A framework for block based image authentication (FBIA)

This study deals with devising and implementing a novel technique for image authentication and secured message transmission based on hiding large volume of data into gray scale images. Image authentication is done by embedding message / image in spatial domain by choosing image blocks of size 3 × 3 from the source image in row major order. Three bits of authenticating message /image/message-digest are fabricated within each source image byte of each image block where the position is chosen randomly using a hash function b₇b₆b₅¿k where b₇, b₆, b₅ are higher order three bits of each source image byte and k is an integer number varies from 0 to 7, and the process is repeated for the whole image. The dimension of authenticating image followed by message digest (MD) and the content of authenticating message/image are also embedded. To enhance the security a layer has also been fabricated by XOR operation of the embedded image with a self generated MD obtained from the source image. Reverse process is applied for decoding. The results have been tested through histogram analysis, noise analysis and standard deviation computation of the source image with the embedded image and compared with popular existing steganographic algorithms like S-Tools. It is seen that the proposed FBIA is capable to embed more information than S-Tools with better fidelity.