一种基于码字分布特性的G.729A压缩语音流隐写分析方法

A Steganalysis Method for G.729A Compressed Speech Stream Based on Codeword Distribution Characteristics

有学者提出了一种在压缩语音编码过程中进行QIM(Quantization Index Modulation)隐写的方法.该方法可用于在G.729A压缩语音流中高隐蔽性地嵌入秘密信息,研究其隐写分析方法很有必要.本文首先分析了QIM隐写对G.729A码流造成的显著性特征变化,发现该种隐写将使码流中LPC滤波器的量化索引(码字)发生转移,并导致码字分布的不均衡性及相关性特性发生改变.本文设计了统计模型,实现了对码字分布特性的量化特征抽取;结合支持向量机,本文构造了用于隐写检测的集成分类器系统.实验结果显示本文方法能够在低于30ms的时间内,获得超过98%的检测准确率,实现了对QIM隐写的快速有效检测.

An improved QIM（Quantization Index Modulation） steganography was proposed and it can be used for efficient information hiding in G.729A compressed speech stream.This paper wants to detect this type of steganography.This paper proves that such steganography will significantly change the imbalance and correlation distribution characteristics of codeword（quantization index） in the stream.And then it designs statistical models to extract the quantitative feature vectors of these characteristics.Combining the extracted vectors with the support vector machine,this paper constructs an ensemble classifier for detecting the QIM-based steganography in the G.729A speech stream.The experimental results show that the classifier can achieve up to 98% correct detection towards G.729A encoded speech stream with detection time less than 30 milliseconds.