Secure DCT-SVD Domain Image Watermarking: Embedding Data in All Frequencies

Both Discrete Cosine Transform (DCT) and Singular Value Decomposition (SVD) have been used as mathematical tools for embedding data into an image. In the DCT-domain, the DCT coefficients are modified by the elements of a pseudo-random sequence of real values. In the SVD domain, a common approach is to modify the singular values by the singular values of a visual watermark. In this paper, we present a new robust hybrid watermarking schemes based on DCT and SVD. After applying the DCT to the cover image, we map the DCT coefficients in a zig-zag order into four quadrants, and apply the SVD to each quadrant. These four quadrants represent frequency bands from the lowest to the highest. The singular values in each quadrant are then modified by the singular values of the DCT-transformed visual watermark. We assume that the size of the visual watermark is one quarter of the size of the cover image. Modification in all frequencies enables a watermarking scheme that is robust to normal A/V processes or intentional attacks that destroy the watermark in either lower or higher frequencies. We show that embedding data in lowest frequencies is resistant to one set of attacks while embedding data in highest frequencies is resistant to another set of attacks. The only exception is the rotation attack for which the data embedded in middle frequencies survive better.