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    INTRODUCTION:

    Digital watermarking is a technique which allows an individual to add

    hidden copyright notices or other verification messages to digital audio,

    video, or image signals and documents. Such a message is a group of bits

    describing information pertaining to the signal or to the author of the signal

    (name, place, etc.). The technique takes its name from watermarking of

    paper or money as a security measure. Digital watermarking can be a form

    of steganography, in which data is hidden in the message without the end

    user's knowledge

    In other words Digital watermarking is the process of embedding

    information, or a watermark, into a digital multimedia object such that

    the watermark can be detected or extracted later to make an assertion

    about the object. Watermarking has proven to be a reliable mean toprovide copy protection and authenticity proof for digital media, and

    therefore a lot of research has been performed in these areas.

    The concept of watermarking comes from more than 700 years back. It was

    a technique used by paper manufacturers to identify their products. Today,

    watermarks in paper can still be seen. Along with the years the concept of

    watermarking has penetrated into the field of security. Currency, such as

    dollar bills, checks, postal stamps, and official documents from

    government can be seen to carry watermarks. Besides these paper-based

    applications, watermarking can also be used to provide the same degreeof security to digital media data, such as audio, text and still images.

    Digital watermarking is an adaptation of the commonly used and well

    known paper watermarks to the digital world. Digital watermarking

    describes methods and technologies that allow hiding information, for

    example a number or text, in digital media, such as images, video and audio.

    The embedding takes place by manipulating the content of the digital data

    that means the information is not embedded in the frame around the data.

    The hiding process has to be such that the modifications of the media are

    imperceptible. For images this means that the modifications of the pixel

    values have to be invisible. Furthermore, the watermark has to be robust or

    fragile, depending on the application. With robustness we refer to the

    capability of the watermark to resist to manipulations of the media, such as

    lossy compression, scaling, and cropping, just to enumerate some. An

    example of watermarking is shown below

    http://en.wikipedia.org/wiki/Copyrighthttp://en.wikipedia.org/wiki/Watermarkhttp://en.wikipedia.org/wiki/Steganographyhttp://en.wikipedia.org/wiki/Copyrighthttp://en.wikipedia.org/wiki/Watermarkhttp://en.wikipedia.org/wiki/Steganography
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    A watermark is a recognizable image or pattern in paper that appears lighter

    when viewed by transmitted light (or darker when viewed by reflected light,

    atop a dark background). A watermark is made by impressing a water-coated

    metal stamp or dandy roll onto the paper during manufacturing. Watermarks

    were first introduced in Bologna, Italy in 1282; they have been used by

    papermakers to identify their product, and also on postage stamps, currency,

    and other government documents to discourage counterfeiting.

    An image with visible digital watermarking

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    Hardware implementations in digital watermarking are scarce and may

    not be justified for most applications. Several hardware implementations

    are intended for various applications, were software solutions tend to

    struggle to satisfy the computational demands. A high percentage of these

    works are ASIC-based implementations (Application Specific Integrated

    Circuit). Only two of the works found are FPGA-based implementations

    (Field Programmable Gate Array).

    FPGA devices have improved on speed, capacity, flexibility, and power

    dissipation over the years. Current applications where FPGA can be

    utilized include digital signal processing, computer vision, speech

    recognition, computer hardware emulation, and cryptography. Applications

    that contain heavy amounts of parallelism can benefit the most from

    the FPGA architecture . For video watermarking, the FPGA should

    provide the benefits of parallel processing and specific-architecturedesign offered by Application Specific Integrated Circuits(ASIC), but at a

    fraction of the price.

    Therefore, the goals of this thesis are to select a watermarking method

    appropriate for working on various images, and to develop a hardware

    implementation of the watermarking algorithm for these images in an

    FPGA device, in order to study the issues related to implementing

    such an algorithm in an FPGA device, and explore the potential of

    performing such algorithms in hardware platforms. Since the Digital

    Signal Processor (DSP) is traditionally used to handle similar tasks, acomparison with the FPGA implementation is provided. The comparison

    will be in terms of performance or speed, power dissipation, unit cost,

    and development cost. The results will be discussed and compared to

    previous work in the area.

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    Background and Review:

    Watermarking is defined as the direct embedding of additional

    information into the original content or host signal, and in as a

    technique to embed invisible or inaudible data within multimedia

    content. Usually the watermark is imperceptible to the human. There should

    be no way to remove or modify the watermark without changing or altering

    the content (or signal). The watermark can carry or provide information. In

    general, watermarking must comply with the following three

    requirements: (1) imperceptibility, (2) robustness and (3) capacity. In

    [3] the authors found that sometimes these requirements conflict with

    each other. The tradeoff between these requirements depends on the

    application the watermark is intended for. For example, if one desires

    to test for tampering, one would employ an algorithm that guaranteesimperceptibility but that is not robust to any modification of the

    content (this is termed as fragile or semi-fragile watermark). On the

    other hand, if one desires a copyright protection that must withstand an

    irreversible or lossy transformation or additional attacks, a very robust

    watermarking algorithm would then be selected. Some transformations,

    or attacks, that the signal may be subject to are resampling rescaling,

    compression, linear and nonlinear filtering, additive noise, A/D and D/A

    conversion. Watermarks typically are not retrieved, they are only detected.

    Detection is usually performed by correlation methods, correlating the

    watermarked data with the watermark sequence. The value of

    correlation is compared against a threshold value, which is then used

    to decide if the watermark was detected or not. The threshold value is

    determined by the application and trial-and-error runs.

    Watermarking can have various purposes which include copyright

    protection, authentication, tamper detection, and data hiding. It can be

    applied to different media types such as digital images, video, graphics,

    audio, text, and multimedia content. The creation of the internet and the

    conversion of audio-visual and textual content to digital format haveallowed replicating and distributing digital content over and over,

    without any visible penalty on the data. Therefore, there seems to be an

    increasing desire to protect property rights for digital media. The authors

    agree that in the past 10 years there has been a new and great interest in the

    area of digital watermarking as a way to help to protect authenticity and

    prevent unauthorized replication of media.

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    Watermarking is as old as paper manufacturing itself because watermarks

    were a by-product of the process of making paper. Years ago our ancients,

    during the process of making paper, poured a mix of slurry of fiber and

    water on to mesh molds to collect the fiber. Then this slurry was dispersed to

    add shape and uniformity, and finally great pressure was applied to the

    mesh molds in order to expel the water and cohere the fiber [6]. Years

    ago this by-product, coined watermark, was use to establish the

    authenticity of a product or certify something about the product. In

    present days this same principle is applied using digital watermarks. And as

    the authors in [6] state, whether the product of paper press or discrete

    cosine transformations, watermarks of varying degrees of visibility are

    added to presentation media as a guarantee of authenticity, quality

    ownership and source.

    The watermarking technique has evolved from steganography, but

    steganography and watermarking have their differences. In watermarking,

    protecting the content that carries the watermark is essential, whereas in

    steganography the content is of no value and the message that is

    covered in the content is the significant one. So the applications of both

    concepts are very different, but the uses sometimes overlap.

    Typical application for watermarking include digital archives, copyright

    protection, legal delivery of content, anti-piracy, and automatic broadcast

    monitoring. One example of a practical use of watermarking comes from

    the Academy Awards. When the Academy sends screeners to its voters,

    the movies include a watermark in each of its frames. A distinct watermark

    is used for each recipient. If the movie gets illegally distributed, the

    watermark then allows the Academy to know which voter was the source

    for the pirated version.

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    Applications of Watermarking:

    This section describes seven applications of watermark-ing: broadcast

    monitoring, owner identification, proof of ownership, authentication,

    transactional watermarks, copy control and covert communication.

    (i) Broadcast monitoring:

    This is one of the most exclusive applications of Watermarking. In 1997, a

    scandal broke out in Japan regarding television advertising. At least two

    stations had been routinely overbooking air time. Advertisers were paying

    for thousands of commercials that were never aired .The practice had

    remained largely undetected for over twenty years, in part because therewere no systems in place to monitor the actual broadcast of advertisements.

    There are several types of organizations and individuals interested in

    broadcast monitoring. Advertisers, of course, want to ensure that they

    receive the air time purchased from broadcasting firms. Musicians and actors

    want to ensure that they receive accurate royalty payments for broadcasts of

    their performances and copyright owners want to ensure that their property

    is not illegally rebroadcast by pirate stations. We can use watermarks for

    broadcast monitoring by putting a unique watermark in each video or sound

    clip prior to broadcast. Automated monitoring stations can then receive

    broadcasts and look for these watermarks, identifying when and where eachclip appears. Commercial systems have been deployed for a number of years

    and the basic concepts have a long history.

    (ii) Owner identification

    Although a copyright notice is no longer necessary to guarantee copy rights,

    it is still recommended. The form of the copyright notice is usually c_date,owner. On books and photographs, the copyright is placed in plane sight. In

    movies, it is appended to the end of the credits. And on prerecorded music, itis placed on the packaging. One disadvantage of such text copyright notices

    is that they can often be removed from the protected material. And images

    can be spatially cropped. A digital watermark can be used to provide

    complementary copyright marking functionality because it becomes an

    integral part of the content, i.e. the copyright information is embedded in the

    music to supplement the text notice printed on the packaging. The Digimarc

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    Corporation has marketed a watermarking system designed for this

    application. Their watermark embedder and detector are bundled with

    Adobes popular image processing program, Photoshop. When the detector

    finds a watermark, it contacts a central database to identify the watermarks

    owner (who must pay a fee to keep the information in the database).

    (iii) Proof of ownership

    Multimedia owners may want to use watermarks not just to identify

    copyright ownership, but to actually prove ownership. To illustrate the

    problem, lets quickly introduce some characters who are well known in the

    watermarking literature. Suppose Alice creates an image and puts it on her

    website, with a copyright notice c_Alice 2000. Bob then steals the image,

    uses an image processing program to replace the copyright notice with c

    _Bob 2000, and then claims to own the copyright himself. How can thedispute resolved?

    Traditionally, Alice could register the image with the Copyright Office by

    sending a copy to them. The Copyright Office archives the image, together

    with information about the rightful owner. When the dispute between Alice

    and Bob comes up, Alice contacts the Copyright Office to obtain proof that

    she is the rightful owner. If Alice did not register the image, then she should

    at least be able to show the film negative. However, with the rapid

    acceptance of digital photography, there might never have been a negative.

    In theory, it is possible for Alice to use a watermark embedded in the image

    to prove that she owns it. However, this is not a trivial problem.

    (IV) Authentication

    As both still and video cameras increasingly embrace digital technology, the

    ability for undetectable tampering also increases. The content of digital

    photographs can easily be altered in such a way that it is very difficult to

    detect what has been changed. In this case there is not even an original

    negative to examine. There are many applications where the veracity of an

    image is crucial, especially in legal cases and medical imaging.

    Authentication is a well studied problem in cryptography .Friedman first

    discussed its application to create a trustworthy camera by computing a

    cryptographic signature that is associated with an image. If even one bit of

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    one pixel of the image is modified, it will no longer match the signature, so

    any tampering can be detected. However, this signature is metadata that

    must be transmitted along with the photograph, perhaps in a header field of a

    particular image format. If the image is subsequently copied to another file

    format that does not contain this header field, the signature will be lost, and

    the image can no longer be authenticated.

    A preferable solution is to embed the signature directly into the image using

    watermarking. This eliminates the problem of ensuring that the signature

    stays with the image. It also opens up the possibility that we can learn more

    about what tampering has occurred, since any changes made to the image

    will also be made to the watermark. Thus, there are several systems that can

    indicate the rough location of changes that have been made to the image.

    There are also systems designed to allow certain changes, such as JPEG

    compression [18, 19], and only disallow more substantial changes, such asremoving an individual from a crime scene.

    (v)Transactional watermarks (Fingerprinting)

    Monitoring and owner identification applications place the same watermark

    in all copies of the same content. However, electronic distribution of content

    allows each copy distributed to be customized for each recipient. This

    capability allows a unique watermark to be embedded in each individualcopy. Transactional watermarks, also called fingerprints, allow a content

    owner or content distributor to identify the source of an illegal copy. This is

    potentially valuable both as a deterrent to illegal use and as a technological

    aid to investigation.

    One possible application of transactional watermarks is in the distribution of

    movie dailies. During the course of making a movie, the result of each days

    photography is often distributed to a number of people involved in its

    production. These dailies are highly confidential, yet occasionally, a daily is

    leaked to the press. When this happens, studios quickly try to identify the

    source of the leak. Clearly, if each copy of the daily contains a unique

    transactional watermark that identifies the recipient, then identification of

    the source of the leak is much easier.

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    Another application of transactional watermarks was deployed by the DiVX

    Corporation. DiVX marketed a modified version of DVD. One of the

    security measures implemented in DiVX hardware was a transactional

    watermark that could be used to identify a player used for piracy. If illegal

    copies of a DiVX movie turned up on the black market, DiVX could use the

    watermark to track them to the source.

    (VI) Copy Control

    Transactional watermarks as well as watermarks for monitoring,

    identification, and proof of ownership do notpreventillegal copying. Rather,

    they serve as powerful deterrents and investigative tools. However, it is also

    possible for recording and playback devices to react to embedded signals. In

    this way, a recording device might inhibit recording of a signal if it detects a

    watermark that indicates recording is prohibited. Of course, for such asystem to work, all manufactured recorders must include watermark

    detection circuitry. Such systems are currently being developed for DVD

    video and for digital music distribution. Interestingly, the use of watermarks

    in video to control equipment dates back to at least 1989 and in audio to

    perhaps 1953.

    (vii) Covert communication

    One of the earliest applications of watermarking, or more precisely, data

    hiding, is as a method of sending secret messages. The application has beenformulated by Simmons as the prisoners problem, in which we imagine

    two prisoners in separate cells trying to pass messages back and forth. Their

    problem is that they cannot pass these messages directly, but rather, must

    rely on the prison warden to act as a messenger. The warden is willing to

    carry innocuous messages between them, but will punish them if he finds

    that, for example, their messages relate to a plan for escape. The solution is

    to disguise the escape-plan messages by hiding them in innocuous messages.

    There are several commercially available programs designed for this

    application, including Stego Tools.

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    Properties:

    There are a number of properties that have discussed the characteristics of

    watermarks some of the properties discussed are robustness, tamper

    resistance, fidelity, computational cost, and false positive rate. In practice, it

    is probably impossible to design a watermarking system that excels at all of

    these. Thus, it is necessary to make tradeoffs between them, and those

    tradeoffs must be chosen with careful analysis of the application. In addition,

    the application can affect the very definition of a property. In the following

    subsections, we look at each of the five properties listed above, and discuss

    how its importance and definition varies with application.

    (i) Robustness

    A watermark is said to be robust if it survives common signal processing

    operations such as digital-to-analog-to conversions and lossy compression.

    More recently, there has been an increased concern that video and still image

    watermarks also be robust to geometric transformations.

    Robustness is often thought of as a single-dimensional value, but this is

    incorrect. A watermark that is robust against one process may be very fragile

    against another. In many applications, robustness to all possible processing

    is excessive and unnecessary.

    Usually, a watermark must survive common signal processing only between

    the time of embedding and the time of detection. For example, in television

    and radio broadcast monitoring, the watermark need only survive the

    transmission process. For television, this means lossy compression, analog

    transmission, and some small amount of horizontal and vertical translation.

    It need not survive rotation, scaling, high-pass filtering, or any of a wide

    variety of distortions that do not occur during broadcast.

    In some cases, robustness may be completely irrelevant, or even undesirable.Watermarks used for covert communication need not be robust at all, if the

    cover media will be transmitted digitally without compression. A watermark

    For simple authentication, which just indicates whether the media has been

    altered, should be fragile.

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    On the other hand, when the signal processing between embedding and

    detection is unpredictable, the watermark may need to be robust to every

    conceivable distortion. This is the case for owner identification, proof of

    ownership, fingerprinting, and copy control. It is also true for any

    application in which hackers might want to remove the watermark.

    (ii)Tamper resistance

    Tamper resistance refers to a watermarking systems resistance to hostile

    attacks. There are several types of tamper resistance. Depending on the

    application, certain types of attacks are more important than others. In fact,

    there are several applications in which the watermark has no hostile

    enemies, and tamper resistance is irrelevant. Some basic types of attack are

    Activeattacks. Here the hacker tries to remove the watermark or make itundetectable. This type of attack is critical for many applications, including

    owner identification, proof of ownership, fingerprinting, and copy control, in

    which the purpose of the mark is defeated when it cannot be detected

    .However; it is not a serious problem for authentication or covert

    communication.

    Passive attacks. In this case, the hacker is not trying to remove the

    watermark, but is simply trying to determine whether a mark is present, i.e.

    is trying to identify a covert communication. Most of the scenarios above are

    not concerned with this type of attack. In fact, we might even advertise thepresence of the mark so that it can serve as a deterrent. But for covert

    communication, our primary interest is to prevent the watermark from being

    observed.

    Collusionattacks. These are a special case of active attacks, in which the

    hacker uses several copies of one piece of media, each with a different

    watermark, to construct a copy with no watermark .Resistance to collusion

    attacks can be critical in a fingerprinting application, which entails putting a

    different mark in each copy of a piece of media. However, the number of

    copies that we can expect the hacker to obtain varies greatly from

    application to application. For example, in the DiVX application, a hacker

    can buy any number of DiVX players, and play one movie on all of them to

    obtain any number of differently-watermarked copies. On the other hand, in

    the film-studio dailies application, each employee can only obtain one copy

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    of the watermarked material. A collusion attack would require that several

    employees conspire to steal the material, which is an unlikely prospect.

    Forgery attacks. Here, the hacker tries to embed a valid watermark,

    rather than remove one. These are our main security concern in

    authentication applications, since, if hackers can embed valid authentication

    marks, they can cause the watermark detector to accept bogus or modified

    media this type of attack is a serious concern in proof of ownership.

    (iii) Fidelity

    A watermark is said to have high fidelity if the degradation it causes is very

    difficult for a viewer to perceive. However, it only needs to be imperceptible

    at the time that the media is viewed. If we can be certain that the media will

    be seriously degraded before it is viewed, we can rely on that degradation tohelp mask the watermark. Such a case occurs when we watermark video that

    will be transmitted over NTSC, or audio that will be transmitted over AM

    radio. The quality of these broadcast technologies is so low that our initial

    fidelity need not be very good. Conversely, in HDTV and DVD video and

    audio, the signals are very high quality, and require much higher fidelity

    watermarks (though, of course, the quality of the content remains the same -

    a bad movie is a bad movie whether on VHS or DVD).

    In some applications, we can accept mildly perceptible watermarks in

    exchange for higher robustness or lower cost. For example, Hollywooddailies are not finished products. They are usually the results of poor

    transfers from film to video. Their only purpose is to show those involved in

    a film production the raw material that has been shot so far. A small visible

    distortion caused by a watermark will not diminish their value.

    (iv) Computational cost

    Different applications require the embedders and detectors to work atdifferent speeds. In broadcast monitoring, both embedders and detectors

    must work in (at least) real time. The embedders must not slow down the

    media production schedule, and the detectors must keep up with real-time

    broadcasts. On the other hand, a detector for proof of ownership will be

    valuable even if it takes days to find a watermark. Such a detector will only

    be used during ownership disputes, which are rare, and its conclusion about

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    whether the watermark is present is important enough that the user will be

    willing to wait.

    Furthermore, different applications require different numbers of embedders

    and detectors. Broadcast monitoring typically requires a few embedders and

    perhaps several hundred detectors at different geographic locations. Copy

    control applications may need only a handful of embedders but millions of

    detectors. Conversely, in the fingerprinting application implemented by

    DiVX, in which each player embeds a distinct watermark, there would be

    millions of embedders and only a handful of detectors. In general, the more

    numerous a device needs to be for a given application, the less it must cost.

    The wide variation in dollar cost and in speed requirements means that there

    is a wide variation in the required computational efficiency of watermark

    embedders and detectors.

    (v) False positive rate

    A false positive is a detection of a watermark in a piece of media that does

    not actually contain that watermark. When we talk of the false positive rate,

    we refer to the number of false positives we expect to occur in a given

    number of runs of the detector. Equivalently, we can discuss the probability

    that a false positive will occur in any given detector run. There are two

    subtly different ways to define this probability that are often confused in the

    literature. They differ in whether the watermark or the media is consideredto be the random variable.

    In the first definition, the probability of a false positive is the probability

    that, given a fixed piece of media and a randomly-selected watermark, the

    detector will report that the watermark is in the media. The watermarks are

    drawn from a distribution that is defined by the design of a watermark

    generation system. Typically, watermarks are generated by either a bit-

    encoding algorithm or by a Gaussian, independent random number

    generator. In many cases, probability of false positives, according to this

    first definition, is actually independent of the piece of media, and depends

    only on the method of watermark generation.

    In the second definition, the probability of a false positive is the probability

    that, given a fixed watermarkand a randomly-selected piece of media, the

    detector will detect the watermark in the media. The media is chosen from

    the distribution of natural media, which is defined by either nature or

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    Hollywood, depending on the application. This distribution is very different

    from that defined by the watermark generation system, and thus probabilities

    based on this definition can be quite different from those based on the first

    definition.

    In most applications, we are more interested in the second definition of false

    positive probability than in the first. However, in a few cases, the first

    definition is also important, such as in the case of fingerprinting, where the

    detection of a random watermark in a given image might lead to a false

    accusation of theft.

    The probability of false positives that is required depends on the application.

    In the case of proof of ownership, the detector is used so rarely that a

    probability should suffice to make false positives unheard of. On the other

    hand, in the copy control application, millions of watermark detectors areconstantly being run on millions of pieces of media all over the world. If one

    piece of unwatermarked media consistently generates false positives, it

    could cause serious trouble. For this reason, the false positive rate should be

    in-finitesimal. For example, the general consensus is that watermark

    detectors for DVD video should have a false positive rate of 1 in 1012frames.

    Types of Watermark:

    In we have a good decomposition of the variety of watermarks

    currently available, their definitions, their features and possible

    applications, advantages and disadvantages . One thing to point out of

    this classification is that video watermarking is an extension of image

    watermarking, which utilizes characteristics of the Human Visual

    System (HVS) to embed the watermark. HVS methods take advantage of

    the way the human eye processes images in order to add watermarks to the

    images. The video method requires that the watermarking encoding or

    decoding process be done in real-time and that the watermark is robustfor compression, that is, the watermark should be present in the signal

    after compressing the video. According to the survey done in

    Podilchuk et al. were the first to state that for the watermark to be robust

    it had to be embedded into the perceptually significant portions of the

    data, although Cox et al. were also pioneers in watermarking perceptually

    significant areas.

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    Watermark processing methods fall into two categories: spatial domain and

    frequency domain. Spatial domain usually changes the value of the

    pixels in a minor way so it is not perceived by the human eye and the

    watermark is scattered through the entire object. Frequency domain

    watermarking transforms the object into its frequency counterpart and

    then embeds the watermark in the transform coefficients, distributing the

    watermark over the entire frequency distribution of the object. The

    frequency domain watermarking methods are relatively robust to noise,

    image processing and compression compared with the spatial domain

    methods [4, 6]. Extensive work has been done in both processing areas,

    but watermarking techniques based on the transfer domain are more

    popular than those of the spatial domain.

    Types of Digital Watermarking

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    Watermarking Hardware Implementations:

    Over the past decade, numerous watermarking algorithms have been

    invented and their software is available, however recently, hardware

    implementations are being presented in literature . Only a few hardware

    schemes have been proposed. As proof of that, the following table of most of

    the watermarking hardware implementations available in current literature.

    Watermarking Hardware Implementations

    Hardware implementations of watermarking can be implemented in

    Application Specific Integrated Circuits (ASICs) or in FieldProgrammable Gate Arrays (FPGAs). As can be seen from the table

    above, most of the current hardware implementations have been done

    for ASIC designs. Recent advances in FPGA technology, such as

    90nm process devices, higher gate densities, better interconnect

    architectures, reduction in power consumption, multiple I/O formats

    and embedded optimized logic, have allowed for applications that were

    previously intended for ASICs to be implemented in FPGA devices,

    with the added value of a lower FPGA cost when compared to an

    ASIC. But for some reason that field has been understudied.

    Watermarking implementation in hardware is a recent interest in the area. In

    1999 there were still no works of video watermarking implementation in

    hardware. Therefore, all of the works in this area are from the past 5

    years, and nevertheless there are still very few works published.

    Although the small amount of available works is a fact, the that there is a

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    strong motivation for hardware implementations because real-time

    watermarking of video streams is too expensive for software. Audio and

    Image watermarking are typically done in software because their low data

    rates allow them to be processed in software.

    As can be seen, watermarking implementations can be done in

    software or in hardware. Although it might be faster to implement an

    algorithm in software, there are a few compelling reasons for a move toward

    hardware implementation. They add that in consumer electronic devices,

    a hardware watermarking solution is often more economical because

    adding the watermarking component takes up a small dedicated area of

    silicon. In software, implementation requires the addition of a dedicated

    processor such as a DSP core that occupies considerably more area,

    consumes significantly more power, and may still not perform adequately

    fast .

    The Scientists presented a 0.18m CMOS technology implementation

    of the Just Another Watermarking System (JAWS) embedder and

    detector. The scientist selected this watermarking algorithm because it

    is a well-known algorithm, because it works on raw video data

    allowing the author to concentrate on the watermark process and not on the

    compression issues, and because there was a previous implementation on

    a Trimedia TM-1000 VLIW DSP done before, useful work to compare

    their design . The JAWS processes uncompressed real-time video. The

    authors claim that their work is the first step toward analyzing the

    relationship between watermarking algorithmic features and

    implementation cost for practical systems, and the first 0.18 micron

    implementation published at that time. The implementation features a

    pipelined architecture, and FFT and IFFT processing cores. The results show

    watermarking of video streams at a rate of 30 frames/sec and 320 x 320

    pixels/frame. The chip is capable of operating at 75 MHz and process a peak

    pixel rate of over 3 MegaPixels/sec. The watermark is 4 bits/frame. The

    power consumption for the embedder is 60 mW and for the detector is 100

    mW.

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    Hardware implementation:

    For the hardware implementation several design practices were taken into

    account:

    Word length: The word size used has an impact on the power

    consumption of the hardware. Therefore, with a smaller word size,

    less power dissipation we will have. The word size should be

    limited to the smallest possible size in order to minimize power

    consumption.

    Frequency: CMOS-based circuits dissipate power only when a

    transition from one logic state to another logic state occurs (although

    recently this is not completely true due to higher sub-threshold

    leakage currents).

    Total power is determined by the sum of static power

    dissipation and dynamic power dissipation. Static power is almost

    zero (for this analysis) and dynamic power is , where is the

    switching activity, or the percentage of time the circuit is switching,

    C is the total load capacitance, V2 is the supply voltage squared,

    and f is the operational frequency. In sequential circuits f is

    regulated by the clock of the system, and the power consumption

    of the system can be partially controlled by controlling f. A fastcircuit dissipates more power than a slow circuit [49]. In FPGA-

    based implementations this is especially true due to the ability of

    the device to allow the designer to determine the clock

    frequency, and to design clock networks with various frequencies.

    For low-power design a lower f is better. In areas of the system

    where operating with a lower clock frequency is viable, the

    option should be considered.

    Switching: From the previous discussion about clock frequencyit can be inferred that if no switching occurs in the circuit, no

    power is dissipated. Therefore switching should not be allowed

    in a section of the system when that section is not in use. This

    basically resumes to preventing the outputs of the circuits from

    changing, by using chip enable controls.

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    Clock Gating: clock gating is a very popular low-power design

    technique that is based on the previous discussion of the switching

    principle. You can prevent circuit outputs from changing, but still

    the clock network will be switching and dissipating power

    although the circuits are not in use. Disconnecting the clockaltogether will prevent not only the circuits from switching and

    dissipating power, but also clock network from dissipating power.

    This is usually applied to whole sections of the system that are turned

    off when not in use.

    Area: Usually less area means less power, because fewer circuits

    are needed to perform the work. More circuits mean more

    switching, and therefore more power dissipation. Lowering area

    typically means lowering performance in digital circuit design,

    since fast-performing circuits generally require more logic.Arithmetic functions that utilize less logic are preferred in this

    case. Area optimization techniques in the algorithmic description

    should also be explored.

    Fixed-point representation: Floating-point number representations

    allow a larger dynamic range and precision, but fixed-point

    representation is easier to implement, require less area, increases

    speed, and decreases power consumption. Therefore a fixed-point

    number representation should be used for a low-powerimplementation.

    Arithmetic circuits: Arithmetic circuits should be employed that

    reduce the number of operations performed in order to generate

    a result, and that their switching activity is lower

    Field programmable Gate Array (FPGA):

    Field Programmable Gate Arrays, or FPGAs, are electronic devices that

    contain a number of programmable logic, programmable interconnects,

    and programmable I/O. This programmable logic can be used to

    implement any logic based on logic gates such as ANDs, ORs, and

    NOTs. Simple functions and complex functions, such as arithmetic

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    elements can be performed in an FPGA. They also provide memory

    elements in the form of flip flops, or dedicated memory units. The high

    density of programmable logic blocks found in FPGA and their relative

    fast speeds have made them serious alternatives to Application Specific

    Integrated Circuits (ASICs), microprocessors, and Digital Signal

    Processors (DSPs). Also, their ability to perform any digital circuit,

    their low time-to-market times, lower development costs, faster

    debugging, and the re-programmability are additional benefits over

    ASICs. An example of a simplified programmable logic block found in an

    FPGA can be seen below.

    FPGA programmable logic block

    As can be seen from the picture above, the basic building block for

    performing logic functions in FPGA are SRAMs, which are programmedas an n-input Look-Up Table (LUT).

    The FPGA device used for this work is the Xilinx Spartan-3 X

    C3S200ft256-4. It has 200,000 logic gates which translate to 4,320

    programmable logic blocks, or cells. Also has 216k bits of dedicated

    RAM, 12 18-bit-input dedicated multipliers, 4 Digital Clock Managers

    with clock skew control, and frequency synthesis and shifting and 173

    I/O pins with 18 single-ended programmable standards, and 8

    differential-pair programmable standards. Xilinx products allow the LUTSRAMs to be also used as distributed RAM, or shift-registers. The device is

    powered by a 1.32V internal voltage, a 3.00V auxiliary voltage and a

    3.75V output driver supply voltage. The Xilinx Spartan-3 is marketed as

    being the lowest-cost device per logic and I/O, and as a device that

    can be used to develop high volume applications for a variety of

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    markets including broadband access, home networking,

    display/projection and digital television equipment

    Pseudo-Random Generator

    The pseudo-random generator is implemented by using a Linear

    Feedback Shift Register (LFSR). The LFSR provides the random

    characteristics needed for the application [5, 12, 50]. The LFSR is 13-

    bit wide register, thus producing a 2^13-1 or 8,191-bit long sequence (see

    Figure 21). This modulates a total of ((2^13-1)/64), or 128, 8x8 blocks (one

    block not completely watermarked). If we are using a 480x640 pixel

    video frame, the available watermark bits are ((640x480)/64)/ 128, or 36,

    bits. Therefore, according to these specifications, a 36 bit watermark word is

    available for every frame.

    These specifications can be varied easily making the watermark wordsmaller for increased watermark robustness. The LFSR used was a

    Fibonacci LFSR with parallel load and chip enable generated using the

    Xilinx Core Generator. The modulation of blocks is controlled by counters.

    Eight binary values are generated consecutively, and these 8 values are

    then used to select the 8-bit amplified value from a multiplexer. Since

    the pseudo-random only generates 1s and 0s, we can think of the 0s as

    being -1s. The amplification factor multiplied by 1 or -1 will result in the

    amplification factor, or the negative of the amplification factor; therefore

    we can take advantage of that and avoid a multiplication step. The

    amplification factor, and its negative, is stored in a register and the

    proper value is selected by the output of the pseudo-random generator.

    These eight 8-bit amplified pseudo-random numbers are then passed on to

    the DCT stage, to compute their Discrete Cosine Transform. This process

    is repeated 8 times in order to generate a 8x8 block. The 13-bit

    initialization value of the LFSR represents the key that only the watermark

    decoder unit knows in order to retrieve the watermark from the video. If

    each video camera in the surveillance system contains a different key then

    we can identify the video stream from each camera when detecting the

    watermark. The Pseudo-Random Generator outputs one number everyclock cycle. The 8 numbers are generated in 8 clock cycles; the 64 numbers

    of the 8x8 block are generated in 64 clock cycles, but take 64 + 16

    cycles to be read by the DCT core due to its timing limitations.

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    Watermarking Algorithm:

    Our algorithm is invisible-robust algorithm which is implemented in

    VLSI.In algorithm there are following notation :

    : I original gray scale image, W binary or ternary watermark image,

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    I * watermarked image, (i, j) pixel location, E1 ,E2 watermark

    embedding

    functions, D watermark detection function, r neighborhood radius, IN

    neighborhood image, K - digital watermark key, and a1 ,a2 scaling

    constants.

    The watermark insertion process consists of the following: First, the

    watermark W

    which is a ternary image having pixel values {0,1 or 2} is generated using

    the digital key K. Then, watermark insertion is performed by altering the

    pixels of original image using watermark embedding functions.

    I*(i,j) = I(i,j) if W(i, j) = 0

    I*(i,j) = E1 (I(i, j)), IN (i, j) ) if W(i, j) = 1

    I*(i,j) = E1 ( I(i, j)), IN(i, j) ) if W(i, j) = 2

    Where E1 and E2 are encoding function and these are defined as follows:

    E1(I, IN ) = (1- a1)IN(i, j) + a1I(i, j)

    E 2(I, IN ) = (1- a1) IN (i, j) + a2 I(i, j) The signs of

    a1 and a2 are used for the detection function and their actual values

    determine the watermark strength. The neighborhood image pixel gray value

    IN is calculated as the average gray value of the neighboring pixels of the

    original image for a neighborhood radius r. For example, for neighborhood

    radius r =1.

    IN(i, j) = [ {I(i+1,j)+I(i+1,j+1)}/2+ I(i, j + 1)]/2

    The scaling (1 - a1 ) is used to scale IN to ensure that watermarked imagegray value I* never exceeds the maximum gray value for 8-bit image

    representation correspond-ing to pure white pixel. The neighborhood radius

    determines the upper bound of the watermarked pixels in an image.The first

    step of detection process is the generation of watermark W using the wa-

    termark key K. Next, the watermark is extracted from the test

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    (watermarked) image using the detection function given below, for a1 > 0

    and a2 < 0.

    W(i, j) = 1 ifI*(i, j) - IN(i, j) > 0

    2 ifI*(i, j) - IN(i, j) < 0 ]

    By comparing the original ternary watermark image W and the extracted

    binary wa-termark image W* , the ownership can be established when the

    detection ratio is largerthan a predefined threshold. The value of the

    threshold determines the minimum ac-ceptable level of watermark

    detection.

    Architectural Design :

    In this section, the architecture of the invisible-robust watermarking encoder

    algorithm described in the previous section, is elaborated. We first provide

    high level description of the enco der, followed by their architectural details.

    Description of various terms:

    1. Datapath and Controller:

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    The high-level view of the proposed chip is shown in Fig. 1. The encoder

    includes the units, such as watermark generation, watermark insertion,

    control, row and column address decoder, and registers. The generation unit

    is used to produce the watermark, andinsertion unit is used to insert the

    watermark into the host image as per the described algorithm. The control

    unit controls the operationof the above two modules and the data .ow in

    encoder. The address decoders are used to decode the memory address

    where the image and watermark are stored. The registers are used for

    buffering purpose. We assume that there are two external RAMs, one to

    store the original image and other to serve as a storage space for watermark

    data available. The watermarked image is written back to the RAM storing

    the original image.

    2 Watermark Generation Unit

    The ternary watermark is generated by pseudorandom sequence generator.

    The water-mark generation unit consists of linear feedback shift register

    (LFSR). LFSR has a mul-titude of uses in digital system design and is a

    very crucial unit in watermark security and detection. It is a sequential shift

    register with combinational feedback logic around it that causes it to cycle

    pseudo randomly through a sequence of binary values. Therefore, we have

    studied the difficulties of a LFSR and have taken ap propriate measures to

    ensure quality design [2123]. The LFSR consists of ip-ops (FFs) as

    sequential elements with feedback loops. The feedback around a LFSR

    comes from a selected set of points called taps in the FF chain and these

    taps are fed back to FFs after either XORing or XNORing

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    Watermark Generation Unit: Linear Feedback Shift Register (LFSR).

    The design aspects considered when modeling LFSRs are as follows [21

    23]. XOR or XNOR Feed Back Gates: The feedback path may consistof

    either all XORgates or all XNOR gates; LFSR will produce same number of

    values with different sequence for a particular tap setting. One-to-Many or

    Many-to-One Feedback Structure: Both one-to-many or many-to-one feed

    back structures can be implemented using same number of gates. However, a

    one-to-many feedback structure will have a shorter worst case delay. Pro

    hibited or Lockup State: Special care should be placed on the design aspect

    such that LFSR avoids the prohibited or lockup state. In the case of XORgates, the LFSR will not sequence through the binary value when all bits are

    at logic zero. Similarly, for XNOR gates the LFSR will not sequence

    through the binary values if all bits are at logic one. Thus, the LFSR should

    bypass these initializations during power up.

    Ensuring a Sequence of All 2n Values : If taps provided for a maximal

    length se-quence are used, the LFSR configurations described so far will

    sequence through (2n - 1) binary values. The feedback path can be modified

    with extra circuitry to ensure that all 2n binary values are included in the

    sequence. Fig. 2 shows the LFSR we designed adopting the abovediscussed facts. The 8-bit LFSR is modeled so as to use one-to-many

    feedback structure and has been modified for a 2n looping sequence. It

    calculates and holds the next value of the LFSR which is then assigned to

    the output signal WM DATA after each clock edge. The NOR of all LFSR

    bits minus the most significant bit that is LFSR REG (6:0) generates the

    extra circuitry needed for all 2n sequence values.

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    3.3 Watermarking Insertion Unit

    Fig. shows the architecture of the watermark insertion unit designed to

    perform the watermarking insertion. The invisible-robust watermarking

    involves adding or sub- tracting a constant times the pixel value to be

    watermarked to or from a constant times the neighborhood function as

    described in the watermark encoder function in the previous section. The

    four data lines provide the pixels I(i, j), I(i +1,j), I (i, j +1),

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