A More Secure Chaos Based Encryption System with High Compression Capability

The Baptista cryptosystem uses the logistic map to generate chaotic sequence. The encryption process of a given plaintext character consists of iterating the chaotic map until the state reaches the subinterval assigned to that symbol. The cipher text corresponding to the plaintext symbol is the number of iterations in the chaotic map. We propose a method to enhance the security and compression capability of Baptistatype cryptosystem. Unlike the present chaotic cryptosystem which uses the parameter and the initial condition of the chaotic map as the key, this cryptosystem uses an external key to generate the initial condition for the chaotic map. The lookup table used for encryption process is determined adaptively based on the frequency of occurrence of plaintext symbols and is dynamically updated in the searching process.