明文Jsteg及变形隐写的检测和消息提取方法  

Detection and Extraction Method for the Plaintext Jsteg Steganography

作　　者：王俊超[1,2] 刘九芬[1,2] 张武军[2] 

机构地区：[1]数学工程与先进计算国家重点实验室,河南郑州450001 [2]信息工程大学,河南郑州450001

出　　处：《信息工程大学学报》2015年第5期521-528,共8页Journal of Information Engineering University

基　　金：国家自然科学基金资助项目(61170234);河南省杰出青年科学基金资助项目(14410051000)

摘　　要：在嵌入消息为明文的情况下,利用中英文字节比特的统计特性,研究针对Jsteg及变形隐写的检测和消息提取方法。首先,提出一种检测方法,取出待检测图像量化后DCT系数(跳过0、1)的LSB(least significant bit),以该LSB序列第1字节的每一比特为起点间隔7采样获得8条子序列,通过实验方法获得窗口长度W,用W分割8条子序列,若某一条子序列中存在全0(1)窗口,则判断该图像为载密图像,且把该子序列确定为最大优势序列。其次,提出一种消息提取方法:从载密图像估计出载体图像的直方图,计算载体图像量化后DCT系数(跳过0、1)的LSB中0(1)频率,进而推导出一个较小的窗口长度W*;用W*分割最大优势序列,从中估计出消息嵌入的起止点并还原明文。最后,提出一种改进的消息提取方法,直接利用载密图像量化后DCT系数(跳过0、1)的LSB中0(1)的频率,得到一个更小的窗口长度W**,用W**代替W*估计消息嵌入的起止点。该方法不需要估计载体图像的直方图,实现简单,计算复杂度低。实验结果也表明了本文方法的可行性和有效性。By using the bit＇ s statistical property of both English and Chinese words, a detecting and extracting method for the Plaintext Jsteg Steganography under the condition of plaintext has been studied for the first time in this paper. First, a detection method is proposed. The LSB （Least Sig- nificant Bit） of the quantitative DCT coefficient （skip 0, 1 ） of the image to be detected is obtained and 8 subsequences are gained by using every bit of the first byte as the beginning to sample at an interval of 7 bits. The window length W is obtained through the experiment to segment the 8 subse- quences. The image is stego image if the subsequence has all-zero or all non-zero window, and the subsequence is identified as the priority sequence. Next, an extracting method is put forward in this paper： a small window length W＊ is calculated after estimating the cover image histogram and calcu- lating the 0 （1） frequency in the LSB of the quantitative DCT coefficient （skip 0, 1 ） of cover im- age; the priority sequence are cut apart by the window W , secret message are estimated and the plaintext is recovered. and the beginning and the end of the Finally, an improved extraction methodis proposed. A smaller window length W＂ ＂ is calculated by directly calculating the 0 （ 1 ） frequency in the LSB of the quantitative DCT coefficient （ skip 0, 1 ） of stego image, and the beginning and the end of the secret message are estimated after substituting W＂ with W＂ ＂ The method does not need to estimate the cover image histogram, and thus has simple implementation and low computa- tional complexity. The experimental results have proved the feasibility and effectiveness of the meth- od.

关 键 词：明文消息 Jsteg隐写 检测 提取 

分 类 号：TN918.1[电子电信—通信与信息系统]