Asymmetric Watermarking Method Based on Subspace Projection

This paper presents an asymmetric watermarking method of a new detection matrix to protect the copyright of the digital image. Lifting-wavelet and singular value decomposition (SVD) are applied to extract the features of the images and determine the robust subspace. Subspace projection is used to construct the embedding matrix (private key) and detection matrix (public key), embedding and detecting the watermarking respectively. The embedding matrix is kept secret while the detection matrix is public to anyone. The simulation shows that the proposed algorithm achieves a high detection probability and security, a low false alarm probability, and a strong robustness against many image manipulations.