Modified Playfair Cipher using Rectangular Matrix

One of the well known polyalphabetic ciphers is the Playfair cipher. In this cipher digrams or groups of 2 letters in the plain text is converted to cipher text digrams during encryption using a key. Similarly during decryption cipher text digrams are converted to plain text digrams using the same key. However the original 5 x 5 Playfair cipher can support only 25 uppercase alphabets. To overcome this drawback we propose a rectangular matrix having 10 columns and 9 rows which can support almost all the printable characters including white space. This paper analyses the original Playfair cipher, the different variations that have been proposed and the modified Playfair cipher that we propose. Cryptanalysis is done to show that the proposed cipher is a strong one