基于流媒体的网络隐信道研究

发布时间：2018-04-03 06:07

本文选题：隐信道　切入点：流媒体　出处：《中国科学技术大学》2014年博士论文

【摘要】：基于流媒体的网络隐信道研究吸引了越来越多学者的关注,作为一种“多通道”载体,流媒体具有瞬时性和不可预测性,以它作为载体构建隐信道进行隐蔽通信,具有其他媒介无法比拟的优势。目前为止,流媒体隐信道在构建算法研究方面已经有不少研究成果,与正向研究相比,其逆向检测研究仍然处于起步阶段,有效的检测算法很少。现有的流媒体隐信道大多局限在G711, G.723.1, G.729a等互联网VoIP编码流中,而随着3G移动网络的迅速发展,基于移动流媒体的隐信道研究必将是未来隐信道的发展趋势。除此以外,流媒体隐信道在系统设计研究和应用研究方面也远远不足。针对目前流媒体隐信道的研究现状,本文从逆向检测研究、正向构建算法研究、系统设计与实现以及应用研究这四个方面展开工作。在逆向检测研究方面,本文设计了两种高效的盲检测算法。第一种是基于马尔科夫状态转移的检测方法,利用多维马尔科夫链对流媒体参数进行建模分析,并将马尔科夫状态转移矩阵作为分类特征矢量。第二种是基于信源熵率的检测方法,该方法使用马尔科夫信源模型对流媒体参数进行统计分析,将马尔科夫信源极限熵作为分类特征值。实验结果表明,这两种方法在检测准确率和检测窗口尺寸方面都要优于现有算法,大大提高了在线检测的能力。在正向研究方面,本文首先提出了基于次优编码的自适应隐信道算法。该方法利用代数码本搜索的冗余性来设计隐写嵌入算法,并引入自适应参数,在变速率编码过程中自动调节嵌入率,使隐写后得到的语音始终保持良好的听觉效果。该方法构建的隐信道带宽最高可达3.2kbpso实验表明,基于次优编码的隐写算法不会给编码器带来额外的计算复杂度,具有良好的不可感知性(语音质量高)和较强的抗检测性,现有的检测算法无法进行有效检测。此外,本文还提出了一种基于码率伪装的高速率隐信道算法,该方法利用流媒体变速率编码器的多码率冗余性设计隐写嵌入算法,它将隐蔽信息填充在低码率编码器语音帧尾部,伪装成高码率的编码器语音帧,并采用SRTP协议加密语音帧保证其安全性。该方法构建的隐信道带宽达到5.6kbps,实验表明该方法在隐藏容量和安全性方面都有较强的实用性。在系统设计与实现研究方面,本文基于正向研究的成果,设计并实现了3G手机上的隐信道系统软件—Stegdroid,该系统引入半可靠的传输控制机制,支持任意形式的数据传输,Stegdroid可以构建单双工隐信道,传输带宽为3.2kbps-5.6kbps。测试结果表明Stegdroid运行稳定,可以在3G、4G和Wifi等网络中使用,具有实际应用意义。在应用研究方面,本文提出使用隐信道来节省流媒体的传输带宽。论文以AMR-WB为例,详细介绍了隐信道降低流媒体传输带宽的基本原理和工作流程,实验结果表明该方法可以为AMR-WB节省10.7%-15.1%(1.6kbps-2.55kbps)的带宽,且基本不会降低AMR-WB的语音质量。该方法有效节约了网络带宽资源,减轻流媒体网络负载。虽然论文只是以AMR-WB为例进行介绍,但基于隐信道降低传输带宽的思想也可以应用到其他流媒体中,其基本原理是一样的。
[Abstract]:Research of network covert channel streaming media has attracted more and more attention based on as a multi-channel carrier, streaming media has instantaneity and unpredictability, taking it as the vector of covert communication covert channel, has incomparable advantages of other media. So far, the covert channel in streaming media the construction algorithm has been studied a lot of research results, compared with the positive research, the reverse detection research is still in its infancy, effective detection algorithm of streaming media rarely. Most of the existing limitations of the covert channel in G711, G.723.1, G.729a and other Internet VoIP encoding stream, with the rapid development of 3G mobile network, mobile streaming media hidden based on the research channel will be the future development trend of the covert channel. In addition, the streaming media in the covert channel research and application system design is also insufficient.
In view of the current research status of the hidden channel in streaming media, this paper starts from the following four aspects: reverse detection research, forward construction algorithm research, system design and implementation, and application research.
In the research of reverse detection, this paper designs two efficient blind detection algorithm. The first method is based on the Markoff state transfer, modeling and analysis using multidimensional Markoff chain convection media parameters, and the vector Markoff state transition matrix as the classification features. The second method is based on entropy rate, this method using the Markoff source model of streaming media parameters for statistical analysis, the Markoff limit source entropy as feature values of classification. The experimental results show that the two methods in the detection accuracy and detection is superior to the existing algorithm of window size, greatly improving the ability of on-line detection.
In the positive research, this paper proposed an adaptive implicit channel algorithm based on suboptimal encoding. The method to design the embedding algorithm using redundant algebraic codebook search, and the adaptive parameters, automatically adjust the embedding rate in variable rate encoding process, the steganographic speech obtained after always maintain good hearing results. Show hidden channel bandwidth up to 3.2kbpso the experimental method to construct the suboptimal encoding algorithm of steganography can give additional encoder based on computational complexity, has good imperceptibility (high voice quality) and strong anti detection, the existing detection algorithms can not effectively detect. In addition, this paper also proposed a high-speed channel algorithm based on implicit rate camouflage by using this method, flow rate redundancy design of hidden media speed encoder write embedding algorithm, it will fill the hidden information In charge of low bit rate speech coder frame tail, disguised as a high bit rate encoder speech frame, and uses the SRTP protocol to encrypt the speech frame to ensure their safety. The method of constructing the hidden channel bandwidth reaches 5.6kbps, experiments show that this method has good practicability in hiding capacity and safety.
The research and implementation of system design, this paper is based on the results of the study, design and implement the software system of 3G - Stegdroid covert channel on the mobile phone, the transmission control mechanism of the semi reliable data transmission system, support arbitrary form, Stegdroid can build single duplex covert channel, the transmission bandwidth for the 3.2kbps-5.6kbps. test results show that the Stegdroid stable operation in 3G, using 4G and Wifi network, has practical significance.
In the aspect of application research, this paper put forward the use of covert channel to save the transmission bandwidth of streaming media. This paper takes AMR-WB as an example, describes the hidden channel to reduce the basic principle and working process of streaming media transmission bandwidth, the experimental results show that this method can save AMR-WB 10.7%-15.1% (1.6kbps-2.55kbps) bandwidth, and will not reduce the AMR-WB voice quality. This method effectively saves network bandwidth resources, reducing network load of streaming media. Although the thesis is in the case of AMR-WB are introduced, but the implicit channel reduced transmission bandwidth of thought can also be applied to other streaming media based on its basic principle is the same.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN919.8

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