Randomly tampered image detection and self-recovery for a text document using Shamir secret sharing

Forgery of the digital image is to hide or to remove some meaningful or useful information of the image. In this paper (k, n) Shamir threshold scheme is applied to an image where the tampering is done randomly all over the image. Performance parameters are checked with the random tampering. Comparative study of algorithm for different block sizes is presented. The algorithm is checked for four different block sizes 2×2, 2×4, 3×3, 2×5. Effect of these blocks sizes on stego image and reconstructed image is observed. PSNR is calculated for various block sized algorithm and the visual quality is compared.