11 × 11 Playfair Cipher based on a Cascade of LFSRs

Abstract

Playfair cipher is one of the better-known multiple letter encryption ciphers. In this method, the diagrams in the plaintext are treated as a single unit and then these units converted into ciphertext diagrams. This paper implements and discusses a new system which proposed by using 11 × 11 Playfair cipher that supports all 26 alphabets in both: upper case letters (A-Z) as well as lower case letters (a-z), ten digits (0-9), special characters and the extended special characters. This combination will tackle the limitation of 5×5 Playfair cipher in which both i and j letters could not appear simultaneously. In order to increase the level of security of this method, the output of an 11×11 Playfair procedure will be an input to the complete procedure of a cascade LFSRs. Finally, this system was implemented using MATLAB 8.0 (R2012b).