, Pei-Yan Pai 2

In the exploiting modification direction (EMD) method, a secret digit in (2n+1)-ary notational system is embedded into a group that is consisted of n pixels. Only one pixel in a group at most is being modified by either increasing or decreasing one. Therefore, the maximum embedding rate of EMD method is (log2(2n+1))/n when n≧2. In order to increase the embedding capacity of EMD method, a new adjustment data hiding method based on c n-ary notational system is proposed in this paper. In the proposed method, at most n pixels in a group can be modified and each pixel has c different ways of modification. As the result, the maximal embedding rate of the proposed method is log2c. The experimental results demonstrated that the proposed method provides a higher embedding capacity than the compared methods and a satisfied image quality of stego-image. The proposed method provides an average 1~4.75 bits per pixel (bpp) and an average peak signal-to-noise rate (PSNR) of 51.14~30.30 dB with different c. In addition, the proposed method also inherits the advantageous properties of EMD method: the computation efficiency and the ability to resist steganographic attack