GREYSCALE IMAGE AUTHENTICATION AND REPAIRING

Jyoti Rao, Sarika Jankar

Abstract: 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. If still Content modifications of the stego-image is detected, then data is repaired at the pixel level using reverse secrete sharing scheme. In case if the alpha channel is completely removed from the stegoimage, the integral resulting image is regarded as unauthentic, meaning that the integrity check of the image fails. The proposed method is based on the generation of (k, n)-threshold secret sharing scheme proposed by Shamir. In this method a secret message is converted into n shares which is used as authentication signal for keeping by n participants; and when k of the n shares are collected, the secret image can be recovered without any loss[8]. This type of secret sharing scheme is helpful for reducing the risk of incidental partial data loss

Keywords: Alpha Channel, Secrete sharing scheme, Data repair, Encryption, greyscale image

DOI: https://doi.org/10.15623/ijret.2013.0209039