A Watermarking Scheme for Image Authentication

Abstract

In today s world, availability of authentic information is the priority of one and all. Information in digital format offers significant advantages over analog format in terms of its quality and efficiency in creation, storage and distribution. Recent advancements in the technology of signal processing tools have led to their possible usage to modify the visual or audio content of digital documents without leaving any perceptible traces of the modification. This creates doubts that information contained in the digital documents has been tampered with in a way that substantially changes the initial data content. To overcome such a problem, it is necessary that proper countermeasures are taken to authenticate signals recorded in digital form, i.e. to ensure that signals have not been tampered with (data integrity) and to prove their true origin. Data authentication through digital watermarking is a promising solution to both the above problems. newlineThe objective of the research was to design and develop a watermarking scheme for image authentication that can detect and improve the localization of the tampered image while maintaining a good value of Peak Signal to Noise Ratio, Mean Square Error, Similarity Function and Tamper Assessment Function. newlineThis thesis presents a fragile watermarking technique for image authentication with localization for the purpose of tamper detection. In the proposed work, a watermark in the form of a visually meaningful binary pattern is modulated by the suggested pseudo random sequence implemented by means of elliptic curve over Galois Fields. The modulated watermark is then embedded in the discrete cosine transform coefficients of the host image by quantizing the coefficients proportionally according to the watermarked bit. Experimental results demonstrate the performance and effectiveness of the suggested fragile watermarking scheme for image authentication by maintaining good values for Peak Signal to Noise Ratio (PSNR), Tamper Assessment Function (TAF), Similarity function, Mean Square E