Novel approach of playfair cipher for multilevel information security

2D advance playfair technique for generating more secure cipher text. Diagraph (combination of 2 characters) of the plaintext are treated as single unit and converted into corresponding cipher text Diagraph and vice-versa. Classical Playfair Cipher supports English alphabets with limitation that only one alphabet “i” or “j” will be considered at a time. 2d advance Playfair Cipher came into focus to eliminate this limitation.2d advance Playfair cipher supports all 26 English upper alphabets {A-Z}, lower alphabets [a-z], 10 digits {0-9} and 28 special characters including {! “ * # $ % & ` +, -. /:; ( ) <; = > ? @ [ ] \ ̂ _ I }. For enhance the security, use the diffie-hillmen key exchange algorithm with the advanced substitution encryption techniques to provide security. 2d advance Playfair Cipher use for enhance the security of text files that contains alphabets, numerals and special characters.