Sharing Multiple Digital Images via Halftoning Methods
The visual secret sharing for multiple secrets (VSSM) technique allows for the encryption of more than one secret images in a given image area. Previous research on VSSM schemes has a pixel expansion problem that limits the capability to increase the capacity of secret image encryption. Moreover, the VSSM schemes focus on sharing binary images to date. These drawbacks limit the applicability of existing VSSM schemes. In this study, we propose a novel encryption algorithm to address these problems. The proposed algorithm adopts a visual cryptography (VC)–based encryption method that can eliminate the pixel expansion problem and is applicable to halftone secret images. The experimental results demonstrate that the proposed approach not only can increase the capacity of VSSM schemes, but also can maintain an excellent level of display quality in the recovered secret images.