International Journal of Security and Its Applications Vol.9, No.1 (2015), pp.237-248 http://dx.doi.org/10.14257/ijsia.2015.9.1.23 ISSN: 1738-9976 IJSIA Copyright ⓒ 2015 SERSC Hiding Messages using Musical Notes: A Fuzzy Logic Approach Chandan Kumar 1 , Sandip Dutta 2 and Soubhik Chakraborty 3 1,2 Department of CSE, Birla Institute of Technology, Mesra, Ranchi- 835215, India 3 Department of Applied Mathematics, Birla Institute of Technology Mesra, Ranchi- 835215, India 1 chandankr@bitmesra.ac.in, 2 sandipdutta@bitmesra.ac.in 3 soubhikc@yahoo.co.in Abstract “Music can be used as a communicable language”. Musical symbols and musical notes have been used as codes and ciphers from early days. The art of encrypting messages using music is termed as Musical cryptography and it uses predefined set of notes and set of rules for composing musical pieces which in turn are musical cryptograms. Traditional algorithms applied to musical cryptography used simple substitution cipher which merely produced good musical sequences. To overcome this problem a fuzzy logic based algorithm for musical cryptography is proposed in this paper. The paper proposes a symmetric key substitution cipher which uses one of the n candidate notes to encrypt a particular character. The application of fuzzy logic in musical cryptography produces acceptable musical sequences which are hard to be suspected as cipher. Keywords: Musical Cryptography, musical notes, algorithmic composition, fuzzy logic, encryption, decryption 1. Introduction Various techniques have been employed for private communication from the age of Julius Caesar. The process of secure information exchange demands techniques that convert the message into unintelligible form so that the intruder cannot guess the content of the message. For secure information exchange cryptography and steganography have been used. Cryptography is the art of transforming the plain text message into an unintelligible form (cipher text) which cannot be understood by untrustworthy parties [1-2]. The process of converting plain text message into cipher text is known as encryption, while the process of getting plain text back from cipher text is known as decryption. Various mathematical transformations are used to convert the plain text message into cipher text. These transformations can be simple permutation and combination, transposition, substitution, matrix multiplication, use of number theoretic approaches etc. For encryption and decryption process usually a key is used, if the same key is used for both encryption and decryption the process is known as symmetric key cryptography while two different keys, private and public keys are used in asymmetric key cryptography. In asymmetric key cryptography the public key is known to public which can be used to encrypt the message while the private key remains private to the receiver which is used to decrypt the message. Cipher algorithms can also be classified as block ciphers and stream cipher depending on the working. A block cipher algorithm encrypts a particular fixed length sized block while a stream cipher encrypts a stream of plain text and can encrypt a particular character at a time. Steganography is the art of hiding messages into another message; by doing this the