Hiding information by context-based synonym substitution

Many methods of linguistic steganography have been proposed by using synonym-substitution to preserve the meaning of the text. However, most of these methods replace words simply according to a static synonym set without considering the context. In this paper, we present a novel method that replaces a word by its synonym on condition that its synonym is suitable for the context. A synonym's candidates are chosen according to context, therefore, in different context the candidates can be different although the word to be replaced is the same. As a result, both of the synonym set and the encoding are dynamic. In our experiment, we use Chinese language to implement our method. The experimental results show that the method is almost twice as good as other two existing methods.