A Hierarchical Image Cryptosystem Based on Visual Cryptography and Vector Quantization

The meaningless shares generated in visual cryptography scheme may attract hackers during transmission and thus possess a threat that if shares are captured and stacked by hacker, secret image may be revealed. To evade the attention of the hackers, Shamir’s (k, m)—secret sharing scheme may be used to encode the pixels of meaningless share images. The proposed image cryptosystem utilizes a three-dimensional vector quantization method to reduce the encoded data volume, as the Shamir’s scheme increases the size of the encoded data m times. Thus an image cryptosystem based on visual cryptography scheme, that encodes the meaningless shares and also manages the encoded data volume efficiently, is proposed here.