| Digital watermarking technology is an approach for the protection of digital information against illegal duplication and manipulation. In this thesis, we concentrate on the problem of robust watermarking in the presence of lossy compression. We investigate how the embedding of the watermark signal in a suitable transform domain can improve performance.; Two typical classes of watermarking techniques are considered: one is the spread spectrum watermarking method, the other is the quantization based watermarking method. Based on a communication paradigm for watermarking, we present an information-theoretic approach to estimate the number of watermark bits that can be reliably hidden. The best domain for watermarking is determined to maximize the watermark channel capacity.; Based on the advantages and disadvantages of both watermarking methods, a novel hybrid watermarking technique is proposed which combines the best of both spread spectrum and quantization based methods. |
