Authentication of Grayscale Images and Data Repairing Using Secret Sharing Method

Digital images are used to safeguard confidential & important information. But the problem is providing authentication, integrity and data security to these digital images. In existing techniques of security and authentication conventional watermarking schemes are used. In these techniques cryptography is the basic method adopted which has problem of tampering of information easily by hackers. Therefore in this paper a new efficient authentication method is proposed for grayscale document images using the Portable Network Graphics (PNG) image with data repair capability. In this concept an authentication signal is generated by each block of a grayscale document image and then, using Shamir secret sharing scheme, authentication signal and binarized block content is combined and transformed into number of shares and then combined into an alpha channel plane forming the PNG image. This layer together forms a stego image. This stego image is sent to the receiver for authentication. If the grayscale image is tampered at the receiving end we can then make use of reverse Shamir's secret method and repair the tampered image. Keywords—data repair, grayscale document image, Portable Network Graphics (PNG) image, secret sharing.