Cheating in (halftone-secret) visual cryptography: Analysis of blind authentication schemes

In visual cryptography (VC), cheating is an important security concern where dishonest participants will fool honest ones and make them accept a fake secret by providing fake shares. Share and blind authentications are two categories of cheating prevention, and the last one relies on the inherent robust of shares against cheating attacks. In the previous studies, cheating in VC only focuses on operating a ‘pixel block’ instead of a region of adjacent pixels. However, the well-known advantage of VC is to decode the secret image by using the human vision system (HVS), so it leads to a natural issue to reconsider cheating a region. In this paper, we formally address the binocular cheating attack (BCA) for a region to augment effectiveness of original cheating for a block. Finally, we demonstrate how to realize BCA by presenting non-trivial techniques against some blind authentication schemes, and further obtain implausible results. The BCA can also be applied to halftone secret.