ASN.1/BER/DER 编码子集入门指南。PKI证书交换时常用，有助于密码系统开发。PDF文件-Encoding a subset ASN.1/BER/DER Getting Started Guide. The exchange of PKI certificates often used to help the development of cryptography. PDF document

DES算法的实现，比较初级，适合入门使用-the c++ code of DES, very easy and suitable for students