Date Added: Nov 2012
In this paper conventional Playfair Cipher is being modified by encrypting the plaintext in blocks. For each block the keyword would be the same but the matrix will shift by some random value. As a result of which the diagram analysis would be very difficult which is done in the traditional Playfair Cipher to obtain the plaintext from the ciphertext. The shift value will be generated using SHA-1 which is very secure. Playfair Cipher method, based on poly alphabetic cipher is relatively easy to break because it still leaves much of the structure and a few hundred of letters of ciphertext are sufficient.