Enhanced Watermarking Technique for Color Images using Visual Cryptography

Transcription

1 Informaton Assurance and Securty Letters 1 (2010) Enhanced Watermarkng Technque for Color Images usng Vsual Cryptography Enas F. Al rawashdeh 1, Rawan I.Zaghloul 2 1 Balqa Appled Unversty, MIS Department, Amman,Jordan Enas_fasal@yahoo.com 2 Balqa Appled Unversty, MIS Department, Amman,Jordan rawanzaghloul@yahoo.com Abstract: In s paper we consder a watermarkng technque based on vsual cryptography at offers enhancng e securty ssues n prevous works. The proposed meod s appled over color mages, where e RGB mage s converted to e HSV color scheme. The embeddng process depends on e saturaton plane (S) on whch we apply logcal X-OR, most sgnfcant, and party operatons; to generate e actual plane n whch we want to embed our watermark -upon e rules of vsual cryptography (as nvented by Noar and Shamr, 1995). Fnally e generated master share s regstered n e rd party. In e extracton process, applyng e same meod over e watermarked mage wll generate e master share agan; combne t w at of e rd party to generate e embedded watermark. Dfferent attack scenaros are taken nto consderaton such as flterng, addtve nose, compresson, rotaton, flppng, croppng, and dstorton. Keywords: Watermarkng, Secret Sharng, Vsual Cryptography, Party bt. 1. Introducton The rapd grow of multmeda content n dgtal form made e dgtal mages easy to steal, modfy, or used llegally by unauorzed people, s creates a pressng need for buldng more secure meods for legal dstrbuton of e dgtal content. So, dgtal watermarkng has been proposed to protect e ntegrty of multmeda. An mage watermark meod s now drawng e need for good schemes to protect copyrghts for dgtal data. But e chosen meod must be hard to detect and remove. There are many artcles reveal and proposes some watermark meods [2, 4, 9, 10], however ere are several watermarkng meods at are not robust or easy to remove [5]. In s paper we devse a watermarkng meod based on e vsual cryptography at ntroduced by Naor and Shamr [1]. The paper s organzed as follows: Vsual Cryptography s dscussed n Secton 2. In secton 3 e used measures are presented. Secton 4 dscusses e proposed algorm. The expermental results are provded n Secton 5. Fnally, e conclusons are presented n Secton Vsual Cryptography Cryptography at can be decoded drectly by e human vsual system wout any specal calculaton for decrypton s called Vsual Cryptography. It was proposed for e frst tme by Naor and Shamr. In vsual cryptography a secret message can be vewed as nong more an a collecton of black and whte pxels as depcted on fgure. 1. Each pxel n e orgnal mage s represented by at least one subpxel n each of e n generated shares. Fgure 1. The basc scheme of vsual cryptography Each share s comprsed of collectons of m black and whte subpxels where each collecton represents a partcular orgnal pxel [1, 2, 3]. R.J. Hwang proposed a watermark meod based on vsual cryptography, accordng to hs meod, e owner should select an h n black/whte mage as e watermark. In e embeddng processes, e owner should randomly select a number as hs secret key S, to embed e watermark nto e mage K at s a k l (256 gray-leveled) mage. The owner embeds e watermark pattern W nto e mage K by generatng e secret key S, and e verfcaton nformaton V. As llustrated n table 1, f e pxel n e watermark W s zero and e left most sgnfcant bt (LMB) of e R pxel n mage M s 1 en e verfcaton nformaton equals (0,1), and so on. In e extracton process, e notaral organzaton retreves e verfcaton nformaton V and e watermark pattern W, whch e owner has regstered, and verfes e ownershp of e watermarked mage K, for more detals see [2]. Table 1. Verfcaton Rules On 2009, Surekha proposed a vsual cryptography algorm n mage watermarkng at offers better securty an Hwang s meod, so at, attackers wll not be able to detect ownershp nformaton [3]. Our proposed meod offers an enhancement for Surekha s algorm. Receved June 21, $ Dynamc Publshers, Inc.

2 025 Rawashdeh and Zaghloul 3. Measures To prove e effect of our meod eoretcally by measures, e followng metrcs are used to measure dstorton and smlarty between e orgnal watermark and e extracted watermark: 1. Root Mean Square Error (RMSE), as defned n equaton 1, (1) Where m n s e sze of e watermark, Wj s e watermark pxel n e row and j column, and W'j s e W' n e row and j column. 2. Peak Sgnal to Nose Rato (PSNR), as defned n equaton 2.[7,6] (2) Where e MSE s e Mean Square Error whch defned by equaton 3: (3) Where m n s e sze of e watermark, Wj s e watermark pxel n e row and j column, and W'j s e W' n e row and j column. [7,8] Fgure 2. Embeddng Model Fgure.3 shows e extracton Model, n whch we start by readng e watermarked mage I' and convert t to e HSV scheme, en we extract e saturaton from e HSV mage. Then we start e extractng process as dscussed n secton 4.3. Fnally e secret mage s extracted. 3. Correlaton (Corr), as defned n (3), (4) Where and are e mean for e orgnal watermark and e extracted watermark respectvely. [7,8] 4. Proposed Algorm Ths secton reveals e proposed meod for watermark embeddng and detecton. 4.1 General Model The general dagrams of our meod are descrbed n Fgure.2 and Fgure.3. Where Fgure.2 shows e watermark embeddng Model, n whch we convert e host mage from RGB color scheme to e HSV color scheme. Then we extract e S (saturaton) from HSV mage. After at we start e embeddng process as llustrated n secton 4.2, at e end we generate e Master share M, at s regstered n a trusted rd party. Fgure 3. Extracton Model 4.2 Watermark Embeddng As shown n Fgure.5 e embeddng process s as follows: Read e RGB mage I of sze rxc Convert e mage to e HSV scheme Extract e saturaton plane (S) from e HSV mage Read e black-whte watermark mage (W) of sze wxh Select a secret key K as a seed to generate wxh random numbers over e nterval [1 to rxc]. Let R be e random number.

3 Enhanced Watermarkng Technque for Color Images usng Vsual Cryptography 026 Create a bnary matrx MSB of sze wxh, t contans e most sgnfcant bts of R pxel of e host mage. Create a bnary matrx P of sze wxh at represents e party for e frst ree bts of R pxel of e host mage. Compute Y such at t fnds e logcal xor between P and MSB as n e followng equaton, Y = P MSB Create a bnary matrx Z of sze wxh such at e entres n e array are e most sgnfcant bts of e R random number. Create a bnary matrx Y of sze wxh such at F = XOR (Y, Z ) Generate e Master Share M by assgnng a par of bts for each element n e bnary matrx F accordng to e encrypton rules of VC. As dscussed before n table 1. M s regstered to e trusted rd party. Fgure 5. Watermark embeddng Fgure 6. Watermark extracton

4 027 Rawashdeh and Zaghloul 4.3 Watermark Extracton As shown n Fgure.6 e extracton process s as follows: Read e watermarked mage I of sze rxc Convert I to HSV scheme Extract e saturaton plane (S) from I Read e black-whte watermark mage (W) of sze wxh Use e secret key K as a seed to generate wxh random numbers over e nterval [1 to rxc]. Let R be e random number. Create a bnary matrx MSB of sze wxh, t contans e most sgnfcant bts of R pxel of e host mage. Create a bnary matrx P of sze wxh at represents e party for e frst ree bts of R pxel of e host mage. Create a bnary matrx Z of sze wxh such at e entres n e array are e most sgnfcant bts of e R random number. Create a bnary matrx F of sze wxh such at F = XOR (Y, Z ) Create e Verfcaton Share such at, f e element n e bnary matrx F s 0 en V = (0, 1), else V = (1, 0) The secret mage can be extracted by performng logcal OR between e master share M and e Verfcaton share V. 5. Expermental Results The robustness of our approach s tested by applyng several attacks over e Peppers mage of sze (512x512) and e bnary watermark mage of sze (144 x 148). Fgures 7,8 show e orgnal peppers mage and e bnary watermark respectvely. Fgure 7. Peppers orgnal mage Fgure 8. Bnary watermark mage The robustness of e meod s confrmed by expermental results at dsplay e mmunty of e embedded watermark over dfferent types of attacks, such as compresson, flterng, croppng, rotaton, addtve nose, and dstorton. Table.2 shows e detaled results. Attack Watermarked Image RMSE PSNR Corr Extracted Watermark Blurred (gaussan, w flter sze=5) Flterng Lnear moton of a camera by len pxels=31, angle eta degree= Addtve Nose Compresson Table 2. Expermental results

5 Enhanced Watermarkng Technque for Color Images usng Vsual Cryptography 028 Rotaton Flppng Croppng Dstorton Table 2. Expermental results (contnued) 6. Conclusons The need of effcent meod at makes t hard to detect e marked mage, t wll become more prevalent. Ths paper, proposed a good watermark meod at s buld up on e vsual cryptography watermarkng technque for secure mage auentcaton for colored mages. The features of our meod are lsted below: Ths meod s appled over colored mages; especally we have used e saturaton plane from e HSV model for secure auentcaton. To ncrease e securty of e proposed model, e logcal X-OR and partes are used. Accordng to our model we acheve good results aganst several knds of attacks such as flterng, addtve nose, compresson, rotaton, flppng, croppng and dstorton. References [1] M. Noar and A. Shamr, Vsual Cryptography, Advances n Cryptography Eurocrypt 94, Lecture Notes n Computer Scence, Sprnger-Verlag, Berln, Vol. 950, pp. 1-12, [2] R. Hwang, A dgtal Image Copyrght Protecton Scheme Based on Vsual Cryptography, Tambang Journal of scence and Engneerng, vol.3, No.2, pp , [3] B.Surekha,GN.Swamy, K.Rao and A.Kumar, A Watermarkng Technque based on Vsual Cryptography, Journal of Informaton Assurance and Securty No.4.pp , [4] M.Prasad and S.Kolwad, A Comprehensve Survey of Contemporary Researches n Watermarkng for Copyrght Protecton of Dgtal Images, IJCSNS Internatonal Journal of Computer Scence and Network Securty, VOL.9 No.4, Aprl 2009 [5] Inoue H., Myazak A., Yamamoto A. and Katsura T., A Dgtal Watermark Technque Based on e Wavelet Transform and Its Robustness on Image Compresson and Transformaton, IEICE Transactons on Fundamentals of Electroncs, Communcatons and Computer Scences, Vol. E82- A, No. 1, pp.2-10(1999). [6] B.Verma, S.Jan, D. Agarwal, and A.Phadkar, A New Color Image Watermarkng Scheme ; INFOCOMP, vol. 5, No.2, pp (2006). [7] Rawan I. Zaghloul, Enas F. Al-Rawashdeh, "HSV Image Watermarkng Scheme Based on Vsual Cryptography", Proceedngs of World Academy of Scence, Engneerng and Technology, Vol. 34, October [8] MaWorks, Image Processng Toolbox User's Gude 4.2. [9] P.S.Revenkar, Ansa Anjum, and W.Z.Gandhare, Secure Irs Auentcaton Usng Vsual Cryptography, (IJCSIS) Internatonal Journal of Computer Scence and Informaton Securty, Vol. 7, No.3, 2010 [10] Er.Suprya Knger, Effcent Vsual Cryptography, Journal of emergng technology n web ntellgent, Vol. 2, No. 2, 2010 Auor Bographes E Rawashdeh receved a B.S. degree n Computer nformaton system from appled scence Unversty, Jordan n 2004 and e M.S. degrees n Computer scence from Jordanan Unversty, Jordan n 2006, where she s currently workng n MIS Department of Al-Balqa a Appled Unversty, Jordan. Her research nterests nclude mage processng. R Zaghloul receved a B.S. degree n Computer Scence from Al- Balqa a Appled Unversty, Jordan n 2003 and e M.S. degrees n Computer scence from Jordanan Unversty, Jordan n 2005, where she s currently workng n MIS Department of Al-Balqa a Appled Unversty, Jordan. Her research nterests nclude mage processng.