密码学研究生课程笔记。有加解密算法描述和试算过程。有古典密码、现代密码基本内容简介和例题。对于学习密码学有指导意义，特别是例题。-Cryptography postgraduate course notes. Encryption and decryption algorithm descr iption and spreadsheet process. Introduction and examples of classical cryptography, modern cryptograph