DIGITAL WATERMAKING BASED ON FAST FOURIER TRANSFORMATION USING ENCRYPTION

Abstract

Digital watermarking is a technique that embeds data called watermark in an image without knowing its existence to the human eye. However, digital watermarking is an emerging technology which is vulnerable to a number of attacks. Careful selection must be done while selecting a technique for embedding a watermark that might be a tradeoff between the robustness and quality of the information recovered. This selection depends on the need of the application and the use of the watermarked media. In this thesis, Fourier Transform-based invariant is used for digital image watermarking. Middle frequencies are used to embed data in a circular ring. The embedded mark is designed to be robust against a number of attacks. The original image is not required for extracting the embedded mark. Based on obscured watermark scheme based on the Fourier Transform, the targeted data is encrypted using an encryption key to enhance security of the secret information. The embedded marks are designed to be robust against a number of exploiting attacks like cropping, flipping, AWGN, histogram equalization and lossy compression etc. The thesis concludes with a discussion on the findings and outcomes when exposed to attacks and results are compared with LSB based spatial domain algorithm. Also future direction of the research is included at the end.