原文地址：http://www.theonionrouter.com/about/overview.html.en#overview
概述
“The Tor network is a group of volunteer-operated servers that allows people to improve their privacy and security on the Internet. Tor’s users employ this network by connecting through a series of virtual tunnels rather than making a direct connection, thus allowing both organizations and individuals to share information over public networks without compromising their privacy. Along the same line, Tor is an effective censorship circumvention tool, allowing its users to reach otherwise blocked destinations or content. Tor can also be used as a building block for software developers to create new communication tools with built-in privacy features.”
Tor网络由一组自运行服务器组成，满足了人们提升网络隐私和安全等级的需要。与传统直连不同，tor用户通过连接一系列虚拟隧道来访问网络。这样一来，机构和个人都不在需要以妥协隐私为代价来进行公共网络活动。同时，tor也是一款优秀的避开审查制度的工具。使用者可以访问本被禁止的地址或内容。它还在一些时候被软件开发者们内置于带隐私功能的通讯类软件。
“Individuals use Tor to keep websites from tracking them and their family members, or to connect to news sites, instant messaging services, or the like when these are blocked by their local Internet providers. Tor’s onion services let users publish web sites and other services without needing to reveal the location of the site. Individuals also use Tor for socially sensitive communication: chat rooms and web forums for rape and abuse survivors, or people with illnesses.”
个人用户可通过tor摆脱网站的跟踪、访问当地运营商禁掉的新闻站点和网络服务。Tor提供的“洋葱服务”允许用户在不暴露真实地址的情况下发布网站以及提供服务！个人用户同样可以用其交流一些较敏感的话题。如：
“Journalists use Tor to communicate more safely with whistleblowers and dissidents. Non-governmental organizations (NGOs) use Tor to allow their workers to connect to their home website while they’re in a foreign country, without notifying everybody nearby that they’re working with that organization.”
新闻工作者可以用其保证自身不遭受打击报复。NGO的工作人员可以通过Tor在异国访问组织的网站。并且不需要暴露自己和该组织的关系。
Groups such as Indymedia recommend Tor for safeguarding their members’ online privacy and security. Activist groups like the Electronic Frontier Foundation (EFF) recommend Tor as a mechanism for maintaining civil liberties online. Corporations use Tor as a safe way to conduct competitive analysis, and to protect sensitive procurement patterns from eavesdroppers. They also use it to replace traditional VPNs, which reveal the exact amount and timing of communication. Which locations have employees working late? Which locations have employees consulting job-hunting websites? Which research divisions are communicating with the company’s patent lawyers?
如Indymedia之类的团体出于保护其成员的网络隐私和安全也建议成员使用Tor。激进主义团体如EFF也推荐使用Tor作为一种维护网络自由的机制。大型集团经常使用Tor来防止被监听，以确保能安全地实施竞争调查以及保护敏感的采购规律。Tor也被用于替代传统虚拟代理，其能够显示准确的通讯时间和通讯量。哪个地区的员工加班晚？那个地区的雇员在找猎头公司？哪家调查机构和公司的专利律师有联络？
A branch of the U.S. Navy uses Tor for open source intelligence gathering, and one of its teams used Tor while deployed in the Middle East recently. Law enforcement uses Tor for visiting or surveilling web sites without leaving government IP addresses in their web logs, and for security during sting operations.
一直美国海军部队使用Tor公开招募智囊，其中一支小队在最近的中东部署中也用到了Tor。一些执法机关用Tor访问监控站点而不会在其网络日志中留下政府的IP地址，这也保证了钓鱼执法的安全有效。
The variety of people who use Tor is actually part of what makes it so secure. Tor hides you among the other users on the network, so the more populous and diverse the user base for Tor is, the more your anonymity will be protected.
用户多样性是保证Tor安全性中的重要一环。Tor让你隐藏在网络的其他用户之中。因此，Tor的用户群体越大越多样，你的隐匿性就会越发得到保护。
为什么需要Tor？
Using Tor protects you against a common form of Internet surveillance known as “traffic analysis.” Traffic analysis can be used to infer who is talking to whom over a public network. Knowing the source and destination of your Internet traffic allows others to track your behavior and interests. This can impact your checkbook if, for example, an e-commerce site uses price discrimination based on your country or institution of origin. It can even threaten your job and physical safety by revealing who and where you are. For example, if you’re travelling abroad and you connect to your employer’s computers to check or send mail, you can inadvertently reveal your national origin and professional affiliation to anyone observing the network, even if the connection is encrypted.
使用Tor能让你有效避免一种叫做“流量分析”的东东。流量分析可以被用于找出公共网络上哪两个人在通信。通过了解你的源和目的地址，其他人可以由此分析你的行为规律和喜好。这很大程度上会影响你的决策，比如说，一个电商网站可以根据你的人所在国家以及机构制定价格歧视策略。说得严重一些，它甚至有可能暴露你的实际地理位置，从而对你的现实人身安全造成威胁。比如说，如果你出国了然后你连了你雇主的计算机查发邮件，这个时候其实你已经一不小心就把你的国籍和单位信息暴露给了这个监听这个网络的人，就算链接是加密的也不例外。
How does traffic analysis work? Internet data packets have two parts: a data payload and a header used for routing. The data payload is whatever is being sent, whether that’s an email message, a web page, or an audio file. Even if you encrypt the data payload of your communications, traffic analysis still reveals a great deal about what you’re doing and, possibly, what you’re saying. That’s because it focuses on the header, which discloses source, destination, size, timing, and so on.
流量分析是怎么回事？网络数据包分两部分：用户数据和用来路由的数据包头。数据部分就是你真正要发送的部分，可能是一封电邮，一个网页，或者一个音频文件。即使你在通信过程中对数据部分进行了加密，数据分析仍然还是能分析出一大部分你正在干的事儿或者你正在说的话。那是因为它主要分析数据包头，包头里包含有源、目的、大小、时间以及其他种种信息。
A basic problem for the privacy minded is that the recipient of your communications can see that you sent it by looking at headers. So can authorized intermediaries like Internet service providers, and sometimes unauthorized intermediaries as well. A very simple form of traffic analysis might involve sitting somewhere between sender and recipient on the network, looking at headers.
从隐私的角度来说，有一个基础的问题要解决，就是接收方可以通过数据包头部信息知道是你发送了这些数据。被授权的网络中间方也可以看到，例如，运营商们。更可怕的是，有的时候，甚至未被授权的人也能查看这些信息。
But there are also more powerful kinds of traffic analysis. Some attackers spy on multiple parts of the Internet and use sophisticated statistical techniques to track the communications patterns of many different organizations and individuals. Encryption does not help against these attackers, since it only hides the content of Internet traffic, not the headers.
而流量分析的手段还远不止于此。有些攻击者监听着互联网的多个部分，并利用一些复杂的技术来跟踪许多不同机构或个人的通信规律。加密对于这种攻击者来说束手无策，因为它只能帮你隐藏数据内容，而包头部信息则赤裸裸地暴露在攻击者面前。
本文为纯翻译，不带有个人观点。有不当的地方请指正。
