: (1) an operation of measuring, within a window, the printed tone values ​​of the intaglio modules of the verified base Intaglio pattern from the pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid through the arrangement of symbols with the respective sites of their two-dimensional elements E1 and E2 corresponding to said verified reference pattern. The measurement of the tone value results from the sum of the R, G, and B (red, green, and blue) intensity components of each of the detected pixels. This measurement provides an initial (i.e., from the pixel position corresponding to the pixel of the decoding stage) tone value attributable to each element E1 and E2 of the symbol of the verified reference pattern associated with the verified base Intaglio pattern. Then, for each symbol of the sampling grid, the difference between the initial tone value attributable to the element E1 and the initial tone value attributable to the element E2 is calculated by the processor to obtain an initial differential symbol tone value for each symbol of the sampling grid (i.e., of the corresponding reference pattern), and the obtained initial differential symbol tone values ​​attributable to the elements of the symbol of the verified reference pattern (corresponding to the tone pair {Ta, Tb}) are stored in the memory of the smartphone. These stored initial differential symbol tone values ​​may be considered to correspond in practice to a zero shift. Next, for each of the two allowed tones {Ta, Tb} of the verified reference pattern, a corresponding zero-shift sum is obtained by summing the initial differential symbol tone values ​​of all symbols of the sampling grid (i.e., the verified reference pattern) corresponding to tone Ta and tone Tb, respectively, and the obtained zero-shift sum of allowed tone Ta and zero-shift sum of allowed tone Tb are stored in a memory. (2) through image processing of the digital image by the processor, backwards and forwards along each of a number of distinct directions (for the vertical direction, see Figs. 6D-6E, forward corresponds to the top as in Fig. 6D, and backward corresponds to the bottom as in Fig. 6E) relative to the digital image (which in this example has only two directions, vertical and horizontal), shifting the pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, whose first element E1 corresponds to the allowable tone Ta, by at least one pixel size to obtain corresponding shifted pixels whose position has been shifted relative to the elements of the symbol of the sampling grid (see Fig. 6C); in fact, all pixels within the window are shifted within a block along a direction via image processing, so that the pixels that were initially within the site of the element E1 or E2 are shifted within a block, and the (new) shifted pixels of the digital image that are within the site of E1 or E2 (respectively) are used to measure new tone values ​​at this site. Notably, this is equivalent to saying that the window, together with the sampling grid, is shifted in the opposite sense along a direction relative to the digital image. - measuring, through the sampling grid for a backward and forward shift along each direction (i.e. there are two shifts per direction), respectively, from the shifted pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid (the first element of which corresponds to the permissible tone Ta), the corresponding backward and forward shifted tone values ​​attributed to the respective elements E1 and E2 of the symbol of the sampling grid, the first element E1 of which corresponds to the permissible tone Ta, and storing the obtained shifted tone values ​​in a memory. For example, in said sampling grid of a symbol, when the pixels of an intaglio module are shifted from their initial position in the symbol, only a part of said pixels may be located within the site of the element E1 of the symbol, and these remaining pixels are used to determine the new tone value (shifted tone value) of this element of the symbol. - for each shift, calculating for each symbol of the sampling grid whose first element corresponds to the allowed tone Ta the difference between the shifted tone value due to element E1 and the shifted tone value due to element E2 to obtain a corresponding shifted differential symbol tone value (i.e. δ=tone value due to E1-tone value due to E2) and storing in a memory the obtained shifted differential symbol tone value due to an element of a symbol of the verified reference pattern (whose first element corresponds to the allowed tone Ta); - for each shift, summing the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Ta to obtain a corresponding verified reference pattern shift sum for the allowed tone Ta; - selecting, for the verified reference pattern, the best shift for the allowed tone Ta, which corresponds to the maximum calculated shift sum among the calculated shift sums (in this example there are four shift sums) and the zero shift sums. It is therefore possible that the best shift for the allowed tone Ta actually corresponds to a zero shift, if the zero shift sum for the allowed tone Ta has a maximum value. This makes it possible to select, in practice, the shift that gives the best match between the pixel of the intaglio module and the element E1 of the corresponding symbol. Then, - when the above-mentioned operations are repeated for each of the verified base intaglio patterns forming the two-dimensional intaglio pattern (and having a corresponding pair of acceptable tones {Ta, Tb}), a global shift Δ of the two-dimensional intaglio pattern is calculated by determining the average of all selected best shifts for the acceptable tones Ta over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of acceptable tones. a Thus, only the best shifts of the verified reference patterns are added and then divided by the number of said verified reference patterns to obtain the global shift of the 2D intaglio pattern. (3) shifting pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowed tone Tb, backward and forward along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; - measuring corresponding backward and forward shifted tone values ​​attributable to each element E1 and E2 of the symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, respectively, for backward and forward shifts along each direction through the sampling grid from shifted pixels of the digital image located within each site of the elements E1 and E2 of each symbol of the sampling grid, the first element of which corresponds to the allowable tone Tb, and storing the obtained shifted tone values ​​in a memory; - for each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Tb, calculating the difference between the shifted tone value attributable to the element E1 and the shifted tone value attributable to the element E2 to obtain a corresponding shifted differential symbol tone value, and storing in a memory the obtained shifted differential symbol tone value attributable to an element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Tb; - for each shift, summing the calculated shifted differential symbol tone values ​​of all symbols of the sampling grid corresponding to the allowed tone Tb to obtain a corresponding verified reference pattern shift sum for the allowed tone Tb; - for the verified reference pattern, select the best shift for the allowed tone Tb that corresponds to the maximum calculated shift sum among the calculated shift sums and the zero shift sums, then - when the above-mentioned operations are repeated for each of the verified base intaglio patterns forming the two-dimensional intaglio pattern (and having a corresponding pair of acceptable tones {Ta, Tb}), a global shift Δ of the two-dimensional intaglio pattern is calculated by determining the average of all selected best shifts for the acceptable tones Tb over the verified reference patterns associated with each verified base intaglio pattern of the two-dimensional intaglio pattern with the corresponding pair of acceptable tones {Ta, Tb}. b As a result of the operations (1) to (3) performed for all verified base intaglio patterns of the two-dimensional intaglio pattern (for the pair of allowed tones {Ta, Tb}), a coordinate (Δ a ,Δ b )1, (Δ a ,Δ b )2...Get the set of points. (4) For each remaining pair of allowable tones {Ta', Tb'} from the pairs of allowable tones of the stored verified base intaglio pattern of the 2D intaglio pattern, perform the above operations (1-3) to obtain a global shift (Δ a’ ,Δ b’ As a result of the operations (1) to (4) performed for all verified base intaglio patterns of the two-dimensional intaglio pattern (for the pair of allowed tones {Ta', Tb'}), a coordinate (Δ a’ ,Δ b’ )1, (Δ a’ ,Δ b’ )2...Get the set of points. (5) The misregistration value r(a,b) of the intaglio module corresponding to any allowable tone pair {Ta,Tb} of all verified base intaglio patterns of the 2D intaglio pattern is expressed as r(a,b)=(Δ a 2 +Δ b 2 ) 1 / 2 where λ is the size in μm of the digital image pixel and f is the magnification of the digital image. Therefore, the points (Δ a ,Δ b )1, (Δ a ,Δ b )2... there are corresponding registration errors r1(a,b), r2(a,b).... The processor then determines that a two-dimensional intaglio pattern is genuine only if each registration error value r1(a,b), r2(a,b)... of each tolerance tone pair {Ta,Tb} of each verified base intaglio pattern of the two-dimensional intaglio pattern is less than or equal to 10 μm (preferably less than or equal to 5 μm).

[0070]

[0069] The above-mentioned operation of shifting the positions of the intaglio modules of the verified base intaglio pattern on the digital image from their initial positions in the decoding stage of said base intaglio pattern to their shifted positions in order to measure the resulting differences between the measured print tone values ​​symbol by symbol is illustrated in Fig. 6D-6E. For simplicity, only two shift directions are considered, namely the vertical direction and the horizontal direction on the digital image. Starting from the initial positions of the intaglio modules on the digital image of the verified base intaglio pattern of Fig. 6C (i.e. the initial positions of the pixels on the digital image corresponding to the detected intaglio modules in the decoding stage), a forward shift along the vertical direction of the intaglio modules corresponding to the darker tones is represented in Fig. 6D and a backward shift along said direction of the intaglio modules corresponding to the darker tones is represented in Fig. 6E. As is evident from these two figures, said shift sum in the vertical direction (and intaglio modules of dark tones) having a maximum value corresponds to the backward shift represented in FIG. 6E, where the majority of the "dark" intaglio modules are well aligned with the position of the (black) element E1 in the symbol of the verified reference pattern associated with the verified base intaglio pattern of FIG. 6C. The above-mentioned forward and backward shifts (of the dark intaglio modules) are repeated, but this time for the horizontal direction, as represented in the corresponding FIGS. 6F and 6G, respectively. From these two figures, it can be seen that said shift sum in the horizontal direction (and intaglio modules of dark tones), taking into account all the "dark" symbols, each forward and backward shift provides a shift sum whose value is smaller than the above-mentioned shift sum for FIG. 6E. As a result, for the dark intaglio modules, the best shift from the backward and forward shifts across the two directions is the backward shift in Figure 6E, and the shift corresponding to this shift sum is the global shift Δ for all intaglio modules (corresponding to dark tones) of all verified base intaglio patterns of the two-dimensional intaglio patterns, since only one base intaglio pattern (i.e., the one in Figure 6C) is considered here for simplicity. a (for the allowable tone Ta)

[0071] As is evident from FIGS. 6D-6G, where neither all the dark (black) nor all the light (gray) Intaglio modules are in register, the global shift Δ a The results of the above detailed calculations of are compared with the global shift Δ b (At or below this threshold of 10 μm, alignment defects of the intaglio modules were not visible to the naked eye in the figure.) As a result, the two-dimensional intaglio pattern of FIG. 6C, although decodable, is considered to be inauthentic.

[0072]

[0071] The above-described method for estimating the registration error between modules of different tones of color works particularly well for security markings that contain a large number of two-dimensional intaglio patterns, for example as in FIG. 1. This is due to the statistical basis of the method: the more symbols in the security marking, the more accurate the detection of the registration error. For example, with a smartphone (e.g. Samsung S10 with 12 megapixels) that has stored about 800 verified base intaglio patterns corresponding to the reference pattern, each having 18 symbols, using the security marking of FIG. 1, it is possible to detect registration errors as small as 5 μm, even though the smartphone has a resolution of about 24 μm (for images taken about 10 cm from the marking). As a result, since it is impossible to realize a multi-tone offset printed copy of a multi-tone intaglio line with a width of 20 μm to 50 μm, in which different parts of the intaglio line of different tones are perfectly in register, a fake security marking obtained by offset printing can be easily detected, although it cannot be detected by the naked eye. The resolution of a camera is its ability to differentiate between two lines (or points) on an image of an object: the greater the resolution, the smaller the minimum distance between two lines or points that it can distinguish. The greater the numerical aperture of the camera's objective lens, the higher the resolution.

[0073]

[0072] The subject matter disclosed above should be considered as illustrative rather than limiting and serves to provide a better understanding of the invention defined by the independent claims.< / tb> < / ta> < / tb> < / ta> < / tb> < / ta>

Claims

1. A security element comprising a substrate and a security marking, said security marking comprising a two-dimensional Intaglio pattern printed on a surface of said substrate by intaglio printing with an Intaglio ink, said two-dimensional Intaglio pattern comprising at least one base Intaglio pattern having related colors and comprising a plurality of intaglio modules, each base Intaglio pattern comprising only intaglio modules whose tones belong to corresponding sets of two different allowed tones, each intaglio module having one tone of said related color, the tones of the intaglio modules being selected from a tone palette of a plurality of different reference tones of said related colors, a CIE color difference ΔE* between said tones being equal to or greater than 2.0, and a width ε of the intaglio modules being greater than 20 μm and less than or equal to 50 μm, said two-dimensional Intaglio pattern is created on the basis of an associated two-dimensional coding pattern comprising at least one reference pattern, each of said at least one base Intaglio pattern being based on an associated reference pattern of said at least one reference pattern, each base Intaglio pattern and the associated reference pattern encoding the same information portion specifying a unique identification number of said associated reference pattern, each reference pattern comprises a particular arrangement of a plurality of symbols, each symbol in said arrangement being capable of encoding data according to a state of said symbol, said state of each symbol consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 in said symbol, each element E having a corresponding parameter value p(E), said parameter of said first element E1 having a positive value different from a zero value of said parameter of said second element E2; each reference pattern comprises only dark and light symbols, said parameter value of said first element of a dark symbol corresponds to a dark tone of said pair of allowed tones of an associated base Intaglio pattern and said parameter value of said first element of a light symbol corresponds to a light tone of said associated pair of allowed tones, each intaglio module of each base intaglio pattern of said two-dimensional intaglio pattern as a separate intaglio module corresponding to a first element of a symbol of an associated reference pattern of said two-dimensional coding pattern and its position within said reference pattern, or a line connecting two first elements having the same parameter value p and belonging respectively to two distinct adjacent symbols of an associated reference pattern of said two-dimensional coding pattern, and as a part of a concave line corresponding to the position of said line in said reference pattern A security element that is printed either in

2. 2. A security element according to claim 1, comprising a plurality of two-dimensional intaglio patterns, each two-dimensional intaglio pattern having a corresponding associated colour that is different from a background colour of said substrate.

3. 3. A security element according to claim 1, wherein at least one two-dimensional intaglio pattern is contained in a cell having a boundary formed by a recessed line higher than the height of any of the intaglio modules of said two-dimensional intaglio pattern, and wherein the distance between an edge of said two-dimensional intaglio pattern and said boundary of said cell is greater than or equal to 40 μm.

4. Security element according to any one of claims 1 to 3, wherein said CIE colour difference ΔE* between said tones is ≧2.

5.

5. 5. An engraving surface for an intaglio printing press, comprising grooves of variable engraving depth adapted to receive intaglio ink and to print a two-dimensional intaglio pattern of a security marking of a security element according to any one of claims 1 to 4 onto a surface of a substrate.

6. A method for producing a security element comprising a security marking comprising a two-dimensional intaglio pattern according to any one of claims 1 to 4, comprising the steps of: (i) generating a two-dimensional coding pattern comprising at least one reference pattern by encoding an information portion in each of the at least one reference pattern forming the two-dimensional coding pattern, the information portion assigning to each reference pattern its unique identification number, each reference pattern comprising a specific arrangement of a plurality of symbols, each symbol in the arrangement enabling encoding data according to a state of the symbol, the state of each symbol consisting of a specific arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 in the symbol, each element E having a corresponding parameter value p(E), the parameter of the first element E1 having a positive value different from a zero value of the parameter of the second element E2, each reference pattern comprising only dark and light symbols, the parameter value of the first element of a dark symbol corresponding to a dark tone of a pair of associated allowed tones selected from a tone palette of a plurality of distinct reference tones of a color associated with the two-dimensional coding pattern, and the parameter value of the first element of a light symbol corresponding to a light tone of the pair of associated allowed tones, said two-dimensional Intaglio pattern to be created comprises, based on said generated two-dimensional coding pattern, at least one base Intaglio pattern comprising a plurality of Intaglio modules, each Intaglio module having one tone of said associated color, the tones of the Intaglio modules being selected from said tone palette, each of said at least one base Intaglio pattern being based on an associated reference pattern of said at least one reference pattern, each base Intaglio pattern encoding the same information portion as its associated reference pattern, each base Intaglio pattern contains only Intaglio modules whose tones belong to the pair of allowed tones of the associated reference pattern; and each intaglio module of each base intaglio pattern of said two-dimensional intaglio pattern as a separate intaglio module corresponding to a first element of a symbol of an associated reference pattern of said two-dimensional coding pattern and its position within said reference pattern, or a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of an associated reference pattern of the two-dimensional coding pattern, and as a part of a concave line corresponding to the position of said line in said reference pattern. The step to be printed is either (ii) engraving an Intaglio printing press plate having a variable engraving depth adapted to receive Intaglio ink of said color and to reproduce said Intaglio modules of said two-dimensional intaglio pattern according to said generated two-dimensional coding pattern; (iii) inking said printing plate with said Intaglio ink and using said inked printing plate to print said corresponding two-dimensional Intaglio pattern onto a surface of a substrate using said Intaglio printing press; A method comprising:

7. 1. A method for decoding information encoded in a two-dimensional intaglio pattern of a security marking of a security element, said two-dimensional intaglio pattern comprising at least one base intaglio pattern comprising a plurality of intaglio modules, imaging said two-dimensional intaglio pattern; - detecting, from the imaged intaglio modules of the imaged two-dimensional intaglio pattern, any reference pattern of at least one reference pattern forming a two-dimensional coding pattern, on the basis of which a corresponding genuine two-dimensional intaglio pattern of a genuine security marking of a genuine security element according to any one of claims 1 to 4 is generated; decoding each detected reference pattern and retrieving corresponding decoded information in the two-dimensional coded pattern; verifying each decoded reference pattern and its corresponding base intaglio pattern; The method of claim 1, further comprising:

8. a) imaging the two-dimensional intaglio pattern of the security marking using a camera equipped with a processor and a memory and whose optical sensor is adapted to detect the colours of the intaglio modules forming the authentic intaglio pattern and the different tones of the tone palette of said colours to obtain a digital image of the two-dimensional intaglio pattern and to store said obtained digital image in said memory, said memory storing a set of associated reference patterns and storing for each stored reference pattern an information portion specifying a corresponding reference pattern identification number, each stored reference pattern comprises a particular arrangement of a plurality of symbols, each symbol within said arrangement being capable of encoding data according to a state of said symbol, said state of each symbol consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 within said symbol, each element E having a corresponding parameter value p(E), said parameter of said first element E1 having a positive value different from a zero value of said parameter of said second element E2; each pair of allowed tones of an Intaglio module of each base Intaglio pattern is associated with a corresponding base Intaglio pattern and is stored in said memory in association with said reference pattern identification number of said reference pattern associated with said base Intaglio pattern, - each stored reference pattern comprising only dark and light symbols, said parameter value of said first element of a dark symbol corresponding to said dark tone of said pair of allowed tones of an associated base Intaglio pattern and said parameter value of said first element of a light symbol corresponding to said light tone of said associated pair of allowed tones; b) detecting, in said stored digital image, an intaglio module within a moving window of the size of a reference pattern through image processing of pixels of said digital image scanned by said processor; b1) for a candidate reference pattern selected from the set of stored reference patterns, each of the detected intaglio modules is a separate intaglio module corresponding to a first element of a symbol of said candidate reference pattern and its position within said candidate reference pattern; or a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of the candidate reference pattern, and a concave line portion corresponding to the position of the line in the candidate reference pattern; and checking whether the b2) if the detected intaglio module corresponds to a respective element of the symbol of the candidate reference pattern, decoding the candidate reference pattern to obtain its candidate reference pattern identification number and thereby decoding the associated base intaglio pattern, verifying the decoded candidate reference pattern and the decoded associated base intaglio pattern to obtain a corresponding associated verified reference pattern and a verified base intaglio pattern, and storing in a memory corresponding position data indicating the position of the verified base intaglio pattern on the digital image; b3) if the detected intaglio modules do not correspond to the respective elements of the symbol of the candidate reference pattern, selecting a new candidate reference pattern from the set of stored reference patterns and performing steps b1) to b2) with the new candidate reference pattern; b4) if the detected Intaglio module does not correspond to a respective element of the symbol of any one of the candidate reference patterns, moving the window with respect to the digital image to scan another area of ​​the digital image and detecting an Intaglio module through the moved window and performing steps b1) to b3) until all the digital image has been scanned through the window; c) delivering a signal indicating that the decoding of the two-dimensional intaglio pattern has failed if the entire digital image is scanned through said window and if said detected intaglio modules do not correspond to a respective element of said symbol of any candidate reference pattern; The method of claim 7, comprising:

9. A device for decoding information coded in a two-dimensional Intaglio pattern of a security marking of a security element, said two-dimensional Intaglio pattern comprising at least one base Intaglio pattern comprising a plurality of Intaglio modules, said device comprising a camera equipped with a processor, a memory and a light sensor adapted to detect colours of a genuine Intaglio pattern and tones that differ from a tone palette of said colours, said genuine two-dimensional Intaglio pattern of a genuine security marking of a genuine security element is as defined in any one of claims 1 to 4, said processor being adapted to perform image processing of a digital image of said genuine two-dimensional Intaglio pattern taken by said camera and stored in said memory and to perform a decoding operation of the coded information detected on said digital image, said memory storing at least one reference pattern forming a two-dimensional coding pattern, said genuine two-dimensional Intaglio pattern being created on the basis of said two-dimensional coding pattern, said device comprising: imaging said two-dimensional intaglio pattern; - detecting an arbitrary reference pattern of the at least one reference pattern of the two-dimensional coding pattern from the imaged intaglio module of the imaged two-dimensional intaglio pattern, on the basis of which the associated authentic two-dimensional intaglio pattern is created; decoding each detected reference pattern and retrieving corresponding decoded information in the two-dimensional coded pattern; verifying each decoded reference pattern and its corresponding base intaglio pattern; An apparatus adapted to perform the steps of:

10. each stored reference pattern comprises a particular arrangement of a plurality of symbols, each symbol within said arrangement being capable of encoding data according to a state of said symbol, said state of each symbol consisting of a particular arrangement of a first two-dimensional element E1 and a second distinct two-dimensional element E2 within said symbol, each element E having a corresponding parameter value p(E), said parameter of said first element E1 having a positive value different from a zero value of said parameter of said second element E2; each pair of allowed tones of an Intaglio module of each base Intaglio pattern is associated with said base Intaglio pattern and stored in said memory in association with said reference pattern identification number of said reference pattern associated with said base Intaglio pattern, each stored reference pattern comprises only dark and light symbols, the parameter value of the first element of a dark symbol corresponds to the dark tone of the pair of allowed tones of an associated base Intaglio pattern, and the parameter value of the first element of a light symbol corresponds to the light tone of the pair of allowed tones of the associated base Intaglio pattern, The apparatus, a) imaging the two-dimensional intaglio pattern of the security marking using the camera to obtain a digital image of the two-dimensional intaglio pattern and storing the obtained digital image in the memory; b) detecting said stored digital image intaglio modules within a movable window of the size of an acceptable fiducial pattern through image processing of pixels of said digital image scanned by said processor through said window; b1) for each of said detected intaglio modules, for a candidate reference pattern selected from said set of reference patterns: a separate intaglio module corresponding to a first element of a symbol of said candidate reference pattern and its position within said candidate reference pattern; or a line connecting two first elements having the same parameter value p, each of which belongs to two distinct adjacent symbols of the candidate reference pattern, and a concave line portion corresponding to the position of the line in the candidate reference pattern; and b2) if the detected intaglio module corresponds to a respective element of the symbol of the candidate reference pattern, decoding the candidate reference pattern to obtain its candidate reference pattern identification number and thereby decoding the associated base intaglio pattern, verifying the decoded candidate reference pattern and the decoded associated base intaglio pattern to obtain a corresponding associated verified reference pattern and a verified base intaglio pattern, and storing in a memory corresponding position data indicating the position of the verified base intaglio pattern on the digital image; b3) if the detected intaglio modules do not correspond to the respective elements of the symbol of the candidate reference pattern, selecting a new candidate reference pattern from the set of stored reference patterns and performing steps b1) to b2) with the new candidate reference pattern; b4) if the detected intaglio module does not correspond to a respective element of the symbol of any one of the candidate reference patterns, moving the window with respect to the digital image to scan another area of ​​the digital image and detect an intaglio module through the moved window and perform steps b1) to b3) until all the digital image has been scanned through the window; c) delivering a signal indicating that the decoding of the two-dimensional intaglio pattern has failed if the entire digital image is scanned through said window and if the detected intaglio modules do not correspond to a respective element of the symbol of any candidate reference pattern; The apparatus of claim 9 , adapted to perform the following:

11. 1. A method for authenticating a two-dimensional intaglio pattern of a security marking of a security element, comprising: - performing the operation of decoding the information encoded in the two-dimensional intaglio pattern according to the method of claim 7 to obtain, from the imaged two-dimensional intaglio pattern, each base intaglio pattern and a corresponding verified reference pattern of the two-dimensional intaglio pattern; - shifting, for each verified base Intaglio pattern, an Intaglio module, which corresponds respectively to a tone of a pair of allowed tones from the tone palette of said colours of said genuine two-dimensional Intaglio pattern, along a number of different directions relative to an initial position corresponding to a respective position of said detected Intaglio module of each verified base Intaglio pattern on the captured image of said two-dimensional Intaglio pattern upon decoding, to obtain corresponding shifted images of said Intaglio modules; determining, for each verified Intaglio pattern, for each corresponding symbol of the associated reference pattern, a pair of shift values ​​respectively for the Intaglio modules corresponding to each tone of the pair of allowed tones from the difference between a measured tone value at an initial position of the shifted Intaglio module on the respective shifted image and a measured tone value at the same initial position of the intaglio module on the image of the two-dimensional Intaglio pattern when decoded, and providing a maximum tone value of the verified base Intaglio pattern for all the intaglio modules respectively corresponding to each tone of the pair of allowed tones; determining that the respective intaglio modules of the two-dimensional intaglio pattern are in register only if, for the pair of admissible tones, the average norm value of the pairs of determined shift values ​​over all of the verified base intaglio patterns of the two-dimensional intaglio pattern is less than or equal to 10 μm; The method of claim 1, further comprising:

12. A) performing the operations a), b), b1), b2), b3), b4) and c) of the method for decoding information encoded in a two-dimensional intaglio pattern according to claim 8 on the two-dimensional intaglio pattern to be authenticated; B) if the decoding of the two-dimensional intaglio pattern in step A) fails, delivering information indicating that the decoding of the two-dimensional intaglio pattern has failed; C) if step A) provides, for each stored location on the digital image of a verified base Intaglio pattern, the information encoded in the two-dimensional Intaglio pattern indicating the reference pattern identification number of the associated verified reference pattern, determining the multi-tone aspect of the verified base Intaglio pattern by: determining their distinct allowed tone pairs Ta, Tb from their respective associated verified reference pattern identification numbers; measuring a printed tone value of each intaglio module of said verified base intaglio pattern on said digital image and determining a dynamic range of said digital image from said measured tone values; calculating an average printed tone value Ta of the intaglio module of the verified base intaglio pattern corresponding to the allowable tones Ta as the average of the measured printed tone values ​​of the intaglio modules corresponding to the allowable tones Ta and calculating an average printed tone value Tb of the intaglio module of the verified base intaglio pattern corresponding to the allowable tones Tb as the average of the measured printed tone values ​​of the intaglio modules corresponding to the allowable tones Tb, For each allowed tone pair Ta, Tb, check whether a multi-tone criterion is met that the difference between the calculated average printed tone values ​​Ta and Tb is greater than 1% of the dynamic range; and determining that said two-dimensional intaglio pattern has said multi-tone aspect if said multi-tone criterion is satisfied for each pair of allowed tones; or If the multi-tone criteria are not met for the pair of allowed tones Ta, Tb, then the two-dimensional intaglio pattern is determined not to have the multi-tone aspect and is not genuine. and verifying by D) for each verified base Intaglio pattern having a corresponding pair of allowed tones Ta, Tb, whose position in the digital image is stored in the memory, if the two-dimensional Intaglio pattern has the multi-tone aspect, using the processor: D1) measuring, within said window located at said position on said digital image, through a sampling grid having an arrangement of symbols with respective sites of their two-dimensional elements E1 and E2 corresponding to said symbols of said verified reference pattern associated with said verified base Intaglio pattern, printed tone values ​​of said intaglio modules of said verified base Intaglio pattern from pixels of said digital image located within said respective sites of elements E1 and E2 of each symbol of said sampling grid to obtain corresponding initial tone values ​​due to said respective elements E1 and E2 of said symbols of said verified reference pattern associated with said verified base Intaglio pattern, calculating a difference between the initial tone value due to the element E1 and the initial tone value due to the element E2 to obtain an initial differential symbol tone value, and storing the obtained initial differential symbol tone value due to the element of the symbol of the verified reference pattern in the memory, wherein for each of the two allowed tones Ta, Tb of the verified reference pattern, a corresponding zero-shift sum is obtained by summing the initial differential symbol tone values ​​of all the symbols of the verified reference pattern corresponding to the tone Ta and the tone Tb, respectively, and the obtained zero-shift sum for the allowed tone Ta and the zero-shift sum for the allowed tone Tb are stored in a memory; D2) shifting pixels of the digital image located within the respective sites of elements E1 and E2 of each symbol of the sampling grid, whose first elements correspond to the allowed tones Ta, backwards and forwards relative to the digital image along each of the plurality of different directions by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to the respective elements E1 and E2 of the symbol of the sampling grid, the first elements of which correspond to the allowed tone Ta, for the backward and forward shifts along each direction through the sampling grid, from shifted pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first elements of which correspond to the allowed tone Ta, and storing the obtained shifted tone values ​​in the memory; for each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Ta, calculate a difference between the shifted tone value due to the element E1 and the shifted tone value due to the element E2 to obtain a corresponding shifted differential symbol tone value, and store in the memory the obtained shifted differential symbol tone value due to the element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Ta; For each shift, summing the calculated shifted differential symbol tone values ​​of all the symbols of the sampling grid corresponding to the allowed tone Ta to obtain a corresponding verified reference pattern shift sum for the allowed tone Ta; and selecting, for the verified reference pattern, a best shift for the allowed tone Ta that corresponds to a maximum calculated shift sum among the calculated shift sums and the zero shift sums; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all the selected best shifts for the tolerance tones Ta across the verified reference patterns associated with the respective verified base intaglio patterns of the two-dimensional intaglio pattern having the corresponding tolerance tone pairs Ta, Tb; ａ The operation of calculating D3) shifting the pixels of the digital image located within the respective sites of elements E1 and E2 of each symbol of the sampling grid, whose first elements correspond to the allowed tones Tb, backwards and forwards along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to the respective elements E1 and E2 of the symbol of the sampling grid, the first elements of which correspond to the allowed tone Tb, respectively, through the sampling grid from shifted pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first elements of which correspond to the allowed tone Tb, and storing the obtained shifted tone values ​​in the memory; for each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Tb, calculate the difference between the shifted tone value due to the element E1 and the shifted tone value due to the element E2 to obtain a corresponding shifted differential symbol tone value, and store in the memory the obtained shifted differential symbol tone value due to the element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Tb; For each shift, summing the calculated shifted differential symbol tone values ​​of all the symbols of the sampling grid corresponding to the allowed tone Tb to obtain a corresponding verified reference pattern shift sum for the allowed tone Tb; and selecting, for the verified reference pattern, a best shift for the allowed tone Tb that corresponds to a maximum calculated shift sum among the calculated shift sums and the zero shift sums; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all the selected best shifts for the tolerance tones Tb across the verified reference patterns associated with the respective verified base intaglio patterns of the two-dimensional intaglio pattern having the corresponding tolerance tone pairs Ta, Tb; ｂ The operation of calculating D4) for each remaining pair of allowed tones Ta′, Tb′ from the pairs of allowed tones of the stored verified base Intaglio pattern of the two-dimensional Intaglio pattern, perform operation D) described above to determine the corresponding pair of global shifts (Δ ａ ', Δ ｂ '), and storing said pair of global shifts in said memory. and E) A misregistration value r(a,b) of the intaglio module corresponding to any pair of allowed tones Ta, Tb of all the verified base intaglio patterns of the two-dimensional intaglio pattern is calculated as r(a,b)=λ / f(Δ ａ ２ +Δ ｂ ２ ) １／２ where λ is the size in μm of a pixel of said digital image, f is the magnification of said digital image, and determining that said two-dimensional intaglio pattern is genuine if each misregistration value r(a,b) of each acceptable tone pair Ta, Tb of said respective verified base intaglio pattern of said two-dimensional intaglio pattern is less than or equal to 10 μm. The method of claim 11 , comprising:

13. A device for authenticating a two-dimensional intaglio pattern of a security marking of a security element, the authentic two-dimensional intaglio pattern of an authentic security marking of an authentic security element being as claimed in any one of claims 1 to 4, comprising a camera equipped with a processor, a memory and a light sensor adapted to detect the colours of the authentic intaglio pattern and the different tones of a tone palette of said colours, said processor being adapted to perform image processing of a digital image of said authentic two-dimensional intaglio pattern taken by said camera and stored in said memory, and to perform a decoding operation on the coded information detected on said digital image, said memory storing at least one reference pattern forming a two-dimensional coded pattern, and on the basis of which said authentic two-dimensional intaglio pattern is created, - decoding the information encoded in the two-dimensional intaglio pattern according to the method of claim 7 to obtain, from the image of the two-dimensional intaglio pattern captured by the camera, each verified base intaglio pattern and a corresponding verified reference pattern of the two-dimensional intaglio pattern; - shifting, for each verified base intaglio pattern, an intaglio module that corresponds respectively to a tone of a pair of allowed tones from the tone palette of the color of the genuine two-dimensional intaglio pattern along a plurality of different directions with respect to an initial position corresponding to a respective position of the detected intaglio module of each verified base intaglio pattern on the captured image of the two-dimensional intaglio pattern, to obtain corresponding shifted images of the intaglio modules; determining, for each verified base Intaglio pattern, for each corresponding symbol of the associated reference pattern, a pair of shift values ​​respectively for the intaglio modules corresponding to each tone of the pair of allowed tones from the difference between the measured tone value at an initial position of the shifted Intaglio module on the respective shifted image and the measured tone value at the same initial position of the intaglio module on the image of the two-dimensional Intaglio pattern when decoded, and providing a maximum tone value of the verified base Intaglio pattern for all the intaglio modules respectively corresponding to each tone of the pair of allowed tones; determining that said respective intaglio modules of said two-dimensional intaglio pattern are in register only if, for said pair of admissible tones, the average norm value of said determined pairs of shift values ​​over all of said verified base intaglio patterns of said two-dimensional intaglio pattern is less than or equal to 10 μm; The apparatus according to claim 1, characterized in that it is adapted to perform the steps of:

14. A) performing the operations a), b), b1), b2), b3), b4) and c) of the method for decoding information encoded in a two-dimensional intaglio pattern using a processor according to claim 8 on the two-dimensional intaglio pattern to be authenticated, B) if the decoding of the two-dimensional intaglio pattern in step A) fails, deliver information indicating that the decoding of the two-dimensional intaglio pattern has failed; C) if step A) provides, for each stored location on the digital image of a verified base Intaglio pattern, the information encoded in the two-dimensional Intaglio pattern indicating the reference pattern identification number of the associated verified reference pattern, determining the multi-tone aspect of the verified base Intaglio pattern by: determining their distinct allowed tone pairs Ta, Tb from their respective associated verified reference pattern identification numbers; measuring a printed tone value of each intaglio module of said verified base intaglio pattern on said digital image and determining a dynamic range of said digital image from said measured tone values; calculating an average printed tone value Ta of the intaglio module of the verified base intaglio pattern corresponding to the allowable tones Ta as the average of the measured printed tone values ​​of the intaglio modules corresponding to the allowable tones Ta and calculating an average printed tone value Tb of the intaglio module of the verified base intaglio pattern corresponding to the allowable tones Tb as the average of the measured printed tone values ​​of the intaglio modules corresponding to the allowable tones Tb, For each allowed tone pair Ta, Tb, check whether a multi-tone criterion is met that the difference between the calculated average printed tone values ​​Ta and Tb is greater than 1% of the dynamic range; and determining that the two-dimensional intaglio pattern has the multi-tone aspect if the multi-tone criterion is satisfied for each pair of allowed tones; or If the multi-tone criteria are not met for the pair of allowed tones Ta, Tb, then the two-dimensional intaglio pattern is determined not to have the multi-tone aspect and is not genuine. As confirmed by D) for each verified base Intaglio pattern having a corresponding pair of allowed tones Ta, Tb, whose position in the digital image is stored in the memory, if the two-dimensional Intaglio pattern has the multi-tone aspect, using the processor: D1) measuring, within said window arranged at said location on said digital image, through a sampling grid having an arrangement of symbols with respective sites of their two-dimensional elements E1 and E2 corresponding to said symbols of said verified reference pattern associated with said verified base Intaglio pattern, printed tone values ​​of said intaglio modules of said verified base Intaglio pattern from pixels of said digital image located within said respective sites of elements E1 and E2 of each symbol of said sampling grid to obtain corresponding initial tone values ​​due to said respective elements E1 and E2 of said symbols of said verified reference pattern associated with said verified base Intaglio pattern, , calculating a difference between the initial tone value attributable to the element E1 and the initial tone value attributable to the element E2 to obtain an initial differential symbol tone value, and storing the obtained initial differential symbol tone value attributable to the element of the symbol of the verified reference pattern in the memory, wherein for each of the two allowed tones Ta, Tb of the verified reference pattern, a corresponding zero-shift sum is obtained by summing the initial differential symbol tone values ​​of all the symbols of the verified reference pattern corresponding to the tone Ta and the tone Tb, respectively, and the obtained zero-shift sum for the allowed tone Ta and the zero-shift sum for the allowed tone Tb are stored in the memory; D2) shifting the pixels of the digital image located within the respective sites of elements E1 and E2 of each symbol of the sampling grid, whose first elements correspond to the allowed tones Ta, backwards and forwards along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to the respective elements E1 and E2 of the symbol of the sampling grid, the first elements of which correspond to the allowed tone Ta, for the backward and forward shifts along each direction through the sampling grid, from shifted pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first elements of which correspond to the allowed tone Ta, and storing the obtained shifted tone values ​​in the memory; for each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Ta, calculate a difference between the shifted tone value due to the element E1 and the shifted tone value due to the element E2 to obtain a corresponding shifted differential symbol tone value, and store in the memory the obtained shifted differential symbol tone value due to the element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Ta; For each shift, summing the calculated shifted differential symbol tone values ​​of all the symbols of the sampling grid corresponding to the allowed tone Ta to obtain a corresponding verified reference pattern shift sum for the allowed tone Ta; and selecting, for the verified reference pattern, a best shift for the allowed tone Ta that corresponds to a maximum calculated shift sum among the calculated shift sums and the calculated zero shift sums; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all the selected best shifts for the tolerance tones Ta across the verified reference patterns associated with the respective verified base intaglio patterns of the two-dimensional intaglio pattern having the corresponding tolerance tone pairs Ta, Tb; ａ The operation of calculating D3) shifting the pixels of the digital image located within the respective sites of elements E1 and E2 of each symbol of the sampling grid, whose first elements correspond to the allowed tones Tb, backwards and forwards along each of the plurality of different directions relative to the digital image by at least one pixel size to obtain corresponding shifted pixels whose positions are shifted relative to the sampling grid; measuring corresponding backward and forward shifted tone values ​​attributable to the respective elements E1 and E2 of the symbol of the sampling grid, the first elements of which correspond to the allowed tone Tb, respectively, through the sampling grid from shifted pixels of the digital image located within the respective sites of the elements E1 and E2 of each symbol of the sampling grid, the first elements of which correspond to the allowed tone Tb, and storing the obtained shifted tone values ​​in the memory; for each shift, for each symbol of the sampling grid whose first element corresponds to the allowed tone Tb, calculate the difference between the shifted tone value due to the element E1 and the shifted tone value due to the element E2 to obtain a corresponding shifted differential symbol tone value, and store in the memory the obtained shifted differential symbol tone value due to the element of the symbol of the verified reference pattern whose first element corresponds to the allowed tone Tb; For each shift, summing the calculated shifted differential symbol tone values ​​of all the symbols of the sampling grid corresponding to the allowed tone Tb to obtain a corresponding verified reference pattern shift sum for the allowed tone Tb; and selecting, for the verified reference pattern, a best shift for the allowed tone Tb that corresponds to a maximum calculated shift sum among the calculated shift sums and the zero shift sums; a global shift Δ of the two-dimensional intaglio pattern by determining the average of all the selected best shifts for the tolerance tones Tb across the verified reference patterns associated with the respective verified base intaglio patterns of the two-dimensional intaglio pattern having the corresponding tolerance tone pairs Ta, Tb; ｂ The operation of calculating D4) for each remaining pair of allowed tones Ta′, Tb′ from the pairs of allowed tones of the stored verified base Intaglio pattern of the two-dimensional Intaglio pattern, perform operation D) described above to determine the corresponding pair of global shifts (Δ ａ ', Δ ｂ '), and storing said pair of global shifts in said memory. To execute E) A misregistration value r(a,b) of the intaglio module corresponding to any pair of allowed tones Ta, Tb of all the verified base intaglio patterns of the two-dimensional intaglio pattern is calculated as r(a,b)=λ / f(Δ ａ ２ +Δ ｂ ２ ) １／２ where λ is the size in μm of a pixel of the digital image, f is the magnification of the digital image, and the two-dimensional intaglio pattern is judged to be genuine if each misregistration value r(a,b) of each acceptable tone pair Ta, Tb of each verified base intaglio pattern of the two-dimensional intaglio pattern is less than or equal to 10 μm.

14. The device according to claim 13 adapted.

15. 15. The device according to claim 13 or 14, which is a smartphone, the light sensor being an RGB light sensor, the camera having a resolution of at least 20 μm, and wherein measuring the tone of an intaglio module of the two-dimensional intaglio pattern illuminated with illumination light is performed by summing the respective red, green and blue light intensity components detected by the RGB light sensor from the received light reflected by the intaglio module.

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