Abstract
To improve the stego-image quality and provide a larger embedding capacity, a novel steganographic method based on four-pixel differencing and modulus function is presented. We process a block of four neighboring pixels, and form three two-pixel groups to record the information of secret data. In each group, the difference value between two pixels is exploited to estimate how many secret bits will be embedded. Two pixels will be adjusted so that the sum of the remainders of them is equal to secret data. In order to extract the secret data exactly, four pixel values in a block are adjusted synchronously by using modulus function. An optimization problem is formulated to minimize the embedding distortion. A theoretical proof is given to ensure the solvability of the problem. The experimental results show the proposed method not only has a larger embedding capacity but also provides better stego-image quality.