ABSTRACT: For secure communication we always use different security algorithms e.g. Caesar cipher, modified Caesar cipher, IDEA, AES, RSA algorithm etc. and in data structures using C we have Linked list, stack ,queue ,tree and graph. In graph we have graph traversal i.e. BFS (Breadth First Search) or DFS (Depth First Search). This paper presents the new technique for security which is combination of Caesar Cipher and graph traversal, Binary search tree together then security will be much higher than only using Caesar cipher or graph traversal or binary search tree.

Keywords: Binary search tree, Breadth First Search, Caesar cipher, Depth First Search, graph traversal

I INTRODUCTION

In binary search tree, less than or equal to elements are stored on left hand side and greater elements are stored on right hand side [1].In BFS, we traverse level by level [2]. In cryptography, many algorithms are available for protecting our online important information which we are transferring from one person to another person [3]. One of these algorithms is Caesar cipher. It is very basic algorithm. In Caesar cipher we replace corresponding letters left or right by some number [4]. In DFS, we select some node and go as deep as possible and we use concept called as backtracking here [5]. Using graph traversal we can reach each and every vertex of the respective graph and for this we use BFS and DFS methods.

II LITERATURE REVIEW Using cryptography we can send our information to respective person securely and third party cannot see this communication if we use good cryptographic algorithms [3].

III IMPLEMENTATION

Given plain-text message is: evaluation technique Step 1: Apply Caesar Cipher Here rule used is

position of the character in the alphabet+1 …(1) e.g. Take first character from the word evaluation and e has 5th position in the alphabet series. So 5+1=6 and f is the 6th position character in the alphabet series. So our 1st character is f. So using above formula we got words as:

fwbmvbujpo ufdiojrvf

Step 2: Give numbers to each characters. The TABLE I and TABLE II shows fwbmvbujpo and ufdiojrvf word.

TABLE I. fwbmvbujpo word

TABLE II. ufdiojrvf word

Step 3: Arrange the above position of characters in the alphabet in ascending order. Ascending order of fwbmvbujpo word: 2, 2,6,10,13,15,16,21,22,23 Ascending order of ufdiojrvf word: 4, 6,6,9,10,15,18,21,22

Step 4: Divide each word into 2 equal parts according to the numbers given in step 3. Lesser than or equal to numbers will go to left side and greater elements will go to right hand side just like binary search tree [1]. If the word is completely divisible by 2 then half part will go to left side and half part will go right side and if word is not completely divisible by 2 then half part+ 1 character will go to left side, half side will go to right side. Each left and right hand side node has at the most 2 children.

fwbmvbujpo: 10 characters . So 10 characters/2=5 and therefore 5 characters will go left hand side and 5 characters will go to right hand side.

First half part: 2,2,6,10,13, Next half part: 15, 16,21,22,23

ufdiojrvf : 9 characters. 9 characters/2=4.5 and therefore 5 elements will go to left side, 4 elements will go to right side

First half part: 4, 6, 6, 9,10 Next half part: 15,18,21,22

Step 5: Draw diagram for the word position and its numbers. Fig. 1 denotes fwbmvbujpo word and Fig. 2 denotes ufdiojrvf word.

Fig. 1 fwbmvbujpo word with its respective word position and its numbers

Fig. 2 ufdiojrvf word with its respective word position and its numbers

Step 5: Figure out cipher text i.e. write down alphabet number and between each alphabet number, write down position number of the character given in step 2 and if the alphabet number is only a single digit then write down alphabet number first and immediately after that respective number write down position number of the character given in step 2(here 6one). Write down values from each circle from the figure 1 and 2 in such a way that we will get the cipher text as below:

Cipher Text for the words fwbmvbujpo and ufdiojrvf respectively are: 1four3_2two3_1eight0_6one_2five2_2seven1_2three_2six_1nine6_1ten5

1six0_2eight2_9four_6two_2one1_1seven8_6two_4three_1five5

Decryption: Step 1: Take the cipher text Cipher Text: 1four3_2two3_1eight0_6one_2five2_2seven1_2three_2six_1nine6_1ten5

1six0_2eight2_9four_6two_2one1_1seven8_6two_4three_1five5

Step 2: Figure out position of each character in the alphabet series and position number of the character in the respective word from the cipher text. e.g. 1four3 Means 13 is the position of characters in the alphabet series and four is the position number in the respective word. Each character in the cipher text is separated by underscore (_). So position of each character in the alphabet series and position number in the fwbmvbujpo and ufdiojrvf words are given in the following TABLE III:

TABLE III. fwbmvbujpo and ufdiojrvf word with its respective word position and its position numbers

Step 3: From the chart drawn in step 2 of decryption, we can find out plain text. e.g. Consider position number in the word and position of characters in the alphabet.

Position number in the word: four Position of characters in the alphabet: 13 that means at fourth position, we have 13 number character from the alphabet i.e. m. Similarly, we can find out remaining characters from the respective cipher text which is given in the TABLE IV.

TABLE IV. fwbmvbujpo and ufdiojrvf words with its respective word position and its position numbers

So we got two words: fwbmvbujpo and ufdiojrvf respectively. Step 4: Apply Caesar Cipher Here rule used is

position of the character in the alphabet-1 … (2) e.g. f has 6th position in the alphabet series. So 6-1=5 and e is the 5th position character in the alphabet series. So our 1st character is e and using this formula we got plain text as:

evaluation technique

This is our original plain text message.

IV CONCLUSION: When we use Caesar cipher with some concepts of data structure using C then result obtained is much harder to detect than only using Caesar cipher or some concepts of data structure using C. We got both plain-text i.e. evaluation technique and cipher text i.e. 1four3_2two3_1eight0_6one_2five2_2seven1_2three_2six_1nine6_1ten5

1six0_2eight2_9four_6two_2one1_1seven8_6two_4three_1five5 using above steps. So security is maintained.

REFERENCES:

[1] JON L. BENTLEY, M, ‘ Multidimensional Binary Search Trees in Database Applications’, IEEE TRANSACTIONS ON SOFTWARE ENGINEERING, VOL. SE-5, NO. 4, JULY 1979, PP 333

[2] Scott Beamer Krste Asanovic David Patterson,’ Direction-Optimizing Breadth-First Search’, SC12, November 10-16, 2012

[3] Programmer Enas Ismael Imran, Programmer Farah abdulameerabdulkareem, ‘Enhancement Caesar Cipher for Better Security’, IOSR Journal of Computer Engineering (IOSR-JCE), Volume 16, Issue 3, Ver. V (May-Jun. 2014), PP 01

[4] S G Srikantaswamy and Dr. H D Phaneendra , ‘IMPROVED CAESAR CIPHER WITH RANDOM NUMBER GENERATION TECHNIQUE AND MULTISTAGE ENCRYPTION’, International Journal on Cryptography and Information Security (IJCIS), Vol.2, No.4, December 2012,page number 39 [5] Mustafa Sakalli, William A. Pearlman, and Masoud Farshchian,’ SPIHT algorithms using Depth First Search Algorithm with minimum memory usage’

[5] Mustafa Sakalli, William A. Pearlman, and Masoud Farshchian,’ SPIHT algorithms using Depth First Search Algorithm with minimum memory usage’

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