There are not any general conclusions about periodicity of DES when itis used in stream ciphersystem.
DES应用于序列密码体制，其周期性问题没有一般的结论。
2
The block cipher with a substitution permutation network is the best known and widely used block ciphersystem.
包含代替置换网络的分组密码是一种广泛使用的分组密码系统。
3
There are inextricably links between chaos theory and simple cryptography, and chaotic dynamics shows some features that are desirable for the ciphersystem.