........Digi Tech Seminar

8/3/2019 ........Digi Tech Seminar

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CHAPTER 1

INTRODUCTION

In recent years, the distribution of works of art, including pictures, music,video and textual documents, has become easier. With the widespread and increasing useof the Internet, digital forms of these media (still images, audio, video, text) are easilyaccessible. This is clearly advantageous, in that it is easier to market and sell one's worksof art. However, this same property threatens copyright protection. Digital documents areeasy to copy and distribute, allowing for pirating. There are a number of methods for protecting ownership. One of these is known as digital watermarking.

Digital watermarking is the process of inserting a digital signal or pattern(indicative of the owner of the content) into digital content. The signal, known as awatermark, can be used later to identify the owner of the work, to authenticate thecontent, and to trace illegal copies of the work.

Watermarks of varying degrees of obtrusiveness are added to presentation media

as a guarantee of authenticity, quality, ownership, and source.To be effective in its purpose, a watermark should adhere to a few requirements.

In particular, it should be robust, and transparent. Robustness requires that it be able tosurvive any alterations or distortions that the watermarked content may undergo,including intentional attacks to remove the watermark, and common signal processingalterations used to make the data more efficient to store and transmit. This is so thatafterwards, the owner can still be identified. Transparency requires a watermark to beimperceptible so that it does not affect the quality of the content, and makes detection,and therefore removal, by pirates less possible.Or digital watermarking is the process of embedding information into a digital signal in

a way that is difficult to remove. The signal may be audio, pictures or video. If the signalis copied, then the information is also carried in the copy. A signal may carry severaldifferent watermarks at the same time.

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More information is transmitted in a digital format now than ever, and the growth in thistrend will not plateau in the foreseeable future. Digital information is susceptible tohaving copies made at the same quality as the original.There are many types of digital information and data. The types are

Digital Images Digital Audio, and Digital Videos

A watermark is a pattern of bits inserted into a digital image, audio or video file thatidentifies the file's copyright information (author, rights, etc.). The name watermark isderived from the faintly visible marks imprinted on organizational stationery.

Unlike printed watermarks, which are intended to be somewhat visible (like the verylight compass stamp watermarking this report), digital watermarks are designed to becompletely invisible, or in the case of audio clips, inaudible.

In addition, the bits representing the watermark must be scattered throughout the file insuch a way that they cannot be identified and manipulated. And finally, a digital

watermark must be robust enough to survive changes to the file its embedded in, such as being saved using a lossy compression algorithm eg: JPEG.

Satisfying all these requirements is no easy feat, but there are a number of companiesoffering competing technologies. All of them work by making the watermark appear asnoise that is, random data that exists in most digital files anyway.

Digital Watermarking works by concealing information within digital data, such that itcannot be detected without special software with the purpose of making sure the

concealed data is present in all copies of the data that are made whether legally or otherwise, regardless of attempts to damage/remove it.

This need for methods and tools to protect ones intellectual property rights initiated the relatively new research field of digital watermarks.Someone familiar with encryption techniques might be tempted to ask why there is such

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an amount of interest in the research community to develop robust watermarkingtechniques, if numerous secure encryption algorithms are readily available. There areseveral reasons for this:

Encryption alone often is insufficient to protect digital content, since unconsidered and erroneous usage by human operators often renders it useless.

If somebody breaks the encryption (e.g. breaking the content scrambling system useon DVDs with tools like DeCSS, VobDec or SmartRipper), copyrightinfringements can still be proven using the embedded watermark.

The decryption process usually depends on the data being unmodified.

Since rightful owners are to be allowed to access the data they paid for, the encryptionneeds to be undone at some point. As the unencrypted data is normally being held in themain memory of computers, its not too difficult to devise tools for storing it onto a localhard disk (e.g. many DVD players for the Windows OS use DirectShow for video output.This proves to be useful for multiangle DVDs, where applications like DeCSS fail. By

using tools that implement appropriate DirectShow filters to write the decoded images toa user-specified file instead of displaying them on the screen (e.g. DVDRip), the rawvideo data is still accessible.

Because of these shortcomings, digital watermarking is sometimesreferred to as being the last line of defence. Consequently, an effective watermark should normally have several properties, whose importance will vary depending upon theapplication. There are a variety of image watermarking techniques, falling into 2 maincategories, depending on in which domain the watermark is constructed: the spatialdomain (producing spatial watermarks) and the frequency domain (producing spectralwatermarks). The effectiveness of a watermark is improved when the technique exploitsknown properties of the human visual system. These are known as perceptually basedwatermarking techniques. Within this category, the class of image-adaptive watermarks proves most effective.

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In conclusion, image watermarking techniques that take advantage of propertiesof the human visual system, and the characteristics of the image create the most robustand transparent watermarks.

History

The term "digital watermark" was first coined in 1992 by Andrew Tirkel and CharlesOsborne. Actually, the term used by Tirkel and Osborne was originally used in Japan--from the Japanese-- "denshi sukashi" -- literally, an "electronic watermark

The Digital Watermark

Digital watermarking is a technology for embedding various types of information in digital content. In general, information for protecting copyrights and proving the validity of data is embedded as a watermark.

A digital watermark is a digital signal or pattern inserted into digitalcontent. The digital content could be a still image, an audio clip, a video clip, a textdocument, or some form of digital data that the creator or owner would like to protect.The main purpose of the watermark is to identify who the owner of the digital data is, butit can also identify the intended recipient.

Why do we need to embed such information in digital content usingdigital watermark technology? The Internet boom is one of the reasons. It has becomeeasy to connect to the Internet from home computers and obtain or provide variousinformation using the World Wide Web (WWW).

All the information handled on the Internet is provided as digital content. Suchdigital content can be easily copied in a way that makes the new file indistinguishablefrom the original. Then the content can be reproduced in large quantities.

For example, if paper bank notes or stock certificates could be easily copied andused, trust in their authenticity would greatly be reduced, resulting in a big loss. To

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prevent this, currencies and stock certificates contain watermarks. These watermarks areone of the methods for preventing counterfeit and illegal use.

Digital watermarks apply a similar method to digital content. Watermarkedcontent can prove its origin, thereby protecting copyright. A watermark also discourages piracy by silently and psychologically deterring criminals from making illegal copies.

Principle of digital watermarks

A watermark on a bank note has a different transparency than the rest of the notewhen a light is shined on it. However, this method is useless in the digital world. Currently there are various techniques for embedding digital watermarks. Basically,they all digitally write desired information directly onto images or audio data in such amanner that the images or audio data are not damaged. Embedding a watermark shouldnot result in a significant increase or reduction in the original data.

Digital watermarks are added to images or audio data in such a way that they areinvisible or inaudible unidentifiable by human eye or ear. Furthermore, they can beembedded in content with a variety of file formats. Digital watermarking is the content protection method for the multimedia era.

Materials suitable for watermarking

Digital watermarking is applicable to any type of digital content, including stillimages, animation, and audio data. It is easy to embed watermarks in material that has acomparatively high redundancy level ("wasted"), such as color still images, animation,and audio data; however, it is difficult to embed watermarks in material with a low

redundancy level, such as black-and-white still images. To solve this problem, we developed a technique for embedding digitalwatermarks in black-and-white still images and a software application that caneffectively embed and detect digital watermarks.

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Structure of a digital watermark

The structure of a digital watermark is shown in the following figures.

Fig 1.1 structure of watermark

The material that contains a digital watermark is called a carrier. A digitalwatermark is not provided as a separate file or a link. It is information that is directly

embedded in the carrier file. Therefore, simply viewing the carrier image containing itcannot identify the digital watermark. Special software is needed to embed and detectsuch digital watermarks. Kowa 's SteganoSign is one of these software packages.

Both images and audio data can carry watermarks. A digital watermark can bedetected as shown in the following illustration.

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Fig 1.2 Detection of watermark

Importance Of Digital Watermark

The Internet has provided worldwide publishing opportunities to creators of various works, including writers, photographers, musicians and artists. However, thesesame opportunities provide ease of access to these works, which has resulted in pirating.It is easy to duplicate audio and visual files, and is therefore probable that duplication onthe Internet occurs without the rightful owners' permission.

An example of an area where copyright protection needs to be enforced is inthe on-line music industry. The Recording Industry Association of America (RIAA) saysthat the value of illegal copies of music that are distributed over the Internet could reach$2 billion a year.

Digital watermarking is being recognized as a way for improving this

situation. RIAA reports that "record labels see watermarking as a crucial piece of thecopy protection system, whether their music is released over the Internet or on DVD-Audio". They are of the opinion that any encryption system can be broken, sooner or later, and that digital watermarking is needed to indicate who the culprit is.

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Another scenario in which the enforcement of copyright is needed is innewsgathering. When digital cameras are used to snapshot an event, the images must bewatermarked as they are captured. This is so that later, image's origin and content can beverified. This suggests that there are many applications that could require imagewatermarking, including Internet imaging, digital libraries, digital cameras, medicalimaging, image and video databases, surveillance imaging, video-on-demand systems,and satellite-delivered video.

The Purpose Of Digital Watermark

Watermarks are a way of dealing with the problems mentioned above by providing a number of services:

1. They aim to mark digital data permanently and unalterably, so that thesource as well as the intended recipient of the digital work is known. Copyrightowners can incorporate identifying information into their work. That is, watermarksare used in the protection of ownership. The presence of a watermark in a work suspected of having been copied can prove that it has been copied.2. By indicating the owner of the work, they demonstrate the quality and

assure the authenticity of the work.3. With a tracking service, owners are able to find illegal copies of their work on the Internet. In addition, because each purchaser of the data has a uniquewatermark embedded in his/her copy, any unauthorized copies that s/he hasdistributed can be traced back to him/her.4. Watermarks can be used to identify any changes that have been made tothe watermarked data.

5. Some more recent techniques are able to correct the alteration as well.

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Overview Of Copyright Act

"In essence, copyright is the right of an author to control the reproduction of his intellectual creation" . When a person reproduces a work that has been copyrighted,without the permission of the owner, s/he may be held liable for copyright infringement.To prove copyright infringement, a copyright owner needs to prove 2 things.

1. She/he owns the copyright in the work, and

2. The other party copied the work (usually determined by establishing thatthe other party had access to the copyrighted work, and that the copy is "substantiallysimilar" to the original).

In cases where it cannot be said that the owner's work and the possible illegal copyare identical, the existence of a digital watermark could prove guilt.

The damages charge can be higher if it can be proven that the party's conductconstitutes willful infringement; that is, s/he copied the work even though s/he knew thatit was copyrighted (for example, copying even after having discovered a watermark inthe work).

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CHAPTER 2

DIGITAL WATERMARK TYPES AND TERMS

w

A c c a c c oW o rk in g d o m a in

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Watermark can be visible or invisible:

a. Visible watermarks are designed to be easily perceived by a viewer (or listener). They clearly identify the owner of the digital data, but should not detractfrom the content of the data. b. Invisible watermarks are designed to be imperceptible under normalviewing (or listening) conditions; more of the current research focuses on this type of watermark than the visible type.Both of these types of watermarks are useful in deterring theft, but they achieve this

in different ways. Visible watermarks give an immediate indication of who the owner of the digital work is, and data watermarked with visible watermarks are not of asmuch usefulness to a potential pirate (because the watermark is visible). Invisiblewatermarks, on the other hand, increase the likelihood of prosecution after the thefthas occurred. These watermarks should therefore not be detectable to thieves,otherwise they would try to remove it; however, they should be easily detectable bythe owners.

A further classification of watermarks is into

fragile, semi-fragile or robust:a. A fragile watermark is embedded in digital data to for the purpose of detecting any changes that have been made to the content of the data. They achievethis because they are distorted, or "broken", easily. Fragile watermarks are applicablein image authentication systems. b. Semi-fragile watermarks detect any changes above a user-specifiedthreshold.c. Robust watermarks are designed to survive "moderate to severe signal processing attacks".

Watermarks for images can further be classified into spatial or spectrumwatermarks, depending on how they are constructed:

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a. Spatial watermarks are created in the spatial domain of the image, and areembedded directly into the pixels of the image. These usually produce images of highquality, but are not robust to the common image alterations. b. Spectral (or transform-based) watermarks are incorporated into theimage's transform coefficients. The inverse-transformed coefficients form thewatermarked data.

Perceptual watermarks are invisible watermarks constructed from techniques thatuse models of the human visual system to adapt the strength of the watermark to theimage content. The most effective of these watermarks are known as image-adaptivewatermarks.

Finally, blind watermarking techniques are techniques that are able to detect thewatermark in a watermarked digital item without use of the original digital item.

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CHAPTER 3

EFFECTIVE DIGITAL WATERMARKS

I. Features of a Good Watermark

The following are features of a good watermark:1. It should be difficult or impossible to remove a digital watermark withoutnoticeably degrading the watermarked content. This is to ensure that the copyrightinformation cannot be removed.

2. The watermark should be robust. This means that it should remain in thecontent after various types of manipulations, both intentional (known as attacks onthe watermark) and unintentional (alterations that the digital data item would undergoregardless of whether it contains a watermark or not). These are described below. If the watermark is a fragile watermark, however, it should not remain in the digitaldata after attacks on it, but should be able to survive certain other alterations (as in

the case of images, where it should be able to survive the common image alteration of cropping).

3. The watermark should be perceptually invisible, or transparent. That is, itshould be imperceptible (if it is of the invisible type). Embedding the watermark signal in the digital data produces alterations, and these should not degrade the

perceived quality of the data. Larger alterations are more robust, and are easier todetect with certainty, but result in greater degradation of the data.

4. It should be easy for the owner or a proper authority to readily detect thewatermark. "Such decodability without requiring the original, unwatermarked [digital

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document or] image would be necessary for efficient recovery of property andsubsequent prosecution".

Further properties that enhance the effectiveness of a watermarking technique, butwhich are not requirements are:5. Hybrid watermarking refers to the embedding of a number of differentwatermarks in the same digital carrier signal. Hybrid watermarking allowsintellectual property rights (IPR) protection, data authentication and data item tracingall in one go.

6. Watermark key: it is beneficial to have a key associated with each

watermark that can be used in the production, embedding, and detection of thewatermark. It should be a private key, because then if the algorithms to produce,embed and detect the watermark are publicly known, without the key, it is difficult toknow what the watermark signal is. The key indicates the owner of the data.

It is of interest to identify the properties of a digital data item (the carrier signal)that assist in watermarking:

1. It should have a high level of redundancy. This is so that it can carry amore robust watermark without the watermark being noticed. (A more robustwatermark usually requires a larger number of alterations to the carrier signal).

2. It must tolerate at least small, well-defined modifications withoutchanging its semantics.

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CHAPTER 4

DIGITAL WATERMARKING LIFE CYCLE PHASE

Fig 4.1 life cycle of DM

General digital watermark life-cycle phases with embedding-, attacking-, and detectionand retrieval functions

The information to be embedded in a signal is called a digital watermark, although insome contexts the phrase digital watermark means the difference between thewatermarked signal and the cover signal. The signal where the watermark is to beembedded is called thehost signal. A watermarking system is usually divided into threedistinct steps, embedding, attack, and detection. In embedding, an algorithm accepts the

host and the data to be embedded, and produces a watermarked signal.

Then the watermarked digital signal is transmitted or stored, usually transmitted toanother person. If this person makes a modification, this is called an attack. While themodification may not be malicious, the term attack arises from copyright protectionapplication, where pirates attempt to remove the digital watermark through modification.

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http://en.wikipedia.org/wiki/File:Watermark_life_cycle.svghttp://en.wikipedia.org/wiki/File:Watermark_life_cycle.svg


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There are many possible modifications, for example, lossy compression of the data (inwhich resolution is diminished), cropping an image or video, or intentionally addingnoise.

Detection (often called extraction) is an algorithm which is applied to the attacked signalto attempt to extract the watermark from it. If the signal was unmodified duringtransmission, then the watermark still is present and it may be extracted. In robust digitalwatermarking applications, the extraction algorithm should be able to produce thewatermark correctly, even if the modifications were strong. In fragile digitalwatermarking, the extraction algorithm should fail if any change is made to the signal.

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CHAPTER 5

DIGITAL WATERMARKING SCHEME

This section details the implementation of a digital audio watermarking scheme, whichcan be used to hide auxiliary information within a sound file. Although thiswatermarking scheme is for instructional use as a tool for perceptual audio education, it provides an overview of techniques which are common to all digital audio watermarkingschemes.The DC watermarking scheme hides watermark data in lower frequency components of

the audio signal, which are below the perceptual threshold of the human auditory system.

Fig 5.1 process

As seen above, Alice creates an original image and watermarks it before passing it toBob. If Bob claims the image and sells copies to other people Alice can extract her watermark from the image proving her copyright to it.

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The caveat here is that Alice will only be able to prove her copyright of the image if Bobhasnt managed to modify the image such that the watermark is damaged enough to beundetectable or added his own watermark such that it is impossible to discover whichwatermark was embedded first.

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CHAPTER 6

THE WATERMARKING PROCESS DEMO

I. Invisible Watermarking Process

Fig 6.1 invisible watermarking process

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II. The Visible Watermarking Process

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Fig 6.2 visible watermarking process

CHAPTER 7

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DIGITAL AUDIO WATERMARK

Digital watermarking is a technology which allows a secret message to be hidden in a

computer file, without the detection of the user. The watermark is not apparent to theuser, and does not affect in any way, the use of the original file. Watermark informationis predominantly used to identify the creator of a digital file, i.e. a picture, a song, or text.Digital audio watermarking involves the concealment of data within a discrete audiofile. Applications for this technology are numerous. Intellectual property protection iscurrently the main driving force behind research in this area. To combat online music piracy, a digital watermark could be added to all recording prior to release, signifying notonly the author of the work, but the user who has purchased a legitimate copy. Newer operating systems equipped with digital rights management software (DRM) will extractthe watermark from audio files prior to playing them on the system. The DRM softwarewill ensure that the user has paid for the song by comparing the watermark to the existing purchased licences on the system.

Other non-rights related uses for watermarking technology include embedding auxiliaryinformation which is related to a particular song, like lyrics, album information, or a

small web page, etc. Watermarking could be used in voice conferencing systems toindicate to others which party is currently speaking. A video application of thistechnology would consist of embedding subtitles or closed captioning information as awatermark.

Technical Details

Digital watermarking technology makes use of the fact that the human eye has only a

limited ability to observe differences. Minor modifications in the colour values of animage are subconsciously corrected by the eye, so that the observer does not notice anydifference.

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While vendors of digital watermarking schemes do not publicly release the exactmethods used to create their watermarks, they do admit to using the following basic procedure (with obvious variations and additions by each vendor).

A secret key (string or integer) produces a random number which determines the particular pixels, which will be protected by the watermarking. The watermark isembedded redundantly over the whole image, so that every part of the image is protected.

Secret key

origionl protected attacked water

image image image mark

watermark

fig 7.1

One way of doing this is by Patchwork. This technique uses a random number generator to select n pairs of pixels and slightly increases or decrease their luminosity(brightness level). Thus the contrast of this set is increased without any change in theaverage luminosity of the image. With suitable parameters, Patchwork even survivescompression using JPEG.

Although the amount of secret information has no direct impact on the visual fidelity of the image or the robustness of the watermark, it plays an important role in the security of the system. The key space, that is the range of all possible values of the secretinformation, x must be large enough to make exhaustive search attacks impossible.

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Embeddingof watermark

attacksDetectionof

watermark


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In the process of extracting the watermark, the secret key is used to identify themanipulated pixels and finally to decode the watermark.

As an example of poor engineering, an early version of Digimarcs watermarking

software gave each licensed user an ID and a two-digitTechnical Details Digital watermarking technology makes use of the fact that the human eye has only alimited ability to observe differences. Minor modifications in the colour values of animage are subconsciously corrected by the eye, so that the observer does not notice anydifference.

While vendors of digital watermarking schemes do not publicly release the exactmethods used to create their watermarks, they do admit to using the following basic

procedure (with obvious variations and additions by each vendor).

A secret key (string or integer) produces a random number which determines the particular pixels, which will be protected by the watermarking. The watermark isembedded redundantly over the whole image, so that every part of the image is protected.

One way of doing this is by Patchwork. This technique uses a random number generator to select n pairs of pixels and slightly increases or decrease their luminosity(brightness level). Thus the contrast of this set is increased without any change in theaverage luminosity of the image. With suitable parameters, Patchwork even survivescompression using JPEG.

Although the amount of secret information has no direct impact on the visual fidelity of the image or the robustness of the watermark, it plays an important role in the security of the system. The key space, that is the range of all possible values of the secretinformation, x must be large enough to make exhaustive search attacks impossible.

In the process of extracting the watermark, the secret key is used to identify themanipulated pixels and finally to decode the watermark.

As an example of poor engineering, an early version of Digimarcs watermarkingsoftware gave each licensed user an ID and a two-digit numeric password, which wereissued when she registers with Digimarc and pays for a subscription.

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The password checking mechanism could easily be removed by flipping a particular flag bit and the passwords had only 99 possibilities so it was short enough to be found by trial and error.

A deeper examination of the image also allowed a villain to change the ID and thus thecopyright of an already marked image as well as the type of use (such as adult -> general public content).Before embedding a mark, watermarking software usually checks whether there isalready a mark in the picture, but this check can be bypassed fairly easily with the resultthat it is possible to overwrite any existing mark and replace it with another one.The quality of digital watermarks can be judged in two ways; firstly it must be able toresist intentional and unintentional attacks and secondly the embedded watermark mustnot detract from the quality of the image.The higher the resistance of a watermark against attacks, the higher the risk of the qualityof the image being reduced, and the greater the chance of obvious visual artefacts beingcreated.

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CHAPTER 8

METHODA USED FOR WATERMARKING ROBUSTESS

These are some of the methods that can be used to test whether a watermark can survivedifferent changes to the image it is embedded in.

Compare this Original Image with the attacked images below, and see if you can spot any changes in quality.

Fig 8.1 original image

Horizontal Flipping

Many images can be flipped horizontally without losing quality. Few watermarks surviveflipping, although resilience to flipping is easy to implement.

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Fig 8.2 horizontal image

Rotation & Cropping

A small rotation with cropping doesnt reduce image quality, but can make watermarksundetectable as rotation realigns horizontal features of an image used to check for the presence of a watermark. The example at left has been rotated 3 degrees to the right, andthen had its edges cropped to make the sides straight again.

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Fig 8.3 rotation and cropping

JPEG Compression/Re-compression

JPEG is a widely used compression algorithms for images and any watermarking systemshould be resilient to some degree to compression or change of compression level e.g.from 71% to 70% in quality like the example at left.

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Fig 8.4 jpeg compression/recompression

Scaling

Uniform scaling increases/decreases an image by the same % rate in the horizontal andvertical directions. Non-uniform scaling like the example at left increases/decreases theimage horizontally and vertically at different % rates. Digital watermarking methods areoften resilient only to uniform scaling.

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Fig 8.5 scaling

Dithering

Dithering approximates colors not in the current palette by alternating two availablesimilar colors from pixel to pixel. If done correctly this method can completely obliteratea watermark, however it can make an image appear to be patchy when the image isover-dithered (as in the elbow area of the image at left).

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Fig 8.5 Dithering

Jitter

The simplest and most effective attack on any audio watermarking scheme is to add jitter to the signal. In our first implementation, we split the signal into chunks of 500 samples,either duplicated or deleted a sample at random in each chunk (resulting in chunks of 499or 501 samples long) and stuck the chunks back together. This turned out to be almostimperceptible after altering, even in classical music; but the jitter prevents the marked

bits from being located, and therefore the watermark is obliterated.In his paper titled Audio watermarking: Features, Applications And Algorithms,Michael Arnold agrees with the Cambridge team stating thatone of the greatest challenges [of watermarking] is the robustness against the so-called jitter attack.

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Fig8.6 Jitter

Video

At present there is no known method to remove a digital watermark from a stream of video. This is probably because those who trade in pirated video, (especially in DivXformat), store their pirated movies locally on their hard disk drives or on CD-R diskswhere they cannot be checked for watermarks by anyone.

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Mosaic

A mosaic attack doesnt damage the watermarked image or make it lose quality in anyway, but still enables the image to be viewed in eg: a web browser by chopping theimage into subsections of equal size and putting it back together again.To the viewer a mosaic image appears to look the same as the original but a webcrawler like DigiMarcs MarcSpider sees many separate images and doesnt detect thatthese separate images are parts of a watermarked image.This means that the watermark cannot be detected, as a problem common to all imagewatermarking schemes is that they have trouble embedding watermarks into smallimages, (less than 256 pixels in height or width).

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Stirmark

StirMark is the industry standard software used by researchers to automatically attemptto remove watermarks created by Digimarc, SysCoP, JK_PGS (TALISMAN project .P.F.L. algorithm), Signum Technologies and EIKONAmark.Stirmark attacks a given watermarked image using all the techniques mentioned in thisreport as well as more esoteric techniques such as low pass filtering, gamma correction,sharpening/unsharpening etc.

All vendors of digital watermarks have their products benchmarked by Stirmark and asof August 2001, no watermark from any vendor survives the test, ie: the watermarks areall removed without degradation to image quality occurring.

Contradicting Requirements

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Fig 8.7 Additive Watermarks

W (x, y): Pseudo Random Pattern {-1,0,1}

kMultiply by gain

factor k

I (x, y) I W (x, y)

Fig 8.8 requirement

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ALGORITHMS

MPEG1 Layer III (MP3) audio compression

A digital audio compression algorithm that achieves a compression factor of abouttwelve while preserving sound quality. What this lossy compression does is remove thefrequencies not heard by the human ear from the audio. If a raw audio file is converted toMP3 at a bit-rate of 128kbps than roughly 90% of the frequencies are removed. Thismeans that a search for the watermark needs to find an unaltered length of samples thatcontains at least 2 watermarked bits to prove the watermarks existence.

Audio Restoration programs

Audio restoration programs are designed to remove hisses, crackles and pops from audiorecordings. They do this by searching through the wavelength, removing samples thatdont fit in amongst neighbouring samples, and replacing them with an average of thetwo neighbour samples. Although the removal of digital watermarks is obviously not a

purpose of these programs, they work remarkably well at doing so as the sample bitsinserted to watermark the audio dont fit in with their surrounding pixels, and aretherefore removed.

Echo Hiding Removal

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Echo hiding relies on the fact that we cannot perceive short echoes, eg: 1millisecond(ms) and embeds data into a cover audio signal by introducing an echocharacterised by its delay and its relative amplitude compared to surrounding samples.The echo delays are chosen between 0.5 ms and 2 ms and the best relative amplitude of the echo is around 0.8 ms.However specialised software which looks for echoes with a length between 0.5 ms and2 ms (as seen below), can be used to detect and remove these echoes without effectingsound quality.

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CHAPTER9

ATTACKS ON

WATERMARKS

Lossy Compression: Many compression schemes like JPEG and MPEG can potentially degrade the datas quality through irretrievable loss of data.

Geometric Distortions: include such operations as rotation, translation, scalingand cropping.

Common Signal Processing Operations: They include the followings. D/A conversion, A/D conversion Resampling, Requantization, Recompression Linear filtering such as high pass and low pass filtering. Addition of a constant offset to the pixel values Local exchange of pixels other intentional attacks: Printing and Rescanning

Watermarking of watermarked image (rewatermarking)

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CHAPTER 10

DIGITAL WATERMARKING APPLICATIONS

Digital watermarking is rapid evolving field, this section identifies digitalwatermarking applications and provides an overview of digital watermarking capabilitiesand useful benefits to customers. The various applications are:

Authentication Broadcast Monitoring Copy Prevention Forensic Tracking E-Commerce/Linking

AUTHENTICATION

Authentication identifies if content has been altered or falsified. For exampledigital watermarking can verify authenticity and identify counterfeiting as a second layer of security for encrypted content. The presence of digital watermark and/or continuity of

watermark can help ensure that the content has not been altered.

BROADCAST MONITORING

Broadcast content is embedded wit a unique identifier, and optionally, distributor information. Detectors are placed at popular markets, where broadcasts are received and

processed, resulting in reports to be sent to the owner.

COPY PREVENTION

Copy prevention helps the digital watermarks to identify whether the content can be copied. It guards against unauthorized duplication.

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FORENSIC TRACKING

Forensic tracking locates the source of the content. The key advantage of digitalwatermarking is that it enables tracking of the content to where it leaves an authorized path.

E-COMMERCE/LINKING

The digital watermarking enables the user to purchase or access informationabout the content, related content, or items with in the content.

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CHAPTER 11

AUSTRALIUN DIGITAL WATERMARKING SCENE

Across all the digital watermarking literature researched no mention was made of anyaustralian company implementing or selling a digital watermarking technique. The onlyknown group researching digital watermarks in Australia is the Secure MultimediaInformation Communication Research Labs at the University Of Wollongonghttp://www.itacs.uow.edu.au/research/smicl/.This research team is supported by theMotorola Australian Research Centre, Visual Information Processing Lab.

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CHAPTER 12

WATERMARKING SOFTWARE&SREVICES

1. Alpha-Tec: watermarking software for copyright protection and infringementtracking.2. Digimarc: For document verification, copyright protection, embeddedmessages and more.3. Stegnosign: For creating, embedding and detecting watermarks.4. Signum: Allow digital fingerprints to be embedded into grahics, audio, videoe.t.c.5. MediaSec: Provide software for various media types, partial encryption, andinternet tracking.

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CHAPTER 13

CONCLUSION

Digital watermarks have been used in the last few years to protect the ownershipof digital data. Various techniques developed make use of the human audio-visualsystem. Legitimate business and webmasters have nothing to fear from copyright law or new form of on-line enforcement technology found in digital watermarks and trackingservices. By using audio files and images only when they have obtained permission of the appropriate owner, webmasters should be free to continue making their sites audiovisually appealing.

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CHAPTER14

REFERENCES

1. Electronics For You2. www.ewatrmark.com3. www.altavita.com4. www.digitalwatermarking.com
http://www.ewatrmark.com/http://www.altavita.com/http://www.ewatrmark.com/http://www.altavita.com/

Date post:	06-Apr-2018
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