first cut of the new, shiny...
Andrew Lewman authored 13 years ago
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9) <a href="<page about/about>">About » </a>
10) <a href="<page about/about>">Overview</a>
11) </div>
12) <div id="maincol">
13) <a name="overview"></a>
14) <h2><a class="anchor" href="#overview">Tor: Overview</a></h2>
15) <!-- BEGIN SIDEBAR -->
16) <div class="sidebar-left">
17) <h3>Topics</h3>
18) <ul>
19) <li><a href="<page about/overview>#overview">Overview</a></li>
20) <li><a href="<page about/overview>#whyweneedtor">Why we need Tor</a></li>
21) <li><a href="<page about/overview>#thesolution">The Solution</a></li>
22) <li><a href="<page about/overview>#hiddenservices">Hidden services</a></li>
23) <li><a href="<page about/overview>#stayinganonymous">Staying anonymous</a></li>
24) <li><a href="<page about/overview>#thefutureoftor">The future of Tor</a></li>
25) </ul>
26) </div>
27) <!-- END SIDEBAR -->
28)
29) <hr />
30)
31) <p>
32) Tor is a network of virtual tunnels that allows people and groups to
33) improve their privacy and security on the Internet. It also enables
34) software developers to create new communication tools
35) with built-in privacy features. Tor provides the foundation for
36) a range of applications that allow organizations and individuals
37) to share information over public networks without compromising their
38) privacy.
39) </p>
40)
41) <p>
42) Individuals use Tor to keep websites from tracking them and their family
43) members, or to connect to news sites, instant messaging services, or the
44) like when these are blocked by their local Internet providers. Tor's <a
45) href="<page docs/hidden-services>">hidden services</a>
46) let users publish web sites and other services without needing to reveal
47) the location of the site. Individuals also use Tor for socially sensitive
48) communication: chat rooms and web forums for rape and abuse survivors,
49) or people with illnesses.
50) </p>
51)
52) <p>
53) Journalists use Tor to communicate more safely with whistleblowers and
54) dissidents. Non-governmental organizations (NGOs) use Tor to allow their
55) workers to connect to their home website while they're in a foreign
56) country, without notifying everybody nearby that they're working with
57) that organization.
58) </p>
59)
60) <p>
61) Groups such as Indymedia recommend Tor for safeguarding their members'
62) online privacy and security. Activist groups like the Electronic Frontier
63) Foundation (EFF) recommend Tor as a mechanism for
64) maintaining civil liberties online. Corporations use Tor as a safe way
65) to conduct competitive analysis, and to protect sensitive procurement
66) patterns from eavesdroppers. They also use it to replace traditional
67) VPNs, which reveal the exact amount and timing of communication. Which
68) locations have employees working late? Which locations have employees
69) consulting job-hunting websites? Which research divisions are communicating
70) with the company's patent lawyers?
71) </p>
72)
73) <p>
74) A branch of the U.S. Navy uses Tor for open source intelligence
75) gathering, and one of its teams used Tor while deployed in the Middle
76) East recently. Law enforcement uses Tor for visiting or surveilling
77) web sites without leaving government IP addresses in their web logs,
78) and for security during sting operations.
79) </p>
80)
81) <p>
82) The variety of people who use Tor is actually <a
83) href="http://freehaven.net/doc/fc03/econymics.pdf">part of what makes
84) it so secure</a>. Tor hides you among <a href="<page about/torusers>">the
85) other users on the network</a>,
86) so the more populous and diverse the user base for Tor is, the more your
87) anonymity will be protected.
88) </p>
89)
90) <a name="whyweneedtor"></a>
91) <h3><a class="anchor" href="#whyweneedtor">Why we need Tor</a></h3>
92)
93) <p>
94) Using Tor protects you against a common form of Internet surveillance
95) known as "traffic analysis." Traffic analysis can be used to infer
96) who is talking to whom over a public network. Knowing the source
97) and destination of your Internet traffic allows others to track your
98) behavior and interests. This can impact your checkbook if, for example,
99) an e-commerce site uses price discrimination based on your country or
100) institution of origin. It can even threaten your job and physical safety
101) by revealing who and where you are. For example, if you're travelling
102) abroad and you connect to your employer's computers to check or send mail,
103) you can inadvertently reveal your national origin and professional
104) affiliation to anyone observing the network, even if the connection
105) is encrypted.
106) </p>
107)
108) <p>
109) How does traffic analysis work? Internet data packets have two parts:
110) a data payload and a header used for routing. The data payload is
111) whatever is being sent, whether that's an email message, a web page, or an
112) audio file. Even if you encrypt the data payload of your communications,
113) traffic analysis still reveals a great deal about what you're doing and,
114) possibly, what you're saying. That's because it focuses on the header,
115) which discloses source, destination, size, timing, and so on.
116) </p>
117)
118) <p>
119) A basic problem for the privacy minded is that the recipient of your
120) communications can see that you sent it by looking at headers. So can
121) authorized intermediaries like Internet service providers, and sometimes
122) unauthorized intermediaries as well. A very simple form of traffic
123) analysis might involve sitting somewhere between sender and recipient on
124) the network, looking at headers.
125) </p>
126)
127) <p>
128) But there are also more powerful kinds of traffic analysis. Some
129) attackers spy on multiple parts of the Internet and use sophisticated
130) statistical techniques to track the communications patterns of many
131) different organizations and individuals. Encryption does not help against
132) these attackers, since it only hides the content of Internet traffic, not
133) the headers.
134) </p>
135)
136) <a name="thesolution"></a>
137) <h3><a class="anchor" href="#thesolution">The solution: a distributed, anonymous network</a></h3>
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first cut of the new, shiny...