Almost all the document and information have been converting into form of digital data; such as: audio, text, image or video. Digital media brings up many advantages and at the same time, various security issues, for instance: copy right protection or intellectual property. To address such issues, watermark systems are introduced which insert an ownership evidence, such as: a secret message, into a cover media. This secret message is an incorporated piece and it is embedded permanently. There are two major steps in the watermarking procedure; in the first step, the watermark signal is embedded into the cover data by watermark embedder. Second, the watermark decoder decodes the watermark signal to prove the ownership right or for any other watermarking applications. The described general model of digital watermarking is shown in Fig. 1. Let us suppose that the watermarking system is a function WS (1), the watermarking signal is W, the media cover is C, and the watermarked cover is C’. Thus, watermarking system can be defined by following (1):

ws(w, c) = c (1)