Abstract: The paper formulated the generating procedure of key stream of chaos in the term of information theory,presentd and proved that generating efficiency of key stream can be improved through sampling-and- encoding method to process real number sequence of chaos. And the paper made research on the relationship between the amount of encoding bits and pseudorandomness and generating efficiency. The amount of encoding bits effects pseudorandomness of binary sequence a little, and the standard device tion of each sample is 0. 0135 at most, specially, when 18, the standard deviations converge apparently. Generating efficiency keeps higher, when the amount of encoding bits falls into the interval of 6 through 15, and arrive to the highest point when 12. The paper compared the binary-field method and the proposed sampling-and- encoding method in terms of theoretic and experimental proof and showed that sampling-and- encoding method can reserve more pseudorandom information so that it can improve the generating efficiency of key stream. The sampling-and- encoding method is a beneficial tentative experience to enrich the generating ways of key stream.

Key words: Chaos, Key stream, Sample and encoding, Stream key generation