A visual cryptography scheme is a secret-sharing mechanism that enables an image to be shared and protected without using a key. In a visual cryptography scheme, the secret image is encoded into shares that appear as random noise. By overlaying these shares, the secret image can be reconstructed. However, the noise-like quality of the shares creates challenges in management and security. The extended visual cryptography scheme creates shares with meaningful cover images to solve these issues. This paper focuses on implementing and analyzing various expansion-free extended visual cryptography algorithms developed between 2013 and 2022. The study includes random grid-based, codebook-based, and block-based extended visual cryptography schemes, encompassing (2, 2), (k, n), and progressive extended visual cryptography schemes. Trials were conducted using grayscale images, and various threshold values were considered. The reconstructed images were assessed based on their contrast and visual quality. The goal is to identify which extended visual cryptography algorithm produces the best results through detailed implementation and analysis.
B et al. (Mon,) studied this question.