A New Symmetric Key Cryptography Algorithm Using Extended MSA Method: DJSA Symmetric Key Algorithm

In the present work the authors introduced a new symmetric key cryptographic method for encryption as well as decryption of any file such as binary file, text file or any other file. Nath et. al. (1) developed an algorithm called MSA for encryption and decryption of any file using a random key square matrix containing 256 elements. The weak point of MSA algorithm is that if someone applies the brute force method then he has to give a trial for factorial 256 to find the actual key matrix. Now in the modern world this number of trial runs may not be impossible for the hacker. To get rid of this problem here the authors suggest a better algorithm than MSA. In the present method the authors considered the size of the key matrix to be 65536 and in each cell we store 2 characters pattern instead of 1 character unlike MSA method. If someone wants to give a brute force method to find our actual key then one has to give a trial for factorial 65536 runs! Theoretically this is an intractable problem. Moreover the authors have also introduced multiple encryptions here to make the system more secured. This method will be suitable in any business house, government sectors, communication network, defense network system, sensor networks etc. In the present work the authors have introduced a square key matrix of size 256 by 256 where in each cell there are all possible 2-lettered words (ASCII code 0-255). The total number of words possible is 65536. The key matrix is then randomized using the method proposed by Nath et. al(1). The user has to enter some secret text-key. The maximum length of the text key should be 16 characters long. To calculate the randomization number and the number of encryption to be done is calculated from the text-key using a method proposed by Nath et.al(1). The present method will be most suitable for encryption of a file whose size is less than or equal to 2MB. If the file size is very big then we suggest choosing small encryption number to speed up the system.