Lossless carrier optical image hiding scheme based on phase-shifting digital holography and canonical cosine transform

In existing optical image hiding schemes, the noise-like pre-encrypted results are typically embedded into carrier images to conceal the original information. However, these schemes suffer from several limitations. First, they have restricted embedding capacities, which limit the amount of data that can be hidden. Second, there is a risk of information leakage during the transmission of stego-carrier images. Moreover, the reliability and robustness of current optical image hiding schemes have largely remained unvalidated through real-world communication system experiments. To address the aforementioned challenges, this paper proposes a lossless carrier optical image hiding scheme based on four-step phase-shifting digital holography and canonical cosine transform (CCT). In the proposed scheme, the original plaintext image undergoes processing through chaotic random phase masks and a four-step phase-shifting digital holography algorithm, yielding four pre-encrypted images. Subsequently, these pre-encrypted images will XOR with the CCT features of the carrier image to generate mapping keys. In this scheme, since the carrier image contains no direct information about the original image, it reveals no actionable data regarding the original content even if intercepted, which significantly enhances the security of the encrypted information. To validate the practicality of the proposed scheme, traditional experiments and comprehensive communication experiments were conducted to assess its reliability and robustness. The experimental results not only demonstrate the feasibility of this optical image hiding scheme but also confirm its excellent security performance and resilience against various attacks.