目录
中文内容摘要
随着网络技术的发展和普及，Virtual Private Network（VPN，虚拟专用网络）得到了越来越多的应用，而基于Secure Sockets Layer（SSL，安全套接层）技术的VPN 系统是目前一种安全易用且低成本的远程访问方案。
SSL VPN是一种新型的VPN技术。随着网络应用的多样性，对远程访问的安全需求日益增加，目前主流IPSec VPN无法满足应用多样性的需求。SSL VPN因其配置方便、与操作系统无关、支持设备广泛等优势，弥补了IPSec VPN的不足，成为VPN领域的研究热点。
本文对SSL VPN的概念、基本原理、关键技术进行了研究，通过OpenVPN软件设计并实现了一个SSL VPN系统，并着重分析了其中的加密算法与安全性，希望提出方法和加密算法来对SSL VPN系统加以提高与完善，其主要内容如下:
1. 详细分析了SSL技术和VPN技术，并对SSL VPN的技术特点进行了总结。
2. 对SSL VPN的体系结构以及其关键技术进行了深入研究。包括代理技术、用户验证技术、访问控制技术和审计日志技术等，并给出SSL VPN的两个解决方案。
3. 归纳总结了一些VPN技术的实现机理，包括PPTP协议、L2F协议和L2TP协议、IPSec VPN和MPLS VPN；在这个基础上，着重对基于SSL的VPN实现方法的代表---OpenVPN做了深入研究，并通过虚拟机(VMware)成功完成两种不同方式实现的实验平台和演示。
4. 针对VPN系统中的研究热点——安全性，对SSL VPN中各种加密算法进行研究，着重分析了ECC加密算法在SSL VPN中的特点与优势；最后将目前发展迅速的量子密码技术引入到VPN系统中，详细分析了QKD(Quantum Key
Distribution)技术在VPN中的体系结构、应用方式以及具体实施情况。关键词：SSL，VPN, SSLVPN，SSL控制协议，OpenVPN，加密算法
Abstract
With the development of networking technology, Virtual Private Network(VPN) plays a more and more important role today. Secure Sockets Layer(SSL) VPN is a secure and low-cost Remote Access system.
Based on the diversity of network applications, the demand of remote access has a significant growth; IPSec VPN can not satisfy the need of various applications. But SSL VPN which has the priority of easy configuration, no associated with the operating system and extensive support equipment, can make up the shortage of IPSec VPN. So, SSL VPN has become a research hotspot.
This paper studies the characteristics of SSL VPN, Such as concept, basic principles, key technologies, and so on. We also realize a system via the software of OpenVPN and fully analyze the encryption algorithms in SSL VPN, trying to propose methods and encryption algorithms to improve VPN system. The main contents include:
1. We detailed research and analyze SSL technology and VPN technology, summarize the technical features of SSL VPN.
2. SSL VPN architecture and its key technology are deeply analyzed, such as Agent technology, User authentication, Access control, Audit log and so forth. Two solutions of SSL VPN are also proposed.
3. The realization mechanisms of VPN are summarized, such as PPTP protocol 、 L2F
protocol 和 L2TP protocol 、 IPSec VPN and MPLS VPN; What we focus on is its representative-OpenVPN; Through VMware, we successfully use two methods to complete the realization demon of SSL VPN.
4. Based on the research topic in VPN system-security, we investigate various encryption algorithm in SSL VPN and detailed analyze ECC encryption algorithm. Finally, with the rapid development of Quantum Cryptography(QC), we propose QC can be better used in VPN system, and deeply analyze architecture and application of Quantum Key Distribution(QKD) is VPN system.
Keyword: SSL, VPN, SSL VPN, OpenVPN, Encryption algorithm, ECC, QKD.
