Apparatus are provided, including a digital two-dimensional authentic image, an image processor, authentication message data, and a screen to be applied to at least a portion of the two-dimensional image. The authentication message data represent an authentication message, which may be a textual message, a symbol, or a pattern, and which may signify that the authentic image is authentic or original. The screen may apply two different halftoning operations. The two different halftoning operations include a first halftoning operation applying halftoning elements arranged in one way and a second halftoning operation applying halftoning elements arranged in second way. The first halftoning operation is applied in a limited area of the authentic image and in a form defined by the authentication message data, and the second halftoning operation is applied in an area surrounding the limited area.