中文摘要：

IPsec协议是互联网中最重要的协议之一，也是多年来用以解决网络安全问题的技术，在路由器、防火墙等设备中有着广泛的应用，同时在各种软件系统中也扮演重要角色。通过对IPsec协议中加密算法的讨论，重点分析了对称密钥加密算法在ESP中的应用，包括DES、3DES、IDEA、AES、SM4等加密算法。分析了各个算法实现的特点、复杂度和安全强度，对比了算法在软硬件平台实现所需资源以及实现速度，为IPsec协议设计应用时提出了建议，能有针对性的使用对称密钥加密算法，合理有效的解决安全方案。

英文摘要：

IPsec protocol is one of the most important protocols in the Internet, and also to resolve the problems of network security technology over the years. It is widely used in devices such as routers, firewalls, and also plays an important role in lots of software systems. Through the discussion of the IPsec protocol encryption algorithm this pa- per analyzes the symmetric key encryption algorithms in ESP, including DES, 3DES, IDEA, AES, etc. The focus is to analyze the characteristics of each algorithm complexity, security strength and the speed of implementation across platforms. In the IPsec protocol design, these analysis can put forward suggestions for the security program with the right symmetric key eneryption algorithm.