IJRIT International Journal of Research in Information Technology, Volume 2, Issue 6, June 2014, Pg: 360-363

International Journal of Research in Information Technology (IJRIT)

www.ijrit.com

ISSN 2001-5569

An Innovative Approach for Information Sharing Through Shared Key Cryptography Arya Apoorva1, Mr. Parikshit Singla2 1

2

Scholar, Department of Computer Science & Engineering, DVIET, Karnal, Haryana, India Assistant Professor, Department of Computer Science & Engineering, DVIET, Karnal, Haryana, India

Abstract Many files are needed to be transmitted over internet in today’s scenario due to various important purposes. So it is an important issue to protect these files. To protect data efficient cryptographic method are there but everything depends on the protection of encryption key which leads to single point failure. Cryptography is of two types : symmetric key and public key cryptography. The public key cryptography is that in which encryption and decryption is done with different key. The encryption is done by sender using the public key of the receiver and the decryption is done by the receiver by using it own private key. The public key cryptography doesn’t achieve all the goals of security. It will only achieve the one goal out of four main goals of security i.e Integrity goal rest of the goals like confidentiality, non- repudiation, authentication are not achieved. The symmetric key cryptography is also known by name i.e shared cryptography. In shared key cryptography same key is used for encryption and decryption of the data Shared cryptography becomes more popular in order to overcome this drawback. Here we are suggesting a novel secret sharing scheme which employs simple masking method, which is performed by simple ANDing for share generation and reconstruction can be done by performing simple ORing the qualified set of legitimate shares. Not only that, it leads to added protection to the secret because each share contains partial secret information.

Keywords: Cryptography, Encryption, Decryption, Non-Repudiation, Key, Integrity, Confidential, Authentication, cryptology.

1. Introduction Cryptography[9] is the science of writing in secret code and is an ancient art; the first documented use of cryptography in writing dates back to circa 1900 B.C. when an Egyptian scribe used non-standard hieroglyphs in an inscription. Some experts argue that cryptography appeared spontaneously sometime after writing was invented, with applications ranging from diplomatic missives to war-time battle plans. It is no surprise, then, that new forms of cryptography came soon after the widespread development of computer communications. In data and telecommunications, cryptography is necessary when communicating over any untrusted medium, which includes just about any network, particularly the Internet. Cryptography is the art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. The message can be deciphered (or decrypted) into plain text only by those who possess a secret key. Encrypted messages sometimes can be broken by cryptanalysis which is also called code-breaking, although modern techniques are virtually unbreakable. Electronic security is becoming increasingly important as the Internet and other forms of electronic communication become more prevalent. Pretty Good Privacy is one of the most popular cryptography systems used on the Internet because it's effective and free. Cryptography is used

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to protect e-mail messages, corporate data and credit card information etc. Cryptography, then, not only protects data from theft or alteration, but can also be used for user authentication. There are, in general, three types of cryptographic schemes typically used to accomplish these goals: secret key (or symmetric) cryptography, public-key (or asymmetric) cryptography, and hash functions, each of which is described below. In all cases, the initial unencrypted data is referred to as plaintext. It is encrypted into ciphertext, which will in turn (usually) be decrypted into usable plaintext. In many of the descriptions below, two communicating parties will be referred to as Alice and Bob; this is the common nomenclature in the crypto field and literature to make it easier to identify the communicating parties. If there is a third or fourth party to the communication, they will be referred to as Carol and Dave. Mallory is a malicious party, Eve is an eavesdropper, and Trent is a trusted third party.

2. Types of Cryptographic Algorithms There are several ways of classifying cryptographic algorithms. For purposes of this paper, they will be categorized based on the number of keys that are employed for encryption and decryption, and further defined by their application and use. The three types of algorithms that will be discussed are (Figure 1)[32]: •

Secret Key Cryptography (SKC): Uses a single key for both encryption and decryption.

•

Public Key Cryptography (PKC): Uses one key for encryption and another for decryption.

•

Hash Functions: Uses a mathematical transformation to irreversibly "encrypt" information.

Figure 1: Three types of cryptography: secret-key, public key, and hash function.

3. Concept of Secret Sharing Scheme The effective and secure protection of sensitive information [15] is primary concern in commercial, medical and military systems (e.g. communication systems or network storage systems). Needless to say, it is also important for an information fusion process to ensure data is not being tampered. Encryption methods are one of the popular approaches to ensure the integrity and secrecy of the protected information. However, one of the critical vulnerabilities of encryption techniques is single-point-failure [Figure-1.5], for example, the secret information cannot be recovered if the decryption key is lost or the encrypted content is corrupted during the transmission.

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To address these reliability problems, a secret sharing scheme (SSS) is a better alternative to take care of such vulnerabilities. Secret sharing technique is best used for protecting sensitive data, such as cryptographic keys. The secure storage of the private keys in cryptography is an important issue. The possession of an extremely sensitive key by an individual may not be advisable as the key can easily be lost or as the individual may not be fully trusted. Again given copies of key to more than one individual increases the risk of compromise. The obvious solution is to give different shares of the key to several individuals, forcing them to co-operate to find the secret key. Secret sharing deals with such problem, namely sharing a highly sensitive secret among a group of n users so that only when a sufficient number k of them come together, the secret can be reconstructed, that reduces the risk of losing the key but also makes compromising the key more difficult. [22]It is a protocol to share a number of secrets among a set of participants in such a way that only qualified sets of participants can recover the secrets, whereas non-qualified sets of participants might have partial information about them.This paper presents a robust and secured secret sharing method which essentially incorporates (k, n)-threshold secret sharing scheme. The technique allows a secret to be divided into n pieces, called shares. Such that any k shares (k ≥ n) can be used to reconstruct the original secret file using cryptographic computation in loss-less manner and less than k shares cannot get sufficient information to reveal the secret. Hence, even if (n-k) shares are destroyed by enemies, we can recover Secret form the remaining k shares. Furthermore, even if an intruder captures any (k-1) shares, no information about the Secret is formed. It is an effective, reliable and secure method to prevent the secret from being lost, stolen or corrupted. For example, consider a (k, n)–threshold Secret Sharing scheme. A secret S is encrypted into n pieces called shares V1, V2, ..., Vn, each of which has no information ofsecret S, but S can be decrypted by collecting k shares whereas (k-1) or fewer cannot be decrypted the secret S.

4. Concept of Cryptography Cryptography is the science of information security. It is nothing but the art of secret writing. The word is derived from the Greek kryptos, meaning hidden. Cryptography is closely related to the disciplines of cryptology and cryptanalysis. Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit. However, in today's computer-centric world, cryptography is most often associated with scrambling plaintext (ordinary text, sometimes referred to as clear text) into cipher text (a process called encryption), then back again (known as decryption). Individuals who practice this field are known as cryptographers. Modern cryptography concerns itself with the following four objectives[33]:  Confidentiality: Confidentiality is probably the most common aspect of information security. We need to protect our confidential information. An organization needs to guard against those malicious actions that endanger the confidentiality of its information. In the military, concealment of sensitive information is the major concern. In industry, hiding some information from competitors is crucial to the operation of the organization.  Integrity: Information or message that is received is identical to what is sent, no change or modification is tolerated during transmission.

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 Non-repudiation: The creator/sender of the information cannot deny at a later stage his or her intentions in the creation or transmission of the information.  Authentication: The sender and receiver can confirm each other’s identity and the origin/destination of the information.

5. Information Sharing Through Shared Key Cryptography Method of work would be as follows: 1.

First of all, we would take a file as input that has to be sent.

2.

Then prompt the user for no. of shares (n) & the threshold value (t).

3.

Then we would consider the file to be sent as secret & hence encrypt it with the key respective to the encryption scheme we would be using.

4.

Then the encrypted cipher text would be divided into n shares based on the masking technique which involves ANDing operation & hence resulting in removal of bits from the secret which are ANDed with 0 thereby reducing the size of the shares.

5.

Similarly the encryptiON key is also divided into shares.

6.

After that shares for both the encrypted secret & the encrypting key are distributed among the intended receivers none of which can individually get to know the secret unless at least it holds t shares of the secret.

7.

A minimum of t shares would be required to retrieve the encrypted secret for which the encryption key needs to be resolved before hand.

8.

And finally the data could be decrypted with the key that has been received & hence put into any further use if any.

The implementation of the above steps would be demonstrated with the help of a java application.

As an example a possible set of masks for 5 shares with threshold of 3 shares is shown below: Share 1: 1 1 1 1 1 1 0 0 0 0 Share 2: 1 1 1 0 0 0 1 1 1 0 Share 3: 1 0 0 1 1 0 1 1 0 1 Share 4: 0 1 0 1 0 1 1 0 1 1 Share 5: 0 0 1 0 1 1 0 1 1 1 One can easily check that ORing any three or more shares we get all 1’s but with less than three shares some positions still have 0’s i.e. remain missing.

5.1 Algorithm Secret sharing scheme which employs simple graphical masking method using simple ANDing for share generation and reconstruction can be done by simple ORing the predefined minimal number of shares. The Background Concept

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For better understanding let us consider any secret as a binary bit file (i.e. it is the smallest unit to work upon, in actual implementation one can consider a byte or group of bytes or group of pixels as the working unit). The secret could be an image, an audio or text etc. We shall decompose the bit file of any size onto n shares in such a way that the original bit file can be reconstructed only ORing any k number of shares where k ≤ n ≥ 2 but in practice we should consider 2 ≤ k < n ≥3. Our basic idea is based on the fact that every share should have some bits missing and those missing bits will be replenished by exactly (k-1) other shares but not less than that. So every individual bit will be missed from exactly (k-1) shares and must be present in all remaining (n-k+1) shares, thus the bit under consideration is available in any set of k shares but not guaranteed in less than k shares. Now for a group of bits, for a particular bit position, (k-1) number of shares should have the bit missed and (n-k+1) number of shares should have the bit present and similarly for different positions there should be different combinations of (k-1) shares having the bits missed and (n-k+1) number of shares having the bits present. Clearly for every bit position there should be nCk-1 such combinations and in our scheme thus forms the mask of size nCk-1, which will be repeatedly ANDed over the secret in any regular order. Different masks will produce different shares from the secret. Thus 0 on the mask will eliminate the bit from the secret and 1 in the mask will retain the bit forming one share. Different masks having different 1 and 0 distributions will thus generate different shares. Next just ORing any k number of shares we get the secret back but individual share having random numbers of 1‟s & 0‟s reflect no idea about the secret. Masking algorithm for n no. of shares & having threshold value k: •

List all row vectors having size n & possessing the combination of (k-1) no. of 0’s and (n-k+1) no. of 1’s and being arranged in the form of a matrix. Dimensions of the matrix would be nCk-1×n.

•

Take the transpose of the matrix that is generated in first step. Dimensions of the transposed matrix would be n×nCk-1. Each row of this matrix would serve as an individual mask for n different shares. nCk1

bits would be the size of each mask. Hence, the value of n and k result in variation in the size of the

mask. Pseudo Code for masking algorithm: Input: n, k Output: mask pattern length say x and masking[n][ ] int masking_algo(n, k, masking[n][]) { mask[][n] (an integer array) x= 0; //initialize maximum_value = 2n–1; //calculate decimal value of n numbers of 1’s for i=(maximum_value)-1 to 0 dec_to_bin(i, mask[x][n]); //calculate decimal i’s binary equivalent and store in mask[][] array

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if(check_zero(mask[x][n], k)) x++; //check existence of (k-1) no. of zeros, if true then x is incremented by 1 end for transpose_matrix(masking, mask); //take transpose matrix of mask[][n] and store in masking[n][] return x; } Example: Let n=5 and k=3. Row vectors of size 5 bits with two 0’s and three 1’s. 1

1

1

0

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Dimension of the matrix is 10×5 i.e. 5C2×5 as seen above. Transpose the matrix of first step and get the desired masks for five shares as shown above in the form of a matrix of dimension 5×10 i.e. 5×5C2. There are 5 masks each of which is 10 bits in size.

6. Results run: Size of master File 2939 com.sun.crypto.provider.DESKey@184fb javax.crypto.spec.SecretKeySpec@fffe8a01 encryption key 6792493797215234

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6792 TOTAL SHARES = 5 THRESHOLD = 3 MASKS GENERATED OF A MATRIX HAVING DIMENSION C(N,K-1)*N HAVING K-1 ZEROES IN EACH COLUMN 0010110111 0101011011 1001101101 1110001110 1111110000 HERE ARE MY SHARES AFTER MASKING THEM 78 13 10 10 0 0 73 68 82 0 0 10 0 8 6 0 0 -115 -67 0 0 112 72 89 0 19 0 11 19 1 -100 0 0 79 105 67 80 111 116 115 104 111 73 67 32 114 111 102 101 0 120 -99 83 103 -23 61 -9 -12 66 75 -108 111 82 8 32 82 -128 -111 38 33 9 16 33 -39 21 -63 17 69 27 -96 -120 -114 -114 -128 81 12 -118 -40 7 -28 -114 -93 -120 -54 -5 -31 107 -68 9 -51 -2 -75 -25 -13 -99 -49 7 -64 -106 51 81 -128 12 -87 17 -125 -57 -58 -31 -28 -127 36 112 16 8 -77 115 35 1 -8 126 60 34 7 -66 1 120 -45 0 77 -101 48 28 -121 -22 -103 92 -128 -124 1 -111 75 8 20 0 64 66 0 64 1 -128 -99 83 -96 4 96 -53 99 0 45 0 39 127 -26 -128 -8 -103 1 0 91 21 -96 -111 32 19 101 0 59 0 -49 86 -118 88 0 20 75 60 57 45 48 73 102 72 0 0 -50 16 -78 0 8 48 -120 -123 0 4 123 -56 35 120 -124 -103 0 -14 60 -15 -82 16 – STEP 1 OF ENCRYPTION DONE STEP 2 OF ENCRYPTION DONE STEP 3 OF ENCRYPTION DONE STEP 4 OF ENCRYPTION DONE STEP 5 OF ENCRYPTION DONE 1 0 0 54 0 57 50 0 57 51 55 0 0 50 0 53 50 0 52 0 0 0 0 2 0 3 0 55 0 50 52 0 51 55 0 55 0 49 0 50 51 0 0 0 0 123 3 5 0 0 55 57 0 52 57 0 55 57 0 0 49 53 0 51 52 0 0 11 0 4 5 3 54 0 0 0 52 57 51 0 57 55 50 0 0 0 51 52 0 0 11 123 5 5 3 54 55 57 50 0 0 0 0 57 55 50 49 53 50 0 0 0 0 11 123 HEADERS IN STRINGS 23 23 23 23 23 HEADERS GENERATED SUCCESSFULLYY

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ENTER THE TOTAL SHARES (MORE THAN OR EQUAL TO K) 3 Enter the 1th share number 1 Enter the 2th share number 3 Enter the 3th share number 5 SHARES ARE READY TO BE SENT NOW WAIT!..SENDING THE SHARES.......... 23

6. CONCLUSION We presented a thoroughly new idea to protect our very crucial information from any kind of theft or privacy. The idea of breaking the information into shares and storing the shares separately, then doing the same to the cryptography key also provides a never before level of security. This work can be extended by storing our shares of cryptography key in various images via steganography. The information can be retrieved from any minimum specified no. of shares and individual share is not of any use. So piracy is prevented and theft of information made almost impossible. We can even try to reduce the size of shares produced and the cover image. If there is not a problem in key sharing with the intended user then it will provide the best results. There should not be any man-in-middle attack. This would further strengthen the security. The shared key cryptography is best for sharing the information. But we have to choose the best shared key for the encryption and decryption.

7. REFERENCES [1]G.R. Blakley, “Safeguarding cryptographic keys “, Proceedings Of AFIPS National Computer Conference, Volume: 48, Pages: 313-317, June 1979 [2]Yvo Desmedt, “Some recent research aspects of threshold cryptography”, Proceedings of ISW (1st International Information Security Workshop), Volume: 1196 of LNCS paper, Pages: 158-173, 1997 [3]Yair Frankel and Moti Yung,” Distributed Public Key CryptoSystems”,LNCS, pp 1-13,Springer-verlag Berlin Heidelberg,1998 [4]P. A. Fouque, G. Poupard, and J. Stern. Sharing decryption in the context of voting or lotteries. In Proc. of FC 2000, 4th International Conference on Financial Cryptography, volume 1962 of LNCS, pages 90–104. Springer-Verlag, 2001. [5]PieriAlain Fouque et al.,”Sharing Decryption in the Cintext of Voting or Lotteries “, 2001 [6]Kamer Kaya, Ali Aydin Selcuk, Zahir Tezcan, “Threshold Cryptography Based on Asmuth-Bloom Secret Sharing”, Information Sciences, Volume: 177 (19), 2007

[7]D.Jeevaratnam ,K.Visala and Uppe Nenji,”Implementation of Object Oriented approach to Authentication of Group Key Transfer using Secret Sharing”,IJMER,Vol 1,Issue 1,pp 049-098,ISSN: 2249-6645

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[8] Dripto Chatterjee, Joyshree Nath, Suvadeep Dasgupta, Asoke Nath “A new Symmetric key Cryptography Algorithm using extended MSA method: DJSA symmetric key algorithm” published in 2011 International Conference on Communication Systems and Network Technologies, 978-0-7695-4437-3/11 2011 IEEE. [9]Prabhir Kr. Naskar etal.,”Ultra Secured and Authentic Key Distribution Protocol and using a Novel Secret Sharing Technique,IJCA,Vol.19,No.7,April 2011. [10]Joyshree Nath et al. “A Challenge in Hiding Encrypted Message in LSB and LSB+1 BIT positions in various Cover Files”, Volume 2, No. 4, April 2011 Journal of Global Research in Computer Science Journal of Global Research in Computer Science [11] Joyshree Nath ,”Advanced Steganography Algorithm using Encrypted secret message”,(IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 2, No.3, March 2011 [12]

R.Velumadhava Rao,K Salamani,R Elakkiya,”A Secure Key Transfer Protocol For Group

Communication”,ACIJ,Vol.3,No.6,Nov 2012. [13] P.V.Khabrogade and Nilesh Uke,” Cognet Sharing of Covert File using Audio Cryptography Scheme”, IJAIS, Vol.1,No.8,April 2012. [14] Ching Fang Hsu et al.,” A Novel Group Key Transfer Protocol”. [15] Mayank Swarankar, Shivani Singh and Dr. Shekhar Verma,”Transaction Security Using Input Bsed Shared Key Cryptography”,IOSRJCE,Vol.7,Issue 5, pp 55-60,dec 2012. [16] Vishwas Gupta et al.“Advance cryptography algorithm for improving data security”, Volume 2, Issue 1, January 2012 ISSN: 2277 128X International Journal of Advanced Research in Computer Science and Software Engineering [17] W. Diffie and M.E. Hellman. ,“New Directions in Cryptography”, IEEE Trans. Information Theory; Vol. IT-22, No. 6, 1976, pp.644-654 [18] Mukund S. Wankhade and Pravin D. Soni ,”Advanced Cryptanalytic Algorithm for Data Security”,International Journal of Application or Innovation in Engineering & Management (IJAIEM)Volume 2, Issue 3, March 2013 [19] Ilker Nadi Bozkurt, Kamer Kaya, Ali Aydın Selcuk, Ahmet M. Guloglu, “Threshold Cryptography Based on Blakley Secret Sharing”, Information Sciences [20] Boina Avinash Kumar,Madhusmita Das,”A Relevant Technique of Hiding Information in an Image Using Shared Cryptography”,International Journal of Computer Applications,Vol.69,No.18,May 2013 [21] Sorin Iftene, “Compartmented Secret Sharing Based on the Chinese Remainder Theorem” [22] Abdulrakeeb M. Al-Ssulami, “A Novel Threshold Secret Sharing Scheme Using FFT Algorithm”, International Journal of Information Security Science, Volume: 2 (1) [23] Sagar A. Yeshwantrao et al.,”Shared Cryptographic Scheme with Efficient data Recovery and Compression for Audio Secret Sharing,IJETAE,Vol.4,Issue 2,Feb 2014 [24] Mohammad Ehdaie, Taraneh Eghlidos, Mohammad Reza Aref, ―A Novel Secret Sharing Scheme from Audio Perspective ―2008 IEEE International al Symposium on Telecommunications 16-19 June pp 13-18. [25] Text book William Stallings, Data and Computer Communications, 6eWilliam 6e 2005

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[26] Data Hiding and Retrieval, A.Nath, S.Das, A.Chakrabarti, Proceedings of IEEE International conference on Computer Intelligence and Computer Network held at Bhopal from 26-28 Nov, 2010 [27] C.-C. Thien and J.-C. Lin, “Secret image sharing”, Computers and Graghics, vol. 26, no. 5, pp. 765-770, 2002. [28] A. Shamir: “How to share a secret ?” Comm ACM, 22(11):612-613, 1979. [29] G. Blakley : “Safeguarding cryptographic keys “ Proc. of AFIPS National Computer Conference, 1979. [30] C. Asmuth and J. Bloom :”A modular approach to key safeguarding” IEEE transaction on Information Theory, 29(2):208-210, 1983. [31] E. D. Karnin, J. W. Greene, and M. E. Hellman, “On secret sharing systems”, vol. IT-29, no. 1, pp. 35-41, Jan 1983. [32] Y. Desmedt “Some recent research aspects of threshold cryptography” Proc of ISW‟97 1st International Information Security Workshop vol.1196 of LNCS paper 158-173 Springer-Verlag 1997. [33] Y. Desmedt and Y. Frankel “Threshold cryptosystems” Proc of CRYPTO‟89 volume 435 of LNCS, paper 307-315 Springer Verlag 1990. [34] Y. Desmedt and Y. Frankel “Shared generation of authenticators and signatures” Proc. of CRYPTO‟91 volume 576 of LNCS pages 457-469 Springer Verlag 1992. [35] Y. Desmedt and Y. Frankel “Homomorphic zero knowledge threshold schemes over any finite abelian group” SIAM journal on Discrete Mathematics 7(4): 667-675, 1994. [9] H. F. Hua

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