A Hybrid Polybius-Playfair Music Cipher

Abstract

Music has a versatile dimensionality; it can be used to express feelings, emotions and can also be used as a communicable language. Music and its attributes have been used in cryptography and steganography from a long time. Musical symbols and notes are used as replacement/substitution cipher. Using music as a cipher or cover media not only enhances the security of the message but also reduces its chance to be detected as an encoded or ciphered message. This paper proposes a hybrid Polybius and Playfair cipher which encodes the message into sequence of musical notes. The Playfair key matrix is generated using the Blum-Blum Shub generator. The bigrams of plain text message is first encrypted using Playfair cipher then individual character of the encrypted message is re-encrypted using Polybius cipher. The Playfair cipher enhances the security of the encrypted message over the simple substitution technique. The Polybius cipher then reduces the character set by appropriate number of symbols (here musical notes) for replacement. The basic 5X5 structure of key matrix in Polybius and Playfair is extended to 10X10 to hold the 95 prinTable characters of ASCII character set.