New size-reduced Visual Secret Sharing schemes with half reduction of shadow size

Abstract

Visual Secret Sharing (VSS) scheme proposed by Naor and Shamir is a perfect secure scheme to share the secret image. By using m subpixels to represent one pixel, the secret image is divided into several shadow images whose size is m times than the secret image. The value of m is known as the pixel expansion. In this paper, we propose the new size-reduced VSS schemes and dramatically decrease the pixel expansion to a half and meantime the contrast is not compromised. © Springer-Verlag Berlin Heidelberg 2005.