Image watermarking algorithm based on fractional Fourier transform and random phase encoding

We propose an optical image watermarking algorithm based on fractional Fourier transform and random phase encoding. The proposed watermarking can be exactly implemented in optics and the secret key is passively generated by the proposed algorithm. In the packaged watermarking system, the host image is unchanged in the embedding procedure. This algorithm is fast and convenient for real-time implementation. PSNR between the host and distorted host images, MSE between the extracted and original watermarks are used to evaluate the performance of the proposed algorithm. Robustnesses against typical attacks are also analyzed. Numerical results have demonstrated its feasibility and effectiveness.