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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)     <li><a href="#Metrics">How many people use Tor? How many relays or
33)     exit nodes are there?</a></li>

34)     </ul>

35) 

36)     <p>Compilation and Installation:</p>
37)     <ul>
38)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
39)     <li><a href="#PGPSigs">What are these "sig" files on the download
40)     page?</a></li>
41)     <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>
42)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
43)     have a virus or spyware?</a></li>
44)     <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</a></li>
45)     </ul>

46) 

47)     <p>Running Tor:</p>

48)     <ul>
49)     <li><a href="#torrc">I'm supposed to "edit my torrc". What does
50)     that mean?</a></li>
51)     </ul>

52) 

53)     <p>Running a Tor client:</p>
54)     <ul>

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

65)     <li><a href="#FirewallPorts">My firewall only allows a few outgoing
66)     ports.</a></li>

67)     </ul>

68) 

69)     <p>Running a Tor relay:</p>
70)     <ul>
71)     <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>
72)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal
73)     with abuse issues.</a></li>
74)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
75)     relay?</a></li>

76)     <li><a href="#ManyRelays">I want to run more than one relay.</a></li>

77)     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?</a></li>
78)     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>
79)     </ul>

80) 

81)     <p>Running a Tor hidden service:</p>

82) 

83)     <p>Anonymity and Security:</p>
84)     <ul>
85)     <li><a href="#KeyManagement">Tell me about all the keys Tor uses.</a></li>

86)     <li><a href="#EntryGuards">What are Entry Guards?</a></li>

87)     </ul>

88) 

89)     <p>Alternate designs that we don't do (yet):</p>
90)     <ul>
91)     <li><a href="#EverybodyARelay">You should make every Tor user be a
92)     relay.</a></li>
93)     </ul>

94) 

95)     <p>Abuse:</p>

96)     <ul>
97)     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
98)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
99)     relay?</a></li>
100)     </ul>

101) 

102)     <p>For other questions not yet on this version of the FAQ, see the <a

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

104) 

105)     <hr>

106) 

107)     <a id="General"></a>

108) 

109)     <a id="WhatIsTor"></a>
110)     <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>

111) 

112)     <p>
113)     The name "Tor" can refer to several different components.
114)     </p>

115) 

116)     <p>
117)     The Tor software is a program you can run on your computer that helps keep
118)     you safe on the Internet. Tor protects you by bouncing your communications
119)     around a distributed network of relays run by volunteers all around
120)     the world: it prevents somebody watching your Internet connection from
121)     learning what sites you visit, and it prevents the sites you visit
122)     from learning your physical location. This set of volunteer relays is
123)     called the Tor network. You can read more about how Tor works on the <a
124)     href="<page about/overview>">overview page</a>.
125)     </p>

126) 

127)     <p>
128)     The Tor Project is a non-profit (charity) organization that maintains
129)     and develops the Tor software.
130)     </p>

131) 

132)     <hr>

133) 

134)     <a id="Torisdifferent"></a>
135)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
136)     <p>

137)     A typical proxy provider sets up a server somewhere on the Internet and
138) allows you to use it to relay your traffic.  This creates a simple, easy to
139) maintain architecture.  The users all enter and leave through the same server.
140) The provider may charge for use of the proxy, or fund their costs through
141) advertisements on the server.  In the simplest configuration, you don't have to
142) install anything.  You just have to point your browser at their proxy server.
143) Simple proxy providers are fine solutions if you do not want protections for
144) your privacy and anonymity online and you trust the provider from doing bad
145) things.  Some simple proxy providers use SSL to secure your connection to them.
146) This may protect you against local eavesdroppers, such as those at a cafe with
147) free wifi Internet.
148)     </p>
149)     <p>
150)     Simple proxy providers also create a single point of failure.  The provider
151) knows who you are and where you browse on the Internet.  They can see your
152) traffic as it passes through their server.  In some cases, they can see your
153) encrypted traffic as they relay it to your banking site or to ecommerce stores.
154) You have to trust the provider isn't doing any number of things, such as
155) watching your traffic, injecting their own advertisements into your traffic
156) stream, and isn't recording your personal details.
157)     </p>
158)     <p>
159)     Tor passes your traffic through at least 3 different servers before sending
160) it on to the destination.  Tor does not modify, or even know, what you are
161) sending into it.  It merely relays your traffic, completely encrypted through
162) the Tor network and has it pop out somewhere else in the world, completely
163) intact.  The Tor client is required because we assume you trust your local
164) computer.  The Tor client manages the encryption and the path chosen through
165) the network.  The relays located all over the world merely pass encrypted
166) packets between themselves.</p>

167)     <p>
168)     <dl>

169)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad first of
170) three servers can see encrypted Tor traffic coming from your computer.  It
171) still doesn't know who you are and what you are doing over Tor.  It merely sees
172) "This IP address is using Tor".  Tor is not illegal anywhere in the world, so
173) using Tor by itself is fine.  You are still protected from this node figuring
174) out who you are and where you are going on the Internet.</dd>
175)     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad third
176) of three servers can see the traffic you sent into Tor.  It won't know who sent
177) this traffic.  If you're using encryption, such as visiting a bank or
178) e-commerce website, or encrypted mail connections, etc, it will only know the
179) destination.  It won't be able to see the data inside the traffic stream.  You
180) are still protected from this node figuring out who you are and if using
181) encryption, what data you're sending to the destination.</dd>

182)     </dl>
183)     </p>

184) 

185)     <hr>

186) 

187)     <a id="CompatibleApplications"></a>
188)     <h3><a class="anchor" href="#CompatibleApplications">What programs can
189)     I use with Tor?</a></h3>

190) 

191)     <p>
192)     There are two pieces to "Torifying" a program: connection-level anonymity
193)     and application-level anonymity. Connection-level anonymity focuses on
194)     making sure the application's Internet connections get sent through Tor.
195)     This step is normally done by configuring
196)     the program to use your Tor client as a "socks" proxy, but there are
197)     other ways to do it too. For application-level anonymity, you need to
198)     make sure that the information the application sends out doesn't hurt
199)     your privacy. (Even if the connections are being routed through Tor, you
200)     still don't want to include sensitive information like your name.) This
201)     second step needs to be done on a program-by-program basis, which is
202)     why we don't yet recommend very many programs for safe use with Tor.
203)     </p>

204) 

205)     <p>
206)     Most of our work so far has focused on the Firefox web browser. The
207)     bundles on the <a href="<page download/download>">download page</a> automatically

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

209)     extension</a> if you have Firefox installed. As of version 1.2.0,
210)     Torbutton now takes care of a lot of the connection-level and
211)     application-level worries.
212)     </p>

213) 

214)     <p>
215)     There are plenty of other programs you can use with Tor,
216)     but we haven't researched the application-level anonymity
217)     issues on them well enough to be able to recommend a safe
218)     configuration. Our wiki has a list of instructions for <a

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

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

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

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

225) 

226)     <hr>

227) 

228)     <a id="WhyCalledTor"></a>
229)     <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>

230) 

231)     <p>
232)     Because Tor is the onion routing network. When we were starting the
233)     new next-generation design and implementation of onion routing in
234)     2001-2002, we would tell people we were working on onion routing,
235)     and they would say "Neat. Which one?" Even if onion routing has
236)     become a standard household term, Tor was born out of the actual <a
237)     href="http://www.onion-router.net/">onion routing project</a> run by
238)     the Naval Research Lab.
239)     </p>

240) 

241)     <p>
242)     (It's also got a fine translation from German and Turkish.)
243)     </p>

244) 

245)     <p>
246)     Note: even though it originally came from an acronym, Tor is not spelled
247)     "TOR". Only the first letter is capitalized. In fact, we can usually
248)     spot people who haven't read any of our website (and have instead learned
249)     everything they know about Tor from news articles) by the fact that they
250)     spell it wrong.
251)     </p>

252) 

253)     <hr>

254) 

255)     <a id="Backdoor"></a>
256)     <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>

257) 

258)     <p>
259)     There is absolutely no backdoor in Tor. Nobody has asked us to put one
260)     in, and we know some smart lawyers who say that it's unlikely that anybody
261)     will try to make us add one in our jurisdiction (U.S.). If they do
262)     ask us, we will fight them, and (the lawyers say) probably win.
263)     </p>

264) 

265)     <p>
266)     We think that putting a backdoor in Tor would be tremendously
267)     irresponsible to our users, and a bad precedent for security software
268)     in general. If we ever put a deliberate backdoor in our security
269)     software, it would ruin our professional reputations. Nobody would
270)     trust our software ever again &mdash; for excellent reason!
271)     </p>

272) 

273)     <p>
274)     But that said, there are still plenty of subtle attacks
275)     people might try. Somebody might impersonate us, or break into our
276)     computers, or something like that. Tor is open source, and you should
277)     always check the source (or at least the diffs since the last release)
278)     for suspicious things. If we (or the distributors) don't give you
279)     source, that's a sure sign something funny might be going on. You
280)     should also check the <a href="<page docs/verifying-signatures>">PGP
281)     signatures</a> on the releases, to make sure nobody messed with the
282)     distribution sites.
283)     </p>

284) 

285)     <p>
286)     Also, there might be accidental bugs in Tor that could affect your
287)     anonymity. We periodically find and fix anonymity-related bugs, so make
288)     sure you keep your Tor versions up-to-date.
289)     </p>

290) 

291)     <hr>

292) 

293)     <a id="DistributingTor"></a>
294)     <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on
295)     my magazine's CD?</a></h3>

296) 

297)     <p>
298)     Yes.
299)     </p>

300) 

301)     <p>
302)     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
303)     means we give you the rights to redistribute the Tor software, either
304)     modified or unmodified, either for a fee or gratis. You don't have to
305)     ask us for specific permission.
306)     </p>

307) 

308)     <p>
309)     However, if you want to redistribute the Tor software you must follow our
310)     <a href="<gitblob>LICENSE">LICENSE</a>.
311)     Essentially this means that you need to include our LICENSE file along
312)     with whatever part of the Tor software you're distributing.
313)     </p>

314) 

315)     <p>
316)     Most people who ask us this question don't want to distribute just the
317)     Tor software, though. They want to distribute the Tor bundles, which
318)     typically include <a href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>
319)     and <a href="<page projects/vidalia>">Vidalia</a>.
320)     You will need to follow the licenses for those programs
321)     as well. Both of them are distributed under the <a
322)     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General
323)     Public License</a>. The simplest way to obey their licenses is to
324)     include the source code for these programs everywhere you include
325)     the bundles themselves. Look for "source" packages on the <a
326)     href="<page projects/vidalia>">Vidalia page</a> and the <a
327)     href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo
328)     download page</a>.
329)     </p>

330) 

331)     <p>
332)     Also, you should make sure not to confuse your readers about what Tor is,
333)     who makes it, and what properties it provides (and doesn't provide). See
334)     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for details.
335)     </p>

336) 

337)     <p>
338)     Lastly, you should realize that we release new versions of the
339)     Tor software frequently, and sometimes we make backward incompatible
340)     changes. So if you distribute a particular version of the Tor software, it
341)     may not be supported &mdash; or even work &mdash; six months later. This
342)     is a fact of life for all security software under heavy development.
343)     </p>

344) 

345)     <hr>

346) 

347)     <a id="SupportMail"></a>
348)     <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
349)     Tor support mail?</a></h3>

350) 

351)     <p>There is no official support for Tor. Your best bet is to try the following:</p>

352)     <ol>
353)     <li>Read through this <a href="<page docs/faq>">FAQ</a>.</li>
354)     <li>Read through the <a href="<page docs/documentation>">documentation</a>.</li>
355)     <li>Read through the <a
356)     href="http://archives.seul.org/or/talk">OR-TALK Archives</a> and
357)     see if your question is already answered.</li>
358)     <li>Join our <a href="irc://irc.oftc.net#tor">irc channel</a> and
359)     state the issue and wait for help.</li>
360)     <li>Send an email to tor-assistants at torproject.org. These are
361)     volunteers who may be able to help you but you may not get a response
362)     for days.</li>
363)     </ol>

364) 

365)     <p>If you find your answer, please stick around on the IRC channel or the
366)     mailing list and answer questions from others.</p>

367) 

368)     <hr>

369) 

370)     <a id="WhySlow"></a>
371)     <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>

372) 

373)     <p>
374)     There are many reasons why the Tor network is currently slow.
375)     </p>

376) 

377)     <p>
378)     Before we answer, though, you should realize that Tor is never going to
379)     be blazing fast. Your traffic is bouncing through volunteers' computers
380)     in various parts of the world, and some bottlenecks and network latency
381)     will always be present. You shouldn't expect to see university-style
382)     bandwidth through Tor.
383)     </p>

384) 

385)     <p>
386)     But that doesn't mean that it can't be improved. The current Tor network
387)     is quite small compared to the number of people trying to use it, and
388)     many of these users don't understand or care that Tor can't currently
389)     handle file-sharing traffic load.
390)     </p>

391) 

392)     <p>
393)     For the much more in-depth answer, see <a

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

395)     post on the topic</a>, which includes both a detailed PDF and a video
396)     to go with it.
397)     </p>

398) 

399)     <p>
400)     What can you do to help?
401)     </p>

402) 

403)     <ul>

404) 

405)     <li>
406)     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
407)     for others</a>. Help make the Tor network large enough that we can handle
408)     all the users who want privacy and security on the Internet.
409)     </li>

410) 

411)     <li>

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

413)     especially need people to help make it easier to configure your Tor
414)     as a relay. Also, we need help with clear simple documentation to
415)     walk people through setting it up.
416)     </li>

417) 

418)     <li>
419)     There are some bottlenecks in the current Tor network. Help us design
420)     experiments to track down and demonstrate where the problems are, and
421)     then we can focus better on fixing them.
422)     </li>

423) 

424)     <li>
425)     There are some steps that individuals
426)     can take to improve their Tor performance. <a

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

428)     can configure your Firefox to handle Tor better</a>, <a
429)     href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
430)     Polipo with Tor</a>, or you can try <a href="<page download/download>">upgrading
431)     to the latest version of Tor</a>.  If this works well, please help by
432)     documenting what you did, and letting us know about it.
433)     </li>

434) 

435)     <li>
436)     Tor needs some architectural changes too. One important change is to
437)     start providing <a href="#EverybodyARelay">better service to people who
438)     relay traffic</a>. We're working on this, and we'll finish faster if we
439)     get to spend more time on it.
440)     </li>

441) 

442)     <li>
443)     Help do other things so we can do the hard stuff. Please take a moment
444)     to figure out what your skills and interests are, and then <a href="<page
445)     getinvolved/volunteer>">look at our volunteer page</a>.
446)     </li>

447) 

448)     <li>
449)     Help find sponsors for Tor. Do you work at a company or government agency
450)     that uses Tor or has a use for Internet privacy, e.g. to browse the
451)     competition's websites discreetly, or to connect back to the home servers
452)     when on the road without revealing affiliations? If your organization has
453)     an interest in keeping the Tor network working, please contact them about
454)     supporting Tor. Without sponsors, Tor is going to become even slower.
455)     </li>

456) 

457)     <li>
458)     If you can't help out with any of the above, you can still help out
459)     individually by <a href="<page donate/donate>">donating a bit of money to the
460)     cause</a>. It adds up!
461)     </li>

462) 

463)     </ul>

464) 

465)     <hr>

466) 

467)     <a id="Funding"></a>
468)     <h3><a class="anchor" href="#Funding">What would The Tor Project do with
469)     more funding?</a></h3>

470) 

471)     <p>
472)     We have about 1800 relays right now, pushing over 150 MB/s average
473)     traffic. We have several hundred thousand active users. But the Tor
474)     network is not yet self-sustaining.
475)     </p>

476) 

477)     <p>
478)     There are six main development/maintenance pushes that need attention:
479)     </p>

480) 

481)     <ul>

482) 

483)     <li>
484)     Scalability: We need to keep scaling and decentralizing the Tor
485)     architecture so it can handle thousands of relays and millions of
486)     users. The upcoming stable release is a major improvement, but there's
487)     lots more to be done next in terms of keeping Tor fast and stable.
488)     </li>

489) 

490)     <li>
491)     User support: With this many users, a lot of people are asking questions
492)     all the time, offering to help out with things, and so on. We need good
493)     clean docs, and we need to spend some effort coordinating volunteers.
494)     </li>

495) 

496)     <li>
497)     Relay support: the Tor network is run by volunteers, but they still need
498)     attention with prompt bug fixes, explanations when things go wrong,
499)     reminders to upgrade, and so on. The network itself is a commons, and
500)     somebody needs to spend some energy making sure the relay operators stay
501)     happy. We also need to work on <a href="#RelayOS">stability</a> on some
502)     platforms &mdash; e.g., Tor relays have problems on Win XP currently.
503)     </li>

504) 

505)     <li>
506)     Usability: Beyond documentation, we also need to work on usability of the
507)     software itself. This includes installers, clean GUIs, easy configuration
508)     to interface with other applications, and generally automating all of
509)     the difficult and confusing steps inside Tor. We've got a start on this

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

511)     remains — usability for privacy software has never been easy.
512)     </li>

513) 

514)     <li>
515)     Incentives: We need to work on ways to encourage people to configure
516)     their Tors as relays and exit nodes rather than just clients.
517)     <a href="#EverybodyARelay">We need to make it easy to become a relay,
518)     and we need to give people incentives to do it.</a>
519)     </li>

520) 

521)     <li>
522)     Research: The anonymous communications field is full
523)     of surprises and gotchas. In our copious free time, we
524)     also help run top anonymity and privacy conferences like <a
525)     href="http://petsymposium.org/">PETS</a>. We've identified a set of
526)     critical <a href="<page getinvolved/volunteer>#Research">Tor research questions</a>
527)     that will help us figure out how to make Tor secure against the variety of
528)     attacks out there. Of course, there are more research questions waiting
529)     behind these.
530)     </li>

531) 

532)     </ul>

533) 

534)     <p>
535)     We're continuing to move forward on all of these, but at this rate
536)     <a href="#WhySlow">the Tor network is growing faster than the developers
537)     can keep up</a>.
538)     Now would be an excellent time to add a few more developers to the effort
539)     so we can continue to grow the network.
540)     </p>

541) 

542)     <p>
543)     We are also excited about tackling related problems, such as
544)     censorship-resistance.
545)     </p>

546) 

547)     <p>
548)     We are proud to have <a href="<page about/sponsors>">sponsorship and support</a>
549)     from the Omidyar Network, the International Broadcasting Bureau, Bell
550)     Security Solutions, the Electronic Frontier Foundation, several government
551)     agencies and research groups, and hundreds of private contributors.
552)     </p>

553) 

554)     <p>
555)     However, this support is not enough to keep Tor abreast of changes in the
556)     Internet privacy landscape. Please <a href="<page donate/donate>">donate</a>
557)     to the project, or <a href="<page about/contact>">contact</a> our executive
558)     director for information on making grants or major donations.
559)     </p>

560) 

561)     <a id="Metrics"></a>

562)     <h3><a class="anchor" href="#Metrics">How many people use Tor?
563)     How many relays or exit nodes are there?</a></h3>

564) 

565)     <p>All this and more about measuring Tor can be found at the <a

566)     href="https://metrics.torproject.org/">Tor Metrics Portal</a>.</p>

567)     <hr>

568) 

569)     <a id="HowUninstallTor"></a>

570)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
571)     Tor?</a></h3>
572) 

573)     <p>
574)     This depends entirely on how you installed it and which operating system you
575)     have. If you installed a package, then hopefully your package has a way to
576)     uninstall itself. The Windows packages include uninstallers. The proper way to
577)     completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any
578)     version of Windows is as follows:
579)     </p>

580) 

581)     <ol>
582)     <li>In your taskbar, right click on Vidalia (the green onion or the black head)
583)     and choose exit.</li>
584)     <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
585)     Process List. If it's running, right click and choose End Process.</li>
586)     <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
587)     This will remove the Vidalia bundle, which includes Tor and Polipo.</li>
588)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
589)     Click the Uninstall button.</li>
590)     </ol>

591) 

592)     <p>
593)     If you do not follow these steps (for example by trying to uninstall
594)     Vidalia, Tor, and Polipo while they are still running), you will need to
595)     reboot and manually remove the directory "Program Files\Vidalia Bundle".
596)     </p>

597) 

598)     <p>
599)     For Mac OS X, follow the <a
600)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
601)     </p>

602) 

603)     <p>
604)     If you installed by source, I'm afraid there is no easy uninstall method. But
605)     on the bright side, by default it only installs into /usr/local/ and it should
606)     be pretty easy to notice things there.
607)     </p>

608) 

609)     <hr>

610) 

611)     <a id="PGPSigs"></a>
612)     <h3><a class="anchor" href="#PGPSigs">What are these "sig" files on the
613)     download page?</a></h3>

614) 

615)     <p>
616)     These are PGP signatures, so you can verify that the file you've downloaded is
617)     exactly the one that we intended you to get.
618)     </p>

619) 

620)     <p>
621)     Please read the <a
622)     href="<page docs/verifying-signatures>">verifying signatures</a> page for details.
623)     </p>

624) 

625)     <hr>

626) 

627)     <a id="CompileTorWindows"></a>
628)     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
629)     Windows?</a></h3>

630) 

631)     <p>
632)     Try following the steps at <a href="<gitblob>doc/tor-win32-mingw-creation.txt">
633)     tor-win32-mingw-creation.txt</a>.
634)     </p>

635) 

636)     <p>
637)     (Note that you don't need to compile Tor yourself in order to use
638)     it. Most people just use the packages available on the <a href="<page
639)     download/download>">download page</a>.)
640)     </p>

641) 

642)     <hr>

643) 

644)     <a id="VirusFalsePositives"></a>
645)     <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
646)     executable appear to have a virus or spyware?</a></h3>

647) 

648)     <p>
649)     Sometimes, overzealous Windows virus and spyware detectors trigger on some
650)     parts of the Tor Windows binary. Our best guess is that these are false
651)     positives &mdash; after all, the anti-virus and anti-spyware business is just a
652)     guessing game anyway. You should contact your vendor and explain that you have
653)     a program that seems to be triggering false positives. Or pick a better vendor.
654)     </p>

655) 

656)     <p>
657)     In the meantime, we encourage you to not just take our word for
658)     it. Our job is to provide the source; if you're concerned, please do <a
659)     href="#CompileTorWindows">recompile it yourself</a>.
660)     </p>

661) 

662)     <hr>

663) 

664)     <a id="LiveCD"></a>
665)     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
666)     includes Tor?</a></h3>

667) 

668)     <p>
669)     There isn't any official LiveCD at this point. We're still trying to find good
670)     solutions and trying to understand the security and anonymity implications of
671)     the various options. In the mean time, feel free to check out the list below
672)     and use your best judgement:
673)     </p>

674) 

675)     <p>
676)     LiveCDs:
677)     </p>

678) 

679)     <ol>
680)     <li><a href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
681)     System</a> is a Live System aimed at preserving your privacy and
682)     anonymity:
683)     <ul>
684)     <li> All outgoing connections to the Internet are forced to go through
685)     the Tor network.</li>
686)     <li> No trace is left on local storage devices unless explicitely asked.</li>
687)     <li> It includes Firefox, Tor, Torbutton, Vidalia graphical Tor
688)     controller, Pidgin Instant Messaging client, and lots of other
689)     software.</li>
690)     <li> It's based upon Debian gnu/linux and comes with the GNOME desktop
691)     environment.</li>
692)     </ul>
693)     <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
694)     is Knoppix-based with an emphasis on user-friendliness. You can work
695)     anonymously or non-anonymously while TorK tries to keep you informed of the
696)     consequences of your activity. The TorK LiveCD is experimental, so the aim is
697)     to provide regular releases through 2007 and beyond.</li>
698)     <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
699)     debian based live-system including tor, firefox and torbutton which can save
700)     bookmarks and other settings or data on an encrypted usb-key</li>
701)     </li>
702)     </ol>

703) 

704)     <p>
705)     Windows bundles:
706)     </p>

707) 

708)     <ol>
709)     <li><a href="<page projects/torbrowser>">Tor Browser Bundle</a>
710)     for Windows comes with a pre-configured web browser and is self contained
711)     so you can run it from a USB stick.</li>
712)     <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
713)     to JanusVM. It needs testing from you!</li>
714)     <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
715)     running in VMWare that sits between your Windows computer and the Internet,
716)     making sure that your Internet traffic is scrubbed and anonymized.</li>
717)     <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
718)     previously known as Torpark, is a Firefox+Tor package for Win32 that can
719)     installed on a USB key. It needs a host Win32 operating system.</li>
720)     </ol>

721) 

722)     <p>
723)     Not currently maintained as far as we know:
724)     </p>

725) 

726)     <ol>
727)     <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
728)     and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
729)     download</a>.</li>
730)     <li>ELE is a Linux LiveCD which is focused on privacy related
731)     software. It includes Tor and you can download it at
732)     <a
733)     href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
734)     <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
735)     Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
736)     non-Tor traffic from accidentally leaving your computer. More information at

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

738)     <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
739)     than Linux for maximum security. It was designed to be anonymous and secure
740)     from the ground up, and thus has some features and limitations not found in
741)     other LiveCDs (Tor related or otherwise). You can obtain more information and
742)     download Anonym.OS from <a href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
743)     <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
744)     recent KNOPPIX release. It comes preconfigured with Privoxy, Tor and Polipo. You can
745)     get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
746)     Website</a>.</li>
747)     </ol>

748) 

749)     <p>
750)     Please contact us if you know any others.
751)     </p>

752) 
753) <hr>
754) 

755) <a id="torrc"></a>
756) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc". What
757) does that mean?</a></h3>
758) 
759) <p>
760) Tor installs a text file called torrc that contains configuration
761) instructions for how your Tor program should behave. The default
762) configuration should work fine for most Tor users. Users of Vidalia can
763) make common changes through the Vidalia interface &mdash; only advanced
764) users should need to modify their torrc file directly.
765) </p>
766) 
767) <p>
768) The location of your torrc file depends on the way you installed Tor:
769) </p>
770) 
771) <ul>
772) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
773) find your torrc file in the Start menu under Programs -&gt; Vidalia
774) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
775) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
776) installed Tor without Vidalia, you can find your torrc in the Start
777) menu under Programs -&gt; Tor, or manually in either <code>\Documents
778) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
779) Settings\<i>username</i>\Application Data\tor\torrc</code>.
780) </li>
781) <li>On OS X, if you use Vidalia, edit
782) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
783) and load <code>/Library/Tor/torrc</code>.
784) </li>
785) <li>On Unix, if you installed a pre-built package, look for
786) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
787) package's documentation.
788) </li>
789) <li>Finally, if you installed from source, you may not have a torrc
790) installed yet: look in <code>/usr/local/etc/</code> and note that you
791) may need to manually copy <code>torrc.sample</code> to <code>torrc</code>.
792) </li>
793) </ul>
794) 
795) <p>
796) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit
797) your torrc file. Otherwise Vidalia might overwrite your changes.
798) </p>
799) 
800) <p>
801) Once you've changed your torrc, you will need to restart Tor for the
802) changes to take effect. (For advanced users on OS X and Unix, note that
803) you actually only need to send Tor a HUP signal, not actually restart it.)
804) </p>
805) 
806) <p>
807) For other configuration options you can use, look at the <a href="<page
808) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
809) with # in torrc are treated as comments and have no effect on Tor's
810) configuration.
811) </p>
812) 
813) <hr>
814) 

815) <a id="DoesntWork"></a>
816) <h3><a class="anchor" href="#DoesntWork">I installed Tor and Polipo but
817) it's not working.</a></h3>
818) 
819) <p>
820) Once you've installed the Tor bundle, there are two questions to ask:
821) first, is your Tor able to establish a circuit? Second, is your
822) Firefox correctly configured to send its traffic through Tor?
823) </p>
824) 
825) <p>If Tor can establish a circuit, the onion icon in
826) Vidalia will turn green. You can also check in the Vidalia
827) Control Panel to make sure it says "Connected to the Tor
828) network!" under Status. For those not using Vidalia, check your <a

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

830) a line saying that Tor "has successfully opened a circuit. Looks like
831) client functionality is working."
832) </p>
833) 
834) <p>
835) If Tor can't establish a circuit, here are some hints:
836) </p>
837) 
838) <ol>
839) <li>Are you sure Tor is running? If you're using Vidalia, you may have
840) to click on the onion and select "Start" to launch Tor.</li>
841) <li>Check your system clock. If it's more than a few hours off, Tor will
842) refuse to build circuits. For XP users, synchronize your clock under
843) the clock -&gt; Internet time tab. In addition, correct the day and date
844) under the 'Date &amp; Time' Tab.</li>
845) <li>Is your Internet connection <a

846) href="#FirewallPorts">firewalled by port</a>,

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

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

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

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

857) logs</a>. Do they give you any hints about what's going wrong?</li>
858) </ol>
859) 
860) <p>
861) Step two is to confirm that Firefox is correctly configured to send its
862) traffic through Tor. Try the <a href="https://check.torproject.org/">Tor
863) Check</a> site and see whether it thinks you are using Tor. See <a

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

865) Tor Check FAQ entry</a> for details.

866) </p>

867) 
868) <p>
869) If it thinks you're not using Tor, here are some hints:
870) </p>
871) 
872) <ol>
873) <li>Did you install the Torbutton extension for Firefox? The installation
874) bundles include it, but sometimes people forget to install it. Make sure
875) it says "Tor enabled" at the bottom right of your Firefox window. (For
876) expert users, make sure your http proxy is set to localhost port
877) 8118.)</li>
878) <li>Do you have incompatible Firefox extensions like FoxyProxy
879) installed? If so, uninstall them. (Note that using FoxyProxy is NOT
880) a sufficient substitute for Torbutton. There are many known attacks
881) against a browser setup that does not include Torbutton. Read more

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

883) href="https://www.torproject.org/torbutton/design/">Torbutton design</a>
884) specification.)</li>
885) <li>If your browser says "The proxy server is refusing connections.",
886) check that Polipo (the http proxy that passes traffic between Firefox
887) and Tor) is running. On Windows, look in the task manager and check for
888) a polipo.exe. On OS X, open the utilities folder in your applications
889) folder, and open Terminal.app. Then run "ps aux|grep polipo".</li>
890) <li>If you're upgrading from OS X, some of the earlier OS X installers
891) were broken in really unfortunate ways. You may find that <a href="<page
892) docs/tor-doc-osx>#uninstall">uninstalling everything</a> and then
893) installing a fresh bundle helps. Alas, the current uninstall instructions
894) may not apply anymore to your old bundle. Sorry.</li>
895) <li>If you're on Linux, make sure Privoxy isn't running, since it will
896) conflict with the port that our Polipo configuration file picks.</li>
897) <li>If you installed Polipo yourself (not from a bundle), did you edit the

898) config file as described? Did you restart Polipo after this change? Are
899) you sure?</li>

900) <li>For Red Hat Linux and related systems, do you have SELinux enabled? If
901) so, it might be preventing Polipo from talking to Tor. We also run across
902) BSD users periodically who have local firewall rules that prevent some
903) connections to localhost.</li>
904) </ol>
905) 
906) <hr />
907) 
908) <a id="VidaliaPassword"></a>
909) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for
910) a password at start.</a></h3>
911) 
912) <p>
913) Vidalia interacts with the Tor software via Tor's "control port". The
914) control port lets Vidalia receive status updates from Tor, request a new
915) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
916) Vidalia sets a random password for Tor's control port to prevent other
917) applications from also connecting to the control port and potentially
918) compromising your anonymity.
919) </p>
920) 
921) <p>
922) Usually this process of generating and setting a random control password
923) happens in the background. There are three common situations, though,
924) where Vidalia may prompt you for a password:
925) </p>
926) 
927) <ol>
928) <li>You're already running Vidalia and Tor. For example, this situation
929) can happen if you installed the Vidalia bundle and now you're trying to
930) run the Tor Browser Bundle. In that case, you'll need to close the old
931) Vidalia and Tor before you can run this one.
932) </li>
933) <li>Vidalia crashed, but left Tor running with the last known random
934) password. After you restart Vidalia, it generates a new random password,
935) but Vidalia can't talk to Tor, because the random passwords are different.
936) <br />
937) If the dialog that prompts you for a control password has a Reset button,
938) you can click the button and Vidalia will restart Tor with a new random
939) control password.
940) <br />
941) If you do not see a Reset button, or if Vidalia is unable to restart
942) Tor for you, you can still fix the problem manually. Simply go into your
943) process or task manager, and terminate the Tor process. Then use Vidalia
944) to restart Tor and all will work again.
945) </li>
946) <li>You had previously set Tor to run as a Windows NT service. When Tor
947) is set to
948) run as a service, it starts up when the system boots. If you configured
949) Tor to start as a service through Vidalia, a random password was set
950) and saved in Tor. When you reboot, Tor starts up and uses the random
951) password it saved. You login and start up Vidalia. Vidalia attempts to
952) talk to the already running Tor. Vidalia generates a random password,
953) but it is different than the saved password in the Tor service.
954) <br />
955) You need to reconfigure Tor to not be a service. See the FAQ entry on

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

957) for more information on how to remove the Tor service.
958) </li>
959) </ol>
960) 

961)     <hr>

962) 

963)     <a id="ChooseEntryExit"></a>
964)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>

965) 

966)     <p>

967)     Yes. You can set preferred entry and exit nodes as well as
968)     inform Tor which nodes you do not want to use.

969)     The following options can be added to your config file <a
970)     href="#torrc">"torrc"</a> or specified on the command line:

971)     </p>
972)     <dl>
973)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
974)         <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
975)         </dd>
976)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

977)         <dd>A list of preferred nodes to use for the last hop in the circuit, if possible.

978)         </dd>
979)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

980)         <dd>A list of nodes to never use when building a circuit.

981)         </dd>
982)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

983)         <dd>A list of nodes to never use when picking an exit.
984)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list.

985)         </dd>
986)     </dl>
987)     <p>

988)     <em>We recommend you do not use these</em>
989)     &mdash; they are intended for testing and may disappear in future versions.
990)     You get the best security that Tor can provide when you leave the
991)     route selection to Tor; overriding the entry / exit nodes can mess
992)     up your anonymity in ways we don't understand.

993)     </p>
994)     <p>

995)     The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are
996)     treated as a request, meaning if the nodes are down or seem slow,
997)     Tor will still avoid them. You can make the option mandatory by
998)     setting <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt>
999)     &mdash; but if you do, your Tor connections will stop working
1000)     if all of the nodes you have specified become unreachable.
1001)     See the <a href="<page docs/documentation>#NeatLinks">Tor status pages</a>

1002)     for some nodes you might pick.
1003)     </p>
1004)     <p>

1005)     Instead of <tt>$fingerprint</tt> you can also specify a 2 letter
1006)     ISO3166 country code in curly braces (for example {de}), or an ip
1007)     address pattern (for example 255.254.0.0/8), or a node nickname. Make
1008)     sure there are no spaces between the commas and the list items.

1009)     </p>
1010)     <p>

1011)     If you want to access a service directly through Tor's SOCKS interface
1012)     (eg. using ssh via connect.c), another option is to set up an
1013)     internal mapping in your configuration file using <tt>MapAddress</tt>.

1014)     See the manual page for details.
1015)     </p>

1016) 

1017)     <hr>

1018) 
1019) <a id="GoogleCaptcha"></a>
1020) <h3><a class="anchor" href="#GoogleCaptcha">Google makes me solve a
1021) Captcha or tells me I have spyware installed.</a></h3>
1022) 
1023) <p>
1024) This is a known and intermittent problem; it does not mean that Google
1025) considers Tor to be spyware.
1026) </p>
1027) 
1028) <p>
1029) When you use Tor, you are sending queries through exit relays that are also
1030) shared by thousands of other users. Tor users typically see this message
1031) when many Tor users are querying Google in a short period of time. Google
1032) interprets the high volume of traffic from a single IP address (the exit
1033) relay you happened to pick) as somebody trying to "crawl" their website,
1034) so it slows down traffic from that IP address for a short time.
1035) </p>
1036) <p>
1037) An alternate explanation is that Google tries to detect certain
1038) kinds of spyware or viruses that send distinctive queries to Google
1039) Search. It notes the IP addresses from which those queries are received
1040) (not realizing that they are Tor exit relays), and tries to warn any
1041) connections coming from those IP addresses that recent queries indicate
1042) an infection.
1043) </p>
1044) 
1045) <p>
1046) To our knowledge, Google is not doing anything intentionally specifically
1047) to deter or block Tor use. The error message about an infected machine
1048) should clear up again after a short time.
1049) </p>
1050) 
1051) <p>
1052) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1053) automatically redirect you to a more Tor-friendly search engine such as
1054) Ixquick or Bing.
1055) </p>
1056) 
1057) <hr />
1058) 
1059) <a id="GmailWarning"></a>
1060) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my account
1061) may have been compromised.</a></h3>
1062) 
1063) <p>
1064) Sometimes, after you've used Gmail over Tor, Google presents a

1065) pop-up notification that your account may have been compromised.
1066) The notification window lists a series of IP addresses and locations
1067) throughout the world recently used to access your account.

1068) </p>
1069) 
1070) <p>
1071) In general this is a false alarm: Google saw a bunch of logins from

1072) different places, as a result of running the service via Tor, and decided
1073) it was a good idea to confirm the account was being accessed by it's
1074) rightful owner.

1075) </p>
1076) 
1077) <p>

1078) Even though this may be a biproduct of using the service via tor,
1079) that doesn't mean you can entirely ignore the warning. It is
1080) <i>probably</i> a false positive, but it might not be since it is
1081) possible for someone to hijack your Google cookie.
1082) </p>
1083) 
1084) <p>
1085) Cookie hijacking is possible by either physical access to your computer
1086) or by watching your network traffic.  In theory only physical access
1087) should compromise your system because Gmail and similar services
1088) should only send the cookie over an SSL link. In practice, alas, it's <a
1089) href="http://fscked.org/blog/fully-automated-active-https-cookie-hijacking">
1090) way more complex than that</a>.

1091) </p>
1092) 
1093) <p>
1094) And if somebody <i>did</i> steal your google cookie, they might end
1095) up logging in from unusual places (though of course they also might
1096) not). So the summary is that since you're using Tor, this security
1097) measure that Google uses isn't so useful for you, because it's full of
1098) false positives. You'll have to use other approaches, like seeing if
1099) anything looks weird on the account, or looking at the timestamps for
1100) recent logins and wondering if you actually logged in at those times.
1101) </p>
1102) 

1103) <hr>
1104) 
1105) <a id="FirewallPorts"></a>
1106) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1107) few outgoing ports.</a></h3>
1108) 
1109) <p>
1110) If your firewall works by blocking ports, then you can tell Tor to only
1111) use the ports that your firewall permits by adding "FascistFirewall 1" to

1112) your <a href="<page docs/faq>#torrc">torrc

1113) configuration file</a>, or by clicking "My firewall only lets me connect
1114) to certain ports" in Vidalia's Network Settings window.
1115) </p>
1116) 
1117) <p>
1118) By default, when you set this Tor assumes that your firewall allows only
1119) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1120) different set of ports with the FirewallPorts torrc option.
1121) </p>
1122) 
1123) <p>
1124) If you want to be more fine-grained with your controls, you can also
1125) use the ReachableAddresses config options, e.g.:
1126) </p>
1127) 
1128) <pre>
1129)   ReachableDirAddresses *:80
1130)   ReachableORAddresses *:443
1131) </pre>
1132) 
1133) <hr>

1134) 

1135)     <a id="RelayFlexible"></a>
1136)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1137)     need to be?</a></h3>

1138) 

1139)     <p>
1140)     We aim to make setting up a Tor relay easy and convenient:
1141)     </p>

1142) 

1143)     <ul>
1144)     <li>Tor has built-in support for <a

1145)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1146)     rate limiting</a>. Further, if you have a fast
1147)     link but want to limit the number of bytes per
1148)     day (or week or month) that you donate, check out the <a

1149)     href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">hibernation

1150)     feature</a>.
1151)     </li>
1152)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
1153)     specifies what sort of outbound connections are allowed or refused from
1154)     that relay. If you are uncomfortable allowing people to exit from your
1155)     relay, you can set it up to only allow connections to other Tor relays.
1156)     </li>
1157)     <li>It's fine if the relay goes offline sometimes. The directories
1158)     notice this quickly and stop advertising the relay. Just try to make
1159)     sure it's not too often, since connections using the relay when it
1160)     disconnects will break.
1161)     </li>
1162)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1163)     leave the Address config option blank, and Tor will try to guess.
1164)     </li>
1165)     <li>If your relay is behind a NAT and it doesn't know its public
1166)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1167)     forwarding. Forwarding TCP connections is system dependent but

1168)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1169)     offers some examples on how to do this.
1170)     </li>
1171)     <li>Your relay will passively estimate and advertise its recent
1172)     bandwidth capacity, so high-bandwidth relays will attract more users than
1173)     low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
1174)     </li>
1175)     </ul>

1176) 

1177)     <hr>

1178) 

1179)     <a id="RunARelayBut"></a>
1180)     <a id="ExitPolicies"></a>
1181)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't
1182)     want to deal with abuse issues.</a></h3>

1183) 

1184)     <p>
1185)     Great. That's exactly why we implemented exit policies.
1186)     </p>

1187) 

1188)     <p>
1189)     Each Tor relay has an exit policy that specifies what sort of
1190)     outbound connections are allowed or refused from that relay. The exit
1191)     policies are propagated to Tor clients via the directory, so clients
1192)     will automatically avoid picking exit relays that would refuse to
1193)     exit to their intended destination. This way each relay can decide
1194)     the services, hosts, and networks he wants to allow connections to,

1195)     based on abuse potential and his own situation. Read the FAQ entry on
1196)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might encounter</a>
1197)     if you use the default exit policy, and then read Mike Perry's

1198)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1199)     for running an exit node with minimal harassment</a>.
1200)     </p>

1201) 

1202)     <p>

1203)     The default exit policy allows access to many popular services

1204)     (e.g. web browsing), but <a href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1205)     some due to abuse potential (e.g. mail) and some since
1206)     the Tor network can't handle the load (e.g. default
1207)     file-sharing ports). You can change your exit policy

1208)     using Vidalia's "Sharing" tab, or by manually editing your

1209)     <a href="<page docs/faq>#torrc">torrc</a>

1210)     file. If you want to avoid most if not all abuse potential, set it to
1211)     "reject *:*" (or un-check all the boxes in Vidalia). This setting means
1212)     that your relay will be used for relaying traffic inside the Tor network,
1213)     but not for connections to external websites or other services.
1214)     </p>

1215) 

1216)     <p>
1217)     If you do allow any exit connections, make sure name resolution works
1218)     (that is, your computer can resolve Internet addresses correctly).
1219)     If there are any resources that your computer can't reach (for example,
1220)     you are behind a restrictive firewall or content filter), please
1221)     explicitly reject them in your exit policy &mdash; otherwise Tor users
1222)     will be impacted too.
1223)     </p>

1224) 

1225)     <hr>

1226) 

1227)     <a id="RelayOrBridge"></a>
1228)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay
1229)     or bridge relay?</a></h3>

1230) 

1231)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for short)
1232)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
1233)     in the main Tor directory. That means
1234)     that even an ISP or government trying to filter connections to the Tor
1235)     network probably won't be able to block all the bridges.
1236)     </p>

1237) 

1238)     <p>Being a normal relay vs being a bridge relay is almost the same
1239)     configuration: it's just a matter of whether your relay is listed
1240)     publically or not.
1241)     </p>

1242) 

1243)     <p>Right now, there are a small number of places in the world that filter

1244)     connections to the Tor network. So getting a lot of bridges running
1245)     right now is mostly a backup measure, a) in case the Tor network does
1246)     get blocked somewhere, and b) for people who want an extra layer of
1247)     security because they're worried somebody will recognize that it's a
1248)     public Tor relay IP address they're contacting.
1249)     </p>

1250) 

1251)     <p>So should you run a normal relay or bridge relay? If you have
1252)     lots of bandwidth, you should definitely run a normal relay &mdash;

1253)     bridge relays see very little use these days. If you're willing to

1254)     <a href="#ExitPolicies">be an exit</a>, you should definitely run a normal
1255)     relay, since we need more exits. If you can't be an exit and only have
1256)     a little bit of bandwidth, then flip a coin. Thanks for volunteering!
1257)     </p>

1258) 

1259)     <hr>

1260) 

1261) <a id="ManyRelays"></a>
1262) <h3><a class="anchor" href="#ManyRelays">I want to run more than one
1263) relay.</a></h3>
1264) 
1265) <p>
1266) Great. If you want to run several relays to donate more to the network,
1267) we're happy with that. But please don't run more than a few dozen on
1268) the same network, since part of the goal of the Tor network is dispersal
1269) and diversity.
1270) </p>
1271) 
1272) <p>
1273) If you do decide to run more than one relay, please set the "MyFamily"

1274) config option in the <a href="#torrc">torrc</a> of each relay, listing
1275) all the relays (comma-separated) that are under your control:

1276) </p>
1277) 
1278) <pre>
1279)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
1280) </pre>
1281) 
1282) <p>
1283) where each fingerprint is the 40 character identity fingerprint (without
1284) spaces). You can also list them by nickname, but fingerprint is safer. Be
1285) sure to prefix the digest strings with a dollar sign ('$') so that the
1286) digest is not confused with a nickname in the config file.
1287) </p>
1288) 
1289) <p>
1290) That way clients will know to avoid using more than one of your relays
1291) in a single circuit. You should set MyFamily if you have administrative
1292) control of the computers or of their network, even if they're not all in
1293) the same geographic location.
1294) </p>
1295) 
1296)     <hr>
1297) 

1298)     <a id="RelayMemory"></a>
1299)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so
1300)     much memory?</a></h3>

1301) 

1302)     <p>If your Tor relay is using more memory than you'd like, here are some
1303)     tips for reducing its footprint:
1304)     </p>

1305) 

1306)     <ol>
1307)     <li>If you're on Linux, you may be encountering memory fragmentation
1308)     bugs in glibc's malloc implementation. That is, when Tor releases memory
1309)     back to the system, the pieces of memory are fragmented so they're hard
1310)     to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
1311)     which doesn't have as many fragmentation bugs (but the tradeoff is higher
1312)     CPU load). You can tell Tor to use this malloc implementation instead:
1313)     <tt>./configure --enable-openbsd-malloc</tt></li>

1314) 

1315)     <li>If you're running a fast relay, meaning you have many TLS connections
1316)     open, you are probably losing a lot of memory to OpenSSL's internal
1317)     buffers (38KB+ per socket). We've patched OpenSSL to <a
1318)     href="http://archives.seul.org/or/dev/Jun-2008/msg00001.html">release
1319)     unused buffer memory more aggressively</a>. If you update to OpenSSL
1320)     1.0.0-beta5, Tor's build process will automatically recognize and use
1321)     this feature.</li>

1322) 

1323)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1324)     old FreeBSD, Tor is probably forking separate processes
1325)     rather than using threads. Consider switching to a <a

1326)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better

1327)     operating system</a>.</li>

1328) 

1329)     <li>If you still can't handle the memory load, consider reducing the
1330)     amount of bandwidth your relay advertises. Advertising less bandwidth
1331)     means you will attract fewer users, so your relay shouldn't grow
1332)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1333)     page.</li>

1334) 

1335)     </ol>

1336) 

1337)     <p>
1338)     All of this said, fast Tor relays do use a lot of ram. It is not unusual
1339)     for a fast exit relay to use 500-1000 MB of memory.
1340)     </p>

1341) 

1342)     <hr>

1343) 

1344)     <a id="WhyNotNamed"></a>

1345)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not
1346)     named?</a></h3>
1347) 

1348)     <p>

1349)     We currently use these metrics to determine if your relay should be named:<br>

1350)     </p>
1351)     <ul>
1352)     <li>The name is not currently mapped to a different key. Existing mappings
1353)     are removed after 6 months of inactivity from a relay.</li>
1354)     <li>The relay must have been around for at least two weeks.</li>
1355)     <li>No other router may have wanted the same name in the past month.</li>
1356)     </ul>

1357) 

1358)     <hr>

1359) 

1360)     <a id="KeyManagement"></a>
1361)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
1362)     Tor uses.</a></h3>

1363) 

1364)     <p>
1365)     Tor uses a variety of different keys, with three goals in mind: 1)
1366)     encryption to ensure privacy of data within the Tor network, 2)
1367)     authentication so clients know they're
1368)     talking to the relays they meant to talk to, and 3) signatures to make
1369)     sure all clients know the same set of relays.
1370)     </p>

1371) 

1372)     <p>
1373)     <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
1374)     so observers can't look inside to see which circuit a given cell is
1375)     intended for. Further, the Tor client establishes an ephemeral encryption
1376)     key with each relay in the circuit, so only the exit relay can read
1377)     the cells. Both sides discard the circuit key when the circuit ends,
1378)     so logging traffic and then breaking into the relay to discover the key
1379)     won't work.
1380)     </p>

1381) 

1382)     <p>
1383)     <b>Authentication</b>:
1384)     Every Tor relay has a public decryption key called the "onion key".
1385)     When the Tor client establishes circuits, at each step it <a
1386)     href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands
1387)     that the Tor relay prove knowledge of its onion key</a>. That way
1388)     the first node in the path can't just spoof the rest of the path.
1389)     Each relay rotates its onion key once a week.
1390)     </p>

1391) 

1392)     <p>
1393)     <b>Coordination</b>:
1394)     How do clients know what the relays are, and how do they know that they
1395)     have the right keys for them? Each relay has a long-term public signing
1396)     key called the "identity key". Each directory authority additionally has a
1397)     "directory signing key". The directory authorities <a
1398)     href="<gitblob>doc/spec/dir-spec.txt">provide a signed list</a>
1399)     of all the known relays, and in that list are a set of certificates from
1400)     each relay (self-signed by their identity key) specifying their keys,
1401)     locations, exit policies, and so on. So unless the adversary can control
1402)     a threshold of the directory authorities, he can't trick the Tor client
1403)     into using other Tor relays.
1404)     </p>

1405) 

1406)     <p>
1407)     How do clients know what the directory authorities are? The Tor software
1408)     comes with a built-in list of location and public key for each directory
1409)     authority. So the only way to trick users into using a fake Tor network
1410)     is to give them a specially modified version of the software.
1411)     </p>

1412) 

1413)     <p>
1414)     How do users know they've got the right software? When we distribute
1415)     the source code or a package, we digitally sign it with <a
1416)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
1417)     href="<page docs/verifying-signatures>">instructions
1418)     on how to check Tor's signatures</a>.
1419)     </p>

1420) 

1421)     <p>
1422)     In order to be certain that it's really signed by us, you need to have
1423)     met us in person and gotten a copy of our GPG key fingerprint, or you
1424)     need to know somebody who has. If you're concerned about an attack on
1425)     this level, we recommend you get involved with the security community
1426)     and start meeting people.
1427)     </p>

1428) 

1429)     <hr>

1430) 

1431) [https://www.torproject.org/docs/faq#EntryGuards Answer moved to our new FAQ page]
1432) 
1433) <a id="EntryGuards"></a>
1434) <h3><a class="anchor" href="#EntryGuards">What are Entry Guards?</a></h3>
1435) 
1436) <p>
1437) Tor (like all current practical low-latency anonymity designs) fails
1438) when the attacker can see both ends of the communications channel. For

1439) example, suppose the attacker controls or watches the Tor relay you choose
1440) to enter the network, and also controls or watches the website you visit. In

1441) this case, the research community knows no practical low-latency design
1442) that can reliably stop the attacker from correlating volume and timing
1443) information on the two sides.
1444) </p>
1445) 
1446) <p>
1447) So, what should we do? Suppose the attacker controls, or can observe,

1448) <i>C</i> relays. Suppose there are <i>N</i> relays total. If you select
1449) new entry and exit relays each time you use the network, the attacker
1450) will be able to correlate all traffic you send with probability
1451) <i>(c/n)<sup>2</sup></i>. But profiling is, for most users, as bad
1452) as being traced all the time: they want to do something often without
1453) an attacker noticing, and the attacker noticing once is as bad as the
1454) attacker noticing more often. Thus, choosing many random entries and exits
1455) gives the user no chance of escaping profiling by this kind of attacker.

1456) </p>
1457) 
1458) <p>
1459) The solution is "entry guards": each user selects a few relays at random

1460) to use as entry points, and uses only those relays for her first hop. If
1461) those relays are not controlled or observed, the attacker can't win,
1462) ever, and the user is secure. If those relays <i>are</i> observed or
1463) controlled by the attacker, the attacker sees a larger <i>fraction</i>
1464) of the user's traffic &mdash; but still the user is no more profiled than
1465) before. Thus, the user has some chance (on the order of <i>(n-c)/n</i>)
1466) of avoiding profiling, whereas she had none before.

1467) </p>
1468) 
1469) <p>

1470) You can read more at <a href="http://freehaven.net/anonbib/#wright02">An
1471) Analysis of the Degradation of Anonymous Protocols</a>, <a
1472) href="http://freehaven.net/anonbib/#wright03">Defending Anonymous
1473) Communication Against Passive Logging Attacks</a>, and especially
1474) <a href="http://freehaven.net/anonbib/#hs-attack06">Locating Hidden
1475) Servers</a>.

1476) </p>
1477) 
1478) <p>
1479) Restricting your entry nodes may also help against attackers who want
1480) to run a few Tor nodes and easily enumerate all of the Tor user IP
1481) addresses. (Even though they can't learn what destinations the users
1482) are talking to, they still might be able to do bad things with just a

1483) list of users.) However, that feature won't really become useful until
1484) we move to a "directory guard" design as well.

1485) </p>
1486) 
1487)     <hr>
1488) 

1489)     <a id="EverybodyARelay"></a>
1490)     <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
1491)     user be a relay.</a></h3>

1492) 

1493)     <p>
1494)     Requiring every Tor user to be a relay would help with scaling the

1495)     network to handle all our users, and <a
1496)     href="<wikifaq>#DoIgetbetteranonymityifIrunarelay">running a Tor

1497)     relay may help your anonymity</a>. However, many Tor users cannot be good
1498)     relays &mdash; for example, some Tor clients operate from behind restrictive
1499)     firewalls, connect via modem, or otherwise aren't in a position where they
1500)     can relay traffic. Providing service to these clients is a critical
1501)     part of providing effective anonymity for everyone, since many Tor users
1502)     are subject to these or similar constraints and including these clients
1503)     increases the size of the anonymity set.
1504)     </p>

1505) 

1506)     <p>
1507)     That said, we do want to encourage Tor users to run relays, so what we
1508)     really want to do is simplify the process of setting up and maintaining
1509)     a relay. We've made a lot of progress with easy configuration in the past
1510)     few years: Vidalia has an easy relay configuration interface, and supports
1511)     uPnP too. Tor is good at automatically detecting whether it's reachable and
1512)     how much bandwidth it can offer.
1513)     </p>

1514) 

1515)     <p>
1516)     There are five steps we need to address before we can do this though:
1517)     </p>

1518) 

1519)     <p>
1520)     First, we need to make Tor stable as a relay on all common
1521)     operating systems. The main remaining platform is Windows,
1522)     and we plan to finally address that in 2009. See Section 4.1 of <a
1523)     href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
1524)     development roadmap</a>.
1525)     </p>

1526) 

1527)     <p>
1528)     Second, we still need to get better at automatically estimating
1529)     the right amount of bandwidth to allow. See item #7 on the
1530)     <a href="<page getinvolved/volunteer>#Research">research section of the
1531)     volunteer page</a>: "Tor doesn't work very well when relays
1532)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

1533)     href="<wikifaq>#YoushouldtransportallIPpacketsnotjustTCPpackets.">switching

1534)     to UDP transport</a> is the simplest answer here &mdash; which alas is
1535)     not a very simple answer at all.
1536)     </p>

1537) 

1538)     <p>
1539)     Third, we need to work on scalability, both of the network (how to
1540)     stop requiring that all Tor relays be able to connect to all Tor
1541)     relays) and of the directory (how to stop requiring that all Tor
1542)     users know about all Tor relays). Changes like this can have large
1543)     impact on potential and actual anonymity. See Section 5 of the <a
1544)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
1545)     for details. Again, UDP transport would help here.
1546)     </p>

1547) 

1548)     <p>
1549)     Fourth, we need to better understand the risks from
1550)     letting the attacker send traffic through your relay while
1551)     you're also initiating your own anonymized traffic. <a
1552)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
1553)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
1554)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
1555)     describe ways to identify the relays in a circuit by running traffic
1556)     through candidate relays and looking for dips in the traffic while the
1557)     circuit is active. These clogging attacks are not that scary in the Tor
1558)     context so long as relays are never clients too. But if we're trying to
1559)     encourage more clients to turn on relay functionality too (whether as
1560)     <a href="<page docs/bridges>">bridge relays</a> or as normal relays), then
1561)     we need to understand this threat better and learn how to mitigate it.
1562)     </p>

1563) 

1564)     <p>
1565)     Fifth, we might need some sort of incentive scheme to encourage people
1566)     to relay traffic for others, and/or to become exit nodes. Here are our

1567)     <a href="<blog>two-incentive-designs-tor">current

1568)     thoughts on Tor incentives</a>.
1569)     </p>

1570) 

1571)     <p>
1572)     Please help on all of these!
1573)     </p>

1574) 

1575)     <hr>

1576) 

1577)     <a id="Criminals"></a>

1578)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals
1579)     to do bad things?</a></h3>
1580) 

1581)     <p>
1582)     For the answer to this question and others, please see our <a
1583)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
1584)     </p>

1585) 

1586)     <hr>

1587) 

1588)     <a id="RespondISP"></a>

1589)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP
1590)     about my exit relay?</a></h3>
1591) 

1592)     <p>
1593)     A collection of templates for successfully responding to ISPs is <a

1594)     href="<wiki>TheOnionRouter/TorAbuseTemplates">collected

1595)     here</a>.
1596)     </p>

1597) 

1598)     <hr>

1599) 

1600)   </div>
1601)   <!-- END MAINCOL -->
1602)   <div id = "sidecol">
1603) #include "side.wmi"
1604) #include "info.wmi"
1605)   </div>
1606)   <!-- END SIDECOL -->
1607) </div>
1608) <!-- END CONTENT -->