Image Tampering Detection and Repairing

Abstract

It is very crucial to design efficient methods to provide authentication to document images mainly for images whose security must be protected. In digital media the authentication, tampering detection and repairing of the tampered data is main concern. Nowadays many digital documents are transferred on the internet regularly e.g. circuit diagrams, scanned cheques, signed documents, drawings, design drafts etc. Here the method of image authentication, tampering detection and repairing is explained. The grayscale image document image authentication with self repair method is provided. The authentication signal is calculated from binary image of the original document image. Secret sharing scheme is used to calculate this authentication signal. The extra alpha channel is embedded in the original grayscale document image. The calculated authentication signal is then embedded in this alpha channel. This is one of the way of visual cryptography in which image is visible but authentication signal will not be recognized. Then this authentic image is encrypted for better security. this whole procedure is done at sender side. In second module i.e. receiver side the image is decrypted. Then the embedded authentication signal is extracted from the received authentic image. The new authentication signal is calculated from the binary image of the received authentic image. This new authentication signal is compared with the extracted signal and the integrity check is provided. If data modification is detected, then the method is proved to repair the tampered pixels using the reverse secret sharing method. The tampering of data is detected successfully in this method without any original image backup. This type of secret sharing scheme is helpful for reducing the risk of incidental partial data loss. This method is also applicable to the color image. Algorithm for color image is also same as grayscale images. In this paper the result is provided only for the grayscale images and supposed to expand for color images as well.