Visual cryptography

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

Voronoi-based image representation applied to binary visual cryptography

Abstract: A common processing scheme of Visual Cryptography (VC) consists of generating two ciphered images from a secret image. The sender transmits these key images via two different channels. The receiver collects the key images and recovers the secret image by superimposing them. In this article, Voronoi tessellation is exploited in Visual Cryptography for the first time to the best of our knowledge. The proposed Voronoi-based Visual Cryptography (VVC) technique permits to drastically reduce the amount of encoded and transmitted information by comparison with a traditional VC scheme. Hence, the technique can be used for transmissions of secret images with enforcement of the transmission reliability by enhancing the redundancy of information or with communication networks and technologies having low bandwidth and memory. Moreover, the random arrangement of the Voronoi polygons makes the transmission of the secret image more secure since the sender and the recipient use a private generator of random points. In addition, shape reconstruction properties of the image-based Voronoi representation are stated.

Enhanced visual secret sharing scheme via halftoning technique

Abstract: The rapid development of networks such as internet, intranet, wireless communication etc., and multimedia techniques has emphasized on the need for copyright protection, authentication and identification and secret sharing of information. Visual cryptography is a secret sharing scheme where a secret binary image (SI) is encoded into n shares of random binary patterns. If the shares are xeroxed onto transparencies, the secret image can be visually decoded by superimposing a qualified subset of transparencies, but no secret information can be obtained from the superposition of a forbidden subset. The binary patterns of the shares, however, have no visual meaning and hinder the objectives of visual cryptography. Extended visual cryptography was proposed recently to construct meaningful binary images as n shares using hypergraph colorings, but the visual quality is poor. In this paper, a novel technique named visual secret sharing scheme using halftoning is proposed to achieve visual cryptography via halftoning. Based on the blue-noise dithering principles, the proposed method utilizes the void and cluster algorithm to encode a secret binary image into n halftone shares (images) carrying significant visual information. The simulation shows that the visual quality of the obtained halftone shares is observably better than that attained by any available visual cryptography method known to date.

Visual cryptography scheme based on pixel expansion for black & white image

Abstract: This paper explains the 2 out of 2 visual cryptography schemes based on pixel expansion m=2 in detail. Visual cryptography enables the secure transmission of images in open and insecure media. The scheme explained in this paper is based on k out of k visual cryptography scheme. To prevent the discloser of the secret by forming copy of the first share randomization of sub pixel is performed on the shares. One single share cannot disclose the secret. To extract the secret message both the shares are needed to superimpose one on another. We provide (2, 2) Visual Cryptography (VC) in detail for black and white image based on pixel expansion scheme.

Segment based visual cryptography for key distribution

Abstract: Security is playing a vital role in this era of information technology, it has become a prerequisite in the digital world for maintaining the secrecy of the information. Many techniques have been proposed for handling textual data, maintenance of confidentiality of pictographic data is also becoming a priority. The trend of pictographic data hiding is pixel based, here a version of Visual Cryptography is presented which is segment-based instead of pixel based. The key or the secret which is in the form of digits that is to be distributed is converted into segment display and then encrypted .The result of encryption is two random shares. The decryption process involves the stacking of these two shares. It is easier to view the secret with the human eye by stacking the shares.

From pixel sieve to bit sieve. Bit level based secret sharing cryptographic method

Abstract: As it often happens in cryptography, a visual cryptographic method serves as primitive for more evolved file encryption algorithm. During the development and evaluation process of the pixel sieve[9] method, several weaknesses popped out. In the attempt of solving these weaknesses a possibility to transform the method from pixel based graphical cryptographic method to a bit based file cryptographic method has emerged. This paper describes the road-map from the graphic encryption to the file encryption version of the pixel sieve. Also because a short application was written to test the method the first test results and conclusions are presented here.