Visual cryptography using two factor biometric system A. Vinodhini

Visual Cryptography Scheme (VCS) is an encryption method that uses combinatorial techniques to encode secret written materials. The idea is to convert the written material into an image and encode this image into n shadow images. The decoding only requires only selecting some subset of these n images, making transparencies of them, and stacking them on top of each other. It is different from traditional cryptography, because it does not need complex computation to decrypt. Это и многое другое вы найдете в книге Visual cryptography using two factor biometric system (A. Vinodhini)