用户自助组件，使得最终用户能够执行某些安全管理任务，而无需管理监督，如周期性地更改密码。

User self-care component, to enable end users to carry out certain security administrative tasks without administrative supervision, such as periodically changing a password.

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利用混沌映射具有对初值的敏感性和遍历性等特点，采用多次迭代的一维均衡混沌映射构造了一种非周期、均匀分布的多表代换密码。

Utilize the sensitivity and ergodic characteristic of the chaos map, a non-periodic and uniformity distributing multi-chart substitution is designed with multi-iterative equilibrium chaos map.

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DES应用于序列密码体制，其周期性问题没有一般的结论。

There are not any general conclusions about periodicity of DES when itis used in stream cipher system.

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