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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

454

Digital Watermarking Technique for Authentication of

Color Image

1 Prof.P.B.Khatkale, Lect in K.B.P.Polytechnic,Kopargaon,

2.Prof. K.P.Jadhav, Lect in K.B.P.Polytechnic,Kopargaon,

3. Prof. M.V.Khasne,Lect in K.B.P.Polytechnic,Kopargaon

1praveenkhatkale@gmail.com

2

kishor268@gmail.com

Abstract: Digital watermarking methods describe the technologies that allow hiding of information in digital media, such as images, video and audio. Watermarking techniques embed information in images by introducing changes that are imperceptible to the human eye but recoverable by a computer program. Generally, the watermark is a code to identify the owner of the image. The locations in which the watermark is embedded are determined by a secret key. Doing so prevents possible pirates from easily removing the watermark. Furthermore it should be possible to recover the watermark from an altered image. Possible alterations of watermarked images include compression, filtering and cropping. These alterations are referred to as attacks. The first watermarking application that might come to mind is related to copyright protection of digital media Watermarking algorithms have been proposed to protect varieties of content, such as official documents.

Keywords: Cropping, Digital Watermark, Embedding, Extraction, Secret key.

I. INTRODUCTION

A watermarking system must allow for a useful amount of information to be embedded into the image. Digital watermarking is the process of embedding information into digital multimedia content such that the information (which we call the watermark) can later be extracted or detected for a variety of purposes including copy prevention and control. Digital watermarking has become an active and important area of research, and development and commercialization of watermarking techniques is being deemed essential to help address some of the challenges faced by the rapid proliferation of digital content.

The process of digital watermarking involves the modification of the original multimedia data to embed a watermark containing key information such as authentication or copyright codes. The embedding method must leave the

original data perceptually unchanged. The major technical challenge is to design a highly robust digital watermarking technique, which discourages copyright infringement by making the process of watermarking removal tedious and costly. A watermarking algorithm consists of the watermark structure, an embedding algorithm, and an extraction, or a detection algorithm. In multimedia applications, embedded watermarks should be invisible, robust, and have a high capacity. Invisibility refers to the degree of distortion introduced by the watermark. The literature survey explain robustness is the resistance of an embedded watermark against intentional attacks such as noise. Capacity is the amount of data that can be represented by an embedded 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 digital content. The digital content could be a still image, an audio clip, a video clip, a text document, 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, but it can also identify the intended recipient.

[image:1.612.316.569.583.697.2]

II. BLOCK DIAGRAM (DWM)

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

455

Digital watermarking is one of the proposed solutions for copyright protection of multimedia data. This technique is better than Digital Signatures and other methods because it does not increase overhead. In this paper plan to present a new image watermarking technique that can embed more number of watermark bits in the cover image without affecting the imperceptibility and increase the security of watermarks .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. In this paper image is the host signal and embedding the secret data and the extract the same. In this process enhancing the network security.

2.1Embedding stage:-

[image:2.612.393.522.131.258.2]

One of the most important features that make the recognition of images possible by humans is color. Color is a property that depends on the reflection of light to the eye and the processing of that information in the brain. The color is used every day to tell the difference between objects, places, and the time of day. Usually colors are defined in three dimensional color spaces usually colors are defined in three dimensional color spaces. These could be RGB (Red, Green, and Blue), HSV (Hue, Saturation, and Value) or HSB (Hue, Saturation, and Brightness). The last two are dependent on the human perception of hue, saturation, and brightness [6]. Color represents the distribution of colors within the entire image. This distribution includes the amounts of each color, but not the locations of colors.

Fig 2. Embedding stage

2.2 Extracting stage:-

[image:2.612.52.291.460.583.2]

In a digital watermarking scheme, it is not convenient to carry the original image all the time in order to detect the owner's signature from the watermarked image. Moreover, for those applications that require different watermarks for different copies, it is preferred to utilize some kind of watermark-independent algorithm for extraction process i.e. dewaters marking. Its robustness against many attacks including rotation, low pass filtering, salt n paper noise addition and compression.

Fig 3. Extracting Stage

III. PROPERTIES

For better activeness, watermark should be acœperceptually invisible within host media, statistically invisible to unauthorized removal, readily extracted by owner of image, robust to accidental and intended signal distortion like filtering, compression, re-sampling, retouching, crapping etc. For a digital watermark to be effective for ownership, it must be robust, recoverable from a document, should provide the original information embedded reliably and also removed by authorized users

3.1.1Robustness:

The watermark should be robust such that it must be difficult to remove. The watermark should be robust to different attacks. The robustness describes whether watermark can be reliably detected after performing some media operations.

3.1.2 Perceptual transparency:

This property describes that whether watermark is visible or invisible to human sensor organ. Perceptible watermarks are visible to human while imperceptible are not. Imperceptible watermarks are such that content remains same after applying digital watermarking technique.

3.1.3 Security:

Security property describes that how easy to remove a watermark. This is generally referred to as attack on watermarking. Attack refers to detection or modification of watermark.

3.1.4 Complexity:

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

456

3.1.5 Capacity:

Capacity property of digital watermarks refers to amount of information that can be embedded within the content. The important point is that more data is used in watermark, watermark will become less robust. In addition to these properties, watermarks are having some extra properties as unambiguity, tamper resistance, inseparable from the works and able to undergo some transformation as works.

IV.CLASSIFICATION

Digital watermarks are classified according to their applications. The watermarks are classified as perceptible watermarks and imperceptible watermarks, robust and fragile, public and private. This classification of watermarks is broadly described in following sections.

4.1 Perceptible watermarks and imperceptible watermarks:

Perceptible watermarks are visible to human eye while imperceptible watermarks are invisible. The perceptible watermarks are useful for primary application i.e. for statement ownership or authorship. So for this reason it should be visible. .On the other hand imperceptible watermarks are useful for complex applications such as document identification in which content being watermarked must appear in unchanged form Examples of visible (perceptible) watermarks are logos on TV, IBM watermark and that of invisible (imperceptible) watermarks are ATT, NEC/MIT, UU etc. Perceptible watermarks i.e. visible one are extension of the concept of logos. They are applicable to images only. These watermarks are embedded into image. They are applicable in maps, graphics and software user interface. Imperceptible watermarks i.e. invisible one remains hidden in the content. They can be detected only by authorized agency. These watermarks are useful for content or author authentication and for detecting unauthorized copier.

4.2 Robust watermarks and fragile watermarks:

Robust or fragile is nothing but degree to which watermarks can withstand any modifications of any types caused due to the transmission or loss compression. Perceptible watermarks are more robust in nature than imperceptible one. But meaning of this is not that imperceptible watermarks are fragile one. Robust watermarks are those watermarks which are difficult to remove from the object in which they are embedded. Fragile watermarks are those watermarks which can be easily destroyed by any attempt to tamper with them. Fragile watermarks are destroyed by data manipulation.

4.3 Private watermarks and public watermarks:

Private watermarks requires at least original data to recover watermark information Public watermarks requires neither original data nor embedded watermarks to recover watermark information. Private watermarks are also known as secure watermarks. To read or retrieve private watermark, it is necessary to have secret key. Public watermark can be read or retrieve by anyone using specialized algorithm. In this sense public watermarks are not secure. Public watermarks are useful for carrying IPR information. They are good alternatives to labels.

V. HIGH CAPACITY WATERMARKING ALGORITHM

In this approach, a block DCT-based algorithm is developed to embed the binary watermark into the colour host image. Since small high frequency components may be discarded in some image processing operation such as JPEG compression, the very low frequency components of the colour host image will be utilized for the watermark embedding.

5.1 The Embedding Algorithm:

In the technique presented here, the colour image is decomposed into three components R, G and B. Watermark information will be embedded in the G plane using equation 1 to produce G'. Assume that f (i, j) represents the pixel of the component of the RGB representation of the colour host image, w (i, j) represents the binary pixel of the watermark

(1) Where Qe is the quantization to the nearest even number and

Qo is the quantization to the nearest odd number ∆ is a scaling quantity and it is also the quantization step used to quantize either to the even or odd number. The predefined coefficients in each 8x8 sub block are represented by NHB.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

457

Different shuffle schemes could be applied. Simple shuffle technique is to reshape the watermark copy as vector and shift the vector by different shifts before the binary watermark digits are randomly scrambled using a secret key; this scrambling process is essential to reduce the spatial correlation between the host image and the embedded watermark. After the scrambling process, a shuffle scheme is applied for each binary watermark copy before embedding. Different shuffle schemes could be applied. Simple shuffle technique is to reshape the watermark copy as vector and shift the vector by different shifts before the .Where WSB is the number of watermark shifted bits, This shift is necessary to reduce the spatial relation and to increase the robustness against vertical cropping attacks.

5.2 The Extraction Algorithm:

The embedded information w (i,j) can be extracted by performing 8x8 DCT transform for the watermarked host image and indicate the same coefficients of the host image that carries the 16 bits of the embedded watermarks using the same secret key in the initial scrambling operation. The scrambled watermarks are descrambled to get the original watermarks. The watermark information can be retrieved by using a reverse process to the shift scheme which has been applied intheembedding process. This will yield the original bits order. It is worth to mention that although the proposed scheme is blind since it does not require the original host image for reconstruction, but it requires information such as the sizes of both host image and watermark image. Finally, discard the totally degraded copy of the extracted watermarks and then calculate the average by summing the resultant watermark copies divided by their number, select the resultant average watermarks as the final reconstructed watermark or choose one copy of the extracted watermarks as the final watermark if it provides better result than the resultant average watermark. The bit extraction formula is shown in equation 2

(2) Where Q is rounded to the nearest integer, the scaling quantity is the same as the one used in the embedding process.

VI. ATTACKS

Due to some reasons, there is need of adding, altering or removing false watermarks. Attacks on watermarks may be accidental or intentional. Accidental

attacks may cause due to the standard image processing or due to the compression procedures. An intentional attack includes cryptanalysis, steganalysis, and image processing techniques or other attempts to overwrite or remove existing watermarks. Following are the methods of attacks vary according to robustness, Perceptibility.

6.1 Mosaic attack:

Mosaic attack is the method in which pictures are displayed so as to confuse watermark-searching program, known as Web Crawler. Mosaic is created by subdividing the original image into randomly sized small images and displaying the resulting image on webpage. Figure no.1 shows the example of mosaic schemes. The aim is to confuse the web crawler into thinking that there is no watermark within the picture because it has been sub divided into smaller separate pictures. This form of attack becomes to a large degree obsolete due to new improved methods of watermarking and more intelligent web crawlers.

6.2 Geometric attack:

Geometric attack is related to geometric properties of data. It is concerned with images, documents and audio files. This attack is further classified as-

Subtractive attack:

It involves the attacker in the area of located watermark if imperceptible and then Removing the mark by cropping or digital editing.

Distortive attack:

In this attack, attacker attempts to make some uniform distortive changes in the images such that mark becomes unrecognizable. These two watermark attacks are usually performed on robust watermark.

6.3 Stirmark attack:

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

458

6.4 Forgery attack:

Forgery attack is also known as Additive attacks in some cases. Forgery attack include the attacker who can add his or her own watermark overlaying the original image and marking the content as their own.

6.5 Inversion attack:

Inversion watermark render the watermark information ambiguous. The idea behind the invasion attack that attacker who receives watermarked data can claim that data contains his watermark also by declaring part of data as his watermark. The attacker can easily generate the original data by subtracting the claimed watermark.

6.6 Cryptanalysis:

It is mostly associated with cryptography. It is a method in which attacker attempts to find the decryption key for an encrypted pieces of information so that it can be made useful again. Attacker can remove licensing watermark that decrypts that data, attacker would use cryptanalysis to find decryption key so that data can use in decrypted form free from its watermark.

VII.DIGITAL WATERMARKING TECHNIQUES

Digital watermarking techniques is nothing but what are the techniques to put digital watermarks onto the digital media. There are two techniques viz image domain and transform domain. Several different methods enable watermarking in the spatial domain. The simplest (too simple for many applications) is just to flip the lowest-order bit of chosen pixels. This works well only if the image is not subject to any modification. A more robust watermark can be embedded by superimposing a symbol over an area of the picture. The resulting mark may be visible or not, depending upon the intensity value. Picture cropping, e.g., (a common operation of image editors), can be used to eliminate the watermark.

Spatial watermarking can also be applied using color separation. In this way, the watermark appears in only one of the color bands. This renders the watermark visibly subtle such that it is difficult to detect under regular viewing. However, the mark appears immediately when the colors are separated for printing. This renders the document useless for the printer unless the watermark can be removed from the color band. This approach is used commercially for journalists to inspect digital pictures from a photo-stock house before buying unmarked versions.

Watermarking can be applied in the frequency domain (and other transform domains) by first applying a transform like the Fast Fourier Transform (FFT). In a similar

manner to spatial domain watermarking, the values of chosen frequencies can be altered from the original. Since high frequencies will be lost by compression or scaling, the watermark signal is applied to lower frequencies, or better yet, applied adaptively to frequencies that contain important information of the original picture.

Since watermarks applied to the frequency domain will be dispersed over the entirety of the spatial image upon inverse transformation, this method is not as susceptible to defeat by cropping as the spatial technique. However, there is more a tradeoff here between invisibility and decodability, since the watermark is in effect applied indiscriminately across the spatial image. Table shows a small comparison between the two different techniques.

Currently there are various techniques for embedding digital watermarks. Basically, they all digitally write desired information directly onto images or audio data in such a manner that the images or audio data are not damaged. Embedding a watermark should not result in a significant increase or reduction in the original data.

Spatial

Frequency

Computation

Cost

Low

High

Robustness

Fragile

More Robust

Perceptual

Quality

High Control

Low Control

Capacity

High (depend on the

size of the image)

Low

Example of

Applications

Mainly

Authentication

[image:5.612.305.577.392.592.2]

Copy Rights

Table. Comparison between Spatial and Frequency

VII. EXAMPLE & APPLICATIONS OF DWM

7.1 Broadcast monitoring:

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

459

7.2 Encoding:

According to the thinking of major music companies and major video studios, encoding happens at mastering level of sound recording.

In such downstream, transactional watermarks are also considered. Each song is assigned with unique ID from the identifier database. After completion of all mastering processes, ID is encoded in sound recording. To enhance encoding of audio or video recordings requiring special processing, the human-assisted watermark key is available.

7.3 Copy and Play Back Control:

The data carried out by watermark may contain information about copy and display permissions. We can add a secure module into copy or playback equipment to automatically extract the permission information and block further processing if required. This approach is being taken in (DVD).

7.4 Content Authentication:

The content authentication is nothing but embedding the signal information in Content. This signature then can be checked to verify that it has not been alter. By watermarks, digital signatures can be embedded into the work and any modification to the work can be detected.

VIII. ADVANTAGES AND DISADVANTAGES OF DWM

8.1 Advantages:

 Uniquely identifies author of copyrighted works.

 Robust design of digital watermark withstand pirating attacks.

 Embedding watermark is easy.

 Implementation on PC platform is possible.

8.2 Disadvantages:

 The blind watermarking algorithm which is really robust is not in existence today. By knowing the exact content of watermark and algorithms to embed and retrieve it.

 Some watermarks vanish if someone manipulates the image in a program like Photoshop.

IX. FUTURESCOPE

The field of digital watermarking is still evolving and is attracting a lot of research interest. The watermarking problem is inherently more difficult that the problem of encryption, since it is easier to execute a successful attack on a watermark. In cryptography, a successful attack often requires deciphering an enciphered message. In the case of digital watermarking, merely destroying the watermark, usually by slightly distorting the medium containing it, is a successful attack, even if one cannot decipher or detect any hidden message contained in the medium.

X. CONCLUSION

In this paper a new high capacity frequency domain blind algorithm for colour digital image watermarking is presented, This algorithm uses the green channel for watermarking embedding. By comparing our algorithm to others, we canconclude that the maximum numbers of bits that can be hidden and recovered successfully from the watermarked images have been increased. Excellent performance for the embedding process is achieved for an embedding strength value of A=24. It has also been demonstrated that for this embedding strength thesignature is immune to a variety of attacks, including filtering, contrast balancing, compression, and geometrical transforms such as resizing. image Adaptive Self Embedding Watermarking proved robust against various attacksperformed. The use of semi-fragile property helps to detect thelocation of fraud in the image. This technique is having a great scope of opportunities; especially in the field of cyber frauds

,

court evidences

,

certificate or identity forgery and even in the preservation and transmission of cultural heritage images The large need of networked multimedia system has created the need of COPYRIGHT PROTECTION. It is very important to protect intellectual properties of digital media. Internet playing an important role of digital data transfer. Digital watermarking is the great solution of the problem of how to protect copyright. Digital watermarking is the solution for the protection of legal rights of digital content owner and customer.

References:

[1]. y'1.Song, RZ.Liu, and T N.Tan, "Digital Watermarking for Forgery Detection in Printed Multimedia Information Processing, Beijing, China, October 24-26, 2001.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 7, July 2012)

460

[3]. S. Shefali and S. M. Deshapande, "Mathematical Model for Improved Capacity Estimations for Data Hiding Techniques under Lossy Compression," in Proceedings of the 2nd IMT-GT Regional Conference in Mathematics, Statistics & Applications, Malaysia , 2006.

[4]. W.-N. Lie, G.-S. Lin, c.-L. Wu, and T C. Wang, " Robust Image Watermarking on OCT Domain," in ISCAS 2000 – IEEE International Symposium on circuits and Systems, Geneva, Switzerland , 2000, pp. 228-231 .

[5].AI-Gindy , H. AI-Ahmad, R Qahwaj, and A. Tawfik, "A novel blind Image watermarking technique for colour RGB images in the DCT domain using green channel "in Mosharaka International Conference on Communications. Computers and Applications (MIC-eCA 2008). , Amman, Jordan, 2008 .

Figure

Fig 1. Basic block diagram
Fig 3. Extracting Stage
Table. Comparison between Spatial and Frequency

References

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