An Improved Chaos-Based Stream Cipher Algorithm

This paper proposes an improved chaos-based stream cipher algorithm to enhance the security of an encryption system under precision limited condition. The key stream generator is constructed by three one dimension chaotic maps and their nonlinear transform. The balance and correlation properties of the key stream are analyzed. The sequence is proved to be a binary Bernoulli sequence and the distribution of the differences between the amounts of 0 and 1 is analyzed. The side lobes of auto and cross correlation are proved to obey normal distribution N(0, 1/N). Compared with the conventional single chaos map based encryption system, the algorithm proposed in this paper enlarges the key space, extends the period and improve the linear complexity of the key stream under precision restricted condition. The theoretical analysis and experimental results indicate that the system is strong against various common attack methods.