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.
