29-07-2011, 10:20 AM
Introduction
The rapid expansion of the Internet in the past years has rapidly increased the
availability of digital data such as audio, images and videos to the public. As we have
witnessed in the past few months, the problem of protecting multimedia information
becomes more and more important and a lot of copyright owners are concerned about
protecting any illegal duplication of their data or work. Some serious work needs to
be done in order to maintain the availability of multimedia information but, in the
meantime, the industry must come up with ways to protect intellectual property of
creators, distributors or simple owners of such data. This is an interesting challenge
and this is probably why so much attention has been drawn toward the development
of digital images protection schemes. Of the many approaches possible to protect
visual data, digital watermarking is probably the one that has received most interest.
The idea of robust watermarking of images is to embed information data within the
image with an insensible form for human visual system but in a way that protects
from attacks such as common image processing operations. The goal is to produce an
image that looks exactly the same to a human eye but still allows its positive
identification in comparison with the owner's key if necessary.
This paper attempts to first introduce general idea behind digital watermarking as
well as some of its basic notions. It is followed by describing some applications of
watermarking techniques and the difficulties faced in this new technology. The paper
ends with an overview on some copyright protection techniques, involving
watermarking and it seen as to why digimarks have become an important research
subject of late.
1 Basis on watermarking
The increasing amount of applications using digital multimedia technologies has
accentuated the need to provide copyright protection to multimedia data. Digital
watermarking is a method that has received a lot of attention in the past few years. A
digital watermark can be described as a visible or preferably invisible identification
code that is permanently embedded in the data . It means that it remains present
within the data after any decryption process. A general definition can be given:
!"Hiding of a secret message or information within an ordinary message
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