Lock and Key Share-based Random Grid Visual Secret Sharing Scheme for Grayscale and Color Images with Two Decoding Options

Grayscale and color images enlarge the area of visual secret sharing scheme. Conventional (2, n) random grid visual secret sharing (RG-VSS) scheme encrypts the secret image into n noise-like share images, called as shares. This scheme generates n shares with equal priorities; thus, decrypts the secret image by stacking any two shares. Recently, concept of two-tier (2, m, n) lock and key share RG-VSS scheme is established to enhance the security of conventional RG-VSS scheme. (2, m, n) scheme generates shares using binary secret image and splits into m lock and n key shares group. The secret image is disclosed only when at least one share is present from each group. The secret image can be revealed using OR-based and XOR-based decryptions. This paper extends the (2, m, n) RG-VSS scheme for grayscale and color images with two decoding option. When the computational device is not available, user gets the preview of the secret information by stacking the shares. User obtains improved visual quality of secret image when computational device is available. Experimental results exhibit the efficiency of the proposed scheme.