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Abstract-With the widespread use of networks, intellectual properties can be obtained and reproduced easily. This creates a high demand for content protection technique like watermarking, which is one of the most efficient ways to protect the digital properties in recent years. This paper reviews several aspects and techniques about digital watermarking.
Index Terms- content protection, watermarking, digital properties.
I. INTRODUCTION
Watermarking is a branch of information hiding which is used to hide proprietary information in digital media like photographs, digital music, or digital video. The ease with which digital content can be exchanged over the Internet has created copyright infringement issues. Copyrighted material can be easily exchanged over peer-to-peer networks, and this has caused major concerns to those content providers who produce these digital contents. This paper provides a survey of techniques to watermark data files like text, images, audio and video.
II. REVIEW ON DIGITAL WATERMARKING
Digital Watermarking technique [1] refers to the process of embedding the given watermark information (such as prossessory name, symbol, signature etc.) into the protective information (such as picture, sound, video) and picking the given watermark information from the protective information, which is not perceived by human perceptual system. Fig.1 shows the fundamental process of digital watermarking technique. "Ref. [1, 2]" gives sufficient detail about watermarking requirements and its type like robust and fragile watermarking.
III. THREE STAGES IN WATERMARKING
A. Generation and Embedding
Pseudo Random Sequence, M- Sequence and Chaotic Sequence are some sequences used for watermark generation [5]. The embedding process can be understood as the combination of watermark signal and original image.
B. Distribution and Possible Attacks
The distribution process can be seen as the transmission of the signal through the watermark channel. Possible attacks in the broadcast channel may be intentional or accidental.
C. Detection
Detection process allows the owner to be identified and provides information to the intended recipient. There are two kinds detection: Informed detection and Blind detection.
IV. TEXT WATERMARKING TECHNIQUES
A. Spread Spectrum Technique of Watermarking
Watermark bits (b) are mixed with PRN (Pseudo Random Noise) generated signal and then this signal is inserted in the host signal (X). This PRN signal functions as a secret key. Fig. 2 shows such mechanism [3].
The watermarked signal's amplitude is much...