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5) #include "head.wmi" TITLE="Tor Project: FAQ" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">

8)     <a href="<page index>">Home &raquo; </a>

9)     <a href="<page docs/documentation>">Documentation &raquo; </a>
10)     <a href="<page docs/faq>">FAQ</a>
11)   </div>
12)   <div id="maincol">
13)     <!-- PUT CONTENT AFTER THIS TAG -->
14)     <h1>Tor FAQ</h1>

15)     <hr>

16)     
17)     <p>General questions:</p>
18)     <ul>
19)     <li><a href="#WhatIsTor">What is Tor?</a></li>
20)     <li><a href="#Torisdifferent">How is Tor different from other proxies?</a></li>
21)     <li><a href="#CompatibleApplications">What programs can I use with
22)     Tor?</a></li>
23)     <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
24)     <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
25)     <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
26)     CD?</a></li>
27)     <li><a href="#SupportMail">How can I get an answer to my
28)     Tor support mail?</a></li>
29)     <li><a href="#WhySlow">Why is Tor so slow?</a></li>
30)     <li><a href="#Funding">What would The Tor Project do with more
31)     funding?</a></li>
32)     </ul>
33)     
34)     <p>Compilation and Installation:</p>
35)     <ul>
36)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
37)     <li><a href="#PGPSigs">What are these "sig" files on the download
38)     page?</a></li>
39)     <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>
40)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
41)     have a virus or spyware?</a></li>
42)     <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</a></li>
43)     </ul>
44)     
45)     <p>Running Tor:</p>
46)     
47)     <p>Running a Tor client:</p>
48)     <ul>

49)     <li><a href="#DoesntWork">I installed Tor and Polipo but it's not
50)     working.</a></li>
51)     <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at
52)     start.</a></li>
53)     <li><a href="#ChooseEntryExit">Can I control which nodes (or country)
54)     are used for entry/exit?</a></li>
55)     <li><a href="#GoogleCaptcha">Google makes me solve a Captcha or tells
56)     me I have spyware installed.</a></li>
57)     <li><a href="#GmailWarning">Gmail warns me that my account may have
58)     been compromised.</a></li>

59)     </ul>
60)     
61)     <p>Running a Tor relay:</p>
62)     <ul>
63)     <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>
64)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal
65)     with abuse issues.</a></li>
66)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
67)     relay?</a></li>
68)     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?</a></li>
69)     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>
70)     </ul>
71)     
72)     <p>Running a Tor hidden service:</p>
73)     
74)     <p>Anonymity and Security:</p>
75)     <ul>
76)     <li><a href="#KeyManagement">Tell me about all the keys Tor uses.</a></li>
77)     </ul>
78)     
79)     <p>Alternate designs that we don't do (yet):</p>
80)     <ul>
81)     <li><a href="#EverybodyARelay">You should make every Tor user be a
82)     relay.</a></li>
83)     </ul>
84)     
85)     <p>Abuse</p>
86)     <ul>
87)     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
88)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
89)     relay?</a></li>
90)     </ul>
91)     
92)     <p>For other questions not yet on this version of the FAQ, see the <a

93)     href="<wikifaq>">wiki FAQ</a> for now.</p>

94)     

95)     <hr>

96)     
97)     <a id="General"></a>
98)     
99)     <a id="WhatIsTor"></a>
100)     <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
101)     
102)     <p>
103)     The name "Tor" can refer to several different components.
104)     </p>
105)     
106)     <p>
107)     The Tor software is a program you can run on your computer that helps keep
108)     you safe on the Internet. Tor protects you by bouncing your communications
109)     around a distributed network of relays run by volunteers all around
110)     the world: it prevents somebody watching your Internet connection from
111)     learning what sites you visit, and it prevents the sites you visit
112)     from learning your physical location. This set of volunteer relays is
113)     called the Tor network. You can read more about how Tor works on the <a
114)     href="<page about/overview>">overview page</a>.
115)     </p>
116)     
117)     <p>
118)     The Tor Project is a non-profit (charity) organization that maintains
119)     and develops the Tor software.
120)     </p>
121)     

122)     <hr>

123)     
124)     <a id="Torisdifferent"></a>
125)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
126)     <p>
127)     A typical proxy provider sets up a server somewhere on the Internet and allows you to use it to relay your traffic.  This creates a simple, easy to maintain architecture.  The users all enter and leave through the same server.  The provider may charge for use of the proxy, or fund their costs through advertisements on the server.  In the simplest configuration, you don't have to install anything.  You just have to point your browser at their proxy server.  Simple proxy providers are fine solutions if you do not want protections for your privacy and anonymity online and you trust the provider from doing bad things.  Some simple proxy providers use SSL to secure your connection to them.  This may protect you against local eavesdroppers, such as those at a cafe with free wifi Internet.
128)     </p>
129)     <p>
130)     Simple proxy providers also create a single point of failure.  The provider knows who you are and where you browse on the Internet.  They can see your traffic as it passes through their server.  In some cases, they can see your encrypted traffic as they relay it to your banking site or to ecommerce stores.  You have to trust the provider isn't doing any number of things, such as watching your traffic, injecting their own advertisements into your traffic stream, and isn't recording your personal details.
131)     </p>
132)     <p>
133)     Tor passes your traffic through at least 3 different servers before sending it on to the destination.  Tor does not modify, or even know, what you are sending into it.  It merely relays your traffic, completely encrypted through the Tor network and has it pop out somewhere else in the world, completely intact.  The Tor client is required because we assume you trust your local computer.  The Tor client manages the encryption and the path chosen through the network.  The relays located all over the world merely pass encrypted packets between themselves.</p>
134)     <p>
135)     <dl>
136)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad first of three servers can see encrypted Tor traffic coming from your computer.  It still doesn't know who you are and what you are doing over Tor.  It merely sees "This IP address is using Tor".  Tor is not illegal anywhere in the world, so using Tor by itself is fine.  You are still protected from this node figuring out who you are and where you are going on the Internet.</dd>
137)     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad third of three servers can see the traffic you sent into Tor.  It won't know who sent this traffic.  If you're using encryption, such as visiting a bank or e-commerce website, or encrypted mail connections, etc, it will only know the destination.  It won't be able to see the data inside the traffic stream.  You are still protected from this node figuring out who you are and if using encryption, what data you're sending to the destination.</dd>
138)     </dl>
139)     </p>
140)     

141)     <hr>

142)     
143)     <a id="CompatibleApplications"></a>
144)     <h3><a class="anchor" href="#CompatibleApplications">What programs can
145)     I use with Tor?</a></h3>
146)     
147)     <p>
148)     There are two pieces to "Torifying" a program: connection-level anonymity
149)     and application-level anonymity. Connection-level anonymity focuses on
150)     making sure the application's Internet connections get sent through Tor.
151)     This step is normally done by configuring
152)     the program to use your Tor client as a "socks" proxy, but there are
153)     other ways to do it too. For application-level anonymity, you need to
154)     make sure that the information the application sends out doesn't hurt
155)     your privacy. (Even if the connections are being routed through Tor, you
156)     still don't want to include sensitive information like your name.) This
157)     second step needs to be done on a program-by-program basis, which is
158)     why we don't yet recommend very many programs for safe use with Tor.
159)     </p>
160)     
161)     <p>
162)     Most of our work so far has focused on the Firefox web browser. The
163)     bundles on the <a href="<page download/download>">download page</a> automatically

164)     install the <a href="<page torbutton/index>">Torbutton Firefox

165)     extension</a> if you have Firefox installed. As of version 1.2.0,
166)     Torbutton now takes care of a lot of the connection-level and
167)     application-level worries.
168)     </p>
169)     
170)     <p>
171)     There are plenty of other programs you can use with Tor,
172)     but we haven't researched the application-level anonymity
173)     issues on them well enough to be able to recommend a safe
174)     configuration. Our wiki has a list of instructions for <a

175)     href="<wiki>TheOnionRouter/TorifyHOWTO">Torifying

176)     specific applications</a>. There's also a <a

177)     href="<wiki>TheOnionRouter/SupportPrograms">list

178)     of applications that help you direct your traffic through Tor</a>.
179)     Please add to these lists and help us keep them accurate!
180)     </p>
181)     

182)     <hr>

183)     
184)     <a id="WhyCalledTor"></a>
185)     <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
186)     
187)     <p>
188)     Because Tor is the onion routing network. When we were starting the
189)     new next-generation design and implementation of onion routing in
190)     2001-2002, we would tell people we were working on onion routing,
191)     and they would say "Neat. Which one?" Even if onion routing has
192)     become a standard household term, Tor was born out of the actual <a
193)     href="http://www.onion-router.net/">onion routing project</a> run by
194)     the Naval Research Lab.
195)     </p>
196)     
197)     <p>
198)     (It's also got a fine translation from German and Turkish.)
199)     </p>
200)     
201)     <p>
202)     Note: even though it originally came from an acronym, Tor is not spelled
203)     "TOR". Only the first letter is capitalized. In fact, we can usually
204)     spot people who haven't read any of our website (and have instead learned
205)     everything they know about Tor from news articles) by the fact that they
206)     spell it wrong.
207)     </p>
208)     

209)     <hr>

210)     
211)     <a id="Backdoor"></a>
212)     <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
213)     
214)     <p>
215)     There is absolutely no backdoor in Tor. Nobody has asked us to put one
216)     in, and we know some smart lawyers who say that it's unlikely that anybody
217)     will try to make us add one in our jurisdiction (U.S.). If they do
218)     ask us, we will fight them, and (the lawyers say) probably win.
219)     </p>
220)     
221)     <p>
222)     We think that putting a backdoor in Tor would be tremendously
223)     irresponsible to our users, and a bad precedent for security software
224)     in general. If we ever put a deliberate backdoor in our security
225)     software, it would ruin our professional reputations. Nobody would
226)     trust our software ever again &mdash; for excellent reason!
227)     </p>
228)     
229)     <p>
230)     But that said, there are still plenty of subtle attacks
231)     people might try. Somebody might impersonate us, or break into our
232)     computers, or something like that. Tor is open source, and you should
233)     always check the source (or at least the diffs since the last release)
234)     for suspicious things. If we (or the distributors) don't give you
235)     source, that's a sure sign something funny might be going on. You
236)     should also check the <a href="<page docs/verifying-signatures>">PGP
237)     signatures</a> on the releases, to make sure nobody messed with the
238)     distribution sites.
239)     </p>
240)     
241)     <p>
242)     Also, there might be accidental bugs in Tor that could affect your
243)     anonymity. We periodically find and fix anonymity-related bugs, so make
244)     sure you keep your Tor versions up-to-date.
245)     </p>
246)     

247)     <hr>

248)     
249)     <a id="DistributingTor"></a>
250)     <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on
251)     my magazine's CD?</a></h3>
252)     
253)     <p>
254)     Yes.
255)     </p>
256)     
257)     <p>
258)     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
259)     means we give you the rights to redistribute the Tor software, either
260)     modified or unmodified, either for a fee or gratis. You don't have to
261)     ask us for specific permission.
262)     </p>
263)     
264)     <p>
265)     However, if you want to redistribute the Tor software you must follow our
266)     <a href="<gitblob>LICENSE">LICENSE</a>.
267)     Essentially this means that you need to include our LICENSE file along
268)     with whatever part of the Tor software you're distributing.
269)     </p>
270)     
271)     <p>
272)     Most people who ask us this question don't want to distribute just the
273)     Tor software, though. They want to distribute the Tor bundles, which
274)     typically include <a href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>
275)     and <a href="<page projects/vidalia>">Vidalia</a>.
276)     You will need to follow the licenses for those programs
277)     as well. Both of them are distributed under the <a
278)     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General
279)     Public License</a>. The simplest way to obey their licenses is to
280)     include the source code for these programs everywhere you include
281)     the bundles themselves. Look for "source" packages on the <a
282)     href="<page projects/vidalia>">Vidalia page</a> and the <a
283)     href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo
284)     download page</a>.
285)     </p>
286)     
287)     <p>
288)     Also, you should make sure not to confuse your readers about what Tor is,
289)     who makes it, and what properties it provides (and doesn't provide). See
290)     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for details.
291)     </p>
292)     
293)     <p>
294)     Lastly, you should realize that we release new versions of the
295)     Tor software frequently, and sometimes we make backward incompatible
296)     changes. So if you distribute a particular version of the Tor software, it
297)     may not be supported &mdash; or even work &mdash; six months later. This
298)     is a fact of life for all security software under heavy development.
299)     </p>
300)     

301)     <hr>

302)     
303)     <a id="SupportMail"></a>
304)     <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
305)     Tor support mail?</a></h3>
306)     
307)     <p>
308)     Many people send the Tor developers mail privately, or send mail to
309)     our internal <a href="<page about/contact>">lists</a>, with questions about their
310)     specific setup &mdash; they can't get their firewall working right,
311)     they can't configure Polipo correctly, or so on. Sometimes our
312)     volunteers can answer these mails, but typically they need to spend
313)     most of their time on development tasks that will benefit more people.
314)     This is especially true if your question is already covered in the <a
315)     href="<page docs/documentation>">documentation</a> or on this FAQ.
316)     </p>
317)     
318)     <p>
319)     So if we don't answer your mail, first check the <a href="<page
320)     docs/documentation>">documentation</a> page, along with this FAQ,
321)     to make sure your question isn't already answered.  Then read <a
322)     href="http://www.catb.org/~esr/faqs/smart-questions.html">"How to ask
323)     questions the smart way"</a>. If this doesn't help you, note that we
324)     have <a href="<page docs/documentation>#Support">an IRC channel</a> where you
325)     can ask your questions (but if they are still open-ended, ill-formed,
326)     or not about Tor, you likely won't get much help there either). Lastly,
327)     people on the <a href="<page docs/documentation>#MailingLists">or-talk
328)     mailing list</a> may be able to provide some hints for you, if
329)     others have experienced your problems too. Be sure to look over <a
330)     href="http://archives.seul.org/or/talk/">the archives</a> first.
331)     </p>
332)     
333)     <p>
334)     Another strategy is to <a href="<page docs/tor-doc-relay>">run a Tor
335)     relay for a while</a>, and/or <a href="<page donate/donate>">donate money</a>
336)     <a href="<page getinvolved/volunteer>">or time</a> to the effort. We're more likely
337)     to pay attention to people who have demonstrated interest and commitment
338)     to giving back to the Tor community.
339)     </p>
340)     
341)     <p>
342)     If you find your answer, please stick around on the IRC channel or the
343)     mailing list and answer questions from others.
344)     </p>
345)     

346)     <hr>

347)     
348)     <a id="WhySlow"></a>
349)     <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
350)     
351)     <p>
352)     There are many reasons why the Tor network is currently slow.
353)     </p>
354)     
355)     <p>
356)     Before we answer, though, you should realize that Tor is never going to
357)     be blazing fast. Your traffic is bouncing through volunteers' computers
358)     in various parts of the world, and some bottlenecks and network latency
359)     will always be present. You shouldn't expect to see university-style
360)     bandwidth through Tor.
361)     </p>
362)     
363)     <p>
364)     But that doesn't mean that it can't be improved. The current Tor network
365)     is quite small compared to the number of people trying to use it, and
366)     many of these users don't understand or care that Tor can't currently
367)     handle file-sharing traffic load.
368)     </p>
369)     
370)     <p>
371)     For the much more in-depth answer, see <a

372)     href="<blog>why-tor-is-slow">Roger's blog

373)     post on the topic</a>, which includes both a detailed PDF and a video
374)     to go with it.
375)     </p>
376)     
377)     <p>
378)     What can you do to help?
379)     </p>
380)     
381)     <ul>
382)     
383)     <li>
384)     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
385)     for others</a>. Help make the Tor network large enough that we can handle
386)     all the users who want privacy and security on the Internet.
387)     </li>
388)     
389)     <li>

390)     <a href="<page projects/vidalia>">Help us make Tor more usable</a>. We

391)     especially need people to help make it easier to configure your Tor
392)     as a relay. Also, we need help with clear simple documentation to
393)     walk people through setting it up.
394)     </li>
395)     
396)     <li>
397)     There are some bottlenecks in the current Tor network. Help us design
398)     experiments to track down and demonstrate where the problems are, and
399)     then we can focus better on fixing them.
400)     </li>
401)     
402)     <li>
403)     There are some steps that individuals
404)     can take to improve their Tor performance. <a

405)     href="<wiki>TheOnionRouter/FireFoxTorPerf">You

406)     can configure your Firefox to handle Tor better</a>, <a
407)     href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
408)     Polipo with Tor</a>, or you can try <a href="<page download/download>">upgrading
409)     to the latest version of Tor</a>.  If this works well, please help by
410)     documenting what you did, and letting us know about it.
411)     </li>
412)     
413)     <li>
414)     Tor needs some architectural changes too. One important change is to
415)     start providing <a href="#EverybodyARelay">better service to people who
416)     relay traffic</a>. We're working on this, and we'll finish faster if we
417)     get to spend more time on it.
418)     </li>
419)     
420)     <li>
421)     Help do other things so we can do the hard stuff. Please take a moment
422)     to figure out what your skills and interests are, and then <a href="<page
423)     getinvolved/volunteer>">look at our volunteer page</a>.
424)     </li>
425)     
426)     <li>
427)     Help find sponsors for Tor. Do you work at a company or government agency
428)     that uses Tor or has a use for Internet privacy, e.g. to browse the
429)     competition's websites discreetly, or to connect back to the home servers
430)     when on the road without revealing affiliations? If your organization has
431)     an interest in keeping the Tor network working, please contact them about
432)     supporting Tor. Without sponsors, Tor is going to become even slower.
433)     </li>
434)     
435)     <li>
436)     If you can't help out with any of the above, you can still help out
437)     individually by <a href="<page donate/donate>">donating a bit of money to the
438)     cause</a>. It adds up!
439)     </li>
440)     
441)     </ul>
442)     

443)     <hr>

444)     
445)     <a id="Funding"></a>
446)     <h3><a class="anchor" href="#Funding">What would The Tor Project do with
447)     more funding?</a></h3>
448)     
449)     <p>
450)     We have about 1800 relays right now, pushing over 150 MB/s average
451)     traffic. We have several hundred thousand active users. But the Tor
452)     network is not yet self-sustaining.
453)     </p>
454)     
455)     <p>
456)     There are six main development/maintenance pushes that need attention:
457)     </p>
458)     
459)     <ul>
460)     
461)     <li>
462)     Scalability: We need to keep scaling and decentralizing the Tor
463)     architecture so it can handle thousands of relays and millions of
464)     users. The upcoming stable release is a major improvement, but there's
465)     lots more to be done next in terms of keeping Tor fast and stable.
466)     </li>
467)     
468)     <li>
469)     User support: With this many users, a lot of people are asking questions
470)     all the time, offering to help out with things, and so on. We need good
471)     clean docs, and we need to spend some effort coordinating volunteers.
472)     </li>
473)     
474)     <li>
475)     Relay support: the Tor network is run by volunteers, but they still need
476)     attention with prompt bug fixes, explanations when things go wrong,
477)     reminders to upgrade, and so on. The network itself is a commons, and
478)     somebody needs to spend some energy making sure the relay operators stay
479)     happy. We also need to work on <a href="#RelayOS">stability</a> on some
480)     platforms &mdash; e.g., Tor relays have problems on Win XP currently.
481)     </li>
482)     
483)     <li>
484)     Usability: Beyond documentation, we also need to work on usability of the
485)     software itself. This includes installers, clean GUIs, easy configuration
486)     to interface with other applications, and generally automating all of
487)     the difficult and confusing steps inside Tor. We've got a start on this

488)     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much more work

489)     remains — usability for privacy software has never been easy.
490)     </li>
491)     
492)     <li>
493)     Incentives: We need to work on ways to encourage people to configure
494)     their Tors as relays and exit nodes rather than just clients.
495)     <a href="#EverybodyARelay">We need to make it easy to become a relay,
496)     and we need to give people incentives to do it.</a>
497)     </li>
498)     
499)     <li>
500)     Research: The anonymous communications field is full
501)     of surprises and gotchas. In our copious free time, we
502)     also help run top anonymity and privacy conferences like <a
503)     href="http://petsymposium.org/">PETS</a>. We've identified a set of
504)     critical <a href="<page getinvolved/volunteer>#Research">Tor research questions</a>
505)     that will help us figure out how to make Tor secure against the variety of
506)     attacks out there. Of course, there are more research questions waiting
507)     behind these.
508)     </li>
509)     
510)     </ul>
511)     
512)     <p>
513)     We're continuing to move forward on all of these, but at this rate
514)     <a href="#WhySlow">the Tor network is growing faster than the developers
515)     can keep up</a>.
516)     Now would be an excellent time to add a few more developers to the effort
517)     so we can continue to grow the network.
518)     </p>
519)     
520)     <p>
521)     We are also excited about tackling related problems, such as
522)     censorship-resistance.
523)     </p>
524)     
525)     <p>
526)     We are proud to have <a href="<page about/sponsors>">sponsorship and support</a>
527)     from the Omidyar Network, the International Broadcasting Bureau, Bell
528)     Security Solutions, the Electronic Frontier Foundation, several government
529)     agencies and research groups, and hundreds of private contributors.
530)     </p>
531)     
532)     <p>
533)     However, this support is not enough to keep Tor abreast of changes in the
534)     Internet privacy landscape. Please <a href="<page donate/donate>">donate</a>
535)     to the project, or <a href="<page about/contact>">contact</a> our executive
536)     director for information on making grants or major donations.
537)     </p>
538)     

539)     <hr>

540)     
541)     <a id="HowUninstallTor"></a>
542)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
543)     
544)     <p>
545)     This depends entirely on how you installed it and which operating system you
546)     have. If you installed a package, then hopefully your package has a way to
547)     uninstall itself. The Windows packages include uninstallers. The proper way to
548)     completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any
549)     version of Windows is as follows:
550)     </p>
551)     
552)     <ol>
553)     <li>In your taskbar, right click on Vidalia (the green onion or the black head)
554)     and choose exit.</li>
555)     <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
556)     Process List. If it's running, right click and choose End Process.</li>
557)     <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
558)     This will remove the Vidalia bundle, which includes Tor and Polipo.</li>
559)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
560)     Click the Uninstall button.</li>
561)     </ol>
562)     
563)     <p>
564)     If you do not follow these steps (for example by trying to uninstall
565)     Vidalia, Tor, and Polipo while they are still running), you will need to
566)     reboot and manually remove the directory "Program Files\Vidalia Bundle".
567)     </p>
568)     
569)     <p>
570)     For Mac OS X, follow the <a
571)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
572)     </p>
573)     
574)     <p>
575)     If you installed by source, I'm afraid there is no easy uninstall method. But
576)     on the bright side, by default it only installs into /usr/local/ and it should
577)     be pretty easy to notice things there.
578)     </p>
579)     

580)     <hr>

581)     
582)     <a id="PGPSigs"></a>
583)     <h3><a class="anchor" href="#PGPSigs">What are these "sig" files on the
584)     download page?</a></h3>
585)     
586)     <p>
587)     These are PGP signatures, so you can verify that the file you've downloaded is
588)     exactly the one that we intended you to get.
589)     </p>
590)     
591)     <p>
592)     Please read the <a
593)     href="<page docs/verifying-signatures>">verifying signatures</a> page for details.
594)     </p>
595)     

596)     <hr>

597)     
598)     <a id="CompileTorWindows"></a>
599)     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
600)     Windows?</a></h3>
601)     
602)     <p>
603)     Try following the steps at <a href="<gitblob>doc/tor-win32-mingw-creation.txt">
604)     tor-win32-mingw-creation.txt</a>.
605)     </p>
606)     
607)     <p>
608)     (Note that you don't need to compile Tor yourself in order to use
609)     it. Most people just use the packages available on the <a href="<page
610)     download/download>">download page</a>.)
611)     </p>
612)     

613)     <hr>

614)     
615)     <a id="VirusFalsePositives"></a>
616)     <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
617)     executable appear to have a virus or spyware?</a></h3>
618)     
619)     <p>
620)     Sometimes, overzealous Windows virus and spyware detectors trigger on some
621)     parts of the Tor Windows binary. Our best guess is that these are false
622)     positives &mdash; after all, the anti-virus and anti-spyware business is just a
623)     guessing game anyway. You should contact your vendor and explain that you have
624)     a program that seems to be triggering false positives. Or pick a better vendor.
625)     </p>
626)     
627)     <p>
628)     In the meantime, we encourage you to not just take our word for
629)     it. Our job is to provide the source; if you're concerned, please do <a
630)     href="#CompileTorWindows">recompile it yourself</a>.
631)     </p>
632)     

633)     <hr>

634)     
635)     <a id="LiveCD"></a>
636)     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
637)     includes Tor?</a></h3>
638)     
639)     <p>
640)     There isn't any official LiveCD at this point. We're still trying to find good
641)     solutions and trying to understand the security and anonymity implications of
642)     the various options. In the mean time, feel free to check out the list below
643)     and use your best judgement:
644)     </p>
645)     
646)     <p>
647)     LiveCDs:
648)     </p>
649)     
650)     <ol>
651)     <li><a href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
652)     System</a> is a Live System aimed at preserving your privacy and
653)     anonymity:
654)     <ul>
655)     <li> All outgoing connections to the Internet are forced to go through
656)     the Tor network.</li>
657)     <li> No trace is left on local storage devices unless explicitely asked.</li>
658)     <li> It includes Firefox, Tor, Torbutton, Vidalia graphical Tor
659)     controller, Pidgin Instant Messaging client, and lots of other
660)     software.</li>
661)     <li> It's based upon Debian gnu/linux and comes with the GNOME desktop
662)     environment.</li>
663)     </ul>
664)     <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
665)     is Knoppix-based with an emphasis on user-friendliness. You can work
666)     anonymously or non-anonymously while TorK tries to keep you informed of the
667)     consequences of your activity. The TorK LiveCD is experimental, so the aim is
668)     to provide regular releases through 2007 and beyond.</li>
669)     <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
670)     debian based live-system including tor, firefox and torbutton which can save
671)     bookmarks and other settings or data on an encrypted usb-key</li>
672)     </li>
673)     </ol>
674)     
675)     <p>
676)     Windows bundles:
677)     </p>
678)     
679)     <ol>
680)     <li><a href="<page projects/torbrowser>">Tor Browser Bundle</a>
681)     for Windows comes with a pre-configured web browser and is self contained
682)     so you can run it from a USB stick.</li>
683)     <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
684)     to JanusVM. It needs testing from you!</li>
685)     <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
686)     running in VMWare that sits between your Windows computer and the Internet,
687)     making sure that your Internet traffic is scrubbed and anonymized.</li>
688)     <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
689)     previously known as Torpark, is a Firefox+Tor package for Win32 that can
690)     installed on a USB key. It needs a host Win32 operating system.</li>
691)     </ol>
692)     
693)     <p>
694)     Not currently maintained as far as we know:
695)     </p>
696)     
697)     <ol>
698)     <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
699)     and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
700)     download</a>.</li>
701)     <li>ELE is a Linux LiveCD which is focused on privacy related
702)     software. It includes Tor and you can download it at
703)     <a
704)     href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
705)     <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
706)     Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
707)     non-Tor traffic from accidentally leaving your computer. More information at

708)     <a href="<wiki>VirtualPrivacyMachine"><wiki>VirtualPrivacyMachine</a>.</li>

709)     <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
710)     than Linux for maximum security. It was designed to be anonymous and secure
711)     from the ground up, and thus has some features and limitations not found in
712)     other LiveCDs (Tor related or otherwise). You can obtain more information and
713)     download Anonym.OS from <a href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
714)     <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
715)     recent KNOPPIX release. It comes preconfigured with Privoxy, Tor and Polipo. You can
716)     get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
717)     Website</a>.</li>
718)     </ol>
719)     
720)     <p>
721)     Please contact us if you know any others.
722)     </p>

723) 
724) <hr>
725) 
726) <a id="DoesntWork"></a>
727) <h3><a class="anchor" href="#DoesntWork">I installed Tor and Polipo but
728) it's not working.</a></h3>
729) 
730) <p>
731) Once you've installed the Tor bundle, there are two questions to ask:
732) first, is your Tor able to establish a circuit? Second, is your
733) Firefox correctly configured to send its traffic through Tor?
734) </p>
735) 
736) <p>If Tor can establish a circuit, the onion icon in
737) Vidalia will turn green. You can also check in the Vidalia
738) Control Panel to make sure it says "Connected to the Tor
739) network!" under Status. For those not using Vidalia, check your <a

740) href="<wikifaq>#HowdoIsetuploggingorseeTorslogs">Tor logs</a> for

741) a line saying that Tor "has successfully opened a circuit. Looks like
742) client functionality is working."
743) </p>
744) 
745) <p>
746) If Tor can't establish a circuit, here are some hints:
747) </p>
748) 
749) <ol>
750) <li>Are you sure Tor is running? If you're using Vidalia, you may have
751) to click on the onion and select "Start" to launch Tor.</li>
752) <li>Check your system clock. If it's more than a few hours off, Tor will
753) refuse to build circuits. For XP users, synchronize your clock under
754) the clock -&gt; Internet time tab. In addition, correct the day and date
755) under the 'Date &amp; Time' Tab.</li>
756) <li>Is your Internet connection <a

757) href="<wikifaq>#Myfirewallonlyallowsafewoutgoingports.">firewalled</a>,

758) or do you normally need to use a <a

759) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</a>?

760) </li>
761) <li>Are you running programs like Norton Internet Security or SELinux that
762) block certain connections, even though you don't realize they do? They
763) could be preventing Tor from making network connections.</li>
764) <li>Are you in China, or behind a restrictive corporate network firewall
765) that blocks the public Tor relays? If so, you should learn about <a

766) href="<page docs/bridges>">Tor bridges</a>.</li>
767) <li>Check your <a href="<wikifaq>#HowdoIsetuploggingorseeTorslogs">Tor

768) logs</a>. Do they give you any hints about what's going wrong?</li>
769) </ol>
770) 
771) <p>
772) Step two is to confirm that Firefox is correctly configured to send its
773) traffic through Tor. Try the <a href="https://check.torproject.org/">Tor
774) Check</a> site and see whether it thinks you are using Tor. See <a

775) href="<wikifaq>#HowcanItellifTorisworkingandthatmyconnectionsreallyareanonymizedArethereexternalserversthatwilltestmyconnection">the

776) Tor Check FAQ entry</a> for details.
777) <p>
778) 
779) <p>
780) If it thinks you're not using Tor, here are some hints:
781) </p>
782) 
783) <ol>
784) <li>Did you install the Torbutton extension for Firefox? The installation
785) bundles include it, but sometimes people forget to install it. Make sure
786) it says "Tor enabled" at the bottom right of your Firefox window. (For
787) expert users, make sure your http proxy is set to localhost port
788) 8118.)</li>
789) <li>Do you have incompatible Firefox extensions like FoxyProxy
790) installed? If so, uninstall them. (Note that using FoxyProxy is NOT
791) a sufficient substitute for Torbutton. There are many known attacks
792) against a browser setup that does not include Torbutton. Read more

793) in the <a href="<page torbutton/torbutton-faq>">Torbutton FAQ</a> and the <a

794) href="https://www.torproject.org/torbutton/design/">Torbutton design</a>
795) specification.)</li>
796) <li>If your browser says "The proxy server is refusing connections.",
797) check that Polipo (the http proxy that passes traffic between Firefox
798) and Tor) is running. On Windows, look in the task manager and check for
799) a polipo.exe. On OS X, open the utilities folder in your applications
800) folder, and open Terminal.app. Then run "ps aux|grep polipo".</li>
801) <li>If you're upgrading from OS X, some of the earlier OS X installers
802) were broken in really unfortunate ways. You may find that <a href="<page
803) docs/tor-doc-osx>#uninstall">uninstalling everything</a> and then
804) installing a fresh bundle helps. Alas, the current uninstall instructions
805) may not apply anymore to your old bundle. Sorry.</li>
806) <li>If you're on Linux, make sure Privoxy isn't running, since it will
807) conflict with the port that our Polipo configuration file picks.</li>
808) <li>If you installed Polipo yourself (not from a bundle), did you edit the
809) config file as described? Did you restart Polipo after this change?</li>
810) <li>For Red Hat Linux and related systems, do you have SELinux enabled? If
811) so, it might be preventing Polipo from talking to Tor. We also run across
812) BSD users periodically who have local firewall rules that prevent some
813) connections to localhost.</li>
814) </ol>
815) 
816) <hr />
817) 
818) <a id="VidaliaPassword"></a>
819) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for
820) a password at start.</a></h3>
821) 
822) <p>
823) Vidalia interacts with the Tor software via Tor's "control port". The
824) control port lets Vidalia receive status updates from Tor, request a new
825) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
826) Vidalia sets a random password for Tor's control port to prevent other
827) applications from also connecting to the control port and potentially
828) compromising your anonymity.
829) </p>
830) 
831) <p>
832) Usually this process of generating and setting a random control password
833) happens in the background. There are three common situations, though,
834) where Vidalia may prompt you for a password:
835) </p>
836) 
837) <ol>
838) <li>You're already running Vidalia and Tor. For example, this situation
839) can happen if you installed the Vidalia bundle and now you're trying to
840) run the Tor Browser Bundle. In that case, you'll need to close the old
841) Vidalia and Tor before you can run this one.
842) </li>
843) <li>Vidalia crashed, but left Tor running with the last known random
844) password. After you restart Vidalia, it generates a new random password,
845) but Vidalia can't talk to Tor, because the random passwords are different.
846) <br />
847) If the dialog that prompts you for a control password has a Reset button,
848) you can click the button and Vidalia will restart Tor with a new random
849) control password.
850) <br />
851) If you do not see a Reset button, or if Vidalia is unable to restart
852) Tor for you, you can still fix the problem manually. Simply go into your
853) process or task manager, and terminate the Tor process. Then use Vidalia
854) to restart Tor and all will work again.
855) </li>
856) <li>You had previously set Tor to run as a Windows NT service. When Tor
857) is set to
858) run as a service, it starts up when the system boots. If you configured
859) Tor to start as a service through Vidalia, a random password was set
860) and saved in Tor. When you reboot, Tor starts up and uses the random
861) password it saved. You login and start up Vidalia. Vidalia attempts to
862) talk to the already running Tor. Vidalia generates a random password,
863) but it is different than the saved password in the Tor service.
864) <br />
865) You need to reconfigure Tor to not be a service. See the FAQ entry on

866) <a href="<wikifaq>#HowdoIrunmyTorrelayasanNTservice">running Tor as a Windows NT service</a>

867) for more information on how to remove the Tor service.
868) </li>
869) </ol>
870) 

871)     <hr>

872)     
873)     <a id="ChooseEntryExit"></a>
874)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>
875)     
876)     <p>
877)     Yes. You can set preferred entry and exit nodes as well as 
878)     inform Tor which nodes you do not want to use. 
879)     The following options can be added to your config file "torrc" 
880)     or specified on the command line:
881)     </p>
882)     <dl>
883)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
884)         <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
885)         </dd>
886)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>
887)         <dd>A list of preferred nodes to use for the last hop in the circuit, if possible. 
888)         </dd>
889)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>
890)         <dd>A list of nodes to never use when building a circuit. 
891)         </dd>
892)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>
893)         <dd>A list of nodes to never use when picking an exit. 
894)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list. 
895)         </dd>
896)     </dl>
897)     <p>
898)     <em>We recommend you do not use these</em> 
899)     &mdash; they are intended for testing and may disappear in future versions. 
900)     You get the best security that Tor can provide when you leave the route selection to Tor; 
901)     overriding the entry / exit nodes can mess up your anonymity in ways we don't understand.
902)     </p>
903)     <p>
904)     The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are treated as a request, 
905)     meaning if the nodes are down or seem slow, Tor will still avoid them. 
906)     You can make the option mandatory by setting 
907)     <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt> 
908)     &mdash; but if you do, your Tor connections will stop working 
909)     if all of the nodes you have specified become unreachable. 

910)     See the <a href="<page docs/documentation>#NeatLinks">Tor status pages</a> 

911)     for some nodes you might pick.
912)     </p>
913)     <p>
914)     Instead of <tt>$fingerprint</tt> you can also specify 
915)     a 2 letter ISO3166 country code in curly braces 
916)     (for example {de}), 
917)     or an ip address pattern (for example 255.254.0.0/8), 
918)     or a node nickname. 
919)     Make sure there are no spaces between the commas and the list items. 
920)     </p>
921)     <p>
922)     If you want to access a service directly through Tor's SOCKS interface 
923)     (eg. using ssh via connect.c), another option is to 
924)     set up an internal mapping in your configuration file using <tt>MapAddress</tt>. 
925)     See the manual page for details.
926)     </p>
927)     

928)     <hr>

929) 
930) <a id="GoogleCaptcha"></a>
931) <h3><a class="anchor" href="#GoogleCaptcha">Google makes me solve a
932) Captcha or tells me I have spyware installed.</a></h3>
933) 
934) <p>
935) This is a known and intermittent problem; it does not mean that Google
936) considers Tor to be spyware.
937) </p>
938) 
939) <p>
940) When you use Tor, you are sending queries through exit relays that are also
941) shared by thousands of other users. Tor users typically see this message
942) when many Tor users are querying Google in a short period of time. Google
943) interprets the high volume of traffic from a single IP address (the exit
944) relay you happened to pick) as somebody trying to "crawl" their website,
945) so it slows down traffic from that IP address for a short time.
946) </p>
947) <p>
948) An alternate explanation is that Google tries to detect certain
949) kinds of spyware or viruses that send distinctive queries to Google
950) Search. It notes the IP addresses from which those queries are received
951) (not realizing that they are Tor exit relays), and tries to warn any
952) connections coming from those IP addresses that recent queries indicate
953) an infection.
954) </p>
955) 
956) <p>
957) To our knowledge, Google is not doing anything intentionally specifically
958) to deter or block Tor use. The error message about an infected machine
959) should clear up again after a short time.
960) </p>
961) 
962) <p>
963) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
964) automatically redirect you to a more Tor-friendly search engine such as
965) Ixquick or Bing.
966) </p>
967) 
968) <hr />
969) 
970) <a id="GmailWarning"></a>
971) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my account
972) may have been compromised.</a></h3>
973) 
974) <p>
975) Sometimes, after you've used Gmail over Tor, Google presents a
976) pop-up notification that your account may have been compromised. The
977) notification window lists a series of IP addresses and locations throughout
978) the world recently used to access your account.
979) </p>
980) 
981) <p>
982) In general this is a false alarm: Google saw a bunch of logins from
983) different places  and wanted to let
984) you know. If you use Tor to access a Google service, then it will appear
985) like you're coming from lots of different places. Nothing to worry about
986) in particular.
987) </p>
988) 
989) <p>
990) But that doesn't mean you can entirely ignore the warning. It's
991) <i>probably</i> a false positive, but it might not be. It is possible
992) that somebody could at some point steal your Google cookie, which would
993) allow them to log in to the Google service as you. They might steal it
994) by breaking into your computer, or by watching your network traffic at
995) Starbucks or sniffing your wireless at home (when you're not using Tor),
996) or by watching traffic going over the Tor network. In theory none of
997) this should be possible because Gmail and similar services should only
998) send the cookie over an SSL link. In practice, alas, it's <a
999) href="http://fscked.org/blog/fully-automated-active-https-cookie-hijacking">way
1000) more complex than that</a>.
1001) </p>
1002) 
1003) <p>
1004) And if somebody <i>did</i> steal your google cookie, they might end
1005) up logging in from unusual places (though of course they also might
1006) not). So the summary is that since you're using Tor, this security
1007) measure that Google uses isn't so useful for you, because it's full of
1008) false positives. You'll have to use other approaches, like seeing if
1009) anything looks weird on the account, or looking at the timestamps for
1010) recent logins and wondering if you actually logged in at those times.
1011) </p>
1012) 
1013) <hr />
1014) 

1015)     <a id="RelayFlexible"></a>
1016)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1017)     need to be?</a></h3>
1018)     
1019)     <p>
1020)     We aim to make setting up a Tor relay easy and convenient:
1021)     </p>
1022)     
1023)     <ul>
1024)     <li>Tor has built-in support for <a

1025)     href="<wikifaq>#LimitBandwidth">

1026)     rate limiting</a>. Further, if you have a fast
1027)     link but want to limit the number of bytes per
1028)     day (or week or month) that you donate, check out the <a

1029)     href="<wikifaq>#Hibernation">hibernation

1030)     feature</a>.
1031)     </li>
1032)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
1033)     specifies what sort of outbound connections are allowed or refused from
1034)     that relay. If you are uncomfortable allowing people to exit from your
1035)     relay, you can set it up to only allow connections to other Tor relays.
1036)     </li>
1037)     <li>It's fine if the relay goes offline sometimes. The directories
1038)     notice this quickly and stop advertising the relay. Just try to make
1039)     sure it's not too often, since connections using the relay when it
1040)     disconnects will break.
1041)     </li>
1042)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1043)     leave the Address config option blank, and Tor will try to guess.
1044)     </li>
1045)     <li>If your relay is behind a NAT and it doesn't know its public
1046)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port
1047)     forwarding. Forwarding TCP connections is system dependent but 

1048)     <a href="<wikifaq>#ServerForFirewalledClients">this FAQ entry</a> 

1049)     offers some examples on how to do this.
1050)     </li>
1051)     <li>Your relay will passively estimate and advertise its recent
1052)     bandwidth capacity, so high-bandwidth relays will attract more users than
1053)     low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
1054)     </li>
1055)     </ul>
1056)     

1057)     <hr>

1058)     
1059)     <a id="RunARelayBut"></a>
1060)     <a id="ExitPolicies"></a>
1061)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't
1062)     want to deal with abuse issues.</a></h3>
1063)     
1064)     <p>
1065)     Great. That's exactly why we implemented exit policies.
1066)     </p>
1067)     
1068)     <p>
1069)     Each Tor relay has an exit policy that specifies what sort of
1070)     outbound connections are allowed or refused from that relay. The exit
1071)     policies are propagated to Tor clients via the directory, so clients
1072)     will automatically avoid picking exit relays that would refuse to
1073)     exit to their intended destination. This way each relay can decide
1074)     the services, hosts, and networks he wants to allow connections to,
1075)     based on abuse potential and his own situation. Read the FAQ entry on 
1076)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might encounter</a> 
1077)     if you use the default exit policy, and then read Mike Perry's 

1078)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1079)     for running an exit node with minimal harassment</a>.
1080)     </p>
1081)     
1082)     <p>
1083)     The default exit policy allows access to many popular services (e.g. web browsing), but 

1084)     <a href="<wikifaq>#DefaultPorts">restricts</a>

1085)     some due to abuse potential (e.g. mail) and some since
1086)     the Tor network can't handle the load (e.g. default
1087)     file-sharing ports). You can change your exit policy
1088)     using Vidalia's "Sharing" tab, or by manually editing your 

1089)     <a href="<wikifaq>#torrc">torrc</a>

1090)     file. If you want to avoid most if not all abuse potential, set it to
1091)     "reject *:*" (or un-check all the boxes in Vidalia). This setting means
1092)     that your relay will be used for relaying traffic inside the Tor network,
1093)     but not for connections to external websites or other services.
1094)     </p>
1095)     
1096)     <p>
1097)     If you do allow any exit connections, make sure name resolution works
1098)     (that is, your computer can resolve Internet addresses correctly).
1099)     If there are any resources that your computer can't reach (for example,
1100)     you are behind a restrictive firewall or content filter), please
1101)     explicitly reject them in your exit policy &mdash; otherwise Tor users
1102)     will be impacted too.
1103)     </p>
1104)     

1105)     <hr>

1106)     
1107)     <a id="RelayOrBridge"></a>
1108)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay
1109)     or bridge relay?</a></h3>
1110)     
1111)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for short)
1112)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
1113)     in the main Tor directory. That means
1114)     that even an ISP or government trying to filter connections to the Tor
1115)     network probably won't be able to block all the bridges.
1116)     </p>
1117)     
1118)     <p>Being a normal relay vs being a bridge relay is almost the same
1119)     configuration: it's just a matter of whether your relay is listed
1120)     publically or not.
1121)     </p>
1122)     

1123)     <p>Right now, there are a small number of places in the world that filter

1124)     connections to the Tor network. So getting a lot of bridges running
1125)     right now is mostly a backup measure, a) in case the Tor network does
1126)     get blocked somewhere, and b) for people who want an extra layer of
1127)     security because they're worried somebody will recognize that it's a
1128)     public Tor relay IP address they're contacting.
1129)     </p>
1130)     
1131)     <p>So should you run a normal relay or bridge relay? If you have
1132)     lots of bandwidth, you should definitely run a normal relay &mdash;
1133)     bridge relays see very little use these days. If you're willing to 
1134)     <a href="#ExitPolicies">be an exit</a>, you should definitely run a normal
1135)     relay, since we need more exits. If you can't be an exit and only have
1136)     a little bit of bandwidth, then flip a coin. Thanks for volunteering!
1137)     </p>
1138)     

1139)     <hr>

1140)     
1141)     <a id="RelayMemory"></a>
1142)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so
1143)     much memory?</a></h3>
1144)     
1145)     <p>If your Tor relay is using more memory than you'd like, here are some
1146)     tips for reducing its footprint:
1147)     </p>
1148)     
1149)     <ol>
1150)     <li>If you're on Linux, you may be encountering memory fragmentation
1151)     bugs in glibc's malloc implementation. That is, when Tor releases memory
1152)     back to the system, the pieces of memory are fragmented so they're hard
1153)     to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
1154)     which doesn't have as many fragmentation bugs (but the tradeoff is higher
1155)     CPU load). You can tell Tor to use this malloc implementation instead:
1156)     <tt>./configure --enable-openbsd-malloc</tt></li>
1157)     
1158)     <li>If you're running a fast relay, meaning you have many TLS connections
1159)     open, you are probably losing a lot of memory to OpenSSL's internal
1160)     buffers (38KB+ per socket). We've patched OpenSSL to <a
1161)     href="http://archives.seul.org/or/dev/Jun-2008/msg00001.html">release
1162)     unused buffer memory more aggressively</a>. If you update to OpenSSL
1163)     1.0.0-beta5, Tor's build process will automatically recognize and use
1164)     this feature.</li>
1165)     
1166)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1167)     old FreeBSD, Tor is probably forking separate processes
1168)     rather than using threads. Consider switching to a <a

1169)     href="<wikifaq>#RelayOS">better

1170)     operating system</a>.</li>
1171)     
1172)     <li>If you still can't handle the memory load, consider reducing the
1173)     amount of bandwidth your relay advertises. Advertising less bandwidth
1174)     means you will attract fewer users, so your relay shouldn't grow
1175)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1176)     page.</li>
1177)     
1178)     </ol>
1179)     
1180)     <p>
1181)     All of this said, fast Tor relays do use a lot of ram. It is not unusual
1182)     for a fast exit relay to use 500-1000 MB of memory.
1183)     </p>
1184)     

1185)     <hr>

1186)     
1187)     <a id="WhyNotNamed"></a>
1188)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not named?</a></h3>
1189)     
1190)     <p>

1191)     We currently use these metrics to determine if your relay should be named:<br>

1192)     </p>
1193)     <ul>
1194)     <li>The name is not currently mapped to a different key. Existing mappings
1195)     are removed after 6 months of inactivity from a relay.</li>
1196)     <li>The relay must have been around for at least two weeks.</li>
1197)     <li>No other router may have wanted the same name in the past month.</li>
1198)     </ul>
1199)     

1200)     <hr>

1201)     
1202)     <a id="KeyManagement"></a>
1203)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
1204)     Tor uses.</a></h3>
1205)     
1206)     <p>
1207)     Tor uses a variety of different keys, with three goals in mind: 1)
1208)     encryption to ensure privacy of data within the Tor network, 2)
1209)     authentication so clients know they're
1210)     talking to the relays they meant to talk to, and 3) signatures to make
1211)     sure all clients know the same set of relays.
1212)     </p>
1213)     
1214)     <p>
1215)     <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
1216)     so observers can't look inside to see which circuit a given cell is
1217)     intended for. Further, the Tor client establishes an ephemeral encryption
1218)     key with each relay in the circuit, so only the exit relay can read
1219)     the cells. Both sides discard the circuit key when the circuit ends,
1220)     so logging traffic and then breaking into the relay to discover the key
1221)     won't work.
1222)     </p>
1223)     
1224)     <p>
1225)     <b>Authentication</b>:
1226)     Every Tor relay has a public decryption key called the "onion key".
1227)     When the Tor client establishes circuits, at each step it <a
1228)     href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands
1229)     that the Tor relay prove knowledge of its onion key</a>. That way
1230)     the first node in the path can't just spoof the rest of the path.
1231)     Each relay rotates its onion key once a week.
1232)     </p>
1233)     
1234)     <p>
1235)     <b>Coordination</b>:
1236)     How do clients know what the relays are, and how do they know that they
1237)     have the right keys for them? Each relay has a long-term public signing
1238)     key called the "identity key". Each directory authority additionally has a
1239)     "directory signing key". The directory authorities <a
1240)     href="<gitblob>doc/spec/dir-spec.txt">provide a signed list</a>
1241)     of all the known relays, and in that list are a set of certificates from
1242)     each relay (self-signed by their identity key) specifying their keys,
1243)     locations, exit policies, and so on. So unless the adversary can control
1244)     a threshold of the directory authorities, he can't trick the Tor client
1245)     into using other Tor relays.
1246)     </p>
1247)     
1248)     <p>
1249)     How do clients know what the directory authorities are? The Tor software
1250)     comes with a built-in list of location and public key for each directory
1251)     authority. So the only way to trick users into using a fake Tor network
1252)     is to give them a specially modified version of the software.
1253)     </p>
1254)     
1255)     <p>
1256)     How do users know they've got the right software? When we distribute
1257)     the source code or a package, we digitally sign it with <a
1258)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
1259)     href="<page docs/verifying-signatures>">instructions
1260)     on how to check Tor's signatures</a>.
1261)     </p>
1262)     
1263)     <p>
1264)     In order to be certain that it's really signed by us, you need to have
1265)     met us in person and gotten a copy of our GPG key fingerprint, or you
1266)     need to know somebody who has. If you're concerned about an attack on
1267)     this level, we recommend you get involved with the security community
1268)     and start meeting people.
1269)     </p>
1270)     

1271)     <hr>

1272)     
1273)     <a id="EverybodyARelay"></a>
1274)     <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
1275)     user be a relay.</a></h3>
1276)     
1277)     <p>
1278)     Requiring every Tor user to be a relay would help with scaling the

1279)     network to handle all our users, and <a href="<wikifaq>#RelayAnonymity">running a Tor

1280)     relay may help your anonymity</a>. However, many Tor users cannot be good
1281)     relays &mdash; for example, some Tor clients operate from behind restrictive
1282)     firewalls, connect via modem, or otherwise aren't in a position where they
1283)     can relay traffic. Providing service to these clients is a critical
1284)     part of providing effective anonymity for everyone, since many Tor users
1285)     are subject to these or similar constraints and including these clients
1286)     increases the size of the anonymity set.
1287)     </p>
1288)     
1289)     <p>
1290)     That said, we do want to encourage Tor users to run relays, so what we
1291)     really want to do is simplify the process of setting up and maintaining
1292)     a relay. We've made a lot of progress with easy configuration in the past
1293)     few years: Vidalia has an easy relay configuration interface, and supports
1294)     uPnP too. Tor is good at automatically detecting whether it's reachable and
1295)     how much bandwidth it can offer.
1296)     </p>
1297)     
1298)     <p>
1299)     There are five steps we need to address before we can do this though:
1300)     </p>
1301)     
1302)     <p>
1303)     First, we need to make Tor stable as a relay on all common
1304)     operating systems. The main remaining platform is Windows,
1305)     and we plan to finally address that in 2009. See Section 4.1 of <a
1306)     href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
1307)     development roadmap</a>.
1308)     </p>
1309)     
1310)     <p>
1311)     Second, we still need to get better at automatically estimating
1312)     the right amount of bandwidth to allow. See item #7 on the
1313)     <a href="<page getinvolved/volunteer>#Research">research section of the
1314)     volunteer page</a>: "Tor doesn't work very well when relays
1315)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

1316)     href="<wikifaq>#TransportIPnotTCP">switching

1317)     to UDP transport</a> is the simplest answer here &mdash; which alas is
1318)     not a very simple answer at all.
1319)     </p>
1320)     
1321)     <p>
1322)     Third, we need to work on scalability, both of the network (how to
1323)     stop requiring that all Tor relays be able to connect to all Tor
1324)     relays) and of the directory (how to stop requiring that all Tor
1325)     users know about all Tor relays). Changes like this can have large
1326)     impact on potential and actual anonymity. See Section 5 of the <a
1327)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
1328)     for details. Again, UDP transport would help here.
1329)     </p>
1330)     
1331)     <p>
1332)     Fourth, we need to better understand the risks from
1333)     letting the attacker send traffic through your relay while
1334)     you're also initiating your own anonymized traffic. <a
1335)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
1336)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
1337)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
1338)     describe ways to identify the relays in a circuit by running traffic
1339)     through candidate relays and looking for dips in the traffic while the
1340)     circuit is active. These clogging attacks are not that scary in the Tor
1341)     context so long as relays are never clients too. But if we're trying to
1342)     encourage more clients to turn on relay functionality too (whether as
1343)     <a href="<page docs/bridges>">bridge relays</a> or as normal relays), then
1344)     we need to understand this threat better and learn how to mitigate it.
1345)     </p>
1346)     
1347)     <p>
1348)     Fifth, we might need some sort of incentive scheme to encourage people
1349)     to relay traffic for others, and/or to become exit nodes. Here are our

1350)     <a href="<blog>two-incentive-designs-tor">current

1351)     thoughts on Tor incentives</a>.
1352)     </p>
1353)     
1354)     <p>
1355)     Please help on all of these!
1356)     </p>
1357)     

1358)     <hr>

1359)     
1360)     <a id="Criminals"></a>
1361)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
1362)     things?</a></h3>
1363)     
1364)     <p>
1365)     For the answer to this question and others, please see our <a
1366)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
1367)     </p>
1368)     

1369)     <hr>

1370)     
1371)     <a id="RespondISP"></a>
1372)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
1373)     exit relay?</a></h3>
1374)     
1375)     <p>
1376)     A collection of templates for successfully responding to ISPs is <a

1377)     href="<wiki>TheOnionRouter/TorAbuseTemplates">collected

1378)     here</a>.
1379)     </p>
1380)     

1381)     <hr>