Visual Secret Sharing of Gray and Color Images using Fuzzy Random Grids

Visual secret sharing is a method used to secure images by converting a secret image into multiple shares so that the original image cannot be recognized from individual shares, and no calculations are required during the image decryption, but the original image can be visually seen by stacking the shares. However, one of the significant challenges in this method is the increased size of the shares and the recovered image, which is called pixel expansion. Researchers have proposed several methods to solve this problem, but many of them are limited to binary images, and they cannot handle gray and color images without converting them to binary. This study proposes a novel fuzzy random grid-based method to directly encrypt gray and color images without any pixel expansions. In this method, fuzzy random grids with decimal values between 0.0 to 1.0 are generated during the encryption stage, and fuzzy operators are used for the decryption stage. The evaluation results demonstrate the ability of the proposed solution in encrypting gray and color images without converting them to binary and without any pixel expansions. The individual shares of the proposed method do not reveal any information from the original image, making it a secure method. The quality of the decrypted images has been evaluated using both subjective and objective evaluation methods such as PSNR and SSIM metrics, which show state-of-the-art results.