中文摘要：

随着互联网的发展,隐私保护问题越来越突出,现有的匿名通信系统如Tor,Freenet等能够隐藏用户的身份,但是不能够隐藏通信的事实.以BitTorrent,emule为代表的P2P文件分享软件已经成互联网的主要应用,而且其用户规模庞大,分布在全球各地.在此基础之上提出一种新的隐蔽通信方法——StegoP2P,该方法不依赖于任何单一的系统或者接入点,而是利用P2P协议的隐蔽通道;并设计一个有效的隐蔽握手协议,让P2P网络中互为好友（合谋）但素未谋面的节点隐蔽握手,秘密交换信息,从而绕过网络审查.实验结果和安全性分析表明我们的系统具有较高的性能和健壮性,并能够抵御常见的流量审查.

英文摘要：

With the development of Internet, privacy-preserving has become an increasingly prominent problem. Existing anonymous communication systems, such as Tor and Freenet, can conceal who communicate with whom. However they can＇t hide the fact that the users are using the anonymous communication technologies. File share software, such as BitTorrent and emule, has become the most popular application in Internet with users all over the world. In this paper, we present StegoP2P, a peer-to-peer based hidden communication method, which doesn＇t rely on a single system or a set of entry points. It is based on embedding the steganographic marker in the peer-to-peer meta-data exchange protocol, unlike other existing covert communication methods that rely on timing channel, and requires time synchronization. An efficient covert handshake protocol with steganographic marker techniques over peer-to-peer networks is proposed for unobservable communications, which allows users in peer-to-peer networks to exchange information secretly for circumventing Internet censorship. The steganography makes it easy for users to find the targeted content and difficult for a censor to identify them. Experimental results and security analysis show that our system has high performance and can defense against certain traffic censorships.