A chaotic cryptography scheme for generating short ciphertext

Recently, we have proposed a chaotic cryptographic scheme based on iterating the logistic map and updating the look-up table dynamically. The encryption and decryption processes become faster as the number of iterations required is reduced. However, the length of the ciphertext is still at least twice that of the original message. This may result in huge ciphertext files and hence long transmission time when encrypting large multimedia files. In this Letter, we modify the chaotic cryptographic scheme proposed previously so as to reduce the length of the ciphertext to the level slightly longer than that of the original message. Moreover, a session key is introduced in the cryptographic scheme so that the ciphertext length for a given message is not fixed. (C) 2003 Elsevier Science B.V. All rights reserved.