An efficient secure reversible authentication watermarking with tamper localization

Abstract

In the recent decade, the digital information revolution has made the manipulation of multimedia data as effortless as possible. As digital media are gaining wider popularity, their security related issues are of greater concern. Digital Watermarking allows an individual to add copyright notices or other verification messages to digital media. The primary objective of authentication is not to protect the contents from being copied or stolen, but is to provide a method to authenticate the image and assure the integrity of the image. A fragile watermark breaks very easily on modifying the host signal. Further, in most conventional authentication techniques based on watermarking, the original image is distorted permanently due to the authentication itself. These distortions are not tolerable in some sensitive applications, such as law enforcement, medical and military images. In this thesis, an AWT which satisfies all these requirements is proposed and referred to as Reversible Authentication Watermarking Techniques with Tamper Localization . Three levels of AWTs have been proposed. In the first level, only the image integrity and authenticity is verified. The proposed second level AWT locates tampers in the image in addition to authenticity and integrity verification. The block-based schemes are vulnerable to vector quantization attack and the pixel-wise schemes are vulnerable to oracle attack, if the pixel scan order is public. Hence, in this thesis, wavelet domain is used for tamper localization which overcomes both the attacks. The proposed scheme finds tamper positions at pixel level. The watermark embedding is carried out in wavelet domain. Most of the existing AWTs provide either tamper localization or reversible authentication, but not both. The proposed third level Reversible AWT verifies authenticity, locates tampers and recovers the original image if the image is authentic. If the image is not authentic, it localizes the tamper positions. newline newline newline