1. INTRODUCTION

THE success of Internet, cost-effective popular digital recording and storage devices, and the promise of higher bandwidth and quality of service for both wired and wireless networks has made it possible to create, replicate, transmit, and distribute digital content in an effortless way. In the past, duplicating artwork was quite complicated and required a great expertise to ensure that the counterfeit looked like the original. However, in the digital world this is not true, because it is extremely easy to duplicate digital data without any loss of quality [1].

In such a situation, there is a threat to digital media sent through a network from digital thieves. As a result, the ownership of the digital media might be misinterpreted. The protection and enforcement of intellectual property rights for digital media has now become an important issue. One of the potential solutions for declaring the ownership of the images is to use watermarks.

Unlike encryption, which is useful for transmission but does not provide a way to examine the original data in its protected form, watermark remains in the content in its original form and does not prevent a user from listening, viewing, examining, or manipulating the content. Also, in steganography the method of hiding the message may be secret and the message itself is secret, while in watermarking, typically the watermark embedding process is known and the

message (except for the use of a secret key) does not have to be secret. Watermarking is the direct embedding of additional information into the original content or host signal. Ideally, there should not be any difference between the watermarked and original signal and the watermark should be difficult to remove or alter without damaging the host signal.

1. WHAT IS DIGITAL WATERMARKING?

Similar to the process in which artist artistically signed their paintings with a brush to claim their copyrights, artists of today can watermark their work and hide for example their name in a multimedia signal. Hence, the embedded watermark will allow identifying the ownership of a multimedia signal. Digital watermarking is an adaptation of the commonly used and well-known paper watermarks. It is a technique for labeling digital media by hiding secret information in it. The important point is that the embedded information can neither be removed nor decoded without the required secret keys. Indeed, there are a number of desirable characteristics that a watermarking technique should exhibit [2,3]. That is, watermarking technique should at least respect the following requirements.

1. Readability: A watermark should convey as much information as possible. A watermark should be statistically undetectable. Moreover, retrieval of the digital watermark can be used to identify the ownership and copyright unambiguously.