1. Apparatus comprising: a media-encoded continuous-tone two-dimensional authentic image; an image processor; media-encoded tamper message data representing a tamper message image; two screens to be applied to at least a portion of the two-dimensional image to embed the tamper message data within a portion of the authentic image, in a manner so as to be substantially not visible in a printed or displayed version of the authentic image absent image processing or tampering to the authentic image, the screens including a first screen applying first elements arranged in a first way and including a second screen applying second elements arranged in a second way; a halftoner to apply each of the first screen and the second screen to visibly portray, in the printed or displayed halftoned version of the authentic image, desired continuous-tone information of the authentic image; and the first screen being applied in a limited area of the authentic image and in a form defined by the tamper message data, and the second screen being applied in an area abutting the limited area; wherein the first elements include halftoning elements of a first shape applied using a first halftone threshold matrix and wherein the second elements include halftoning elements of a second shape applied using a second halftone threshold matrix; wherein the tamper message data includes one or more of a textual message, a symbol, and a pattern; wherein the first shape is the same or different than the second shape; wherein the first and second elements each include different size dots or shapes.