Enhancing the Security of Playfair Cipher by Stream Cipher

Abstract

Cryptography is a science of converting clear message into secret message "nonreadable message",where message was encrypted at sender side then decrypted at receiver side. Playfair is an example of substitution cipher,it has various limitations, inthis paper we proposean advanced encryption algorithm which improves the security of Playfair method by combining it with modern cipher method like Stream cipher, Stream cipher relatively regards as unbreakable method, and bit oriented method (instead of character-oriented) where the Plaintext, Ciphertext and the Key are strings of bits.

When applying the proposed algorithm, we see that the mentioned above combination cipher has a high degree of security, where cipher based on just Playfair method is not secure. Also the proposed algorithm makesthe cryptanalysis more difficult.