DSIS: A Novel (K,N) Threshold Deniable Secret Image Sharing Scheme with Lossless Recovery

Secret image sharing (SIS) schemes have undergone significant development. However, to the best of our knowledge, none of the existing schemes has considered the deniable property during secret sharing. This presents a problem when we need to share secret images through an untrusted and supervised channel, where we may be coerced to reveal the secret to adversary. Here we propose a deniable SIS (DSIS) scheme. Before sharing the secret image, we manipulate the secret area of the image to create a forged image that possesses deniability. Then we employ SIS to distribute the forged image, while generating an auxiliary matrix derived from secret key. This matrix governs rules for sharing secret area. In the event of coercion to reveal the secret, we have the capability to present the adversary with the forged image instead, thereby retaining control over the disclosure of the secret area at our discretion. In DSIS, we can obtain a secret image with the small-sized secret key losslessly, while we can recover another visually-meaningful fake image to safeguard the secrecy and protect ourselves when facing coercion.