Greyscale Image Authentication and Repairing
It is very necessary to design effective methods to solve image authentication problem, particularly for images whose security must be protected. In digital documents it is necessary to provide data authentication and repairing of tampered data e.g. important documents such as certificates, scanned cheques, drawings, circuit diagrams, signed documents, design draft etc. In this paper, a technique for authentication of images with self-repair capability for fixing tampered image data is explained. The input image is assumed to be a binary-type greyscale image with 2 main gray values. Alpha channel is combined in the greyscale image .Using the binary image, authentication signal is calculated which is then embedded in the alpha channel to create an authentic image. After embedding the authentication signal, image is encrypted.