A Novel Model for Encryption of Telugu Text Using Visual Cryptography Scheme G. Lakshmeeswari *, D. Rajya Lakshmi, Y. Srinivas, and G. Hima Bindu GIT, GITAM University, Visakhapatnam, Andhra Pradesh {lak_pr,rdavuluri}@yahoo.com, ysrinivasit@rediffmail.com, nadiminti19@gmail.com Abstract. This article presents a novel methodology of a visual cryptographic system based on Telugu Text. Visual Cryptography concerns with the methodology of hiding a secret message in n shares such that each individual receives one share and only the authorized person can identify the secret messages after superimposing one share upon the other. Many techniques are proposed in literature where in Rotation Visual Cryptography the underlying message of hiding is done by rotating the shares at different angles or directions. The proposed sliding scheme reveals the information by horizontal sliding of a share in downward direction by an angle of 180 0. Keywords: Visual cryptography, Encoded Telugu text, Human Visual System, Sliding Scheme. 1 Introduction An increased dependency on networks for information transmission has provided a large scope for hackers to utilize the leaks during transmission. To provide a secured transmission, senders had to increase the computational complexity which resulted in a higher degree of encryption and decryption process. But this lead to a complicated and time taking process. With the advent of Visual Cryptography this complexity is reduced to maximum extent. Many efforts have been made for secured transmission of data using different methodologies. Amongst them, visual cryptography has evolved as one of the most successful method due to its simplicity and minimized computational complexities. Visual Cryptography Schemes can decode concealed images based purely on human visual systems, without any aid from cryptographic computation. This property has given rise a wide range of encryption applications[1]. Ever since the concept has been introduced in the year 1994 by Shamir and Naor, many techniques have evolved, each of which refines a different aspect of this methodology. [2] Naor and Shamir analyzed (k, n)-threshold visual cryptography schemes. In these schemes, a subset is qualified if and only if it consists of at least k participants. Most work concerning this subject focuses on two aspects, either the pixel expansion, i.e. the number of sub-pixels which is needed on the different levels to represent a N. Meghanathan et al. (Eds.): Advances in Computing & Inform. Technology, AISC 177, pp. 511 520. springerlink.com Springer-Verlag Berlin Heidelberg 2013
512 G. Lakshmeeswari et al. white or a black pixel, or the contrast, i.e. the difference of sub-pixels representing a white or a black pixel. As a further generalization, the existence of a secret image can be concealed by displaying a different image on each transparency. Naor and Shamir [2] solved this problem for the (2, 2)-threshold scheme. By stacking the transparencies of each participant one upon another, a secret image is recovered, and this is in fact the only way to recover it[3]. The optimality of VCS is determined mostly by its pixel expansion m and the relative contrast. Pixel expansion m represents the loss in resolution from the original image to the decoded one. Therefore m needs to be as small as possible. The theme of Rotation Visual Cryptography Schemes is to reveal the underlying message by rotation of a share at different angles[4]. Rotation schemes facilitated storage of multiple secrets in a single share. Many methods are available in literature [1,3,5], which are mostly focused in hiding the text in the form of English language, but very little work is projected towards the usage of Telugu text for the purpose of secret transmission. Among the south central languages, Telugu is mostly preferred language, and it is being used in the government sectors as well as private sectors of Andhra Pradesh, hence in this paper, we propose a model based on Telugu Text. The Telugu coding scheme helps to minimize the bits required for hiding each character along with its diacritic and compound. We can hide a larger message with minimal effort[5]. This methodology using the (k,n) scheme, which can be very useful for secret transmission of messages in areas such as Banks, Home Department, Intelligence and other public services for the state of Andhra Pradesh, where Telugu language is commonly used. We can either transmit a continuous message or a fragmented password using the proposed system. The next section of the paper deals with the encryption model, section-3 deals with the decryption methodology, section-4 presents the proposed methodology, section-5 describes the experimental results of the proposed system and finally the conclusions are given in section-6. 2 Encryption Process Step 1: Convert the Telugu text input into its equalent code[5]. Step 2: Select k number of shares randomly from a total of n shares, where k+1<n. The value of k and n are dynamic. Step 3: Split the coded message obtained from step 1 in to k slices and generate k shares, where each share contains one slice of the coded message. The random selection of shares in step 2 assures that the sequence of shares in which the information would be stored would not be the same always. A single share would contain only one portion of information. 3 The Process Adopted for Decryption Step 1: Retrieve the k out of n shares which contain the embedded message with inverse random process.
A Novel Model for Encryption of Telugu Text Using Visual Cryptography Scheme 513 Step 2: From the remaining n-k shares select a share which has to be slided over the selected k shares to reveal the information. Let the selected share be x. Step 3: Slide the share x on each of the k shares horizontally downwards to reveal the message in each share sequentially. 4 Proposed Scheme We propose the technique of inter-slicing in order to store text in a share. The number of slices is dynamic depending upon the value of k. For example consider 4 out of 7 shares to contain the secret message (k=4 and n=7). Let the numbers of the selected share numbers be 2,3,5 and 7. Each of the k shares are divided into k slices as shown in Figure 1. Slice-1 Slice-2 Slice-3 Slice-4 Share -2 Share -3 Share -5 Share -7 Fig. 1. Inter-sliced arrangement of shares The shaded regions of the shares contain the embedded text. All shares must be of equal size. For example consider the Telugu text. The equalent encoded string for the given text is 0002401000 1A01E84110 0016012801 120021011F [5]. Embed 10 characters each of this code in 4 shares(2,3,5 and 7) as shown in Figure 2. 0002401000 1A01E84110 0016012801 120021011F Share -2 Share -3 Share -5 Share -7 Fig. 2. Images with secret message The original image would contain the complete code generated at step1 on the sender side and would appear as in Figure 3.
514 G. Lakshmeeswari et al. 0002401000 1A01E84110 0016012801 120021011F Fig. 3. Original Image with secret message 5 Experimental Results The system is implemented using matlab. It considers the image containing the original encrypted message as its base image. To make the proposed system dynamic the values of k and n are not taken as constants instead are given as input on execution of the code. Resultant shares after superimposing the share x on each and every share to reveal the underlying text is shown in Figure 4. Share -2 Share -3 Share -5 Share -7 Fig. 4. Shares with disclosed information
A Novel Model for Encryption of Telugu Text Using Visual Cryptography Scheme 515 The final share after combining the information of each share would appear as shown in figure 5. Fig. 5. Final share with complete secret message The final Telugu text is obtained on decrypting the information n the final share[1]. Another application of the same concept can be demonstrated as follows: The Figure 6 shows an image with a message in it. Fig. 6. Original Image with secret message Apply the horizontal slicing technique and put the information in 5 shares, which are selected randomly. The shares would appear as shown in figures 7, 8, 9, 10 and 11.
516 G. Lakshmeeswari et al. Fig. 7. Slice1 of the Original Image Fig. 8. Slice2 of the Original Image Fig. 9. Slice3 of the Original Image Fig. 10. Slice4 of the Original Image
A Novel Model for Encryption of Telugu Text Using Visual Cryptography Scheme 517 Fig. 11. Slice5 of the Original Image Add noise to the shares, and use the share x to disclose the content in the shares as specified in the decryption procedure. Resultant shares after superimposing the share x on each and every share to reveal the underlying text is shown in Figures 12, 13, 14, 15 and 16. Fig. 12. Information of Slice1 disclosed from the first share Fig. 13. Information of slice2 disclosed from the second share
518 G. Lakshmeeswari et al. Fig. 14. Information of slice3 disclosed from the third share Fig. 15. Information of slice4 disclosed from the fourth share Fig. 16. Information of slice5 disclosed from the fifth share The final share on combining all the above 5 shares is shown in figure 17. Fig. 17. Final share with complete disclosed message
A Novel Model for Encryption of Telugu Text Using Visual Cryptography Scheme 519 6 Conclusion The proposed scheme sliding Technique in Visual Cryptography is designed for encrypting a message or a short length password by slicing into k parts and storing each part in a share based on Telugu character code. The decryption of the original message is possible only with the assistance of a share x which has to be commonly stacked on all the shares with secret message. The resultant output is combined into a single share to disclose the complete secret text. The proposed methodology not only works for the experimented Telugu language encryptions, but can be used as a generalized concept applicable for transmitting any secret information of any language in the world. It can also be used for password transmission, where each share can be sent to a person and on recombining we get back the complete password. The probability of guessing the password is much less when compared to the other methodologies as no single alphabet is completely displayed in any of the share. References 1. Dinesh Reddy, B., Valli Kumari, V., Raju, K.V.S.V.N., Prassanna Raju, Y.H.: Rotation Visual Cryptography. Using Basic (2, 2) Scheme. IJCS & CT 3(2) (January 2011) (ISSN 0974-3375) 2. Naor, M., Shamir, A.: Visual Cryptography. In: De Santis, A. (ed.) EUROCRYPT 1994. LNCS, vol. 950, pp. 1 12. Springer, Heidelberg (1995) 3. Tsai, P.-F., Wang, M.-S.: An (3, 3)-Visual Secret Sharing Scheme for Handling Three Secret Data 4. Hsu, H.C., Chen, T.S., Lin, Y.H.: The ringed shadow image technology of Visual Cryptography by applying diverse rotating angles to hide the secret sharing. Networking, Sensing and Control 2, 996 1001 (2004) 5. Lakshmeeswari, G., Rajya Lakshmi, D., Lalitha Bhaskari, D.: Extended Encoding of Telugu Text for Hiding Compatibility. IJCA 30(5) (September 2011) 6. Weir, J., Yan, W.Q.: Sharing Multiple Secrets Using Visual Cryptography. In: IEEE International Symposium on Circuits and Systems, ISCAS 2009 (2009), doi: 10.1109/ISCAS.2009.5117797 7. Ge, L., Tang, S.: Sharing Multi-Secret Based on Circle Properties. In: 2008 International Conference on Computational Intelligence and Security (2008) 8. Ateniese, G., Blundo, C., Santis, A.D., Stinson, D.R.: Extended capabilities for Visual Cryptography. Theoretical Computer Science 250(1-2), 143 161 (2001) 9. Yu, B., Xu, X., Fang, L.: Multi-Secret sharing threshold Visual Cryptography Scheme. International Conference on Computational Intelligence and Security (2007) 10. Lakshmeeswari, G., Rajya Lakshmi, D., Srinivas, Y.: A New Encoding Scheme of Telugu Text for Information Hiding. International Journal of Computational Intelligence Techniques 2(1), 26 28 (2011) ISSN: 0976 20466 & E-ISSN: 0976 0474 11. Wu, H., Chang, C.C.: Sharing Visual Multiple Secrets using Circle Shares. Computer Standards & Interfaces 28, 123 135 (2005)
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