Multiple Watermarking Based on Spread Transform

Multiple watermarking is an embranchment of digital watermarking, which has many desirable characteristics that common singular watermarking does not have, such as robustness to union attacks. But existing multiple watermarking methods have some inherent problems such as low validity and high complexity. In this paper, a novel multiple watermarking method based on spread transform is proposed. Cover vectors extracted from the cover works are projected to multiple orthogonal projection vectors using spread transform in the proposed scheme. Then different watermark signals are embedded in different orientations of these orthogonal projection vectors, so that different watermark signals do not mutually interfere and the capacity of singular watermark signal can be maintained. Besides, the proposed method can be flexibly designed to be robust or fragile watermarking algorithms. Analytical and experimental results show that the validity and capacity of this scheme are good