关键词: 文本隐写, 同义词替换, 失真函数, 隐写分析

Abstract: As overall statistical characteristics of the cover text would be changed in the process of synonym substitutions, this paper proposes a text steganographic algorithm using the prior substitutions with low distortion. Taking the suitability of synonyms in the context into account, the proposed algorithm constructs a distortion function to measure the degree of the statistical characteristics changed by synonym substitutions. It not only selects two words with the highest suitability from each synonymous word set to form a substitution set, but also from the global perspective, gives priority to the substitution sets with low distortions to be embedded secret information after sorting the distortions caused by all the substitution sets in the cover text. Therefore, the changed degree of the statistical characteristics is reduced. The experimental results show that the algorithm can effectively resist the attacks made by detection algorithms using statistical features based on the synonyms pairing and relative frequency. The proposed algorithm has a good resistance to detection, and can improve the security of the secret information.

Key words: text steganography, synonym substitution, distortion function, steganalysis