Over the past few years, increasing concern about the privacy of information shared in computer systems has increased interest in data security. Visual cryptography is a secure secret sharing scheme that divides secret images into shares which on their own reveal no information of the original secret image. Recovery of the secret image can be performed by superimposing the shares. Hence, the process does not require any special software or hardware for cryptographic computations. However, loss of resolution and contrast, and also the image size expansion which results in the need for storage space, are resulting problems and have been the focus of many researchers. In this paper, we propose a novel visual secret sharing scheme without image size expansion. Compared to other schemes of visual cryptography, our perfectly secure scheme not only does not have pixel expansion, but also provides a high quality recovered image.

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A novel visual secret sharing scheme without image size expansion

Over the past few years, increasing concern over personal information in computer systems has increased interest in data security. This paper reviews and applies visual cryptography, a perfectly secure method of keeping images secret, for possible use in biometric identification and protection. The basic concept of visual cryptography is to divide secret images into random shares. Decryption is performed by superimposing the shares. Hence the process does not require any special software or hardware device for cryptographic computations. In this work, we review some visual cryptography schemes and apply them to biometric data such as fingerprint images for the purpose of user authentication.

Application of Visual Cryptography to Biometric Authentication

the extreme development of internet has made the transmission, distribution and access to digital media very convenient. So, media pro- ducers are more frequently dealing with illegal and unauthorized usage of their productions.Over the last two decades, digital watermarking has been addressed as an effective solution to safeguard copyright laws and an extensive effort has been made to design robust watermarking algorithms. Basi- cally, a digital watermark is an invisible mark that is inserted into a digital media such as audio, image, or video to identify illegal distributions of copyright protected digital media and also law breaking customers. A digital watermark must have special features to achieve functionalities desired. The embed- ded mark should be robust enough against various watermarking attacks, while keeping the perceived quality of the host signal unchanged (the imper- ceptibility requirement). Watermarking attacks consist of deliberate attacks made maliciously to remove or change the mark sequence by law- breakers, unintentional modifications caused by coding and compression that are made to the digital media prior to transmission and/or storage, and errors occurred during the transmission of the media through the networks.Digital watermarking using visual cryptography provides improved security for encrypting secret images. Index Terms— Watermarking, Visual cryptography, Image copyright, Cryptography, Digital Envelopeing —————————  ——————————

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Digital Watermarking Scheme For Secret Images Using Visual Cryptography

Distribution channels such as digital music downloads, video-on-demand, and multimedia social networks pose new challenges to the design of content protection measures aimed at preventing copyright violations. Digital watermarking has been proposed as a possible brick of such protection systems. However, application of watermarking for multimedia content protection in realistic scenarios poses several security issues. Secure signal processing, by which name we indicate a set of techniques able to process sensitive signals that have been obfuscated either by encryption or by other privacy-preserving primitives, may offer valuable solutions to the aforementioned issues. More specifically, the adoption of efficient methods for watermark embedding or detection on data that have been secured in some way, which we name in short secure watermarking, provides an elegant way to solve the security concerns of applications. A digital watermarking technique is used to generate meaningful shares. The secret image shares are watermarked with different cover images and are transmitted. At the receiving side the cover images are extracted from the shares and stacked one by one which reveals the secret image progressively. Digital watermarking using visual cryptography provides improved security for encrypting secret imag

/pdf/optimal-number-of-shares-for-digital-water-marking-scheme-5dc0lib0qs.pdf

Optimal Number Of Shares For Digital Water- marking Scheme Using Visual Cryptography

With the growth in digital world, it is becoming more important to find a method to protect the security of digital media. An image watermarking model based on visual secret sharing (VSS) is proposed for protection of ownership. In the embedding phase, the watermark is first divided by VSS into two parts, a hiding watermark and a secret watermark. Then only the hiding watermark is embedded into the original image and the secret watermark is reserved for watermark extracting by the owner. In the extracting phase, the hiding watermark is extracted from the watermarked image first and then directly superimposed on the secret watermark to recover the watermark information. Digital watermarking has been proposed as a possible brick of such protection systems. However, application of watermarking for multimedia content protection in realistic scenarios poses several security issues. A digital watermarking technique is used to generate meaningful shares. The secret image shares are watermarked with different cover images and are transmitted. At the receiving side, the cover images are extracted from the shares and stacked one by one which reveals the secret image progressively. Digital watermarking using visual cryptography provides improved security for encrypting secret images.

Performance Evaluation of watermarking Schemes to Decide Meaningful Number of Shares

In this paper, two secret sharing schemes were proposed. The two schemes both have the characteristic that the share images they produced are with no pixel expansion. In encoding phase, the rotated share scheme creates two share images for hiding three secret images, whereas the Exclusive OR rotated scheme achieve three share images for hiding four secret images. In decoding phase, the first scheme get secret information by stacking images and rotating image with different angles (0°, 90°, 180°). The second scheme get secret information by doing XOR operation, stacking, and rotating image with different angles (0°, 90°, 180°, 270°). Compare with other schemes of Visual Cryptography, our schemes not only increase the quantity of secret information, but also enhance quality of share image without increasing embed data.

Meng-Lin Chiang

Papers

The image multiple secret sharing schemes without pixel expansion