METHOD FOR MARKING, ENCODING AND DECODING CONCEALED INFORMATION IN PRINTED IMAGE FOR IDENTIFICATION AND CONFIRMATION OF AUTHENTICITY OF POLYGRAPHIC PRODUCTS Russian patent published in 2008 - IPC B41M3/14 G09C5/00 

FIELD: polygraphy, method for manufacturing polygraphic product which requires identification and confirmation of authenticity, for example, during manufacture of securities and valuable documents.

SUBSTANCE: method for determining authenticity of polygraphic product on basis of concealed information in printed image includes marking, encoding of input image using a program in computer system, decoding of printed image. Marking and encoding of input image are performed by changing optical density of internal areas of input image and following reflection of that change through printing elements of printing form in printed images in accordance to resolution of printing process. Alteration of optical density of internal areas of input image is performed according to given program with placement of changed areas across whole internal field of input image using doubled marks and encoded information on various internal sections of input image. During the check, reading of encoded information from printed image is performed, information is decoded and authenticity of polygraphic product is determined.

EFFECT: increased degree of protection of polygraphic product from forgery due to creation of concealed information, reproduction of which is difficult.