An optical watermarking scheme with two-layer framework based on computational ghost imaging

Abstract

A two-layer watermarking scheme based on computational ghost imaging and singular value decomposition is proposed. In the first layer, the original watermark is encoded into a significantly small number of measured intensities in the process of computational ghost imaging to constitute a new watermark. In the second layer, the significant blocks chosen from the host image based on spatial frequency are combined to the reference image, which is used to embed the new watermark by using the singular value decomposition. Differing from other watermarking schemes, the information of original watermark can be verified without clear visualization via calculating the nonlinear correlation map between the original one and the reconstructed one. Besides optical parameters such as wavelength and propagation distance, a series of phase-only masks are used as security keys, which can enlarge the key space and enhance the level of security. The results illustrate the feasibility and effectiveness about the proposed watermarking mechanism, which provides an effective alternative for the related work.