A Block Cipher obtained by blending modified playfair Cipher with advanced hill Cipher

Abstract

In this paper we presented a new technique for secure transmission of message based on modified version of playfair cipher combined with Hill cipher to encrypt and decrypt a message from sender and receiver vice versa. The traditional playfair cipher and Hill cipher methods are based on polyalphabetic cipher of 26 letters which is relatively easy to break because it leaves much of loop holes and a small hundreds of letters, digits and other special characters unused. At each stage of encryption and decryption, two different keys are used to encrypt and decrypt the message according to the modified features of the ciphers. From the cryptanalysis performed in this work, we have found that this cipher thwarts any known plaintext attack, chosen plaintext attack and chosen ciphertext attack.