Authentication and scrambling of radio frequency signals using reversible watermarking

Digital watermarking is a well known technique used for copy rights protection of multimedia data. Reversible watermarking techniques allow the restoration of original data, after watermark detection. In this paper, a watermarking scheme for physical layer authentication of radio frequency signals is presented. This scheme is blind, robust and reversible and it is based on CDMA. In proposed algorithm, spreaded watermark is arithmetically added to modulated signal before transmission. At receiver, watermark is extracted, before demodulation, by using spreading codes only. After extraction, the watermark can be removed from watermarked data only using same spreading codes. High intensity watermark can also serve as scrambler.