Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering            Research and Applications ...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering            Research and Applications ...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering             Research and Applications...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering            Research and Applications ...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering            Research and Applications ...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering                 Research and Applicat...
Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering            Research and Applications ...
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  1. 1. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096 An Improved (8, 8) Colour Visual Cryptography Scheme Using Floyd Error Diffusion Anantha Kumar Kondra*, Smt. U. V. Ratna Kumari** *(Department of Electronics and Communications, University College of Engineering, JNTUK, Kakinada) ** (Department of Electronics and Communications, University College of Engineering, JNTUK, Kakinada)ABSTRACT Visual cryptography (VC) is the simplest on cryptography where n images are encoded in aand a perfect way to provide the security to the way that only the human visual system can decryptconfidential information. VC in color images the hidden message without any cryptographicencrypts a color secret message into n color computations when all shares are stacked together.halftone image shares. In earlier VC schemes in Visual cryptography is a very secure and unique wayorder to recover the secret image, one has to to protect secrets. Visual cryptography has twocollect a set of qualified shares and print them important features. The first feature is its perfectonto transparencies. However this VC scheme secrecy, and the second feature is its decryptionshows good results for black and white or gray method which requires neither complex decryptionscale images, but not with the Color Images due to algorithms nor the aid of computers. Consider aits color structure. Using the concept of visual binary secret image B and a set of n participantsinformation pixel (VIP) synchronization and sharing B. A k out of n visual secret sharing schemeerror diffusion to attain a color visual encrypts B into n transparencies (called shares)cryptography encryption method that produces which are distributed to the n participants one by onemeaningful color shares with high visual quality. in such a way that only when k or more shares areNow a days the biggest challenge is to provide the stacked together can the participants see B by theirsecurity in order to protect the confidential visual system; while any group of less than k sharesinformation from Security threats. In this paper obtains nothing about B.we introduce a new solution which helps to Visual cryptography proposed by Naor andidentify the error in the shares and to verify the Shamir [1] discloses the possibility for using humanAuthentication. Using CRC algorithm and Color visual ability to perform the decryption process.VC scheme and error diffusion method generates Neither computational devices nor cryptographicthe quality shares and diffuses the errors and knowledge is required for the decryption process.provides the security from threats like With such an interesting characteristic that theModification ,Fabrication ,Interception and shows decryption process is by the human visual systemthe good results compared to the previous only, instead of any computational device, visualschemes and increases the security level. cryptography attracts much attention from researchers. In particular, it is much useful inKeywords - Colour Meaningful Shares, Cyclic situations where computing devices are not availableRedundancy Check, Binary Information, Visual or not possible to use. Naor and Shamir [1] firstCryptography Scheme, Error Diffusion, Secret presented k out of n visual secret sharing schemes,Sharing. which ensure that the secret is concealed from groups of less than k participants, while it can beI. INTRODUCTION seen by groups of at least k participants when they Visual Cryptography is a perfect way to stack their shares altogether. Since this pioneerprovide the security for the confidential information. research, many theoretical results on theInitially it was introduced by Kafri and Keren in construction or contrast (the relative difference1987 [1] where binary pictures were considered in between the reconstructed white and black pixels inthe encryption of pictures by two random grids. The the superimposed image) of visual secret sharingencryption of a secret picture or shape into two schemes for binary images have been proposed inrandom grids which are printed on transparencies the literature [4, 5, 6, 7]. Some studies [8, 9, 10]such that the areas containing the secret information focused on the practical realization of visualin the two grids are inter-correlated. Similar idea that cryptographic schemes for gray-level or colorthe decryption needs only human visual ability, Naor images.and Shamir initially used the terminology, visual A new method called extended visualcryptography[1], which is defined as the study of cryptography (EVC) was developed by Ateniese[2].secret (crypto) writing (graphy) and the study of In which shares contains not only the secretmathematical techniques related to aspects of information but are also some meaningful images.information security. Visual cryptography is based Hyper graph colorings are used in constructing 1090 | P a g e
  2. 2. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096meaningful binary shares. Since hyper graph securable and meaningful shares and is free of thecolorings are constructed by random distributed previously mentioned limitations. The method ispixels, the resultant binary shares contain strong simple and efficient. It relies on two fundamentalwhite noise leading to inadequate results. Wang principles used in the generation of shares, namely,generalized the Ateniese’s scheme using error diffusion and VIP synchronization. Errorconcatenation of basis matrices and the extended diffusion is a simple and efficient algorithm formatrices collection to achieve more simpler image halftone generation.deviation of basis matrices[12]. Nakajima extended The quantization error at each pixel isEVC to a scheme with natural grayscale images to filtered and fed to future inputs. The error filter isimprove the image quality[13]. Zhou et al. used half designed in a way that the low frequency differencestoning methods to produce good quality halftone between the input and output images are minimizedshares in VC[14]. Fu generated halftone shares that and consequently it produces pleasing halftonecarry visual information by using VC and images to human vision. Synchronization of thewatermarking methods[4]. Myodo proposed a VIPs across the color channels improves visualmethod to generate meaningful halftone images contrast of shares. In color VC schemes, due tousing threshold arrays. Wang et. al. produced random matrix permutation the colors of encryptedhalftone shares showing meaningful images by using pixels and the contrast can be degraded. In grayscaleerror diffusion techniques. This scheme generates VC schemes, it does not affect the visual quality;more pleasing halftone shares owing to errors however, in color schemes, independent execution ofdiffused to neighbor pixels. random matrix permutation for each color channel Visual secret sharing for color images was can cause color distortion by placing VIPs at randomintroduced by Naor and Shamir[1] based upon cover positions in sub pixels which finally degrades thesemi groups. Rijimen presented a 2-out-of-2 VC visual quality. VIP synchronization prevents thescheme by applying the idea of color mixture. color and contrast of original images fromStacking two transparencies with different colors degradation even with matrix permutation.rises a third mixed color. Hou shares by applying The rest of this paper is organized ashalftone methods and color decomposition. Hou follows: Section II provides previous methods aboutdecomposed the secret color image into three (Red, standard VC, the extended VC scheme, and theGreen and Blue) halftone images. He then devised fundamentals of halftone techniques for easythree colored 2-out-of-2 VC schemes which follow understanding of the proposed VC method. Sectionthe subtractive model for color mixture by exploiting III describes the proposed encryption methodsome of the existing binary VC schemes. All of the including the VC matrix ,CRC bits and Binary valuepreviously mentioned methods, however, discuss adding method and a halftone process to generatecolor schemes for 2-out-of-2 or 2-out-of-2 secret final shares. Section IV shows experimental resultssharing where the reconstructed colors are of the new method and comparisons with previousinterpreted by some mixing rules of colors. The approaches to prove its effectiveness. In Section V,general construction of a k-out-of-n VC scheme for we discuss topics about image quality, security andthe color shares was first introduced by Verheul[16]. advantages of our scheme, and concluded this paperHe proposed a k-out-of-n VC scheme for a -colored .image with pixel expansion q k-1, where devised II. PREVIOUS WORKschemes for color q>=c Koga and Yamamoto used In this section, we give a brief descriptiona lattice structure to define the mixing result of of VC, extended VC, color models in VC and anarbitrary two colors. All of these VC schemes for error diffusion quantization.color images produce random pattern shares. Even 2.1 Basic Visual Cryptographythough the decrypted messages show messages with Generally (k, n)-VC scheme encrypts avarious colors, it is more desirable to generate secret message into shares to be distributed to nmeaningful shares which are less suspicious of participants. Each share shows noise-like randomencryption. Other approaches to color VC black and white patterns and does not reveal anyattempting to generate meaningful color shares information of the secret image by itself. In a k -out-include. Ching-Nung Yand and Tse-Shih Chen n of scheme, access to more than k shares allows oneproposed a VCS for color images based upon an to recover the secret image by stacking themadditive color mixing method[18]. In this scheme, together, but access to less than k shares is noteach pixel is expanded by a factor of three. sufficient for decryption. A black and white (k,n)- This scheme suffers from pixel expansion VC scheme consists of two collections of nxmproblem in the size of encrypted shares. In order to binary matrices S0 and S1 , having elements denotedreduce the size of encrypted shares Inkoo Kang by 1 for a black pixel and 0 for a white pixel. Toproposed the VC for color image using visual encrypt a white (black) pixel, a dealer randomlyinformation pixel (VIP) synchronization with error chooses one of the matrices in S0(S1) and distributesdiffusion technique[11]. This paper introduces a new its rows to the n participants. More precisely, acolor VC encryption method which leads to produce 1091 | P a g e
  3. 3. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096formal definition of the black and white (k, n) -VC Where 𝑥(𝑝,𝑞) = 𝑥 𝑖 𝑝,𝑞 1, 𝑥 𝑖 𝑝,𝑞 2 , 𝑥 𝑖 𝑝,𝑞 3 є {0,1}3 𝑖scheme is given next. denotes the binary vector at the ith bit-level with i=1 The security condition ensures that any less denoting the most significant bit.than k shares cannot get any information of thesecret image other than the size of the secret image. 2.4 Error DiffusionBased upon the principle of VC, extended VC has Error diffusion is a simple yet efficient waybeen proposed whose shares take meaningful images to halftone a grayscale image. The quantization errorrather than random noise-like patterns to avoid at each pixel is filtered and fed into a set of futuresuspicion. inputs. Fig. 3 shows a binary error diffusion diagram where f(m, n) represents the pixel at (m, n) position2.2 Extended Color Visual Cryptography of the input image. d(m, n) is the sum of the input Generally, a (n, n ) –EVC scheme takes a pixel value and the diffused errors, g(m, n) is thesecret image and n original images as input and output quantized pixel value. Error diffusion consistsproduces n encrypted shares with approximation of of two main components.original images that satisfy the following three The first component is the thresholdingconditions: block where the output g(m ,n) is given by• all the shares are required to recover the secret 1, 𝑖𝑓 𝑑 𝑚, 𝑛 ≥ 𝑡(𝑚, 𝑛)image; 𝑔 𝑚, 𝑛 = 0, 𝑜𝑡𝑕𝑒𝑟𝑤𝑖𝑠𝑒• any less than shares cannot obtain any information The threshold t(m, n) can be positionof the secret image; dependant. The second component is the error filter• all the shares are meaningful images; encrypted h(k, l) where the input e(n, m) is the differenceshares and the recovered secret image are colored. between d(m ,n) and g(n ,m). Finally, we compute Denote Scc1,c2,....cn as the collection of d(m, n)matrices from which the dealer chooses a matrix toencrypt, where C,C1,........Cn є{0,1}. for i=1,.....n, Ci 𝑑 𝑚, 𝑛 = 𝑓 𝑚, 𝑛 − 𝑕 𝑘, 𝑙 𝑒(𝑚 − 𝑘, 𝑛 − 𝑙)is the bit of the pixel on the ith original image and is 𝑘,𝑙the bit of the secret message. For a black and c Where 𝑕 𝑘, 𝑙 є 𝐻 , H is a2-D filter. Awhite(k ,n) -EVC scheme, we have to construct 2^n widely used filter is the error weight originallypairs of such collection (S0c1,c2,....cn , S1c1,c2,....cn ) , one proposed by Floyd and Steinberg 1 ∗ 7for each possible combination of white and black 𝑕 𝑘, 𝑙 = ×pixels in the n original images. 16 3 5 12.3 Color Models There are two models namely additive andsubtractive color models, which are widely used todescribe the constitutions of colors. In the additivecolor model, the three primary colors are red, green,and blue (RGB), with desired colors being obtainedby mixing different RGB channels. By controlling Fig 1 Block Diagram Of Floyd Error Diffusionthe intensity of red, green, blue channels, we can Techniquemodulate the amount of red, green, blue in thecompound light. The more the colors are mixed, the where * is the current processing pixel. Themore the brightness of the light. When mixing all recursive structure of the block diagram indicatesred, green and blue channels with equal intensity, that the quantization error e(m, n) depends upon notwhite color will result. The computer screen is a only the current input and output but also the entiregood example of the additive color model. In the past history. The error filter is designed in such asubtractive model, color is represented by applying way that the low frequency difference between thethe combination of colored lights reflected from the input and output image is minimized. The error thatsurface of an object. The more the pigments are is diffused away by the error filter is high frequencyadded, the lower the intensity of the light is and, or “blue noise.” These features of error diffusionthus, the darker the light is. This is the reason it is produce halftone images that are pleasant to humancalled the subtractive model. Red, Green, and Blue eyes with high visual quality.are the three primitive colors of pigment whichcannot be composed from other colors. The colorprinter is a typical application of the subtractive III. ENCRYPTION OF SECRET IMAGE WITHmodel and, hence, the VC model of Naor and COLOR IMAGES USING VC MATRICES (S0,S1)Shamir is also of such kind. the color of the pixel AND ERROR DIFFUSIONX(p,q) can be expressed in a binary form as In this section, we describe the encryption 𝑋(𝑝,𝑞 ) = 8 𝑥(𝑝,𝑞) 28−𝑖 𝑖 method for color meaningful shares with a VIP 𝑖=1 synchronization and error diffusion. First, we 1092 | P a g e
  4. 4. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096describe the VC matrix derivation method for VIP є {S0C1...Cn [i], S1C1...Cn 3synchronization from a set of standard VC matrices. [i]}We then introduce an error diffusion process to where 1≤ i ≤ n; p= p. m-x (mx-1);produce the final shares. The halftone process is q= q. m-y (my-1) , m= m-x. m-yindependently applied to each Red (R), Green (G), m-x, m-y are non negative integers decide the aspectand Blue (B) color channel so each has only one bit ratio encrypted color shares. the matrix Sc c1...cn [i]per pixel to reveal colors of original images. A secret shows the ith row of the matrix Sc c1...cn. X is themessage is half toned ahead of the encryption stage. image pixel and Xi (p,q) shows the corresponding pixel on the color channels position at (p, q) and the3.1 Visual Pixel Synchronization sub pixels takes one of the rows in Soc1...cn or S1c1...cn VIPs are pixels on the encrypted shares that according to the bit value of corresponding messagehave color values of the original images, which pixel color channel.make the encrypted shares meaningful. In each ofthe m sub pixels of the encrypted share, there are ƛ 3.3 Share generation Via Error Diffusionnumber of VIPs, denoted as Ci and the remaining Using matrices S0,S1 processed across the(m-ƛ) pixels deliver the message information of the all color channels after half toning algorithm issecret message image. Here each sub pixel m carries applied to generate the final encrypted shares.visual information as well as message information,while other methods extra pixels are needed inaddition to the pixel expansion to producemeaningful shares. Since each VIP is placed at thesame bit position in sub pixels across the three colorchannels, VIP represents accurate colors of theoriginal image Fig. 3.3 Block Diagram to generate half toned Images3.2 Flow Chart For Encryption of Secret Image Fig. 3(a) shows a binary error diffusion diagram designed for our scheme. To produce the i th halftone share, each of the three color layers are fed into the input. The process of generating halftone shares via error diffusion is similar to that shown in Fig.1 except that Fi.j(m, n) is a (m, n) i th pixel on the input channel j(1≤ i ≤ n, 1≤ j ≤ 3) of ith share. Fig. 3(b) depicts this process. 1s and 0s in black are message information pixels that should not be modified and those are in red are VIPs that are already defined by the error diffusion. The Ci are also VIPs whose values are to be decided by referring the corresponding pixel values of original images and errors from neighboring pixels when the error filter window comes. Non Ci elements, however, still affect di,j(m, n) and the quantization error ei,j(m, n) when they are calculated in theFig 2 Flow Chart for Encryption of Secret Image filter window. The non elements may increase quantization errors added to the shares, but in turn, The Secret image and Color images are these errors are diffused away to neighboring pixels.processed using half toning method and the leads to The visual quality of shares via error diffusion canproduce the half toned images. be improved through edge enhancement methods. So the remedy for the apparent blurring of edges caused X ( p ,q )   x R , xG ,xB   ( p ,q ) ( p ,q ) ( p ,q )   ,1 0  by the error diffusion algorithm is to apply an edge 3   Here p, q lies in between ((1,k1),(1,k2)) sharpening filter prior to half toning such thatrespectively. here X that represents the pixel of the Xisharp [n]=X[n]-β(ψ[n]*X[n])secrete image and p,q represents the location of thepixel. The 3 binary bits xR(p,q) , xG(p,q), xB(p,q) which Where X[n] stands for the original image,represents the values for Red ,Green, Blue color ψ[n] is a digital Laplacian filter, * denoteschannels respectively. each message pixel encrypted convolution and β is a scalar constant (β >0)and expanded to sub pixel of length m and the regulating the amount of sharpening with larger βencoded share i as leading to a sharper image Xisharp Consequently, error diffusion produces high quality halftoneX(p1 , q1) i =[xR (p1 , q1) , xG( p1 , q1) , xB(p1 ,q1)] i 1093 | P a g e
  5. 5. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096images. 3.5 CRC checking and Authentication Checking at the Receivers side At the receivers side, all the shares are collected from the communication channel. through the secured channel the VC matrices S0,S1,key and the checker value will be received from the source. once the shares are collected at the receivers end it will processed in a reverse process of encryption . the binary information and crc bits were extracted first from the shares. using the key the crc bits were processed and the result which is equals to check value. if the result not equal to the check value that shows some error in the share and retransmission of the share is needed.Fig. 3 (a) Block diagram of error diffusion withshare encryption.(b)Visualization of error diffusion with VIP3.4 Adding binary information and CRC bits The information will send from the sourceto destination via communication channel. in thatprocess it might be chance of attack of the intruderwhether he can change the information or misguidethe people at the receivers side. so in order to protectfrom the security threats and detect the errors and toidentify the shares to retransmit the shares from thesource we added binary information which tells the Fig 3.5 Color share values with binarysecret information and to detect the error and for the information(0001) and CRC bits for Rauthentication purpose we added CRC bits to the plane..similarly G and B.shares and transmitted to the destination through thecommunication channel.Fig. 3.4 Block Diagram for Encryption process andadding CRC bits A represents the Secret image and Brepresents the Color Shares C shows the half tonedResultants. After generating the shares BinaryInformation and CRC bits added to the shares, whichare extracted first and verified with key at receiverside. Fig 3.6 Flow Chart for CRC , Authentication checking at the receivers side. 1094 | P a g e
  6. 6. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096 If all the shares are verified with CRC checking key 4.3 Reconstructed Secret Image from meaning full and then test for the Authentication checking. in Shares each share the added binary information which represents by 8 bits, in that last 4 bits shows the part information that is order of the part of secret image. which helps to reconstruct the secret image from the shares at the destination side. And the first 4bits represents the authentication check bits. these check bits are collected from the shares according to the binary information in order and processed with the CRC key .if the result of the process and checker value is equal then Authentication Verified unless it shows that Authentication failed that means an Fig:4.3 Reconstructed Secret image(8,8)VCS attack of Intruder on the information. TABLE I IV. SIMULATION RESULTS COMPARISON OF (4,4) AND (8,8) COLOUR VC SCHEME This section presents the information Images (4,4)VCS (8,8)VCS regarding input secret image for encryption, 1st Image(PSNR) 12.0650 dB 12.0650 dB meaningful shares or half toned shares used for encryption process and reconstructed image. 2nd Image(PSNR) 12.5358 dB 12.5358 dB 3rd Image(PSNR) 13.7786 dB 13.7786 dB 4.1 Original Secret Image for (n out of n) VCS 4th Image(PSNR) 15.7007 dB 15.7007 dB 5th Image(PSNR) - 12.0378 dB 6th Image(PSNR) - 12.5083 dB 7th Image(PSNR) - 12.0778 dB 8th Image(PSNR) - 12.5486 dB Fig:4.1 Secret Image Requirement for Meaningful Meaningful Encryption Shares Shares 4.2 Colour Images for (n out of n) VCS for No. of Shares Required All All Encryption for Decryption Reconstructed Image 23.5705dB 25.4563dB PSNR Mean Error 6.0383e+005 1.7202e+006 Quality & Clarity(by Good High vision)1 2 3 4 Security High Very High Computation High Very High Complexity Hard ware High High Implementation 5 6 7 8 Fig: 4.1, The actual secret image which (a) represents the confidential information that we want to send in secure way to the destination. Fig: 4.2 (a), The coloured images which plays the key role for the secure transmission of information. Fig: 4.3 (b), After applying to half toning the generated shares for the encryption of secret information . 1 2 3 4 Fig : 4.3, After the Half toning process the generated shares encrypted using VC matrices (S0,S1). that means the secret information is embedded into the shares which are called as meaning full shares. At the receiver side all the shares are collected and using the VC matrices S0,S1 5 6 7 8 the information is extracted from the meaning full (b) shares. and thus forms the reconstructed secret Fig:4.2 (a) Actual Colour Images for Encryption Of image which showed in figure 4.3. from the figure 4 SI which shows that how binary values and crc bits (b) After Encryption of SI the Meaningful Shares embedded into color channels and at receiver side 1095 | P a g e
  7. 7. Anantha Kumar Kondra, Smt. U. V. Ratna Kumari / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1090-1096the similar way the the information extracted first [7] W. Q. Y, J. Duo, and M. Kankanhalli,and checked with crc key. if the result checked “Visual cryptography for print and scansuccessfully that means no error and identified the applications,” in Proc. IEEE Int. Symp.part of Secret image according the binary value. Circuits Syst., 2004, pp. 572–575.after that header bits (checker, from Fig:3.5) [8] C. Blundo, P. D’Arco, A. D. S. , and D. R.collected from the all shares and verify with CRC Stinson, “Contrast optimal threshold visualkey ,if it shows that success Authentication proved cryptography schemes,” SIAM J. Discreteunless need to retransmit the shares from the source. Math., vol. 16, no. 2, pp. 224–261, 2003.The quality of the reconstructed image can be [9] L. A. MacPherson, “Gray level visualmeasured in different ways. Here the following table cryptography for general access structrue,”presents some quality measuring parameters using M. Eng. thesis, Univ. Waterloo, Ontario,PSNR. Canada, 2000. [10] C. Blundo, A. D. Santis, and M. Naor,V. CONCLUSION “Visual cryptography for grey level This paper develops an encryption method images,” Inf. Process. Lett., vol. 75, no. 6,to construct color EVC scheme with VIP pp. 255–259, 2000.synchronization and error diffusion for visual quality [11] Inkoo Kang, Gonnzoalo R..Arce, Heun-Kyuimprovement. VIPs synchronize the positions of Lee “Color Extened Visual Cryptographypixels that carry visual information of original Using Error Diffusion” IEEE Trans,images across the color channels so as to retain the Image Process., vol. 20 No.1, pp.132-original pixel values the same before and after 145,2011.encryption. Error diffusion is used to construct the [12] D.s Wang, F.Yi, and X.Li,”On generalshares such that the noise introduced by the preset construction for extended visualpixels is diffused away to neighbors when encrypted cryptography schemes” Pattern Recognit.,shares are generated. It is obvious that there is a pp.3071-3082,2009.tradeoff between contrast of encryption shares and [13] M.Nakajima and Y. Yamaguchi, ”Extendedthe decryption share; however, we can recognize the visual cryptography for natural images ,” Jcolorful secret messages having even low contrast. WSCG vol. 10, no. 2, 2002.Either VIP synchronization or error diffusion can be [14] Z. Zhou, G. R Arce, and G. D. Crescenzo,broadly used in many VC schemes for color images. “ Halftone visual cryptography,” IEEEIn this paper has solved for the cryptanalysis which Trans . Image Process., vol 18, no. 8,pp.is helpful in security analysis of confidential 2441-2453,Aug.2006.information. As future work increase the no of share [15] C. N Yang, “ A note on efficient colorand range of CRC which leads to enhance the visual encryption,” J. Inf. Sci.Eng., vol. 18,security level of the confidential information. pp.367-372,2002. [16] E. R.Verheul and H.C.A vanTilborg,REFERENCES ”Construction and properties of k out of n [1] M. Naor and A. Shamir, “Visual visual secret sharing schemes, ” Des. Codes cryptography,” in Proc. EUROCRYPT , Cryptogr., vol. 11, no. 2, pp. 179-196, May 1994, pp. 1–12. 1997. [2] G. Ateniese, C. Blundo, A. D. Santis, and [17] H. Koga and H. Yamamoto, “ Proposal of a D. R. Stinson, “Visual cryptography for lattice based visual secret sharing scheme general access structures,” Inf. Comput., for color and gray –scale images, ” IEICE vol. 129, no. 2, pp. 86–106, 1996. Trans. Fundamentals, vol.E81-A, no. 06, [3] A. Houmansadr and S. Ghaemmaghami, “A pp. 1262-1269, Jun. 1998. novel video watermarking method using [18] C. N Yang and T.S . Chen, "Visual visual cryptography,” in Proc. IEEE Int. Cryptography .Scheme based on additive Conf. Eng. Intell. Syst., 2006, pp. 1–5. color mixing," Pattern Recognit., vol. 41, [4] M. S. Fu and O. C. Au, “Joint visual pp. 3114-3129,2008. cryptography and watermarking,” in Proc. IEEE Int. Conf. Multimedia Expo, 2004, pp. 975–978. [5] C. S. Hsu and Y. C. Hou, “Copyright protection scheme for digital images using visual cryptography and sampling methods,” Opt. Eng., vol. 44, p. 077003, 2005. [6] M. Naor and B. Pinkas, “Visual authentication and identification,” Adv. Cryptol., vol. 1294, pp. 322–336, 1997. 1096 | P a g e

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