对DCT域连续LSB隐写术的提取攻击

基于JPEG图像的空域特征，针对DCT域连续LSB隐写术提出一种唯载密提取攻击方法。根据JPEG图像编码块在空域的块不连续性，将嵌入消息起止点估计问题转化为序列突变点的估计问题，建立逼近理想序列模型估计序列突变点。新模型不仅适用于对连续JSteg算法的提取攻击，对一类可抵抗χ²检验攻击的连续JSteg改进算法同样有效。实验结果表明，对消息嵌入起止点的平均估计误差约为260个系数。

Extracting Attack to DCT Domain Sequential LSB Stegangraphy

A stego-only extracting attack method is proposed based on a spatial domain feature. The discontinuity of JPEG image coding blocks in spatial domain is used to construct a time series. The problem of extracting attack is changed to the problem of estimating the change-points in time series. Then, a technique for order preference by similarity to ideal solution (TOPSIS) model is built to estimate the change-points. The model can be applied to not only sequential JSteg but also an improved sequential JSteg algorithm which resists to Chi-square test attack. The experimental result indicates that average error for estimating the message embedding start point and end point is about 260 coefficients.