VoIP steganography and its Detection—A survey
ACM Computing Surveys (CSUR)
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Embedding transparency is one of the most important criteria for steganography. This paper mainly focuses on transparency-orientated encoding strategies for steganography on Voice over IP (VoIP). Our analysis of the existing encoding strategies proposed for steganography on storage media reveals that they have limited applicability in VoIP-based steganography because they enhance embedding transparency at the expense of a decreased embedding rate (ER). In this paper, we propose three encoding strategies based on digital logic for steganography on VoIP. Differing from the existing approaches, our strategies reduce the embedding distortion by improving the similarity between the cover and the covert message using digital logical transformations, instead of reducing the ER. Therefore, in contrast, our strategies improve the embedding transparency without sacrificing the embedding capacity. Of these three strategies, one adopts logical operations, one employs circular shifting operations and the third combines the operations of the first two. All these schemes are evaluated experimentally through their prototype implementations that are compared with some existing methods in a prototypical covert communication system based on VoIP (called StegVoIP). The experimental results show that the proposed strategies can provide better embedding performance than the existing approaches in terms of embedding transparency and ER.