Threshold Secret Image Sharing

A (k, n) threshold secret image sharing scheme, abbreviated as (k, n)-TSISS, splits a secret image into n shadow images in such a way that any k shadow images can be used to reconstruct the secret image exactly. In 2002, for (k, n)-TSISS, Thien and Lin reduced the size of each shadow image to 1 k of the original secret image. Their main technique is by adopting all coefficients of a (k − 1)-degree polynomial to embed the secret pixels. This benefit of small shadow size has drawn many researcher’s attention and their technique has been extensively used in the following studies. In this paper, we first show that this technique is neither information theoretic secure nor computational secure. Furthermore, we point out the security defect of previous (k, n)-TSISSs for sharing textual images, and then fix up this security defect by adding an AES encryption process. At last, we prove that this new (k, n)-TSISS is computational secure.