Optical robust zero-watermarking scheme based on chaotic facial phase masks and phase-shifting digital holography

Abstract As an effective approach to image copyright protection, optical image watermarking has emerged as a prominent research focus in the field of image information security. However, current optical image watermarking schemes typically embed watermark information into the host image, which is not suitable for applications that require high integrity of the host image. Moreover, existing optical image watermarking schemes based on human biometrics require that the biometric features used in the encoding and decoding processes of the watermark image must be identical; otherwise, the original watermark’s valid information cannot be decoded. To address these issues, this paper proposes an optical robust zero-watermarking scheme based on chaotic facial phase masks and three-step phase-shifting digital holography. In the proposed scheme, we first construct a chaotic facial phase masks using the human face and chaotic systems. Next, we use the chaotic facial phase mask and three-step phase-shifting digital holography to encode the original watermark into three noise-like holograms. Finally, we combine the encoded watermark information with the Canny edge features of the host image to construct a zero-watermark. Since the proposed scheme does not require modification of the host image, it is suitable for application fields that demand high integrity of the host image. Furthermore, in the proposed scheme, even if there are slight deviations in the same user’s face during the encoding and decoding processes, the original watermark image’s valid information can still be decoded. Extensive experiments and analyses demonstrate that the proposed scheme not only has high security but also exhibits strong robustness against common image processing attacks and geometric attacks.