Robust embedding of visual watermarks using discrete wavelet transform and singular value decomposition

Protection of digital multimedia content has become an increasingly important issue for content owners and service providers. As watermarking is identified as a major technology to achieve copyright protection, the relevant literature includes several distinct approaches for embedding data into a multimedia element. Because of its growing popularity, the discrete wavelet transform (DWT) is commonly used in recent watermarking schemes. In a DWT-based scheme, the DWT coefficients are modified with the data that represents the watermark. We present a hybrid nonblind scheme based on DWT and singular value decomposition (SVD). After decomposing the cover image into four bands (LL, HL, LH, and HH, where L stands for lowpass and H stands for highpass), we apply the SVD to each band, and modify the singular values of the cover image with the singular values of the visual watermark. Modification in all frequencies enables the development of a watermarking scheme that is robust to a wide range of attacks. We compare our hybrid algorithm with a pure SVD-based scheme, and show that it is considerably more robust and reliable.