Embedding Ratio Estimation of MB2 Based on Relativity of Intra-block Pixels

The model-based steganographic algorithm MB2 modified the blockiness after secret messages are embedded, which makes the existed detection algorithm based on border artifacts invalidate. By further researching on the embedding principle of MB2, this paper analyzes the coefficients alteration results of given stego image after re-embedding with maximum messages. Based on the conclusions, this paper proposes an evaluation method for the relativity between intra-block pixels, the approximately linear relationship between the evaluated value and embedding ratio is derived by experiments. Based on these, an embedding ratio estimation method to MB2 is proposed. Experimental results show that the proposed method can estimate the embedding ratio of MB2 effectively.