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SVD BASED SECURED HIGH PAYLOAD AUDIO WATERMARKING SCHEMES WITH CHAOTIC ENCRYPTION

As discussed earlier in section 2.2.4.6 SVD is a an important numerical analysis tool that de correlates the samples ,find out a direction along which there is a maximum variation in the sample values and transforms the signal to few coefficients which are robust to common signal processing. Thus, the SVs obtained after SVD transformation are better candidate for hiding watermark information for an audio watermarking scheme. The principle behind SVD based schemes is that the SVs are robust to common signal processing operations and altering the SV by a small value won't distort the audio signal. However, the conventional watermarking schemes embed the watermark directly on the SVs and thus lacking the security of the embedding as the embedding positions are exposed. So, in this chapter two schemes using SVD are proposed which can have a high payload and a high degree of security as compared to the conventional SVD based schemes. To make the watermark secure, watermark bits are not embedded directly into SVs, but rather on the SVs after chaotic encryption using quantization index modulation technique. In this way the singular values which are used for watermark embedding are not known and exposed to the intruder. Also, it becomes difficult for the intruder to decode the watermark message. The security key used for encryption or the chaotic mapping should be known for modifying as well as retrieval of the watermark. Now, because a number of 2-d chaotic combinations of the matrix can be generated using different chaotic keys, the same audio can be watermarked with the same watermark in different ways. Multiple copies can be watermarked with different keys to produce different watermarked audios as the watermark bit is embedded in a smaller block of samples. The rest of the chapter is organized as follows. Section 4.1 gives the analysis of some SVD based schemes followed by the problem statement. The preliminaries for the proposed schemes are discussed in section 4.2. The proposed audio watermarking algorithms are described in section 4.3. The effect of Baker's chaotic mapping on the SNR of the watermarked is discussed in the section 4.4. Also the watermarked audios are evaluated with respect to imperceptibly (inaudibility) and robustness. The chapter is summarized in section 4.5.