Research On The Physical-layer Information Hiding Based On Convolutional Codes

Information plays an important role in the modern world with the development of information society,but the ensuing information security risk leads to an urgent need for information security research.Information hiding technology is an important research branch in the information security research area,which has recently achieved a rapid development on the basis of the research results in cryptography,information processing,computer and other related disciplines.Information hiding technology mainly explores how to hide the secret information in the public carriers and transmit it to an intended recipient without the suspicion of the monitor,accordingly realizing the exchange of the secret in safety.For now,most of the existing information hiding techniques focus more on upper-layer application,such as digital media and Internet applications,though physical-layer information hiding is arousing more and more attentions because of its distinct advantages.In the existing researches,the physicallayer technologies adopted by information hiding mainly include modulation,spread spectrum,channel coding and so on.Even though the proposed techniques are numerous,there are still obvious defects.For one thing,the existing information hiding strategies are so simple and intuitive that they will cause obvious distortion to the carriers,thus causing the suspect's suspicion and reducing the security of the information hiding system.More importantly,the existing physical-layer information hiding systems lack a systematic analysis framework,which brings inconvenience to analyze and compare different physical-layer information hiding algorithms fairly.To overcome the above-mentioned drawbacks,this thesis taking into account the security and robustness of the information hiding system together,proposes a performance analysis framework for physical-layer information hiding system.In the performance analysis framework,this thesis designs security capacity and communication capacity to indicate the security and robustness respectively,and devise a performance index of physical-layer hiding capacity based on the two previous capacity index.In addition,this thesis utilizing the structure characteristics of the physical-layer channel coding,proposes a better physical-layer information hiding scheme.The new information hiding scheme is no longer limited to hide the secret information in the carrier object after encoding,but considers performing the information hiding operation in the process of encoding,further excavating the possibility of embedding carrier and making the embedding operation more concealed.Meanwhile,the new analysis framework and information hiding scheme can be widely applied to other application for physical-layer information hiding,such as steganography,authentication and watermarking.According to the new information hiding scheme,this thesis mainly researches the structure characteristics of convolutional codes,then puts forward two information hiding algorithms.The first proposed algorithm is to embed the secret information in the shift register of convolutional coder that has a weaker influence on the encoding output,by which the influence of embedding operation on the original carrier object is reduced effectively.The second algorithm introduces matrix coding technology on the basis of the first one,which further reduces the influence of embedding operation on the carrier object by improving the embedding efficiency.Through theoretical analysis and simulation,this thesis demonstrates the superiority of the two new algorithms relative to existing algorithms.Moreover,based on the proposed physical-layer information hiding capacity index,we analyze and optimize the parameter of the new information hiding algorithm in different scenarios,thereby verifying the effectiveness of the proposed physical-layer information hiding capacity index.