Cryptography Using Modern Ciphers (Xor and Transposition)

Cryptography Using Modern Ciphers (Xor and Transposition)

Dr Satish Garg

Govt. College for Girls Palwal (Kurukshetra) - 136131

ABSTRACT:

I. INTRODUCTION

In the present digital era, I-ways (Information ways) have enormously influenced the modern age of every individual. When someone feels facilitated by the digital innovations, the threats have also increased manifolds[1,2]. “Cryptography is one of the methods to protect message from illegitimate release. Cryptography makes message illegible to a hacker and it ensures safe and trustful communication among parties to avoid any threat” [3,4]. “The cryptographic algorithms can be classified as :

(i) Symmetric Key Cryptography – in this algorithm same key is used for both encryption and decryption and

(ii) Public Key Cryptography – in this algorithm two different keys are used, one for encryption purpose and the other for decryption purpose” [3,4]. In the present paper the author has introduced a new symmetric key cryptographic method where two modern cipher, namely XOR and transposition ciphers have been used. In the proposed algorithm SKG 3.13 following steps are involved :

(i)                            Firstly, all the characters of the plain text are converted in binary form using Extended ASCII Code (8-bit code)

(ii)                         Secondly, the bits obtained at step (i) are superimposed on a continuous binary pulse in digital form using CNOT operation, which is a reversible operation

(iii)                      Then, Extended ASCII Code is used to convert the bits obtained at step (ii) into corresponding characters and

(iv)                      Finally, transposition cipher is applied, where position of characters are interchanged, thus we get the cipher text.

II. ENCRYPTION ALGORITHM SKG 3.13:

1.     Read the input string of characters and Check the number of characters, N

2.     If N<10, then write Program is Not Applicable

3.     Convert characters into Binary Form using Extended ASCII (8 bit) Code, we get 8N Bits

4.     Generate a binary string of consecutive 0’s & 1’s such that number of consecutive 0 & 1 are from 1 to 7 and length of this binary string is 8 N

5.     Superimposed the binary string obtained at Step 3 on that obtained at Step 4 using CNOT operation

6.     Convert binary string obtained at Step 5 into characters using Extended ASCII (8 bit) Code, we get N Characters

7.     If (N+1)/N1 = 0, Transpose Integral Multiples of LMC with corresponding RMC upto N/2 Characters otherwise proceed upto N Characters

8.     Output is Encrypted String i.e., Cipher Text

III. EXPLANATION OF ALGORITHM SKG 3.13 :

All the steps mentioned in algorithm SKG 3.13 are explained below :

Step 1 : Step 1 requires to take input from any media in the form of characters and then it checks number of characters in that input which is denoted by N

Step 2 : This step checks the value of N which may be less than, equal to or more than 10, if value of N is less than 10 then this particular algorithm shall not be applicable

Step 3 : At this step, if value of N is not less than 10 then the string of input characters will be converted into binary form using Extended ASCII (8-bit) Code. This conversion shall give 8N bits as output

Step 4 : In step 4, a binary string of 8 N Bits of consecutive 0’s & 1’s is generated such that number of consecutive 0’s & 1’s are from 1 to 7

Step 5 : In step 5, binary string obtained at step 3 is superimposed on binary string generated at step 4 using CNOT operation Step 6 : In step 6, the binary string obtained from the last mechanism is converted back into N characters using the same Extended ASCII (8-bit) Code

Step 7 : In step 7, the desired mathematics is performed. If the achieved value is 0, then transposition operation shall stop at middle of string  of characters i.e., at N/2 character otherwise it shall be continue upto                 N characters

Step 8 : The last step denotes the encrypted characters as desired output i.e., Cipher Text

IV. IMPLEMENTATION OF ALGORITHM SKG 3.13

This algorithm is based on three concepts :

(i)                            “each character is represented by a unique 8-bit code in ASCII Code system and if one or more bits are changed in a 8-bit code, then corresponding character is entirely changed. When any text of 10 characters is converted into binary form we get 80 bits which contains about 50% of 0’s and 1’s each. Therefore, total number of possible combinations is about 80!/(40!)²= 1075×10²⁰. The Super Computer available is Teraflop which is capable of doing 10¹² floating point calculations per second, so a teraflop super computer shall take about 3409 Years to find all possible combinations”[5,7,8].

(ii)                         “When control signal of CNOT gate is 0, then output of CNOT gate is same as the input and when control signal of CNOT gate is 1, then output of CNOT gate is reverse of input and CNOT operation is reversible”[5,7,8].

(iii)                      In this algorithm we have used a complex cipher which is a combination of two simple modern ciphers : XOR/CNOT and Transposition Ciphers.

As we start executing the program, in the first step screen shot shown in Fig. 1 appears. Fig.1 denotes the start of the program on desktop. It is shown clearly that software named Net Beam IDE 6.5 has been used and Prj1 is our project.

In the second step as we click on Prj1, screen shot shown in Fig. 2 appears which shows that the project Prj1 consists of two parts : Source Packages and Libraries. Source Packages contains source code of the algorithm while Libraries contains functions and attached packages.

In the third step screen shot shown in Fig. 3 appears. Fig. 3 clearly denotes the entry box, various options available and output box. As per algorithm, option is selected to run the program.

Then, the characters to be encrypted are entered in the entry box as shown in the Fig. 4. For algorithm SKG 3.13, keys A, Ck N1and -A are “Enabled”, then value of Ck and N1 is entered and “Finalize Preferences” button is pressed as shown in the Fig. 4. To implement the algorithm SKG 3.13 for encryption, “Encryption” button is pressed.

The conversion of characters into binary form, its superposition on generated string of bits and transposition of characters is shown in Fig. 5. Fig. 6 shows final output after encryption i.e., cipher text.

For decryption, the “Decryption” button is pressed. The decryption process is represented in Fig. 7 and 8.