M.V. Shakursky – Ph. D. (Eng.), Senior Lecturer, Volga Region State University of Service (Togliatti, RF)
In article concidered the proplem of container forming for steganographic system based on conttraction mapping. The forming means determination of amplitude proportion of informational and masking signals and values of keys. The essential requirement of stego-signal formation is frequency range, which is forming by frequency ranges of information an masking signals.
In article shown derivation of mathematical models of steganographic coder and decoder. Mathematical model of decoder is obtained with contraction mapping which is let the realization of decoding system invariant to masking signal. The invariance achieved by information redundancy in two-component stego.
Stego signal consist of two components, and the components bound to each other, so steganalyst can make different operations with components. So we may speak about one more type of attack on stegosystem. So the requirement to forming of stego have to take into account this type of attack. In article formulated specifics of amplitude proportions of informational and masking signals and values of keys that is allow effective signal masking.
When the signal transferred with radiotechnical channels the question of frequency band forming for stego is significant. In article the analysis of mathematical model of stegocoder is made and shown expressions that are determine frequency band of stego throught parametres of frequency bands of informational and masking signals.
The results of computer modelling of steganographic system is shown. Decoding of informational signal take place with anyband of frequencies of informational and masking signal. Conclusions are made.