Implementation of Digital Watermarking Algorithm based on DWT and DCT

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1 Implementation of Digital Watermarking Algorithm based on DWT and DCT Madhuri Tonge #1, Praveen kumar Malviya *2, Anshu Gupta #3 # Acropolis Institute of Technology & Research, Bhopal Rajiv Gandhi Proudyogiki Vishwavidyalya, Bhopal * Acropolis Institute of Technology & Research, Bhopal Rajiv Gandhi Proudyogiki Vishwavidyalya, Bhopal Abstract This paper deals with Matlab implementation of digital watermarking algorithm based on Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT). The system consists of two parts : Watermark Embedding and Watermark distilling. In watermark embedding, original image is transformed into L-level decomposition using DWT, and watermark image is transformed by using DCT, then watermark is embedded using threshold value. For watermark distilling, DWT of original image and watermark image is computed. The streak blocks of both the transformed images are compared for distilling of watermark. After taking Inverse DCT, distilled watermark is obtained. The results of watermarking is evaluated using the performance parameters: Normalized Cross Correlation(NC) and Peak Signal-to-Noise Ratio(PSNR). Keywords Digital Watermarking, Spatial Domain, Transform Domain, DCT, DWT, JPEG2000, MPEG-4 I. INTRODUCTION Digital Watermarking the process of inserting predefined patterns into multimedia data in a way that the degradation of quality is minimized and remain at an imperceptible level. Many digital watermarking algorithms have been proposed in special and transform domains. The techniques in the spatial domain still have relatively low-bit capacity and are not resistant enough to lossy image compression and other image processing operations. For instance, a simple noise in the image may eliminate the watermark. On the other hand, frequency domain-based techniques can embed more bits for watermark and are more robust to attack. Some transforms such as Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) are used for watermarking in the frequency domain. In this thesis, we compare the DCT watermarking algorithms and especially the DWT watermarking algorithms based on robustness criteria. In other words, the robustness of different transform watermark algorithms is evaluated by applying different transforms. One main reason to consider the DWT watermarking algorithms is that several multimedia standards such as the JPEG2000 and MPEG-4 are based on the DWT. These new standards brought new requirements such as progressive, low bit rate transmission, and regionof-interest coding. This thesis deals the developing the watermarking schemes for digital images stored in both, spatial and transformed domain. In this thesis we mainly focus on the comparison of Discrete Cosine Transform (DCT) and discrete wavelet transform based development. Apart from this, since JPEG is the most commonly used image format over World Wide Web, we pay special attention to robustness against JPEG. We propose comparison results of performance measures of both techniques to give subtle differences for the developers to select the choice with tradeoffs between technology and algorithms of transform. In this thesis, we also present a correlation between the performance of the watermarking scheme and original image. All presented watermarking schemes are robust against common image manipulations and attacks. The growth of high speed computer networks and World Wide Web (WWW) have explored means of new business, scientific, entertainment and social opportunities in the form of electronic publishing and advertising, massaging, real-time information delivery, data sharing, 392

2 collaboration among computers, product ordering, transaction processing, digital repositories and libraries, web newspapers and magazines, network video and audio, personal communication and lots more. The cost effectiveness of selling software in the form of digital images and video sequences by transmission over WWW is greatly enhanced due to the improvement in technology. We know that one of the biggest technological events of the last two decades was the invasion of digital media in an entire range of everyday life aspects. Digital data can be stored efficiently and with a very high quality, and it can be manipulated very easily using computers. Furthermore, digital data can be transmitted in a fast and inexpensive way through data communication networks without losing quality. Digital media offer several distinct advantages over analog media. The quality of digital audio, images and video signals are higher than that of their analog counterparts. Editing is easy because one can access the exact discrete locations that need to be changed. Copying is simple with no loss of fidelity. A copy of a digital media is identical to the original. With digital multimedia distribution over World Wide Web, authentications are more threatened than ever due to the possibility of unlimited copying. The easy transmission and manipulation of digital data constitutes a real threat for information creators, and copyright owners want to be compensated every time their work is used. Furthermore, they want to be sure that their work is not used in an improper way (e. g. modified without their permission). For digital data, copyright enforcement and content verification are very difficult tasks. One solution would be to restrict access to the data using some encryption techniques. However, encryption does not provide overall protection. Once the encrypted data are decrypted, they can be freely distributed or manipulated. Unauthorized use of data creates several problems. For example, if we visit we observe that all the wallpaper images are created by the owners, which are their Intellectual Property Right (IPR). Any user can download the wallpapers. Now, consider that a user downloads the images and posts those images (either after modifying or original) on his/her website. Three issues may arise in this situation: 1) how will the owner of indiafm.com know that there is one more web server on WWW posting their wallpapers? 2) If the owner knows about this fact, where shall he go to make a complaint? 3) The last but very important issue is that even if first two problems are resolved, how the owner will prove the ownership on the wallpaper images posted on another server? The first issue is related to network technologies and involves issues like web crawler and pattern matching etc. Second issue is related to the international copyright laws and is another very tricky issue. This thesis does not deal with these 2 issues. This thesis covers the third issue, the authentication i.e. how to prove the ownership? The above problem can be solved by hiding some ownership data into the multimedia data, which can be extracted later to prove the ownership. This idea is implemented in bank currency notes embedded with the watermark which is used to check the originality of the note. The same watermarking concept may be used in multimedia digital contents for checking the authenticity of the original content. The introduction of watermarking and the related publications date back to However, it was only in 1990 that it gained large international interest. Digital watermarking involves embedding watermark data into original information. In other words, a watermark is a pattern of bits inserted into multimedia data such as digital image, audio or video file that helps to identify the file s copyright information (author, rights, etc.). A simple example of a digital watermark may be a visible signature or seal placed over an image to determine the owner of that image. The name watermark is derived from the faintly visible marks imprinted on organizational stationery. Unlike printed watermarks, which are intended to be somewhat visible, digital watermarks are designed to be completely invisible, or in the case of audio clips, inaudible. In addition, the bits representing the watermark must be scattered throughout the file in such a way that they cannot be identified and manipulated. The embedding technique must keep the original information perceptually unchanged and the watermark data should be detected by an extraction algorithm. To begin with a quick background of watermarking, first we present the history of data hiding and related terminologies. Then, we will move on to a discussion on the watermarking, requirements that watermarking system must meet types of the watermarking, applications and then various attacks on a watermarking attacks. II. RELATED WORK The various literature associated to this study has been surveyed and their relations ship with study has been corelated with solar photovoltaic technology and maximum power point techniques. 1) Clara Cruz Ramos, Rogelio Reyes Reyes, Mariko Nakano Miyatake and Héctor Manuel Pérez Meana 393

3 Now a days, digital images and video are gradually replacing their conventional analog counterparts. This is quite understandable because digital format is easy to edit, modify, and exploit. Digital images and videos can be readily shared via computer networks and conveniently processed for queries in databases. Also, digital storage does not age or degrade with usage. On the other hand, thanks to powerful editing programs, it is very easy even for an amateur to maliciously modify digital media and create "perfect" forgeries. It is usually much more complicated to tamper with analog tapes and images. Tools as digital watermarks help us establish the authenticity and integrity of digital media and can prove vital whenever questions are raised about the origin of an image and its content. A digital watermarking technique embeds an invisible signal with an imperceptible form for human audio/visual systems, which is statistically undetectable and resistant to lossy compression and common signal processing operations. So far there some content authentication of digital image methods, which can be classified in two groups: watermarking based technique (Hsu & Wu, 1999) and digital signature based technique (Friedman, 1993). Some authors had written about digital image authentication systems (Wong, 1998; Holiman & Memos, 2000; Wong &Memon 2001; Celik, et al, 2002; Monzoy, et al, 2007; Cruz, et al, 2008; Cruz, et al, 2009; Hernandez, et al, 2000; Lin & Chang 2001; Maeno, 2006; Hu & Chen, 2007; Zhou, et al, 2004; Lu & Liao 2003) and are classified in three categories: complete authentication, robust authentication and content authentication (Liu & Steinebach, 2006). Complete authentication refers to techniques that consider the whole piece of multimedia data and do not allow any manipulation (Yeung & Mintzer, 1997; Wu & Liu, 1998). Because the non-manipulable data are like generic messages, many existing message authentication techniques can be directly applied. For instance, digital signatures can be placed in the LSB of uncompressed data, or the header of compressed data. Then, manipulations will be detected because the hash values of the altered content bits may not match the information in the altered digital signature. [1] 2) Saeid Saryazdi, MehrnazDemehri (2005) A new Blind gray-level watermarking scheme is described. In the proposed method, the host image is first divided into 4 4 non-overlapping blocks. For each block, five first AC coefficients of its DCT are then estimated using DC coefficients of its neighbour blocks. A gray-level watermark is then added into estimated values. Since embedding watermark does not change the DC coefficients, watermark extracting could be done by estimating AC coefficients and comparing them with their actual values. Several experiments are made and results suggest the robustness of the proposed algorithm. [2] 3)Kamran Hameed, AdeelMumtaz, and S.A.M. Gilani (2006) In this paper, we start by first characterizing the most important and distinguishing features of wavelet-based watermarking schemes. We studied the overwhelming amount of algorithm proposed in the literature. Application scenario, copyright protection is considered and building on the experience that was gained,implemented two distinguishing watermarking schemes. Detailed comparison and obtained results are presented and discussed. We concluded that Joo s technique is more robust for standard noise attacks than Dote s technique. [3] 4) Gengming Zhu, and Nong Sang (2008) In this paper the watermarking programs based on the discrete cosine transform (DCT) domain DC component (DC) is adopted. Through adjusting the block DCT coefficient of the image the watermarks are hidden. And blocking the selected image according to8 8 pixel, then dividing the selected image into four non-overlapped sub image blocks according to 4 4 pixel, and thus the watermarks are embedded through adjusting their DCT coefficient. The experimental results show that the method has strong robust. [4] 5)Mei Jiansheng, Li Sukang1 and Tan Xiaomei(May 2009) This paper introduces an algorithm of digital watermarking based on Discrete Cosine Transform(DCT)and Discrete Wavelet Transform(DWT). According to the characters of human vision, in this algorithm, the information of digital watermarking which has been discrete Cosine transformed, is put into the high frequency band of the image which has been wavelet transformed. then distils the digital watermarking with the help of the original image and the watermarking image. The simulation results show that this algorithm is invisible and has good robustness for some common image processing operations. [5] 6)J SasiKiran, PVRD PrasadaRao, G.CharlesBabu, G Ravi Kumar, Dr A YesuBabu(November 2010) In digital watermarking, an invisible signal referred as a watermark is embedded into multimedia data for various 394

4 purposes such as copyright protection, finger printing, authentication etc. For applications where the availability of original data is essential, irreversible degradation of the original data is not acceptable and incurred distortions need to be removed. Examples of such applications include multimedia archives, military image processing, and medical image processing for electronic patient records(eprs).high capacity watermarking is proposed in the paper and implemented using integer to integer wavelet transform. The proposed scheme divides an input image into non-overlapping blocks and embeds a watermark into the high frequency wavelet coefficients of each block. The conditions to avoid both underflow and overflow in the spatial domain are derived for an arbitrary wavelet and block size. The experimental results show that the implemented scheme achieves higher embedding capacity while maintaining distortion at a lower level than the existing invertible watermarking schemes. [ 6] simulation of different systems. For this work, we have made use of Image Processing and Wavelet Toolbox of Matlab. These toolboxes provide built-in functions required for this type of research work. 3.1 Graphical User Interface (GUI) : The Graphical User Interface (GUI) is made for running the project in interactive mode. To create this GUI, Matlab function guide is used. This function provides GUI development Environment Template. The GUI is shown in figure 1 7) Singh, R.; Bhadoria, S.S;Gupta, R.(2011) 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. Watermarking can be done by using least significant bit (LSB), singular value decomposition (SVD), Discrete Fourier Transform (DFT), Discrete cosine transform (DCT) and Discrete wavelet transform (DWT) techniques. In this paper Discrete cosine transform (DCT) and Discrete wavelet transform (DWT) are used for embedding and extraction of watermark. DWT and DCT are compared with respect to peak signal to noise ratio (PSNR) at a different threshold values. DWT gives better Image quality then DCT.[8] 8)Mei Jiansheng, Li Sukang, & Tan Xiaomer (2011): Introduction of digital watermarking based on DCT & DWT. According to the chacters of human vision, in this algorithm, the information of digital watermarking which has been DCT, is put into the high frequency band of the image which has been wavelet transformed then distills the digital watermarking with the help of the original image & the watermarking image. The simulation result show that this algorithm is invisible & has good robustness for some common image processing operation. Figure 1: GUI The options on GUI menu are classified into: 1) Watermark Embedding 2) Watermark Distilling 3.2 Watermark Embedding : This panel comprises of following push buttons : Select Original Image DWT Select Watermark DCT Embedding Watermark IDWT Watermarked Image III. PROPOSED WORK We have implemented our system using MATLAB. It provides lot of useful features required for modelling and 395

5 Cross-Correlation (NC). The Normalized Cros-Correlation is defined by : Figure 2 Result of Watermark Embedding The value of NC is between 0 and 1.The bigger value is, better is the watermark robustness is. 4.2 Peak Signal-to-Noise Ratio (PSNR) The concealing of the watermark is quantitatively analyzed by using Peak Signal-to-Noise Ratio (PSNR). It is defined as : 3.3 Watermark Distilling : This panel comprises of following push buttons : Select Watermarked image DWT Distilling IDCT The unit of PSNR is db. The bigger PSNR value is, the better the watermark conceals. Figure 4 : Sample original images Figure 3 : Result of watermark distilling IV. RESULTS 4.1 Normalized Cross-Correlation (NC) Generally speaking, the evaluation of watermark algorithm contains two parts : robustness and concealing. The compatibility of distilled watermark with the original watermark is quantitatively analysed by using Normalized Figure 5 : Sample watermark images 396

6 Table 1 : Result Image NC PSNR (db) Car.jpg Elephant1.jpg Elephant2.jpg Flower1.jpg Flower2.jpg Flower3.jpg Flower4.jpg Flower5.jpg Konthilla.jpg River.jpg Figure 7 : Comparison of PSNR between reference method and proposed method V. Conclusion In this research work, I have studied various digital watermarking techniques. The Discrete Wavelet Transform (DWT) digital watermark algorithm based on human vision characters is proposed and implemented. By using the block technology, watermarking signal is embedded into the high frequency band of wavelet transformation domain. The watermark image is discrete cosine transformed in order to improve its robustness. The simulation results reveals that this watermarking system not only can keep the image quality well, but also can be robust many common image processing operations of filter etc. We have compared the results of our proposed technique with the reference method on the basis of evaluation parameters such as Normalized Cross Correlation (NC) and Peak Signal-to-Noise Ratio (PSNR). Figure 6 : Comparison of NC between reference method and proposed method A. References [1] R. R. Reyes, M. N. Miyatake, H. M. Pérez Meana C. C. Ramos, "Watermarking-Based Image Authentication System in the Discrete Wavelet Transform Domain," SEPI ESIME Culhuacan, National Polytechnic Institute of México. [2] M. Demehri S.Saryazdi, "A Blind DCT Domain Digital Watermarking," 3rd International Conference: Sciences of Electronic Technologies of Information and Telecommunications, March [3] A. Mumtaz, S.A.M. Gilani K. Hameed, "Digital Image Watermarking in the Wavelet Transform Domain," World Academy of Science, Engineering and 397

7 Technology 13, [4] N.Sang G.Zhu, "Watermarking Algorithm Research and Implementation Based on DCT Block," World Academy of Science, Engineering and Technology 45, [5] L. Sukang, T. Xiaomei M. Jiansheng, "A Digital Watermarking Algorithm Based On DCT and DWT," Proceedings of the 2009 International Symposium on Web Information Systems and Applications (WISA 09), [6] PVRD Prasada Rao, G.Charles Babu, G Ravi Kumar, Dr A Yesu Babu J Sasi Kiran, "IIWM- An Invertible Image Watermarking," International Journal of Computer Applications ( ), November [7] "Digimarc Discover Implementation Guide," [8] S.S.Bhadhoriya,R. Singh R.Gupta, "Digital Image Watermarking by Using Discrete Wavelet Transform and Discrete Cosine Transform and Comparison Based on PSNR," Communication Systems and Network Technologies (CSNT), 2011 International Conference IEEE, no. 3-5 June 2011, pp. INSPEC Accession Number: , 28 July [9] Mei Jiansheng, Li Sukang, & Tan Xiaomer, A Digital watermarking Algorithm based on DCT & DWT, (CSNT)2011 International conference IEEE