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Abstract-Internet evolution, along with the advancement of
digital multimedia tools have create a major impact in
making the storage and distribution of multimedia content a
straightforward tasks. Thus security of multimedia contents
becomes a vital issue and there is a need in protecting the
digital content against counterfeiting, piracy and malicious
manipulations. Digital watermarking is an evolving field
that requires continuous effort to find for the best possible
method in protecting multimedia content.
In this paper, we describe overview of digital image
watermarking technique and proposed an algorithm for
copy write protection of digital images in neT domain.
Digital watermarking can be defined as the process of
embedding a certain piece of information ,technically known
as watermark into multimedia content including text
documents , images, audio or video streams, such that the
watermark can detected or extracted later to make an
assertion about the data. We have also implemented this
algorithm using MATLAB 7.x and code is also given in this
paper.
Keywords: Digital image watermarking, Spread-Spectrum
techniques, copy Write Protection
I. INTRODUCTION
The recent growth of networked multimedia systems
has increased the need for the protection of digital media.
This is particularly important for the protection and
enforcement of intellectual property rights. Digital media
includes text, digital audio, images, video and software.
Many approaches are available for protecting digital data;
these include encryption, authentication and time stamping.
One way to improve one's claim of ownership over an
image, for instance, is to place a low-level signal directly
into the image data. This signal, known as a digital
watermark, uniquely identifies the owner and can be
easily extracted from the image.
Digital watermarking technology is an emerging field
in computer science, cryptography, signal processing and
communications. Digital Watermarking [4, 5, 6] is
intended by its developers as the solution
to the need to provide value added protection on top of
data encryption and scrambling for content protection.
Like other technology under development [7, 8], digital
watermarking raises a number of essential questions as
follows.
• What is it?
• How can a digital watermark be inserted or detected?
• How robust does it need to be?
• Why and when are digital watermarks necessary?
• What can watermarks achieve or fail to achieve?
• How should digital watermarks be used?
• How can we evaluate the technology?
• How useful are they, that is, what can they do for content
protection in addition to or in conjunction with current
copyright laws or the legal and judicial means used to
resolve copyright grievances?
• What are the business opportunities?
• What roles can digital watermarking play in the content
protection infrastructure?
In this paper we present algorithms for image
authentication and forgery prevention known as watermarks.
Figure 1 shows the block diagram for watermarking digital
images.
Original
Image
Watermark
Watermarked
Image
Figure 1: BlockDiagram of Watermarking Algorithm
A. Types ofDigital Watermarks
Watermarks and watermarking techniques can be divided
into various categories in various ways. The watermarks can
be applied in spatial domain. An alternative to spatial domain
watermarking is frequency domain watermarking. It has been
pointed out that the frequency domain methods are more
robust than the spatial domain techniques. Different types of
watermarks are shown in the Figure 2.

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