Digital Image Watermarking Department of E & C, SJCE,
MysorePage 1 ABSTRACT
Digitalwatermarkingisapromisingsolutionforcontentcopyrightprotectioninthe
global network. It imposes extra robustness on embedded
information. Digital watermarking is the science of embedding
copyright information in the original files. The information
embedded is called watermark. This report deals with the
implementation of digital watermarking on images in spatial and
frequency domain. LSB substitution algorithm is used for
implementation in spatial domain whereas Coxs method is used for
implementation in frequency domain. Digital Image Watermarking
Department of E & C, SJCE, MysorePage 2 CHAPTER 1 INTRODUCTION
1.1 The Need For Watermarking One of the most important properties
of digital information is that it is in principle very easy to
produce and distribute unlimited number of its copies. This might
undermine the music,
film,bookandsoftwareindustriesandthereforeitbringsavarietyofimportantproblems
concerningtheprotectionoftheintellectualandproductionrightsthatbadlyneedtobe
solved. The fact that an unlimited number of perfect copies of
text, audio and video data can be illegally produced and
distributed requires studying ways of embedding copyright
information and serial numbers in audio and video data. This is
where the concept of watermarking comes into the picture. Digital
watermarking is the process of inserting a digital signal or
pattern into digital content. The signal, known as a watermark, can
be used later to identify the owner of the work, to authenticate
the content, and to trace illegal copies of the work. There are a
variety of image watermarking techniques, falling into 2 main
categories, depending on in which domain the watermark is
constructed spatial and frequency domain. Image watermarking
techniques that take advantage of properties of the human visual
system, and the characteristics of the image create the most robust
and transparent watermarks.
1.2 Brief History Of Digital Watermarking It is difficult to
determine when digital watermarking was first discussed. In 1954,
Emil Hembrooke of the Muzak Corporation filed a patent for
watermarking his musical works. Komatsu and Tominaga, in 1988,
appear to have first used the term digital watermark. The
CopyProtectionTechnicalWorkingGroup(CPTWG)testedwatermarkingsystemsfor
protection of video on DVD disks. The International Organization
for Standardization (ISO) took an interest in the technology in the
context of designing advanced MPEG standards. Inthe area of image
watermarking, Digimarc bundledits watermark embedder and detectors
with AdobesPhotoshop.Morerecently,anumberof
companieshaveusedwatermarking technologies for a variety of
applications. Digital Image Watermarking Department of E & C,
SJCE, MysorePage 3 CHAPTER 2 GOALS AND OBJECTIVES OF WATERMARKING
2.1 Criteria To Be Satisfied To be effective in the protection of
the ownership of intellectual property, the invisibly watermarked
document should satisfy several
criteria:Thewatermarkmustbedifficultorimpossibletoremove,atleastwithoutvisibly
degrading the original image. The watermark must survive image
modifications that are common to typical
image-processingapplications(e.g.,scaling,colorrequantization,dithering,cropping,and
image compression).An invisible watermark should be imperceptible
so as not to affect the experience of viewing the image.For some
invisible watermarking applications, watermarks should be readily
detectable
bytheproperauthorities,evenifimperceptibletotheaverageobserver.Such
decodability without requiring the recovery of property and
subsequent prosecution. 2.2 Features Of Digital
Watermarking:Thedigitalwatermarkingtechniqueisappealing,sinceitprovidesfollowingmain
features: 2.2.1 Robustness:Depending on the application, the
digital watermarking technique can support different levels of
robustness against changes made to the watermarked content.If
digital watermarking is used for ownership identification, then the
watermark has to be robust against any modifications. The
watermarks should not get degraded or destroyed as a result of
unintentional or malicious signal and geometric distortions like
A/D conversion, D/A conversion, cropping, re-sampling, rotation,
dithering, quantization, scaling and compression of the
content.Ontheotherhand,ifdigitalwatermarkingisusedforcontentauthentication,the
watermarks should be fragile, i.e., the watermarks should get
destroyed whenever the content is modified so that any modification
to content can be detected. Digital Image Watermarking Department
of E & C, SJCE, MysorePage 4 2.2.2 Inseparability:After the
digital content is embedded with watermark, separating the content
from the watermark to retrieve the original content is not
possible. 2.2.3
Security:Thedigitalwatermarkingtechniquespreventunauthorizedusersfromdetectingand
modifyingthewatermarkembeddedinthecoversignal.Watermarkkeysensurethatonly
authorized users are able to detect/modify the watermark. 2.2.4
Effect On Bandwidth:Watermarking should be donein such a way that
it doesnt increase the bandwidth required for transmission. If
Watermarking becomes a burden for the available bandwidth, the
method will be rejected. CHAPTER 3 APPLICATIONS
Digitalwatermarkingtechniqueshavewiderangingapplications.Someofthe
applications are enlisted below.Copyright Protection: Digital
watermarks can be used to identify and protect copyright
ownership.Digitalcontentcanbeembeddedwithwatermarksdepictingmetadata
identifying the copyright
owners.CopyProtection:Digitalcontentcanbewatermarkedtoindicatethatthecontent
cannotbeillegallyreplicated.Devicescapableofreplicationcanthendetectsuch
watermarks and prevent unauthorized replication of the
content.Broadcast Monitoring: Digital watermarks can be used to
monitor broadcasted content like television and broadcast radio
signals. Advertising companies can use systems that
candetectthebroadcastofadvertisementsforbillingpurposesbyidentifyingthe
watermarks broadcast along with the
content.ConcealedCommunication:Sincewatermarkingisaspecialtechniqueof
steganography, it can be used for concealed communication also.
Digital Image Watermarking Department of E & C, SJCE,
MysorePage 5 CHAPTER 4 WATERMARKING IMPLEMENTATION 4.1 Approach:
There are two parts to building a strong watermark. The watermark
structure The insertion strategy In order for a watermark to be
robust and secure, these two must be designed correctly.In this
project, we have implemented the digital watermarking usingLeast
Significant Bit (LSB) substitution algorithm (Spatial domain) Cox
method using DCT (transform domain) 4.1.1 LSB Substitution
Algorithm Using LSB manipulation, very large amount of information
can be hidden with very little impact to image quality. This is
performed in spatial domain. The embedding of watermark is
performed choosing a subset of image pixels and substituting the
LSB of each of the chosen pixels with watermark bits.Extraction of
watermark is performed by extracting LSB of each of the selected
image pixels. If the extracted bits match the inserted bits then
the watermark is detected. The LSB substitution algorithm can be
represented in the form of an equation as a =x ( b / y ) +c / z
Where 'a' is the watermarked image, 'b' is the cover image, 'c' is
the watermark and x, y and z are integers that decide the amount of
watermark to be applied and 0