Abstract
Visual cryptography (VC) has found numerous applications in privacy protection, online transaction security, and voting security, etc. To counteract potential cheating attacks, Lin et al. proposed flip visual cryptography in 2010, where a second secret image can be revealed by stacking one share with a flipped version of another share. The second secret image can be designed as an additional verification mechanism. However, Lin’s scheme produces meaningless shares and is only applicable to binary secret images. It is interesting to explore whether it is possible to extend the flip VC to having cover images (i.e., extended VC) and these cover images are color images. This problem is challenging since too many restricting conditions need to be met. In this paper, we designed a flip VC for gray-scale and color cover images based on constraint error diffusion. We show that it is possible to meet all the constraints simultaneously. Compared with existing schemes, our scheme enjoys the following features: Color cover images, no computation needed for decoding, and no interference from cover image on the recovered secret image.
Highlights
In today’s world, information is a popular application resource and an essential carrier of communication in our lives
In 2011, Prakash and Govindaraju proposed a color visual cryptography scheme based on direct binary search (DBS) with adaptive searching and exchange functions [23]
In 2010, Lin et al proposed a flipping visual cryptography scheme based on nonexpanded Visual cryptography (VC) [25]
Summary
In today’s world, information is a popular application resource and an essential carrier of communication in our lives. Since each secret pixel can be rendered by a block of pixels in a recovered image, ordinary visual cryptography has better visual quality. In 2002, Nakajima and Yamaguchi proposed extended visual cryptography for natural images [16] This scheme can produce a meaningful share of images. Image encryption often uses halftone images and gray-scale images, so meaningful visual cryptography requires high fidelity for share images. In 2011, Prakash and Govindaraju proposed a color visual cryptography scheme based on direct binary search (DBS) with adaptive searching and exchange functions [23]. Through this solution, a better halftone image can be generated, in addition to lossless recovery.
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