Method and device for securing a document and method and device for authenticating a document, document secured using such a method

A method for authenticating a document comprising a 2D barcode comprising a plurality of cells, at least one cell comprising at least one set of two areas, each area comprising a plurality of dots, a set comprising:

• a first area including dots representing a symbol and
• a second area, different from the first area, including a matrix of dots, wherein said matrix of dots has dimensions smaller than the dimensions of the second area,
• the method being characterised in that it comprises:
• a step of capturing an image of a 2D barcode printed with the document;
• a step of decoding a message encoded in the captured barcode, the message comprising at least one predefined print variation rate;
• a step of determining an unpredictable print variation rate of the captured barcode;
• a step of comparing variation rates;
• a step of verifying the authenticity of the document on the basis of the result of the comparison.

A device for securing a document, comprising:

• a means for statistically determining the average amplitude of an unpredictable print variation, dot by dot, of at least one geometric characteristic among the dimensions, shape and/or position of the dot;
• a means for generating a message representative of at least one predefined print variation rate;
• a means for encoding the message generated in a 2D barcode comprising a plurality of cells, at least one cell comprising at least one set of two areas, each area comprising a plurality of dots, a set comprising:
• a first area including dots representing a symbol, and
• a second area, different from the first area, including a matrix of dots, wherein said matrix of dots has dimensions smaller than the dimensions of the second area and having at least one geometric characteristic, among the dimensions, shape and/or position, of the order of magnitude of the average amplitude of the statistically determined unpredictable print variation;
• and
• a means for printing the document with the barcode, this printing, as a result of unanticipated unknowns in printing, causing an unpredictable variation, dot by dot, of at least one geometric characteristic of the printed dots among the dimensions, shape and/or position, the printed 2D barcode therefore representing two variations, one generated and the other unpredictable dot by dot.

A device for authenticating a document comprising a 2D barcode comprising a plurality of cells, at least one cell comprising at least one set of two areas, each area comprising a plurality of dots, a set comprising:

• a first area including dots representing a symbol and
• a second area, different from the first area, including a matrix of dots, wherein said matrix of dots has dimensions smaller than the dimensions of the second area, the device comprising:
• a means for capturing an image of a 2D barcode printed with the document;
• a means for decoding a message encoded in the captured barcode, the message comprising at least one predefined print variation rate;
• a means for determining an unpredictable print variation rate of the captured barcode;
• a means for comparing variation rates;
• a means for verifying the authenticity of the document on the basis of the result of the comparison.