OFDM based robust digital image watermarking resistant to multipath spatial shifts

A digital watermark is a visible or invisible pattern embedded in a digital image which can be used for copy right protection, authentication, broadcast monitoring, telemedicine and many more. This paper describes how an efficient CDMA based spread spectrum technique can be combined with the most prominent spectrum efficient OFDM technology to formulate a robust watermarking algorithm which is suitable for image distortions due to time delays and spatial shift that may occur during the transmission of watermarked images. A detailed simulation of embedding and decoding algorithm was performed. Simulation results reveal that the algorithm is computationally efficient, robust and is well suited for wireless multipath fading channel. The algorithm was tested against a number of the possible noises in the wireless channels and various geometric and signal processing operations. The proposed algorithm is proved to be robust enough to extract a good quality watermark compared to well-known techniques.