Security Aspects of the Extended Playfair Cipher

Abstract

The well known multiple letter encryption cipher is the Playfair cipher. Here the digrams in the plaintext are treated as single units and converted into corresponding cipher text digrams. However because of the drawbacks inherent in the 5*5 Playfair cipher which adversely affects the security we proposed an 8*8 Playfair cipher and then coupled it with LFSR (Linear Feedback Shift Register) to make the traditional Playfair cipher at par with the advanced ciphers available like AES and DES. For details one can refer to [1]. Now for all practical applications, performance and speed are also prime concerns besides security. The LFSR not only enhances the security up to a considerable level by generating random sequences but also provides a much faster rate of encryption and decryption. This paper deals in with the security issues of the new proposed system. Various types of cryptography attacks have been taken under consideration and the resistance of the proposed cipher to all these attacks has been discussed. At the end we find that the proposed cipher is not vulnerable to attacks.