Abstract— A novel and fast technique for cryptographic applications is designed and developed using the symmetric key algorithm “MAJE4” and the popular asymmetric key algorithm “RSA”. The MAJE4 algorithm is used for encryption / decryption of files since it is much faster and occupies less memory than RSA. The RSA algorithm is used to solve the problem of key exchange as well as to accomplish scalability and message authentication. The focus is to develop a new hybrid system called MARS4 by combining the two cryptographic methods with an aim to get the advantages of both. The performance evaluation of MARS4 is done in comparison with MAJE4 and RSA. Index Terms— Cryptography, Decryption, Encryption, Message Authentication, Symmetric key. I. INTRODUCTION YMMETRIC key cryptographic algorithms, which use the same key for encryption and decryption are faster and efficient, but they have the disadvantage of key exchange problems[1]-[2]. Whereas asymmetric key cryptographic algorithms solve the major problem of key exchange as well as scalability and also achieve the purpose of non-repudiation [3]-[5]. The dawn of asymmetric key cryptography does not indicate the end of secret key cryptography. In practice, the symmetric key and asymmetric key systems are not in competition. Most cryptographic schemes on which e- commerce operations rely use a hybrid of these systems. Here the asymmetric key system is used for the distribution of a secret key, which can be a long-term key or specific to a particular communication session. Then the securely distributed secret key is used to encrypt and decrypt messages in a communication channel between two users. The performance of secret key cryptography over that of asymmetric key, and the appeal of key distribution inherent to asymmetric key cryptography, are the main reasons for the wide adoption of these hybrid systems [6]. As shown in Fig. 1 the plain text is encrypted with fast symmetric encryption algorithm, MAJE4 to form the cipher text and then the symmetric key K1 of MAJE4 is encrypted with public key K2 of asymmetric algorithm RSA [7]-[13]. Sheena Mathew is a Reader in the Computer Science and Engineering Division of Cochin University of Science and Technology, Kochi, Kerala, India (e-mail: sheenamathew@cusat.ac.in). K. Paulose Jacob is a Professor and Dean of Faculty of Engineering of Cochin University of Science and Technology, Kochi, Kerala, India (e-mail: kpj@cusat.ac.in). 1-4244-0370-7/06/$20.00 ©2006 IEEE Then the cipher text and encrypted symmetric key K1 are sent together by the sender to the receiver. In the receiver side, first RSA algorithm is run with its private key K3 to recover the symmetric key K1. Then by using K1 and MAJE4 the entire cipher text is converted into plain text. Fig. 1. Hybrid cryptographic system MARS4 using MAJE4 symmetric algorithm and RSA asymmetric algorithm. II. DESIGN OBJECTIVES FOR MARS4 The following objectives are considered while combining the two cryptographic algorithms with a view to obtain the merits of both the systems. 1) The method should be completely secure. A Novel Fast Hybrid Cryptographic System: MARS4 Sheena Mathew, and K. Paulose Jacob S ENCRYPTED KEY K1 K2 PRIVATE KEY K3 PLAIN TEXT SYMETRIC ENCRYPTION KEY K1 PUBLIC KEY SYMMETRIC KEY K1 CIPHER TEXT + ENCRYPTED SYMMETRIC KEY K1 ASYMMETRIC ALGORITHM (RSA) CYPHER TEXT + SYMMETRIC KEY K1 SYMMETRIC ALGORITHM (MAJE4) CIPHER TEXT ASSYMETRIC ALGORITHM (RSA) PLAIN TEXT SYMMETRIC ALGORITHM (MAJE 4) NEW HYBRID CRIPTOGRAPHIC SYSTEM (MARS 4)