Visual cryptography

About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.

Enhanced Multi Level Secret Data Hiding

Abstract: In this paper we present enhanced multi-level secret data hiding which integrates two different methods of encryption namely visual cryptography and steganography. First as a pre-processing step we are using a method called halftoning which is used to reduce the pixels and simplify the processing. After that visual cryptography is performed that produces the shares which forms first level of security and then steganography in which we hide the shares in different media like image, audio and video. Hence we get the enhanced multi-level secret data hiding which improves the security over the network.

Invisible Visual Cryptography

Abstract: We propose to realize visual cryptography in an indirect way with the help of diffractive optics, the pure-amplitude keys being substituted with the phase-only keys that are invisible for common-used intensity detectors, leading to the significantly enhanced security and improved usability for practice. Three typical realizations are provided by using static or dynamic diffractive optical elements, and the new concept of invisible visual cryptography (IVC) may be established. This concept is demonstrated by a compact opto-electronic system with only one spatial light modulator within time-delayed exposure, maintaining the fast speed of decryption and no requirement to the calculation of decryption in conventional visual cryptography. Further, IVC shows the immunity to noises and good information capacity, which is partly inherited from diffractive optics. IVC might suggest a new strategy for visual cryptography with the respective of diverse realizations, such as opto-electronic or even bio-chemical or other methods.

Random Grids-Based Threshold Visual Secret Sharing with Improved Visual Quality

Abstract: Visual secret sharing (VSS) by random grids (RG) has gained much attention since it avoids the pixel expansion problem as well as requires no codebook design. However, most of the previous RG-based threshold VSS still suffer from low visual quality or worse reconstructed secrets when more shares are stacked. In this paper, a new RG-based VSS with improved visual quality is proposed. The random bits are utilized to improve the visual quality as well as to decrease the darkness of the reconstructed secret image in the proposed scheme. Experimental results and analyses show the effectiveness of the proposed scheme.

A new visual cryptography using natural images

Abstract: In this paper an (n, n) visual cryptography scheme without dithering is proposed. This scheme takes n grayscale input images to cover a target image across n grayscale images and produces n grayscale output images which are very close to the input images, respectively. Since the output images are visibly innocuous and natural, it may be easy to pass visual inspection, which is a very desirable property in terms of the steganography aspect. This method is different from the existing schemes by the fact that it keeps the input images almost intact.

Security analysis of ‘A novel copyright protection scheme using Visual Cryptography’

Abstract: Digital image copyright protection techniques have drawn substantial interest from the research community for the last two decades. In particular, Copyright Protection schemes based on Visual Cryptography (CPVC) are designed to protect sensitive images without degrading the quality of host images. In this paper, the security of one such CPVC scheme proposed by A. Nag et al. is analyzed. We demonstrate that this technique is insecure as it leads to high ambiguity in detecting the right owner. This is proved by means of theoretical analysis and by conducting false positive tests.