To provide the forming method, forming system and program for forming of dot image data, which can realize at low cost and has a high antifalsification effects and can easily judge authenticity, and the authenticating system and program for authenticating of the dot image data or dot printed matter.

Image data used for forming the dot printed matter are inputted and converted to monochromatic gray tone image, resulting in forming a dot image, in which a plurality of sets of one first halftone region and a second halftone region adjoining thereto are arranged. After that, dots in the first halftone regions is erased so as to form the dot image data consisting only of the second halftone regions. In order to tonally express in the second halftone region, a pictorial image data processing for coloring dots with black ink having infrared absorbency or a pictorial image data processing for coloring the surroundings of the dots with cyan-, magenta- and yellow-inks belonging to the same colorimetric system having no infrared absorbency is performed so as to output the obtained dot image data.

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