Summary form only given. This paper proposes a new robust watermarking algorithm. Application of this algorithm to copyright protection is studied. The new watermarking system is robust against known attacks such as lossy compression and general signal processing operations. This algorithm uses the discrete cosine transform (DCT) for the watermarking process. It is compared with the well known spread spectrum algorithm studied by Cox et al. It embeds the watermark in a different way. It has a high data payload and robustness in comparison to existing ones. The detection phase is blind - which gives it an advantage over most existing algorithms. An experimental study and analysis are introduced.