Secret Image Sharing Based on Encrypted Pixels

The well-known Thien and Lin's (k, n) secret image sharing (SIS) scheme and its extended versions are threshold schemes, in which a secret image is shared among n shadow images and it can be recovered from any k shadow images. To reduce the size of shadow image, in those schemes, secret image pixels are embedded in all coefficients of (k -1)-degree polynomial to generate the shadows. Also, the secret pixels are permuted before the sharing to address the residual-image problem on shadow images. Due to the above two approaches, partial secret information can be exposed from (k - 1) shadow images, and thus the threshold properties of those schemes will be compromised. To overcome this weakness, we propose a novel (k, n)-SIS scheme based on encrypted pixels, whose shadow image size is slightly larger than that of Thien and Lin's scheme. By slightly modifying the secret image, we also propose a modified (k, n)-SIS scheme with the same shadow size of Thien and Lin's scheme.