A SIFT-based DWT-SVD blind watermark method against geometrical attacks

Most Discrete Wavelet Transform(DWT)/Singular Value Decomposition(SVD) watermark methods are robust to common attacks, such as loss compression, noise and filtering attacks, but they cannot resist geometrical attacks. As Scale Invariant Feature Transform(SIFT) feature points are invariant to rotation, scaling and translation, a blind DWT-SVD watermark method against geometrical attacks based on SIFT is proposed. The square of the inscribed circle of the host image matrix is chosen as the watermark embedding area. Firstly, the watermark embedding area is decomposed with 1-level DWT and the low-frequency sub-band is divided into non-overlapping blocks; then the SVD is applied to every block. Secondly, the watermark is embedded by quantifying the maximum singular value of each block. Finally, SIFT feature points of the watermarked image are saved to detect and correct possible geometrical attacks. The experimental results show that the proposed method not only has the robustness to any angle of rotation attacks, wide range of scaling attacks and translation attacks, but also can achieve blind extraction.