Secret communication via image hiding in image by pixel value differencing
Steganographic method for embedding secret messages into a gray-valued cover image is proposed. Cover image is partitioned into non-overlapping blocks of two consecutive pixels. Difference between the two consecutive pixel values is calculated and classified into number of ranges. Range intervals are selected according to the characteristics of human vision's sensitivity to gray value variations from smoothness to contrast. The pixels in edged areas can tolerate larger changes of pixel values than those in the smooth areas. So, in the proposed method we can embed more data in edged areas than in the smooth areas. The difference value then is replaced by a new value to embed the value of a sub-stream of the secret message. The number of bits which can be embedded in a pixel pair is decided by the width of the range that the difference value belongs to.