IAJIT First Online Publication

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1 Content Protecton n Vdeo Data Based on Robust Dgtal Watermarkng Resstant to Intentonal and Unntentonal Attacks Mad Masoum and Shervn Amr Department of Electrcal Engneerng, Islamc Azad Unversty Qazvn Branch, Iran Scentfc Member of electrcal engneerng Department, Iranan Research Organzaton for Scence and Technology, Iran IAJIT Frst Onlne Publcaton Abstract: Embeddng a dgtal watermark nto an electronc document s provng to be a feasble soluton for multmeda copyrght protecton and authentcaton purposes. In the present paper we propose a new dgtal vdeo watermarkng scheme based on scene change analyss. By detectng the moton scene of vdeo and usng CDMA technques the watermark s embedded nto md-frequency sub-bands of wavelet coeffcents. In ths experment n order to enhance the securty of our algorthm four keys are consdered. Three of them are formed n watermark encrypton process and one key s related to CDMA embeddng process. Also, wth the am of makng a good compatblty between the proposed scheme and Human Vsual System (HVS), the blue channel of RGB vdeo s utlzed to embed the watermark. Expermental results show the hgh robustness of the proposed method aganst both ntentonal and unntentonal attacks durng the transfer of vdeo data. The mplemented attacks are Gaussan nose, medan flterng, frame averagng, frame droppng, geometrc attacks and dfferent knds of lossy compressons ncludng MPEG-, MPEG-4, MJPEG and H.64/AVC. Keywords: Dgtal watermarkng, scene change analyss, geometrc attacks, nformaton securty, HVS. Receved May 3, ; accepted December 3,. Introducton In the past decade, the global rfe access of nternet technologes makes the communcaton and crculaton of dgtal multmeda contents lke mages, audo and vdeo very easy. However, ths convenence also causes substantal ncrease n llegal operatons such as duplcaton, modfcaton, forgery, copy-rght protecton and others n dgtal meda. Therefore, the protecton of dgtal meda has become an mperatve ssue. Recently, dgtal watermarkng has drawn much attenton of research communty to resolve these pressng problems [3, 6]. The basc procedure for dgtal watermarkng s to embed some hdden nformaton nto multmeda data, whle the qualty of the watermarked data s retaned, and the watermark can stll be detected under dfferent knds of ntentonal and unntentonal attacks. An effectve watermarkng scheme s dstngushed by three characterstcs, namely, mperceptblty, robustness and capacty. Also, n order to enhance the safety of algorthm another feature,.e., securty, can be added to the man necesstes of vdeo watermarkng. Imperceptblty: A degree that an embedded watermark remans unnotceable when a user vews the watermarked dgtal meda. The nformaton should embed the watermark n the regons of the vdeo frame n whch mperceptblty s least affected [3]. Robustness: The reslence of an embedded watermark aganst beng removed by ncdental and ntended attacks. Maor attacks on the vdeos are flterng, addng nose, compresson, scalng [3]. In some of the watermarkng technques, robustness s more a property and not a requrement []. Capacty: The amount of nformaton that can relably be hdden when the scheme provdes the ablty to change dgtal data [8,,, 9] These three requrements of watermarkng make a trangle. Improvement n any one of them, affects the other two negatvely. We have to fnd the correct balance between these conflctng requrements of watermarkng [3]. Securty: The ablty of the watermark to resst aganst attempts by a sophstcated attacker to remove t or destroy t va cryptanalyss, wthout modfyng the vdeo tself [6]. Applcatons of vdeo watermarkng contan fngerprntng, broadcast montorng, vdeo authentcaton and copyrght protecton. A varety of watermarkng algorthms have been proposed n the lterature. These algorthms can be broadly classfed n two categores accordng to the embeddng doman: spatal and transform doman. Spatal doman approaches [, ] are the smplest and the earlest algorthms based on the modfcaton of pxel ntenstes. These algorthms are less robust aganst the

2 attacks. On the other hand, transform doman approaches nsert the watermark nto transform coeffcents, such as Dscrete Fourer Transform (DFT) [9], Dscrete Cosne Transform (DCT) [], and Dscrete Wavelet Transform (DWT) [3, 5, 3]. L [5] proposed a scheme based on 3D-DWT and Artfcal Neural Network (ANN). Frst the average frame of the vdeo shot s computed. Then the resultng frame s transformed to the wavelet doman. Afterwards, the LL subband s dvded nto non overlappng 3 3 blocks. The blocks whch satsfy a relatonshp among the center of block, mean eght neghbors and standard devaton are selected as the tranng sets. The center of each block s the output whle the mean and standard devaton of the neghbor are the nputs. Consequently a traned network for watermark embeddng and extracton process s obtaned. So n the extracton stage, statstcal features of coeffcents and ther relatonshp are used whch means, ths scheme s not completely blnd; on the contrary, a large amount of data s requred to detect the watermark sequence. On the other hand embeddng the watermark nformaton n low frequency coeffcent enhances the robustness of system; however t severely destroys the qualty of vdeo and ts transparency. A DWT-based watermarkng scheme whch embeds the watermark n successve frames s proposed n [4]; ths scheme defned a general algorthm based on scene change detecton for embeddng the watermark by alterng the magntude of some wavelet coeffcents. In fact they nsert the watermark n both moton and motonless parts of vdeo. However, HVS s more senstve to motonless part of vdeo, so embeddng the watermark n ths part leads to the perceptblty of the watermark. On the other hand compresson algorthms used to destroy the motonless part of vdeo meanwhle mantan the moton part of t. Also, these motonless regons may be statstcally compared or averaged to remove the ndependent watermarks. From the other pont of vew, dvdng the vdeo based on scenechange detecton wll not be useful f the vdeo changes occur rapdly or contans too many dfferent short scenes, because t demands dfferent algorthms n each scene for embeddng and detectng the watermark n the watermarkng process. Furthermore they had no estmaton or dscusson about the acqurng of frame number based on a factor of n. Snce each algorthm whch has a 3D shape (e.g., 3D-DWT, 3D-DCT, ) should has a frame number of factor n for embeddng and extracton of watermark. Otherwse t faces problems n executng the nverse DWT, because f the number of frames s not a factor of n the coeffcents wll have zero values whch lead to maor damage n vdeo qualty and destructon of watermark nformaton. Among the delvered technques n recent years, the ones whch are based on the Dscrete Wavelet Transform (DWT) are ganng more popularty due to ther excellent spatal localzaton, frequency spread, and mult-resoluton characterstcs. The DWT s chosen because t s more computatonally effcent than other transform methods. The speed s faster than DCT and DFT as only sum or dfference of the pxel have to be calculated. From the other pont of vew, watermarkng n vdeo doman can be done on compressed or uncompressed vdeo. Generally the watermarkng n compressed vdeo has more compatblty for real-tme systems [4]. However, the goal of ths paper s to embed the watermark n uncompressed vdeo, because format conversons destroy the watermark whch s embedded n compressed watermarked vdeo. The huge memory requrement of the algorthms that compute the 3D- DWT s one of the man drawbacks n practcal mplementatons. Orgnally the algorthms whch are based on 3D-DWT and 3D-DCT, demand hgh computatonal complexty and have enormous memory usage. Also, f the 3D algorthms perform on all vdeo streams (contanng moton and motonless regons) they requre hgher computatonal complexty and are expensve for mplementaton and eventually cannot be useful for real-tme systems. The vdeo watermarkng methods whch have lower computatonal complexty (e.g. D based algorthms) are sutable for real-tme systems. Many of the exstent algorthms meet the mperceptblty necessty qute easly and survey robustness only aganst a subset of attacks not all knds of attacks, meanwhle robustness aganst dfferent attacks s the key challenge n watermarkng process. In ths study, a secure vdeo watermarkng scheme whch s robust aganst dfferent vdeo attacks and yet s sutable for real-tme systems s delvered. The rest of paper s planned as follows: The descrpton of used termnologes.e. Dscrete Wavelet Transform and watermark scramblng are explaned n Secton. Secton 3 llustrates the proposed watermarkng scheme n three sub-sectons. The expermental results are presented n Secton 4. Fnally, the concludng remarks are gven n Secton 5. IAJIT Frst Onlne Publcaton. Prelmnares In ths secton, we provde the man termnologes whch are used n the proposed algorthm to acheve the desred goal. These termnologes are as follows:.. Dscrete Wavelet Transform... One Dmensonal Dscrete Wavelet Transform A general -D dscrete wavelet transform can be wrtten as [9]:

3 W(,k)= f ( x) ( x k ) M x () x.5 =.5 x otherwse. () Where W represents the wavelet coeffcents functon, and k denote the dlaton and translaton parameters respectvely, and M s the length of sequence f.... Two Dmensonal Dscrete Wavelet Transform The one-dmensonal wavelet transform can be easly extended to two-dmensonal functons lke mages. In two dmensons, a two-dmensonal scalng functon, ( x, y ) and three, two-dmensonal wavelets, H V D ( x, y ), ( x, y ), ( x, y ) are requred. Each s the product of a one-dmensonal scalng functon and correspondng wavelet. Excludng products that produce one-dmensonal results, lke ( x ) ( x ), the four remanng products produce the separable scalng functon: ( x, y) = ( x) ( y) (3) and separable, "drectonally senstve" wavelets : H ( x, y) = ( x) ( y) (4) W (, m, n) coeffcents add horzontal, vertcal, and dagonal detals for scales. Gven the W and W of equatons. (9) and (), f ( x, y) s obtaned va the nverse dscrete wavelet transform: IAJIT Frst Onlne Publcaton f(x,y)= W (, m, n), m, n( x, y) + MN m n W (, m, n), m, n( x, y) MN = H, V, D = m n ()..3 Three Dmensonal Dscrete Wavelet Transform In three dmenson, a three-dmensonal scalng functon, ( x, y, z ) and seven three-dmensonal LLH LHL wavelet functons, ( x, y, z), ( x, y, z), LHH HLL HLH ( x, y, z), ( x, y, z), ( x, y, z), HHL HHH ( x, y, z) and ( x, y, z) are requred. Each s the product of a one-dmensonal scalng functon and correspondng wavelet.excludng products that produce one-dmensonal results, lke ( x, y, z ) ( x, y, z), the eght resdual products produce the separable scalng functon: ( x, y, z) = ( x) ( y) ( z) () and separable, "drectonally senstve" wavelets : V ( x, y) = ( x) ( y) (5) D ( x, y) = ( x) ( y) (6) Gven separable two-dmensonal scalng and wavelet functons, extenson of the one-dmensonal DWT to two dmensons s straghtforward. The scaled and translated bass functons are:, m, n( x, y ) = ( x m, y n ) (7), m, n( x, y ) = ( x m, y n ) ={H,V,D} (8) Where ndex dentfes the drectonal wavelets n equatons (4) to (6). The dscrete wavelet transform of functon f ( x, y) of sze M N s then: M N W (, m, n) = f ( x, y ), m, n( x ) (9) MN x = y = M N W (, m, n) = f ( x, y), m, n( x ) MN x = y = ={H,V,D} () As n the one-dmensonal case, s an arbtrary startng scale and the W (, m, n) coeffcents defne an approxmaton of f ( x, y ) at scale. The LLH ( x, y, z) = ( x) ( y) ( z ) LHL ( x, y, z) = ( x) ( y) ( z) LHH ( x, y, z) = ( x) ( y) ( z) HLL ( x, y, z) = ( y) ( y) ( z) HLH ( x, y, z) = ( x) ( y) ( z) HHL ( x, y, z) = ( x) ( y) ( z ) HHH ( x, y, z) = ( x) ( y) ( z) (3) Gven separable three-dmensonal scalng and wavelet functons, extenson of the one-dmensonal DWT to three dmensons s smple. The scaled and translated bass functons are:,,, ( x, y, z) = ( x m, y n, z o) mno m n o z,,, ( x, y, z ) = ( x m, y n, o) ={LLH,LHL,LHH,HLL,HLH,HHL,HHH} (4) Where ndex dentfes the drectonal wavelets n equaton (3). The dscrete wavelet transform of functon f ( x, y, z) of sze M N O s then: O M N W(, m, n, o) = f ( xyz,, ), m, no, ( xyz MNO,, ) (5) z= x= y =

4 W(, m, n, o) = MNO ={LLH,LHL,LHH,HLL,HLH,HHL,HHH} O M N f ( x, y, z) mno,,, ( x, y, z) z= x= y = (6) As n the one-dmensonal case, s an arbtrary startng scale and the W (, m, n, o) coeffcents defne an approxmaton of f ( x, y, z) at scale. The W (, m, n, o) coeffcents add horzontal, vertcal, and dagonal detals for scales. Gven the W and W of equatons (5) and (6), f ( x, y, z ) s obtaned va the nverse dscrete wavelet transform: f(x,y)= MN MNO W (, m, n, o) ( x, y, z), m, n, o o m n HHH W ( mno,,, ), m, n, o( x, y, z) O = LLH = o m n.. Watermark Scramblng + (7) Usually scramblng transform s used n the pretreatment stage of the watermark as a way of encrypton. Generally, a meanngful watermark mage becomes meanngless and dsordered after scramblng. For mprovng the securty and confdentalty, a scramblng method [7] s used to encrypt the bnary watermark mage. After scramblng, human eyes cannot dstngush the shape of the orgnal watermark. Wthout the scramblng algorthm and the key, the attacker wll not recover the watermark at all even f t has been extracted from the watermarked vdeo. So shufflng the mage gves a secondary securty for the dgtal products. Ths method s defned as follows: x n+ α x n = mod( N ) y n + β αβ y + n (8) Where ( x n, y n) s the pxels poston n an N N mage; ( x n+, y n+ ) s the transformed poston after cat map; α and β are the system parameters and must be the postve ntegers. The determnant value s, so cat map s a map whch keepng area (no attractor). At the same tme, the cat map s one-to-one mappng; each pont n matrx can be transformed to another pont unquely. Cat map has two typcal factors, whch brng chaotc movement: tenson (multply matrx n order to enlarge x, y) and fold (takng mod n order to brng x, y n unt matrx). In fact, cat map s a chaotc map. Image poston can be scrambled va the teraton of cat map, by consderng ( α = 7, β = 3), consequently the encrypted mage wll be acheved. After a perod of teraton the watermark mage wll be attaned. So teraton tmes and system parameters (α, β ) can be used as the encrypton keys. By usng these three keys the securty of our scheme wll be enhanced. Fgure. Encryptng the watermark; Orgnal watermark Scrambled watermark (Iteraton tmes= 9). IAJIT Frst Onlne Publcaton 3. The Proposed Watermarkng Algorthm 3.. Preprocessng of Vdeo Applyng ndependent watermarks to each frame presents a problem, f regons n each vdeo frames reman lttle or no moton frame after frame. These motonless regons may be statstcally compared or averaged to remove the ndependent watermarks [4]. From the other pont of vew, dvdng the vdeo based on scene-change detecton wll not be useful f the vdeo changes occur rapdly or contans too many dfferent short scenes, because t demands dfferent algorthms of embeddng and detectng the watermark n a watermarkng process, especally f they use a 3Dbased watermarkng algorthm. Also, f the vdeo contans long motonless scenes, the algorthm wll face the same dffcultes. Therefore, n ths experment, we decded to nsert the watermark nto moton part of vdeo. In order to detect the moton part of vdeo, the followng crteron should be satsfed: n D (, + ) = H ( ) H ( ) (9) = + For ths purpose, only the hstograms of green components for all frames are utlzed. Ths s because of the ntended moton part of vdeo contans a large texture of green color whch dstngush t from the other scenes. In ths method s the number of frames, s the green component of frames and H s the calculated hstogram. So by meetng D (, + ) > thresholdt ( ) a scene change wll be occurred. Wth the purpose of obtanng the desred moton part of vdeo T s regarded as 535. In the consdered vdeo sequence.e. wldlfe sequence, we have chosen the scene that the brds start to fly, frames from the detected moton part are randomly shown n Fgure. Fgure. Two randomly frames from the detected moton scene. Two other reasons for choosng the moton scene of vdeo for embeddng the watermark can be llustrated as follows; Embeddng the watermark n moton scene

5 leads to less mperceptblty of the watermark, because HVS s less senstve to moton part of vdeo, on the other hand compresson algorthms used to destroy the motonless part of vdeo, at the same tme, mantan the moton part of t. In the Human Vsual System (HVS), there are three types of cones that react to the basc three colors: red, green and blue. The number of cones reacted to blue s 3 tmes smaller than the number of cones reacted to red or green, whch means the HVS has lack of sensblty to blue color []. Fgure 3 shows fracton of lght absorbed by each type of cone, here R, G, and B represent red, green and blue colors, respectvely. For ths reason, the proposed algorthm ntends to embed the watermark sgnal nto the blue channel; hence a good compatblty between the watermarkng and HVS wll be acheved. each frame and one dmensonal DWT wthn the temporal axs over frames. The three dmensonal coeffcents of HL, LH and HL3, LH3 are chosen for embeddng the watermark. Coeffcent of LL3 (.e. the low frequency sub-band) s not watermarked, as vdeo energy s concentrated on lower frequency wavelet coeffcent. If t s altered, t wll affect on perceptual qualty. Also the coeffcents of HH (.e. the hgh frequency sub-bands) are excluded from embeddng the watermark, as data loss usually occurs among the hgh frequency components due to lossy compresson [7]. Coeffcents of wavelet decomposton n three levels are shown n Fgure 4. IAJIT Frst Onlne Publcaton Fgure 4. Three levels of dscrete wavelet decomposton. Fgure 3. Sensblty of HVS to dfferent wavelength related to three basc colors. 3.. Watermark Inserton In ths secton n order to nsert the watermark a Code Dvson Multple Access (CDMA) technque s used. In ths technque watermarkng algorthm can be vewed n terms of a telecommuncaton system: a message (the watermark) has to be sent through a nose channel (the mage/vdeo) to a recever that has to recover the orgnal message []. Generally, n CDMA technque, the watermark nformaton s consdered as pseudo random numbers, then by usng an algorthm, each bt of watermark nformaton s scattered randomly throughout the vdeo frames, whch leads to ncrease n capacty of embeddng and mprovng the resstance of watermarkng system (specally aganst addng nose). Utlzng CDMA technque makes hard to detect the watermark because t uses wde-band, nose-lke sgnals. Also, by applyng pseudo-random numbers whch are ndependent from the data, both the band spread and securty of the system wll be provded. The process of embeddng the watermark s as follows: Frst of all, a three dmensonal wavelet n three levels s appled on the detected moton scene, namely two dmensonal DWT n terms of space on Embeddng process s followed by applyng CDMA technques n a way that pseudo random numbers based on Mersenne Twster algorthm whch s proposed by Nshmura and Matsumoto [6] are created. Ths method generates numbers wth a 9937 perod of ( - )/. By usng a key, four sets of pseudo random numbers whch W (,, k) {, + }, are acheved based on the adaptve sze of wavelet coeffcents. So ths key s consdered as our fourth key n the proposed algorthm whch guarantees the securty of the proposed watermarkng scheme. Accordng to magntudes of the 3D-DWT coeffcents, the scrambled watermark s adaptvely spread and embedded nto these coeffcents. Followng algorthm shows the embeddng process: C (,, k ) = C (,, k ) + QW. (,, k) f b = C (,, k ) = C (,, k ) f b = Where C (,, k) s the 3D wavelet coeffcent, C (,, k) s the watermarked 3D wavelet coeffcent, Q s the modulaton ndex, W (,, k) s the PRN matrx, b s bt of the scrambled watermark that has to be embedded and { HL, LH, HL3, LH 3}. Fnally by performng nverse 3D wavelet over the moton part of vdeo, the process of nsertng the watermark wll be accomplshed.

6 3.3. Watermark Detecton Durng extracton process the orgnal vdeo s not needed, namely, blnd detecton. The detecton s the nverse process of watermark embeddng: Performng the 3D wavelet on moton part of vdeo, that s, D wavelet on each frame and D-DWT along temporal axs over frames. Selectng the three dmensonal coeffcents of HL, LH, HL3, and LH3 for extractng the watermark. Generatng four sets of pseudo random numbers based on Mersenne Twster algorthm by applyng the same key whch s used n nsertng process. Calculatng the correlaton between the extracted coeffcents and ther relatve pseudo-random numbers gves the hdden watermark: f ( ρ ( EC (,, k ), W (,, k ))) > th watermark s Avalabe end f Where { HL, LH, HL3,LH3} and EC (,, k ) s the extracted 3D wavelet coeffcents. It should be noted that th (threshold) s consdered by experence. Also the correlaton coeffcent between the extracted wavelet coeffcents and the pseudo random numbers s determned by [3]: ρωω (, ) = m n ( ω(, ) ϖ).( ω (, ) ϖ ) = = m n m n ω ϖ ω ϖ = = = = ( ( (, ) ) ).( ( (, ) ) ) () Where ϖ and ϖ are the mean of ω(, ) and ω (, ), respectvely. The value of ρ wll be equal to unty f the watermark s extracted wthout any error and ρ = for an error rate of 5%. 4. Expermental Results The mage whch s consdered as the watermark has a sze of whch s shown n Fgure. The watermarkng process s performed on true colour wldlfe vdeo sequence whch contans 33 frames and 5 fps wth CIF format. Generally, the accurate measurement of the mperceptblty as perceved by a human observer s a great challenge n mage/vdeo processng. The reason s that the amount and vsblty of the dstortons ntroduced by the watermarkng attacks strongly depend on the actual mage/vdeo content [8]. To measure the perceptual qualty, the Peak Sgnal-to- Nose Rato (PSNR) s calculated whch s used to estmate the qualty of the watermarked frames n comparson wth the orgnal ones. The PSNR [7] s defned as follows: PSNR max log ( ) MSE = () m m MSE = F Fˆ m = = where max max { ˆ,, } () = F m and the MSE s the mean squared error between the cover frame F and the watermarked frame ˆF.Ths parameter s declared as db. Based on [8] a PSNR value over 3 db wll be desrable. An example of watermarked frame s shown n Fgure 5. After extractng and refnng the watermark, a smlarty measurement between the extracted and reference watermark s used for obectve udgment of the extracton fdelty whch defned as: IAJIT Frst Onlne Publcaton W (, ). Wˆ (, ) NC = (3) [ W (, )] Whch s the cross-correlaton normalzed by the reference watermark energy to gve unty as the peak correlaton [5]. In the presented experment ths measurement s used to evaluate the robustness of the proposed scheme. In order to acheve a hgh vsual qualty for watermarked vdeo sequence, the modulaton ndex Q should be taken nto consderaton. In addton, for mplementng a good trade-off between the robustness and mperceptblty Q plays an mportant role. So, for ths sgnfcance, n ths experment Q s consdered as 3.5. By applyng ths value there wll be an acceptable PSNR of 36 db. Furthermore the extracted watermark has an admrable NC value of.9969 meanwhle th s consdered as.9. In all robustness evaluatons, the watermarked vdeos are analyzed usng possble watermark sgnals generated by dfferent keys; and the embedded watermark generated by the owner corresponds to the key equal to 5. Fgure 5. Watermarked frame Detector Response for In order to show the robustness of the presented scheme aganst ntentonal and unntentonal attacks dfferent knds of compresson methods lke MJEPG, MPEG-, MPEG-4 and H.64/AVC and also medan flterng and Gaussan nose, frame averagng, frame swappng, rotaton and rescalng are performed on the proposed watermarkng scheme, so the embedded watermark s retreved usng the proposed algorthm and the NC value of the recovered watermark s recorded for all knds of attacks. Compresson s one of the most basc attacks to

7 vdeo watermark. In most applcatons nvolvng storage and transmsson of dgtal vdeo, a lossy codng operaton s performed on the vdeo to reduce bt rates and ncrease effcency. For ths sgnfcance, the vdeo watermarkng scheme must be robust aganst lossy compresson. Any of aforementoned compressons have specfc method for compressng of vdeo frames. The mpact of these attacks over the watermarked vdeo s shown n Fgure 6. In order to show the robustness of the proposed algorthm aganst lossy compresson, watermarked vdeo s severely compressed wth hgh Compresson Rato (CR) for all knds of lossy compresson. As Fgure 6 shows the proposed algorthm has a good robustness aganst all of appled compresson methods. Furthermore, H.64/AVC lossy compresson whch recently s used as the most modern compresson codec n the worldwde s performed on our scheme. As Fgure 6(c) shows our approach has a very good robustness aganst ths wdely used knd of compresson, too. (c) (d) Fgure 6. Watermark robustness aganst lossy compresson; Detector response for MPEG-4 (CR=95:), MJPEG (CR=95:), (c) H.64/AVC (CR=93:), (d) MPEG- (CR=95:), respectvely. NC value. Fgure 7 shows the detector response for appled medan flterng and Gaussan nose attacks. IAJIT Frst Onlne Publcaton Fgure 7.Detector response for Gaussan nose (%), Medan flterng(3 3). Due to large amounts of data and nherent redundancy between frames, vdeo sgnals are hghly susceptble to prate attacks, ncludng frame averagng, frame droppng and generally statstcal analyss. In frame droppng, selected frames are removed from the watermarked vdeo and replaced by ther correspondng orgnal frames. Ths attack s often used as an effectve vdeo watermarkng attack, snce t leads lttle or no damage to the vdeo sgnal. For ths purpose 5% of the watermarked vdeo frames are dropped. Moreover, frame averagng s another sgnfcant vdeo watermarkng attack. It s clear that the average of multple frames wll remove the dynamc composton of the watermark. Frame averagng s the average of the current frame and ts two nearest neghbors to replace the current frame. Averagng s defned by: [ F (,) + F (,) + F (,)] F k n 3 k k k+ (, ),3,4,..., - k = = (4) Ths attack s also performed on 5% of the watermarked vdeo frames. The robustness of the presented algorthm aganst these two statstcal attacks s shown n Fgure 8. Addton of nose s another method to estmate the robustness of the watermark. Generally, addton of nose s responsble for the degradaton and dstorton of the vdeo. The watermark nformaton s also degraded by nose addton and results n dffculty n watermark extracton. So, n order to test the robustness of the proposed system % Gaussan nose wth zero mean s added to watermarked vdeo. As Fgure 7 depcts, the great acheved robustness aganst nose attack, declares the power of utlzed CDMA technque for watermarkng process. On the other hand, one of the most common manpulatons n dgtal vdeos s flterng. The extracted watermark, after applyng 3 3 medan flterng s retreved. By applyng ths flter, vdeo s sgnfcantly degraded and lots of data are lost but the extracted watermark can stll be recognzed wth hgh Fgure 8. Detector response for Frame averagng Frame droppng. For more showng the robustness of the proposed scheme another group of attacks n mage/vdeo processng doman.e. geometrc attack are tested over the presented algorthm. Rescalng and rotaton are two commonly geometrc attacks whch are wdely used n ths doman. As Fgure 9 shows these attacks have the least effects on the robustness of the proposed scheme.

8 Fgure 9. Detector response for Rescalng (-5-%), Rotaton (-.6º). 5. Conclusons In ths paper a novel watermarkng approach for mantanng the copyrght n dgtal vdeos was nvestgated. Because of embeddng the watermark n blue channel of vdeo, the delvered algorthm has a good compatblty wth HVS. Also, the securty of our scheme s guaranteed by addng four keys durng the embeddng process. Furthermore, the blnd retreval of watermark s the strength pont of the presented algorthm. So, t can be used for publc watermarkng applcatons, where the orgnal vdeo s not avalable for watermark extracton. As the expermental results showed the proposed method has a good robustness aganst dfferent knds of attacks ncludng ntentonal or unntentonal ones. References [] Al-Ha A.M., Advanced technques n multmeda watermarkng: mage, vdeo and audo applcatons, Hershey, New York,. [] Barn M., Bartoln F., Pva A., A DCT doman system for robust mage watermarkng, Sgnal Processng, vol. 66, no. 3, pp , 998. [3] Bhatnagar G., Jonathan Wu Q. M., Raman B., A new aspect n robust dgtal watermarkng, Multmeda Tools Applcaton,. [4] Chetan K.R., Raghavendra K., DWT based blnd dgtal vdeo watermarkng scheme for vdeo authentcaton, Internatonal Journal of Computer Applcaton,. [5] Chou-Tung H., Ja-Lng W., Dgtal watermarkng for vdeo, In Proc. 3th Internatonal Conf. on Dgtal Sgnal Processng (DSP 97), pp. 7-, 997. [6] Cox I.J., Mller M.L., Bloom J.A., Dgtal Watermarkng, Morgan Kaufmann, San Francsco,. [7] Cox J., Klan J., Leghton F.T., Shamoon T., Secure Spread Spectrum Watermarkng for Multmeda, IEEE Trans. Image Processng, vol. 6, no., 997. [8] Dutot T., Marqu es F., Appled sgnal processng, Sprnger, New York, 9. [9] Gonzalez R. C., Woods R. E., Dgtal Image Processng, thrd Edton, publshed by Pearson Educaton (Sngapore) Pte. Ltr., Indan Branch, 48 F.I.F. Patpargan, Delh 9, Inda, 4. [] Hartung F., Grod B., Watermarkng of uncompressed and compressed vdeo, Sgnal Processng, vol. 66, no. 3, pp. 83-3, 998. [] Hsu C.T., Wu J. L., Hdden dgtal watermarks n mages, IEEE Trans. Image Processng, vol. 8, no., pp , 999. [] Hwang M. S., Chang C. C., Hwang K. F., A watermarkng technque based on one-way hash functons, IEEE Trans. Consum Electron vol. 45, no., pp.86 94, 999. [3] Ishtaq M., Jaffar M. A., Khan M. A., Jan Z., Mrza A. M., Robust and mperceptble watermarkng of vdeo streams for low power devces, Communcaton Computer Informaton Scence, vol. 6, pp , 9. [4] langelaar G. C., Real-tme Watermarkng Technques for Compressed Vdeo Data, Ph.D thess,. [5] L., Wang R., A Vdeo Watermarkng Scheme based on 3D-DWT and Neural Network, Nnth IEEE Internatonal Symposum on Multmeda, Tachung, Tawan, December, pp. -5, 7. [6] Matsumoto M., Nshmura T., Mersenne Twster, A 63-dmensonally equlstrbuted unform pseudorandom number generator, ACM Trans. on Modelng and Computer Smulaton, vol. 8, pp. 3 3, 998. [7] Netraval A.N., Haskell B.G., Dgtal pctures: representaton, compresson, and standards, Plenum, 9ew York, 995. [8] Pettcolas F. A. P., Watermarkng schemes evaluaton, IEEE Sgnal Processng Magazne, vol. 7, no. 5, pp ,. [9] Pun C. M., A novel DFT-based dgtal watermarkng system for mages, In Proc. nternatonal, conference of sgnal processng, Venna, Austra, vol., pp 4, 6. [] Rosa L., Hgh Capacty Wavelet Watermarkng Usng CDMA Multlevel Codes, advancedsourcecode, 9 [] Sayood K., Introducton to Data Compresson, nd Edton, Morgan Kaufmann Publshers,. [] Schyndle R. G., Trkel A. Z., Osbrone C. F., A dgtal watermark, In Proc. IEEE nternatonal conference on mage processng, Austn, Texas, vol., pp. 86 9, 994. [3] Suatha S., Sathk M., Blnd Wavelet Based Watermarkng Technque for Image Authentcaton, Internatonal Arab Journal of Informaton Technology (IAJIT), vol., no. 3, 3, to be publshed. [4] Swanson M., Zhu B., Tewfk A., Multresoluton vdeo watermarkng usng perceptual models and scene segmentaton, In Proc. IAJIT Frst Onlne Publcaton

9 Internatonal Conference on Image Processng, Washngton, DC, pp , 997. [5] Wang Y., Doherty J. F., Van-dyck R. E., A wavelet based watermarkng algorthm for ownershp verfcaton of dgtal mages, IEEE Trans. Image Processng, vol., no. pp.77 88,. [6] Wang R., Hu L., u D., A Watermarkng Algorthm Based on the CABAC Entropy Codng for H.64/AVC, Journal of Computer Informaton System, vol. 7, no. 6 pp. 3-4,. [7] We Y., Hao Y., L Y., A Multpurpose Dgtal Watermarkng Algorthm of Color Image, In Proc. IEEE Internatonal Conf on Mechatroncs and Automaton, Changchun, Chna, pp. -7, 9. [8] Wnkler S., Gelasca E. D., Ebrahm T., Toward perceptual metrcs for vdeo watermark evaluaton, In Proc. SPIE, Applcatons of Dgtal Image Processng, pp , 3. [9] Wolfgang R. B., Podlchuk C. I., Delp E. J., Perceptual watermarks for dgtal mages and vdeo, In Proc. of IEEE, vol. 87, no. 7, pp. 8-6, 999. [3] a., Boncelet C. G., A multresoluton watermark for dgtal mages, In Proc IEEE nternatonal conference on mage processng,washngton, DC, USA, vol. 3, pp , 997. [3] Zhang F., Image watermarkng algorthm based on the code dvson multple access technque, Lecture Notes n Computer Scence, pp. 4, 6. Mad Masoum was born n Lahan, Iran, n 986. He s a Master student n electrcal engneerng at Azad Unversty of Qazvn. He receved hs B.Sc. degree n electrcal engneerng n 8. Hs prevously researches nclude audo watermarkng, opto-electroncs and photonc crystals. He s currently nterested n watermarkng, mage & vdeo processng, cryptography, optmzaton, and communcaton systems. Specally usng spread spectrum for makng secure the networks aganst attacks and ammers. He s presently workng at Iranan Research Organzaton for Scence and Technology (IROST) as a researcher. Shervn Amr was born n Tehran, Iran, n 966. He receved hs B.Sc., M.Sc. and Ph.D. from Iran Unversty of Scence & Technology (IUST) n communcaton systems. Now he s a Scentfc Member of electrcal engneerng department n Iranan Research Organzaton for Scence and Technology (IROST). He s supervsor of many PhD and MSc students n the felds of communcaton system and subsystems. IAJIT Frst Onlne Publcaton