Abstract: A method for producing security elements in an image which are not visible to the human eye and which cannot be copied, in particular for checking the authenticity of images. The image is imaged by means of a halftone, the halftone consisting of individual image dots arranged adjacent to each other. This is characterized in that at least one field having a random geometric shape or freeform is defined in the image/the halftone. By means of manipulation of image dots in the field and/or by means of manipulation of the entire field, an encrypted information that cannot be copied is stored for comparison with at least one database and the serial number is displayed by means of contours formed in the halftone.