Bi-directional pixel-value differencing approach for RGB color image

A two layer data hiding method for RGB color image has been proposed in this paper. It is an enhancement of Wu and Tsai´s method (PVD) and J. K. Mandal´s method (Color Image Steganography Based on Pixel Value Differencing in Spatial Domain). J. K. Mandal´s method will be referred as “Color PVD” in this research paper. Proposed method is relatively secure and efficient in term of data hiding capability and quality of stego image. Caesar cipher is considered to play the role of security wall for this approach. Difference of pixel pairs (non overlapping consecutive pixels in the cover image) drives the data hiding capacity of this method. Two layer data hiding and LZW compression technique are also involved to enlarge the data hiding capability of this method. In second layer of data hiding, left pixel of the pixel pair is considered as right pixel and viceversa to improve the stego image quality. Stego image in this technique is totally indistinguishable from the original image by the human eye and it is secure against the RS detection attack. Beside this it also avoids falling of boundary problem of the pixels.