Robust and reversible watermarking scheme in DFT domain

Digital watermarking is a fast growing research area nowadays. An invisible signal called watermark is added into the cover data. Using this watermark, many security services can be provided to host data e.g. illegal copying of data can be avoided, any tempering with the data can be stopped and unauthorized users misusing the data can be caught along with other securities. In this paper, robustness and reversibility of watermarking scheme in Discrete Fourier Transform (DFT) domain based on Code Division Multiple Access (CDMA) is discussed by comparing with the robustness and reversibility in Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT). Experimental results have shown DFT domain gives better robustness than DCT and DWT. In the proposed scheme, spreaded watermark is arithmetically added, in the form of vectors, to Fourier coefficients. Watermark is detected by calculating inner product with the spreading codes. After detection, the watermark removal process can easily be done even without using the original watermark.