A symmetric key watermark for halftone images

In many printer and publishing applications, it is desirable to embed data in halftone images for copyright control and authentication purposes. While intentional attacks on printed matters may not be likely, unintentional attacks such as cropping and distortion due to dirt or human writing/marking are likely. In this paper, we proposed a novel halftone image watermarking method called watermarking error diffusion (WED) to embed a watermark in the parity domain of halftone images with symmetric key during halftoning while introducing minimal distortion.