An image watermarking technique based on cascaded iterative Fourier transform

Abstract

As an optical image encryption technique, the double random phase encoding (DRPE) technique can be used to encrypt the watermark image. However, since the DRPE system may be attacked with cryptanlysis, the security of the DRPE technique is somewhat weak. To improve the security, an image watermark generation algorithm based on cascaded iterative Fourier transform algorithm (CIFT) was proposed. In the proposed algorithm, two phase masks were obtained by applying the CIFT algorithm on the original reference watermark image and the final embedded watermark image was obtained with them. One of the phase masks was kept as the secret key. When detecting the watermark, the embedded watermark was extracted from the watermarked host image. Then, the recovered watermarked was obtained with the extracted watermark and the secret key. By comparing the recovered watermark and the original reference watermark, whether the tested image containing the watermark or not can be judged. With the CIFT algorithm, it is more secure to generate the embedded watermark. In addition, it is practical because only one of the phase masks is needed for watermark recovery. The simulation results show that the proposed method has good imperceptibility and robustness.