A method of verifying an authenticity of a printed item, the method comprising: a) photographing the printed item to obtain a photographic image of the printed item, b) retrieving reference data of the printed item, the reference data comprising a reference image of an authentic one of the printed item, the authentic one of the printed item comprising a noise pattern in at least two colour channels, c) determining a test noise parameter from the photographic image of the printed item, wherein the test noise parameter reflects a noise pattern in at least two colour channels of the photographic image of the printed item, d) determining a reference noise parameter from the reference image, wherein the reference noise parameter reflects the noise pattern in the at least two colour channels of the reference image, e) comparing the test noise parameter to the reference noise parameter thereby deriving, from a difference between the test noise parameter and the reference noise parameter, a noise pattern change as a result of a colour modulation change per raster point between the at least two colour channels of the photographic image of the printed item and the at least two colour channels of the reference image of the printed item, and f) determining an authenticity of the printed item from a result of the comparing, thereby determining the authenticity from the noise pattern change as a result of the colour modulation change per raster point, characterized in that the test noise parameter from the photographic image of the printed item is a test signal to noise ratio from the photographic image of the printed item and the reference noise parameter from the reference image is a reference signal to noise ratio from the reference image of the printed item. a) photographing the printed item to obtain a photographic image of the printed item, b) retrieving reference data of the printed item, the reference data comprising a reference image of an authentic one of the printed item, the authentic one of the printed item comprising a noise pattern in at least two colour channels, c) determining a test noise parameter from the photographic image of the printed item, wherein the test noise parameter reflects a noise pattern in at least two colour channels of the photographic image of the printed item, d) determining a reference noise parameter from the reference image, wherein the reference noise parameter reflects the noise pattern in the at least two colour channels of the reference image, e) comparing the test noise parameter to the reference noise parameter thereby deriving, from a difference between the test noise parameter and the reference noise parameter, a noise pattern change as a result of a colour modulation change per raster point between the at least two colour channels of the photographic image of the printed item and the at least two colour channels of the reference image of the printed item, and f) determining an authenticity of the printed item from a result of the comparing, thereby determining the authenticity from the noise pattern change as a result of the colour modulation change per raster point, characterized in that the test noise parameter from the photographic image of the printed item is a test signal to noise ratio from the photographic image of the printed item and the reference noise parameter from the reference image is a reference signal to noise ratio from the reference image of the printed item. <EOS>