Theory And Method For Research On Covert Secrecy Communication Based On Steganography

Currently information hiding is a popular research field of information security.Steganography is a significant embranchment of information hiding,on which researched how tosend secret message covertly by embedding it into some public digital multimedia. In addition toproviding legal protection, Steganography can be used by enemy organizations or terroristorganization for the planning and coordination of criminal activity. Steganography can be adangerous tool for national politics and economy security. Therefore, the security researches ofsteganography become the maintenance of state security, social stability.It’s also an importanttechnical means wihch is urgent faced by the nation and army.In this paper, steganographic security is the core, using information theory, mathematicalstatistics, algebraic coding theory and optimization method, combining steganography theoryand methods, from the coding, algorithm and software three levels respectively, we discusses theproblems of steganography analysis and design. The main work of this paper includes thefollowing three aspects:1. Steganographic encoding analysis and design.First of all, proposed a kind of optimal notational system conversion coding algorithmbased on double layer coding method.For any k sequence to the p sequence of the notation system conversion problems, a kind ofefficient double layer coding algorithm is put forward.The optimal binary notational systemconversion code is defined.The optimization of double layer code optimality is proved based onthe information theory methods. Using the new algorithm to improve the existing variety ofmulti-ary or mix-ary steganography, can effectively improve the steganographic security.Secondly, analysis of the security of matrix embedding. In known-cover condition, the keyequivocation and message equivocation is given by the matrix coding security measure. In thechosen-ciphertext attack conditions,the conclusions that n differential equations can recover thematrix embedding shared key is given. Considering the wet paper coding condition, analysis ofthe relationship between wet ratios and embedding rate,the upper bound of the unicity distance isgiven. It points out that the existing fixed key matrix encoding cannot be effective againstknown-cover attack and chosen-ciphertext attacks.Again, an effective matrix embedding method based on random linear code. Noted in thebasic coding model and the side information coding model, the problem of constructingsteganographic code family close to the embedding efficiency upper bound can be attributed tothe problem of constructing large embedding rate matrix embedding. Based on binary randomlinear code, it constructs a large embedding rate matrix embedding which performance close tothe embedding efficiency upper bound. Fast Hadamard transform is used to improve embeddingefficiency. And bit control method is proposed to improve the coding efficiency of theembedding matrix. From the constructed large embedding rate matrix embedding, based onGZZW (Generalization of Zhang, Zhang and Wang) construction steganographic code family under the basic coding model has been constructed. And based on the paper folding algorithm,high efficiency wet paper code family has been constructed under the wet paper coding model.2. Steganographic algorithm analysis and design.First of all, this paper proposes an efficient adaptive steganography. It points out that theexisting additive distortion adaptive steganography is insufficient,A kind of add distortion typesteganography analysis method-RF(Restricted point&Free point) analysis is proposed.Structure a function based on mode function with texture order preserving to solve thesynchronous problem of side information. Combined with wet paper coding and multi layerembedding method, this paper proposes an adaptive steganographic algorithm. The newalgorithm not only can ensure fast synchronization edge information between the two sides ofthe communication, but also with very high resistance to steganographic detection performance.Secondly, proposed a kind of secure ciphertext domain steganography. Steganographyschemes in the ciphertext domain are classified into three feasible modes. Based on the modifiedhomomorphic encryption and double-layer steganographic encoding, communication message isembedded in plaintext domain and extracted in ciphertext domain. The proposed method canreach traditional text steganography capacity, and effectively resist steganalysis detectionanalysis both in the ciphertext and the plaintext domain. The method is applicable not only to thecloud among users of covert communication, can also be used for cloud services on the datamanagement under ciphertext domain.3. Secure steganographic software analysis and design.It proposed stego key recovery method for the cover format based steganography, sequentialsteganography and random steganography. Aiming at the random steganographic mechanism, thestego key recovery model is established by combining steganalysis and cryptanalysis. Therelation between the stego key recovery problem and traditional cryptanalysis problem isdiscussed. Three types of system attack method to steganography software is proposed:known-message attack based on dynamic identification feature, known-cover attack based on aonline matching cover search algorithm and a local collision objects search algorithm, as well aschosen key attack based on equivalent key analysis. By analyzing of the existing steganographysoftware security defects, the design guidelines for steganographic software are proposed.