A new steganography method which preserves histogram: Generalization of LSB++

Histogram-based steganalysis methods diagnose abnormalities in the stego histogram. LSB+ and outguess are two steganography methods which preserve the cover histogram completely. These methods embed some extra bits to retain the cover histogram. However, these techniques adversely affect the statistical and perceptual attributes of the cover media. LSB++ was proposed to improve LSB+ by prohibiting some pixels from changing, resulting in the reduction of the extra bits. In this paper, we improve the LSB++ method by proposing a technique to distinguish sensitive pixels and protect them from extra bit embedding, which causes lower distortion in the co-occurrence matrices. In addition, we extend LSB++ to preserve the DCT coefficients histogram of jpeg images and generalize this method to the case where more than one bit of the cover elements are used. The experimental results show that the improved LSB++ method produces fewer traces in the co-occurrence matrices than the LSB++ method. Furthermore, the histogram based attacks cannot detect stego images produced by the proposed method with or without extra bits embedding. Therefore, the visual quality of the cover can be improved by the elimination of extra bit embedding.