The cipher code parameter selection and its impact on output cycles

摘要

This paper gives the circuit design for logistic digital chaotic system, with the analysis of parameter selection for logistic cipher code, effecting factors and calculating method of sequence cycle. Through experiments it is shown that different calculating precisions and u value can be the factor that effects the cycle period most, changing u value can change the cycle and the larger precision can get the bigger cycle basically. For one thing, fixing u value and precision to test the effect of the initial value and find some good precisions; for another, further research shows there are some small cycles in good precisions. Therefore, it is unsafe to use initial value directly as the cipher code, for which the paper supposes an improvement program. This paper tests the cycle under certain conditions, and firstly deduces the cycle calculation formula, proposes the main conditions of cycles effected by the digital chaoic sequences and the cycle calculation method, then gives the scatter gram of precision-u-cycle. The methods given above have actual significances for estimating chaotic sequence cycle of finite precision in assured chaotic application field.