Development of Copyright Protection and Authentication Schemes with Extended Visual Cryptography

Abstract

The existing image watermarking schemes protect the digital image by embedding watermark that degrades the visual quality of the image. This embedded watermark is extracted to prove the copyright or authentication. Visual Cryptography based watermarking schemes have gained a lot of attention in recent years since they aid in protecting the images without modifying them. The focus of this thesis is on two key uses of watermarking, namely copyright protection and authentication. Most of the existing Visual Cryptography based image authentication schemes have high computational cost as they embed the constructed shares and authentication data into the cover images. Most of these schemes create expanded and noisy shares, leading to pixel expansion and security threat of some sensitive information being shared, respectively. To address these problems, an imperceptible authentication scheme is introduced for grey images where meaningful and un-expanded authentication shares are generated from watermark and cover images. Cellular Automata is used to construct the master share that provides self-construction capacity to the share, thereby saving the storage cost and enhancing stability. The watermark is recovered just by superimposing these authentication shares, thereby helping to reduce the computational cost at receiver s side. The scheme possesses the ability of tamper detection, localization and lossless recovery as of the tampered data as well. The copyright protection schemes are proposed to protect the ownership of the digital images. Most of the existing copyright protection schemes based on visual cryptography produce noisy shares that is a security threat. For this purpose, a robust and secure copyright protection scheme based on curvelet transform, K-means clustering and extended visual cryptography for color images is proposed that creates meaningful noiseless shares. The scheme is robust to withstand a range of image manipulation attacks and provide greater imperceptibility.