Study Of Pixel Contractible Visual Secret Sharing Scheme

Secret sharing is an important technology in the field of data encryption and information security. It plays a crucial role in the safe keeping, transfer and legitimate use of information and data. As one of the secret sharing technologies, visual secret sharing has some prominent features such as more security, simpler implementation, etc. and surpasses other traditional encryption systems which generally have the drawbacks such as the excessive right concentration, weak anti-jamming, etc. The visual secret sharing has been widely applied to banking system management, identity authentication, military and other fields. Although there are many kinds of visual secret sharing schemes, there still exist some problems such as low contrast for reconstructed images, pixel expansion for share images, etc.In this dissertation, I propose a pixel contractible (2n,2n) visual secret sharing scheme. In this scheme, a secret image is scrambled and then the scrambled image is divided into several blocks according to the actual demand. Each block is encoded into2n share images whose size is1/2n of the original image. These share images are distributed to the participants to keep. The smaller size of share images reduces the storage burden on participants and decreases the system's storage and transmission bandwidth requirements. When decoding, only by all the available share images can we get secret reconstruction which has ideal contrast. Any less than2n share images can not reveal any information about the secret image. By comparison with other secret sharing schemes, we analyze the performance of this method in different aspects, such as image format, pixel expansion, secret image reconstructed quality, algorithm's security, etc. The simulation results show that the proposed scheme is effective and reliable.