对基于小波对比度和LSB逐层隐写方法的分析

Analysis Against the Layer-Wise Steganographic Method Based on Wavelet Contrast and LSB

基于小波对比度和LSB的逐层隐写方法按图像小块的小波对比度确定可嵌入位平面层数,然后在时空域中逐层对可在该层嵌入信息的小块嵌入秘密信息,具有较大的信息嵌入量和良好的视觉隐蔽性.针对这种隐写方法,本文从图论的角度直观分析了隐写行为,导出两个基于直方图特性的统计量,理论证明了这两个统计量与嵌入率间存在的线性关系和不同的比例关系,并据此提出隐写检测方法.理论分析和实验结果均表明:本文方法不但能检测出秘密信息的存在性,而且可以大致估计出秘密信息嵌入量.本文方法对分析检测其它位平面逐层隐写也有借鉴作用.

In the Layer-Wise steganographic method based on wavelet contrast and Least-Significant-Bit（LSB）,the number of bit-plane embedded is decided by wavelet contrast,and secret information is embedded by the layer-wise model.The steganographic method can provide large embedding capacity and good imperceptibility.Aimed at this steganographic method,this paper visually analyzes steganographic actions by the methods in graph theory.Two feature statistics are defined based upon the histogram of the image under investigation.It is proved that there are linear relationships and different ratio relationships between the two feature statistics and the embedding rate.Then,a new steganalytic method is proposed.Theory analysis and experimental results show that our steganalytic method can not only announce the presence of hidden information,but also provide a approximative estimation of the embedding capacity.The steganalytic technique proposed in this paper is also useful to against other Layer-Wise steganographic methods.