An embedding multiplex signatures in binary images by using pattern dither method

A “signature checking”, one can recognize the signature pattern by piling up the two images, is one of the interesting application. The piling up is carried out by coded image or printed image. Matsui proposed information embedding technique for “signature checking” on making binary image from gray scale image by using pattern dither method. We extended Matsui´s method to plural signature patterns. However, in simple method, we can recognize the signature patterns by piling up not only key image and public image but also among public images. We propose an improved method that plural signature is able to embed and no one can recognize signature without key image. In the improved method, we inverse a 25% part of pixel which is in each signature pattern, and the locations of inverted pixel are exclusively in four signature patterns. In this method, four images can be embedded into an original image. However, if any information contained in signature patterns must disappear without key image, up to three images can be embedded into an original image