HIDDEN CHARACTER DETECTION Russian patent published in 2004 - IPC

FIELD: image processing and hidden character detection in data signal (image or video signal). SUBSTANCE: in processing suspect image with hidden character it was labeled with by means of modified data signal in compliance with respective meanings of hidden character pattern use is made of method of symmetrical phase of matched filtration only prior to detecting degree of correlation between data signal and hidden character. Mentioned degree of correlation between signals is calculated using forward and inverted Fourier transforms of data signal and hidden character into respective Fourier coefficients, and then degree of correlation is compared with desired threshold value. Too high threshold value points to detection of hidden character. EFFECT: enhanced reliability and reduced vulnerability of method and device. 9 cl, 10 dwg