Signed digit data hiding scheme

The EMD (Exploiting Modification Direction) method by Zhang and Wang uses (2n+1)-ary notation to achieve secret message embedding into a cover image. However, the maximum capacity of this method is 1.16bpp for cover pixel number n=2. Its embedding capacity rapidly decreases when selected pixels increase. In order to improve this shortcoming, a new data hiding scheme based on MSD (Modified Signed-Digit) is proposed. There are three major contributions in this proposed scheme. The first is only ⌈n2⌉ pixels will be modified and the value is +1 or −1 when the group has n pixels. Secondly, the embedded capacity maintains at least 1bpp when n is increasing. The last is the stego image quality is better than 52dB when the cover image's pixels are greater than 4 for each group.