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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 support?</a></li>

28)     <li><a href="#Forum">Is there a Tor forum?</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)     <li><a href="#SSLcertfingerprint">What are your SSL certificate

35)     fingerprints?</a></li>

36)     </ul>

37) 

38)     <p>Compilation and Installation:</p>
39)     <ul>
40)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
41)     <li><a href="#PGPSigs">What are these "sig" files on the download
42)     page?</a></li>

43)     <li><a href="#GetTor">Your website is blocked in my country. How
44)     do I download Tor?</a></li>

45)     <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>
46)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
47)     have a virus or spyware?</a></li>
48)     <li><a href="#LiveCD">Is there a LiveCD or other bundle that includes Tor?</a></li>
49)     </ul>

50) 

51)     <p>Tor Browser Bundle:</p>
52)     <ul>

53) 

54)     <li><a href="#TBBFlash">Why can't I view videos on YouTube and other
55)     Flash-based sites?</a></li>

56)     <li><a href="#TBBSocksPort">I'm on OSX or Linux and I want to
57)     run another application through the Tor launched by Tor Browser

58)     Bundle. How do I predict my Socks port?</a></li>

59)     <li><a href="#TBBPolipo">I need an HTTP proxy. Where did Polipo
60)     go?</a></li>

61)     <li><a href="#TBBOtherExtensions">Can I install other Firefox
62)     extensions?</a></li>

63)     <li><a href="#TBBJavaScriptEnabled">Why is NoScript configured to allow JavaScript by default in the Tor Browser Bundle?  Isn't that unsafe?</a></li>
64)     <li><a href="#TBBCanIBlockJS">I'm an expert!  (No, really!)  Can I configure NoScript to block JavaScript by default?</a></li>

65)     <li><a href="#TBBOtherBrowser">I want to use Chrome/IE/Opera/etc
66)     with Tor.</a></li>
67)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
68)     running but close the browser.</a></li>
69) 

70)     <li><a href="#GoogleCaptcha">Google makes me solve a Captcha or tells
71)     me I have spyware installed.</a></li>
72)     <li><a href="#GmailWarning">Gmail warns me that my account may have
73)     been compromised.</a></li>
74)     </ul>
75) 
76)     <p>Advanced Tor usage:</p>

77)     <ul>
78)     <li><a href="#torrc">I'm supposed to "edit my torrc". What does
79)     that mean?</a></li>

80)     <li><a href="#Logs">How do I set up logging, or see Tor's

81)     logs?</a></li>

82)     <li><a href="#DoesntWork">Tor is running, but it's not working
83)     correctly.</a></li>

84)     <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at
85)     start.</a></li>
86)     <li><a href="#ChooseEntryExit">Can I control which nodes (or country)
87)     are used for entry/exit?</a></li>

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

90)     </ul>

91) 

92)     <p>Running a Tor relay:</p>
93)     <ul>
94)     <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>
95)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal
96)     with abuse issues.</a></li>
97)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
98)     relay?</a></li>

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

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

102)     <li><a href="#RelayDonations">Can I donate for a relay rather than
103)     run my own?</a></li>

104)     </ul>

105) 

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

107) 

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

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

112)     </ul>

113) 

114)     <p>Alternate designs that we don't do (yet):</p>
115)     <ul>
116)     <li><a href="#EverybodyARelay">You should make every Tor user be a
117)     relay.</a></li>

118)     <li><a href="#TransportIPnotTCP">You should transport all IP packets,
119)     not just TCP packets.</a></li>

120)     <li><a href="#HideExits">You should hide the list of Tor relays,
121)     so people can't block the exits.</a></li>

122)     </ul>

123) 

124)     <p>Abuse:</p>

125)     <ul>
126)     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
127)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
128)     relay?</a></li>
129)     </ul>

130) 

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

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

133) 

134)     <hr>

135) 

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

137) 

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

140) 

141)     <p>
142)     The name "Tor" can refer to several different components.
143)     </p>

144) 

145)     <p>
146)     The Tor software is a program you can run on your computer that helps keep
147)     you safe on the Internet. Tor protects you by bouncing your communications
148)     around a distributed network of relays run by volunteers all around
149)     the world: it prevents somebody watching your Internet connection from
150)     learning what sites you visit, and it prevents the sites you visit
151)     from learning your physical location. This set of volunteer relays is
152)     called the Tor network. You can read more about how Tor works on the <a
153)     href="<page about/overview>">overview page</a>.
154)     </p>

155) 

156)     <p>
157)     The Tor Project is a non-profit (charity) organization that maintains
158)     and develops the Tor software.
159)     </p>

160) 

161)     <hr>

162) 

163)     <a id="Torisdifferent"></a>
164)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
165)     <p>

166)     A typical proxy provider sets up a server somewhere on the Internet and
167) allows you to use it to relay your traffic.  This creates a simple, easy to
168) maintain architecture.  The users all enter and leave through the same server.
169) The provider may charge for use of the proxy, or fund their costs through
170) advertisements on the server.  In the simplest configuration, you don't have to
171) install anything.  You just have to point your browser at their proxy server.
172) Simple proxy providers are fine solutions if you do not want protections for
173) your privacy and anonymity online and you trust the provider from doing bad
174) things.  Some simple proxy providers use SSL to secure your connection to them.
175) This may protect you against local eavesdroppers, such as those at a cafe with
176) free wifi Internet.
177)     </p>
178)     <p>
179)     Simple proxy providers also create a single point of failure.  The provider
180) knows who you are and where you browse on the Internet.  They can see your

181) traffic as it passes through their server.  In some cases, they can even see
182) inside your

183) encrypted traffic as they relay it to your banking site or to ecommerce stores.
184) You have to trust the provider isn't doing any number of things, such as
185) watching your traffic, injecting their own advertisements into your traffic

186) stream, and recording your personal details.

187)     </p>
188)     <p>
189)     Tor passes your traffic through at least 3 different servers before sending

190) it on to the destination. Because there's a separate layer of encryption for
191) each of the three relays, Tor does not modify, or even know, what you are

192) sending into it.  It merely relays your traffic, completely encrypted through
193) the Tor network and has it pop out somewhere else in the world, completely
194) intact.  The Tor client is required because we assume you trust your local
195) computer.  The Tor client manages the encryption and the path chosen through
196) the network.  The relays located all over the world merely pass encrypted
197) packets between themselves.</p>

198)     <p>
199)     <dl>

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

213)     </dl>
214)     </p>

215) 

216)     <hr>

217) 

218)     <a id="CompatibleApplications"></a>

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

220) 

221)     <p>
222)     There are two pieces to "Torifying" a program: connection-level anonymity
223)     and application-level anonymity. Connection-level anonymity focuses on
224)     making sure the application's Internet connections get sent through Tor.
225)     This step is normally done by configuring
226)     the program to use your Tor client as a "socks" proxy, but there are
227)     other ways to do it too. For application-level anonymity, you need to
228)     make sure that the information the application sends out doesn't hurt
229)     your privacy. (Even if the connections are being routed through Tor, you
230)     still don't want to include sensitive information like your name.) This
231)     second step needs to be done on a program-by-program basis, which is
232)     why we don't yet recommend very many programs for safe use with Tor.
233)     </p>

234) 

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

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

239)     extension</a> if you have Firefox installed. As of version 1.2.0,
240)     Torbutton now takes care of a lot of the connection-level and
241)     application-level worries.
242)     </p>

243) 

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

249)     href="<wiki>doc/TorifyHOWTO">Torifying

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

251)     href="<wiki>doc/SupportPrograms">list

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

255) 

256)     <hr>

257) 

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

260) 

261)     <p>
262)     Because Tor is the onion routing network. When we were starting the
263)     new next-generation design and implementation of onion routing in
264)     2001-2002, we would tell people we were working on onion routing,
265)     and they would say "Neat. Which one?" Even if onion routing has
266)     become a standard household term, Tor was born out of the actual <a
267)     href="http://www.onion-router.net/">onion routing project</a> run by
268)     the Naval Research Lab.
269)     </p>

270) 

271)     <p>
272)     (It's also got a fine translation from German and Turkish.)
273)     </p>

274) 

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

282) 

283)     <hr>

284) 

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

287) 

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

294) 

295)     <p>
296)     We think that putting a backdoor in Tor would be tremendously
297)     irresponsible to our users, and a bad precedent for security software
298)     in general. If we ever put a deliberate backdoor in our security
299)     software, it would ruin our professional reputations. Nobody would
300)     trust our software ever again &mdash; for excellent reason!
301)     </p>

302) 

303)     <p>
304)     But that said, there are still plenty of subtle attacks
305)     people might try. Somebody might impersonate us, or break into our
306)     computers, or something like that. Tor is open source, and you should
307)     always check the source (or at least the diffs since the last release)
308)     for suspicious things. If we (or the distributors) don't give you
309)     source, that's a sure sign something funny might be going on. You
310)     should also check the <a href="<page docs/verifying-signatures>">PGP
311)     signatures</a> on the releases, to make sure nobody messed with the
312)     distribution sites.
313)     </p>

314) 

315)     <p>
316)     Also, there might be accidental bugs in Tor that could affect your
317)     anonymity. We periodically find and fix anonymity-related bugs, so make
318)     sure you keep your Tor versions up-to-date.
319)     </p>

320) 

321)     <hr>

322) 

323)     <a id="DistributingTor"></a>

324)     <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor?</a></h3>

325) 

326)     <p>
327)     Yes.
328)     </p>

329) 

330)     <p>
331)     The Tor software is <a href="https://www.fsf.org/">free software</a>. This
332)     means we give you the rights to redistribute the Tor software, either
333)     modified or unmodified, either for a fee or gratis. You don't have to
334)     ask us for specific permission.
335)     </p>

336) 

337)     <p>
338)     However, if you want to redistribute the Tor software you must follow our
339)     <a href="<gitblob>LICENSE">LICENSE</a>.
340)     Essentially this means that you need to include our LICENSE file along
341)     with whatever part of the Tor software you're distributing.
342)     </p>

343) 

344)     <p>
345)     Most people who ask us this question don't want to distribute just the

346)     Tor software, though. They want to distribute the <a
347)     href="https://www.torproject.org/projects/torbrowser.html.en">Tor
348)     Browser</a>. This includes <a
349)     href="https://www.mozilla.org/en-US/firefox/all-aurora.html">Mozilla
350)     Aurora</a> and <a href="<page projects/vidalia>">Vidalia</a>.

351)     You will need to follow the licenses for those programs
352)     as well. Both of them are distributed under the <a
353)     href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General

354)     Public License</a>. The simplest way to obey their licenses is
355)     to include the source code for these programs everywhere you
356)     include the bundles themselves. Look for "source" packages on
357)     the <a href="<page projects/vidalia>">Vidalia page</a> and <a
358)     href="https://www.mozilla.org/en-US/firefox/all-aurora.html">Mozilla
359)     Aurora</a> pages.

360)     </p>

361) 

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

367) 

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

375) 

376)     <hr>

377) 

378)     <a id="SupportMail"></a>

379)     <h3><a class="anchor" href="#SupportMail">How can I get support?</a></h3>

380) 

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

382)     <ol>
383)     <li>Read through this <a href="<page docs/faq>">FAQ</a>.</li>
384)     <li>Read through the <a href="<page docs/documentation>">documentation</a>.</li>
385)     <li>Read through the <a

386)     href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">tor-talk

387)     archives</a> and see if your question is already answered.</li>

388)     <li>Join our <a href="irc://irc.oftc.net#tor">irc channel</a> and
389)     state the issue and wait for help.</li>

390)     <li>Send an email to <a

391)     href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.

392)     These are volunteers who may be able to help you but you may not
393)     get a response for days.</li>

394)     </ol>

395) 

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

398) 

399)     <hr>

400) 

401)     <a id="Forum"></a>
402)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
403) 
404)     <p>Not yet, but we're working on it. Most forum software is
405)     a disaster to maintain and keep secure, and at the same time
406)     too many of the Tor developers are spread too thin to be able
407)     to contribute enough to a forum. As of June 2012, we have a
408)     funder who wants to help us do it right. Stay tuned! (Tickets <a
409)     href="https://trac.torproject.org/projects/tor/ticket/3592">3592</a>
410)     and <a
411)     href="https://trac.torproject.org/projects/tor/ticket/5995">5995</a>
412)     relate to forums too.)
413)     </p>
414) 
415)     <hr>
416) 

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

419) 

420)     <p>
421)     There are many reasons why the Tor network is currently slow.
422)     </p>

423) 

424)     <p>
425)     Before we answer, though, you should realize that Tor is never going to
426)     be blazing fast. Your traffic is bouncing through volunteers' computers
427)     in various parts of the world, and some bottlenecks and network latency
428)     will always be present. You shouldn't expect to see university-style
429)     bandwidth through Tor.
430)     </p>

431) 

432)     <p>
433)     But that doesn't mean that it can't be improved. The current Tor network
434)     is quite small compared to the number of people trying to use it, and
435)     many of these users don't understand or care that Tor can't currently
436)     handle file-sharing traffic load.
437)     </p>

438) 

439)     <p>
440)     For the much more in-depth answer, see <a

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

442)     post on the topic</a>, which includes both a detailed PDF and a video
443)     to go with it.
444)     </p>

445) 

446)     <p>
447)     What can you do to help?
448)     </p>

449) 

450)     <ul>

451) 

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

457) 

458)     <li>

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

460)     especially need people to help make it easier to configure your Tor
461)     as a relay. Also, we need help with clear simple documentation to
462)     walk people through setting it up.
463)     </li>

464) 

465)     <li>
466)     There are some bottlenecks in the current Tor network. Help us design
467)     experiments to track down and demonstrate where the problems are, and
468)     then we can focus better on fixing them.
469)     </li>

470) 

471)     <li>
472)     There are some steps that individuals
473)     can take to improve their Tor performance. <a

474)     href="<wiki>doc/FireFoxTorPerf">You

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

481) 

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

488) 

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

494) 

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

503) 

504)     <li>
505)     If you can't help out with any of the above, you can still help out
506)     individually by <a href="<page donate/donate>">donating a bit of money to the
507)     cause</a>. It adds up!
508)     </li>

509) 

510)     </ul>

511) 

512)     <hr>

513) 

514)     <a id="Funding"></a>

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

516) 

517)     <p>

518)     The Tor network's <a
519)     href="https://metrics.torproject.org/network.html#networksize">several
520)     thousand</a> relays push <a
521)     href="https://metrics.torproject.org/network.html#bandwidth">over
522)     1GB per second on average</a>. We have <a
523)     href="https://metrics.torproject.org/users.html#direct-users">several
524)     hundred thousand daily users</a>. But the Tor network is not yet
525)     self-sustaining.

526)     </p>

527) 

528)     <p>
529)     There are six main development/maintenance pushes that need attention:
530)     </p>

531) 

532)     <ul>

533) 

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

540) 

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

546) 

547)     <li>
548)     Relay support: the Tor network is run by volunteers, but they still need
549)     attention with prompt bug fixes, explanations when things go wrong,
550)     reminders to upgrade, and so on. The network itself is a commons, and
551)     somebody needs to spend some energy making sure the relay operators stay

552)     happy. We also need to work on stability on some platforms — e.g.,
553)     Tor relays have problems on Win XP currently.

554)     </li>

555) 

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

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

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

564) 

565)     <li>
566)     Incentives: We need to work on ways to encourage people to configure
567)     their Tors as relays and exit nodes rather than just clients.
568)     <a href="#EverybodyARelay">We need to make it easy to become a relay,
569)     and we need to give people incentives to do it.</a>
570)     </li>

571) 

572)     <li>
573)     Research: The anonymous communications field is full
574)     of surprises and gotchas. In our copious free time, we
575)     also help run top anonymity and privacy conferences like <a
576)     href="http://petsymposium.org/">PETS</a>. We've identified a set of
577)     critical <a href="<page getinvolved/volunteer>#Research">Tor research questions</a>
578)     that will help us figure out how to make Tor secure against the variety of
579)     attacks out there. Of course, there are more research questions waiting
580)     behind these.
581)     </li>

582) 

583)     </ul>

584) 

585)     <p>
586)     We're continuing to move forward on all of these, but at this rate
587)     <a href="#WhySlow">the Tor network is growing faster than the developers
588)     can keep up</a>.
589)     Now would be an excellent time to add a few more developers to the effort
590)     so we can continue to grow the network.
591)     </p>

592) 

593)     <p>
594)     We are also excited about tackling related problems, such as
595)     censorship-resistance.
596)     </p>

597) 

598)     <p>
599)     We are proud to have <a href="<page about/sponsors>">sponsorship and support</a>
600)     from the Omidyar Network, the International Broadcasting Bureau, Bell
601)     Security Solutions, the Electronic Frontier Foundation, several government
602)     agencies and research groups, and hundreds of private contributors.
603)     </p>

604) 

605)     <p>
606)     However, this support is not enough to keep Tor abreast of changes in the
607)     Internet privacy landscape. Please <a href="<page donate/donate>">donate</a>
608)     to the project, or <a href="<page about/contact>">contact</a> our executive
609)     director for information on making grants or major donations.
610)     </p>

611) 

612)     <hr>
613) 

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

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

616) 

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

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

619)     <hr>

620) 

621)     <a id="SSLcertfingerprint"></a>
622)     <h3><a class="anchor" href="#SSLcertfingerprint">What are the SSL

623) certificate fingerprints for Tor's various websites?</a></h3>
624)     <p>

625)     <pre>

626)     *.torproject.org SSL certificate from Digicert:

627)     The serial number is: 02:DA:41:04:89:A5:FD:A2:B5:DB:DB:F8:ED:15:0D:BE
628)     The SHA-1 fingerprint is: a7e70f8a648fe04a9677f13eedf6f91b5f7f2e25
629)     The SHA-256 fingerprint is: 23b854af6b96co224fd173382c520b46fa94f2d4e7238893f63ad2d783e27b4b
630) 

631)     blog.torproject.org SSL certificate from RapidSSL:

632)     The serial number is: 00:EF:A3
633)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

634)     </pre>

635)     </p>
636)     <hr>
637) 

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

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

640) 

641)     <p>
642)     This depends entirely on how you installed it and which operating system you
643)     have. If you installed a package, then hopefully your package has a way to
644)     uninstall itself. The Windows packages include uninstallers. The proper way to
645)     completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any
646)     version of Windows is as follows:
647)     </p>

648) 

649)     <ol>
650)     <li>In your taskbar, right click on Vidalia (the green onion or the black head)
651)     and choose exit.</li>
652)     <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
653)     Process List. If it's running, right click and choose End Process.</li>
654)     <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
655)     This will remove the Vidalia bundle, which includes Tor and Polipo.</li>
656)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
657)     Click the Uninstall button.</li>
658)     </ol>

659) 

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

665) 

666)     <p>
667)     For Mac OS X, follow the <a
668)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
669)     </p>

670) 

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

676) 

677)     <hr>

678) 

679)     <a id="PGPSigs"></a>

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

681) 

682)     <p>
683)     These are PGP signatures, so you can verify that the file you've downloaded is
684)     exactly the one that we intended you to get.
685)     </p>

686) 

687)     <p>
688)     Please read the <a
689)     href="<page docs/verifying-signatures>">verifying signatures</a> page for details.
690)     </p>

691) 

692) <hr>
693) 
694) <a id="GetTor"></a>
695) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
696) country. How do I download Tor?</a></h3>
697) 
698) <p>
699) Some government or corporate firewalls censor connections to Tor's
700) website. In those cases, you have three options. First, get it from

701) a friend &mdash; the <a href="<page projects/torbrowser>">Tor Browser

702) Bundle</a> fits nicely on a USB key. Second, find the <a
703) href="https://encrypted.google.com/search?q=tor+mirrors">google cache</a>

704) for the <a href="<page getinvolved/mirrors>">Tor mirrors</a> page
705) and see if any of those copies of our website work for you. Third,
706) you can download Tor via email: log in to your Gmail account and mail

707) '<tt>gettor@gettor.torproject.org</tt>'. If you include the word 'help'

708) in the body of the email, it will reply with instructions. Note that
709) only a few webmail providers are supported, since they need to be able
710) to receive very large attachments.
711) </p>
712) 
713) <p>

714) Be sure to <a href="<page docs/verifying-signatures>">verify the signature</a>

715) of any package you download, especially when you get it from somewhere
716) other than our official HTTPS website.

717) </p>
718) 
719) <hr>

720) 

721)     <a id="CompileTorWindows"></a>

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

723) 

724)     <p>
725)     Try following the steps at <a href="<gitblob>doc/tor-win32-mingw-creation.txt">
726)     tor-win32-mingw-creation.txt</a>.
727)     </p>

728) 

729)     <p>
730)     (Note that you don't need to compile Tor yourself in order to use
731)     it. Most people just use the packages available on the <a href="<page
732)     download/download>">download page</a>.)
733)     </p>

734) 

735)     <hr>

736) 

737)     <a id="VirusFalsePositives"></a>

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

739) 

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

747) 

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

753) 

754)     <hr>

755) 

756)     <a id="LiveCD"></a>

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

758) 

759)     <p>

760)     Yes.  Use <a href="https://tails.boum.org/">The Amnesic Incognito

761)     Live System</a> or <a href="<page projects/torbrowser>">the Tor Browser
762)     Bundle</a>.

763)     </p>

764) 
765) <hr>
766) 

767) <a id="TBBFlash"></a>

768) <h3><a class="anchor" href="#TBBFlash">Why can't I view videos on YouTube
769) and other Flash-based sites?</a></h3>

770) 
771) <p>
772) <a href="https://www.torproject.org/torbutton/torbutton-faq.html.en#noflash">Answer</a>
773) </p>
774) 
775) <hr>
776) 

777) <a id="TBBSocksPort"></a>
778) <h3><a class="anchor" href="#TBBSocksPort">I'm on OSX or Linux and
779) I want to run another application through the Tor launched by Tor

780) Browser Bundle. How do I predict my Socks port?</a></h3>

781) 
782) <p>

783) Typically Tor listens for Socks connections on port 9050. TBB

784) on OSX and Linux has an experimental feature where Tor listens
785) on random unused ports rather than a fixed port each time. The
786) goal is to avoid conflicting with a "system" Tor install,
787) so you can run a system Tor and TBB at the same time. We're <a
788) href="https://trac.torproject.org/projects/tor/ticket/3948">working on
789) a feature</a> where Tor will try the usual ports first and then back
790) off to a random choice if they're already in use. Until then, if you

791) want to configure some other application to use Tor as a Socks proxy,

792) here's a workaround:
793) </p>
794) 
795) <p>
796) In Vidalia, go to Settings-&gt;Advanced and uncheck the box that says
797) 'Configure ControlPort automatically'. Click OK and restart TBB. Your

798) Socks port will then be on 9050.

799) </p>
800) 
801) <hr>
802) 
803) <a id="TBBPolipo"></a>
804) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
805) Polipo go?</a></h3>
806) 
807) <p>
808) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
809) solely to work around a bug in Firefox that was finally fixed in Firefox
810) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
811) leaving it out makes you safer because Torbutton has better control over
812) Firefox's interaction with websites.
813) </p>
814) 
815) <p>
816) If you are trying to use some external application with Tor, step zero

817) should be to <a href="<page download/download>#warning">reread the set

818) of warnings</a> for ways you can screw up. Step one should be to try

819) to use a Socks proxy rather than an http proxy — Tor runs a Socks

820) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
821) for OSX and Linux.
822) </p>
823) 
824) <p>

825) If that fails, feel free to install <a
826) href="http://www.privoxy.org/">privoxy</a> or <a
827) href="https://archive.torproject.org/tor-package-archive/polipo/">polipo</a>.
828) You can use <a

829) href="https://gitweb.torproject.org/torbrowser.git/blob_plain/1ffcd9dafb9dd76c3a29dd686e05a71a95599fb5:/build-scripts/config/polipo.conf">our

830) old polipo config file</a> if you like. However, please realize that

831) this approach is not recommended for novice users.

832) </p>
833) 
834) <hr>
835) 

836) <a id="TBBOtherExtensions"></a>
837) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
838) Firefox extensions?</a></h3>
839) 
840) <p>
841) Yes. Just install them like normal. But be sure to avoid extensions like
842) Foxyproxy that screw up your proxy settings. Also, avoid privacy-invasive
843) extensions (for example, pretty much anything with the word Toolbar in
844) its name).
845) </p>
846) 
847) <hr>
848) 

849) <a id="TBBJavaScriptEnabled"></a>
850) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript configured to allow JavaScript by default in the Tor Browser Bundle?  Isn't that unsafe?</a></h3>
851) 
852) <p>
853) We configure NoScript to allow JavaScript by default in the Tor
854) Browser Bundle because many websites will not work with JavaScript
855) disabled.  Most users would give up on Tor entirely if a website
856) they want to use requires JavaScript, because they would not know
857) how to allow a website to use JavaScript (or that enabling
858) JavaScript might make a website work).
859) </p>
860) 
861) <hr>
862) 
863) <a id="TBBCanIBlockJS"></a>
864) <h3><a class="anchor" href="#CanIBlockJS">I'm an expert!  (No, really!)  Can I configure NoScript to block JavaScript by default?</a></h3>
865) 
866) <p>
867) You can configure your copies of Tor Browser Bundle however you want
868) to.  However, we recommend that even users who know how to use
869) NoScript leave JavaScript enabled if possible, because a website or
870) exit node can easily distinguish users who disable JavaScript from
871) users who use Tor Browser bundle with its default settings (thus
872) users who disable JavaScript are less anonymous).
873) </p>
874) 
875) <p>
876) Disabling JavaScript by default, then allowing a few websites to run
877) scripts, is especially bad for your anonymity: the set of websites
878) which you allow to run scripts is very likely to <em>uniquely</em>
879) identify your browser.
880) </p>
881) 
882) <hr>
883) 

884) <a id="TBBOtherBrowser"></a>
885) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
886) Chrome/IE/Opera/etc with Tor.</a></h3>
887) 
888) <p>
889) Unfortunately, Torbutton only works with Firefox right now, and without
890) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
891) extensive privacy fixes</a> there are many ways for websites or other
892) attackers to recognize you, track you back to your IP address, and so on.
893) In short, using any browser besides Tor Browser Bundle with Tor is a
894) really bad idea.
895) </p>
896) 
897) <p>
898) We're working with the Chrome team to <a
899) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-and-fingerprinting">fix
900) some bugs and missing APIs in Chrome</a> so it will be possible to write a
901) Torbutton for Chrome. No support for any other browser is on the horizon.
902) </p>
903) 
904) <hr>
905) 
906) <a id="TBBCloseBrowser"></a>
907) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor Browser
908) Bundle running but close the browser.</a></h3>
909) 
910) <p>
911) We're working on a way to make this possible on all platforms. Please
912) be patient.
913) </p>
914) 
915) <hr>
916) 

917) <a id="GoogleCaptcha"></a>
918) <h3><a class="anchor" href="#GoogleCaptcha">Google makes me solve a Captcha or tells me I have spyware installed.</a></h3>
919) 
920) <p>
921) This is a known and intermittent problem; it does not mean that Google
922) considers Tor to be spyware.
923) </p>
924) 
925) <p>
926) When you use Tor, you are sending queries through exit relays that are also
927) shared by thousands of other users. Tor users typically see this message
928) when many Tor users are querying Google in a short period of time. Google
929) interprets the high volume of traffic from a single IP address (the exit
930) relay you happened to pick) as somebody trying to "crawl" their website,
931) so it slows down traffic from that IP address for a short time.
932) </p>
933) <p>
934) An alternate explanation is that Google tries to detect certain
935) kinds of spyware or viruses that send distinctive queries to Google
936) Search. It notes the IP addresses from which those queries are received
937) (not realizing that they are Tor exit relays), and tries to warn any
938) connections coming from those IP addresses that recent queries indicate
939) an infection.
940) </p>
941) 
942) <p>
943) To our knowledge, Google is not doing anything intentionally specifically
944) to deter or block Tor use. The error message about an infected machine
945) should clear up again after a short time.
946) </p>
947) 
948) <p>
949) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
950) automatically redirect you to a more Tor-friendly search engine such as

951) DuckDuckGo, ixquick, or Bing.

952) </p>
953) 
954) <hr />
955) 
956) <a id="GmailWarning"></a>

957) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my account
958) may have been compromised.</a></h3>

959) 
960) <p>
961) Sometimes, after you've used Gmail over Tor, Google presents a
962) pop-up notification that your account may have been compromised.
963) The notification window lists a series of IP addresses and locations
964) throughout the world recently used to access your account.
965) </p>
966) 
967) <p>
968) In general this is a false alarm: Google saw a bunch of logins from
969) different places, as a result of running the service via Tor, and decided
970) it was a good idea to confirm the account was being accessed by it's
971) rightful owner.
972) </p>
973) 
974) <p>
975) Even though this may be a biproduct of using the service via tor,
976) that doesn't mean you can entirely ignore the warning. It is
977) <i>probably</i> a false positive, but it might not be since it is
978) possible for someone to hijack your Google cookie.
979) </p>
980) 
981) <p>
982) Cookie hijacking is possible by either physical access to your computer
983) or by watching your network traffic.  In theory only physical access
984) should compromise your system because Gmail and similar services
985) should only send the cookie over an SSL link. In practice, alas, it's <a
986) href="http://fscked.org/blog/fully-automated-active-https-cookie-hijacking">
987) way more complex than that</a>.
988) </p>
989) 
990) <p>
991) And if somebody <i>did</i> steal your google cookie, they might end
992) up logging in from unusual places (though of course they also might
993) not). So the summary is that since you're using Tor, this security
994) measure that Google uses isn't so useful for you, because it's full of
995) false positives. You'll have to use other approaches, like seeing if
996) anything looks weird on the account, or looking at the timestamps for
997) recent logins and wondering if you actually logged in at those times.
998) </p>
999) 
1000) <hr>
1001) 

1002) <a id="torrc"></a>

1003) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc". What does that mean?</a></h3>

1004) 
1005) <p>
1006) Tor installs a text file called torrc that contains configuration
1007) instructions for how your Tor program should behave. The default
1008) configuration should work fine for most Tor users. Users of Vidalia can
1009) make common changes through the Vidalia interface &mdash; only advanced
1010) users should need to modify their torrc file directly.
1011) </p>

1012) <p>

1013) Tor Browser Bundle users should edit your torrc through Vidalia. Open the

1014) Vidalia Control Panel. Choose Settings. Choose Advanced. Click the button
1015) labelled "Edit current torrc". Remember to make sure the checkbox for
1016) "Save Settings." is checked. Hit the Ok button and you are done.
1017) </p>

1018) <p>

1019) Otherwise, you will need to edit the file manually.

1020) The location of your torrc file depends on the way you installed Tor:
1021) </p>
1022) <ul>

1023) <li>If you installed Tor Browser Bundle, look for
1024) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
1025) </li>

1026) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
1027) find your torrc file in the Start menu under Programs -&gt; Vidalia
1028) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
1029) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
1030) installed Tor without Vidalia, you can find your torrc in the Start
1031) menu under Programs -&gt; Tor, or manually in either <code>\Documents
1032) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
1033) Settings\<i>username</i>\Application Data\tor\torrc</code>.
1034) </li>
1035) <li>On OS X, if you use Vidalia, edit
1036) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
1037) and load <code>/Library/Tor/torrc</code>.
1038) </li>
1039) <li>On Unix, if you installed a pre-built package, look for
1040) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
1041) package's documentation.
1042) </li>
1043) <li>Finally, if you installed from source, you may not have a torrc
1044) installed yet: look in <code>/usr/local/etc/</code> and note that you
1045) may need to manually copy <code>torrc.sample</code> to <code>torrc</code>.
1046) </li>
1047) </ul>
1048) 
1049) <p>
1050) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit

1051) your torrc file manually. Otherwise Vidalia might overwrite your changes.

1052) </p>
1053) 
1054) <p>
1055) Once you've changed your torrc, you will need to restart Tor for the
1056) changes to take effect. (For advanced users on OS X and Unix, note that
1057) you actually only need to send Tor a HUP signal, not actually restart it.)
1058) </p>
1059) 
1060) <p>
1061) For other configuration options you can use, look at the <a href="<page
1062) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1063) with # in torrc are treated as comments and have no effect on Tor's
1064) configuration.
1065) </p>
1066) 
1067) <hr>
1068) 

1069) <a id="Logs"></a>

1070) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's logs?</a></h3>

1071) 
1072) <p>

1073) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1074) window called "Message Log" that will show you Tor's log messages. Click
1075) on "Advanced" to see more details. You can click on "Settings" to change
1076) your log verbosity or save the messages to a file. You're all set.

1077) </p>
1078) 
1079) <p>
1080) If you're not using Vidalia, you'll have to go find the log files by

1081) hand. Here are some likely places for your logs to be:

1082) </p>
1083) 
1084) <ul>
1085) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1086) </li>

1087) <li>On Windows, there are no default log files currently. If you enable
1088) logs in your torrc file, they default to <code>\username\Application
1089) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1090) </li>
1091) <li>If you compiled Tor from source, by default your Tor logs to <a
1092) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1093) at log-level notice. If you enable logs in your torrc file, they
1094) default to <code>/usr/local/var/log/tor/</code>.

1095) </li>
1096) </ul>
1097) 
1098) <p>

1099) To change your logging setup by hand, <a href="#torrc">edit your torrc</a>
1100) and find the section (near the top of the file) which contains the
1101) following line:

1102) </p>
1103) 
1104) <pre>

1105) \## Logs go to stdout at level "notice" unless redirected by something
1106) \## else, like one of the below lines.

1107) </pre>

1108) 
1109) <p>

1110) For example, if you want Tor to send complete debug, info, notice, warn,

1111) and err level messages to a file, append the following line to the end
1112) of the section:
1113) </p>
1114) 
1115) <pre>
1116) Log debug file c:/program files/tor/debug.log
1117) </pre>
1118) 
1119) <p>

1120) Replace <code>c:/program files/tor/debug.log</code> with a directory
1121) and filename for your Tor log.

1122) </p>
1123) 
1124) <hr>
1125) 

1126) <a id="DoesntWork"></a>

1127) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not working.</a></h3>

1128) 
1129) <p>

1130) Once you've got the Tor bundle up and running, the first question to
1131) ask is whether your Tor client is able to establish a circuit.

1132) </p>
1133) 
1134) <p>If Tor can establish a circuit, the onion icon in

1135) Vidalia will turn green (and if you're running Tor Browser Bundle, it will
1136) automatically launch a browser for you). You can also check in the Vidalia

1137) Control Panel to make sure it says "Connected to the Tor
1138) network!" under Status. For those not using Vidalia, check your <a

1139) href="#Logs">Tor logs</a> for

1140) a line saying that Tor "has successfully opened a circuit. Looks like
1141) client functionality is working."
1142) </p>
1143) 
1144) <p>
1145) If Tor can't establish a circuit, here are some hints:
1146) </p>
1147) 
1148) <ol>
1149) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1150) to click on the onion and select "Start" to launch Tor.</li>
1151) <li>Check your system clock. If it's more than a few hours off, Tor will

1152) refuse to build circuits. For Microsoft Windows users, synchronize your
1153) clock under the clock -> Internet time tab. In addition, correct the

1154) day and date under the 'Date & Time' Tab. Also make sure your time
1155) zone is correct.</li>

1156) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1157) by port</a>, or do you normally need to use a <a

1158) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</a>?

1159) </li>
1160) <li>Are you running programs like Norton Internet Security or SELinux that
1161) block certain connections, even though you don't realize they do? They
1162) could be preventing Tor from making network connections.</li>
1163) <li>Are you in China, or behind a restrictive corporate network firewall
1164) that blocks the public Tor relays? If so, you should learn about <a

1165) href="<page docs/bridges>">Tor bridges</a>.</li>

1166) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1167) about what's going wrong?</li>

1168) </ol>
1169) 
1170) <hr />
1171) 
1172) <a id="VidaliaPassword"></a>

1173) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a password at start.</a></h3>

1174) 
1175) <p>
1176) Vidalia interacts with the Tor software via Tor's "control port". The
1177) control port lets Vidalia receive status updates from Tor, request a new
1178) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1179) Vidalia sets a random password for Tor's control port to prevent other
1180) applications from also connecting to the control port and potentially
1181) compromising your anonymity.
1182) </p>
1183) 
1184) <p>
1185) Usually this process of generating and setting a random control password
1186) happens in the background. There are three common situations, though,
1187) where Vidalia may prompt you for a password:
1188) </p>
1189) 
1190) <ol>
1191) <li>You're already running Vidalia and Tor. For example, this situation
1192) can happen if you installed the Vidalia bundle and now you're trying to
1193) run the Tor Browser Bundle. In that case, you'll need to close the old
1194) Vidalia and Tor before you can run this one.
1195) </li>
1196) <li>Vidalia crashed, but left Tor running with the last known random
1197) password. After you restart Vidalia, it generates a new random password,
1198) but Vidalia can't talk to Tor, because the random passwords are different.
1199) <br />
1200) If the dialog that prompts you for a control password has a Reset button,
1201) you can click the button and Vidalia will restart Tor with a new random
1202) control password.
1203) <br />
1204) If you do not see a Reset button, or if Vidalia is unable to restart
1205) Tor for you, you can still fix the problem manually. Simply go into your
1206) process or task manager, and terminate the Tor process. Then use Vidalia
1207) to restart Tor and all will work again.
1208) </li>
1209) <li>You had previously set Tor to run as a Windows NT service. When Tor
1210) is set to
1211) run as a service, it starts up when the system boots. If you configured
1212) Tor to start as a service through Vidalia, a random password was set
1213) and saved in Tor. When you reboot, Tor starts up and uses the random
1214) password it saved. You login and start up Vidalia. Vidalia attempts to
1215) talk to the already running Tor. Vidalia generates a random password,
1216) but it is different than the saved password in the Tor service.
1217) <br />
1218) You need to reconfigure Tor to not be a service. See the FAQ entry on

1219) <a href="<wikifaq>#HowdoIrunmyTorrelayasanNTservice">running Tor as a Windows NT service</a>

1220) for more information on how to remove the Tor service.
1221) </li>
1222) </ol>
1223) 

1224)     <hr>

1225) 

1226)     <a id="ChooseEntryExit"></a>
1227)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>

1228) 

1229)     <p>

1230)     Yes. You can set preferred entry and exit nodes as well as
1231)     inform Tor which nodes you do not want to use.

1232)     The following options can be added to your config file <a
1233)     href="#torrc">"torrc"</a> or specified on the command line:

1234)     </p>
1235)     <dl>
1236)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
1237)         <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
1238)         </dd>
1239)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1240)         <dd>A list of preferred nodes to use for the last hop in the circuit, if possible.

1241)         </dd>
1242)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1243)         <dd>A list of nodes to never use when building a circuit.

1244)         </dd>
1245)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1246)         <dd>A list of nodes to never use when picking an exit.
1247)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list.

1248)         </dd>
1249)     </dl>
1250)     <p>

1251)     <em>We recommend you do not use these</em>
1252)     &mdash; they are intended for testing and may disappear in future versions.
1253)     You get the best security that Tor can provide when you leave the
1254)     route selection to Tor; overriding the entry / exit nodes can mess
1255)     up your anonymity in ways we don't understand.

1256)     </p>
1257)     <p>

1258)     The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are
1259)     treated as a request, meaning if the nodes are down or seem slow,
1260)     Tor will still avoid them. You can make the option mandatory by
1261)     setting <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt>
1262)     &mdash; but if you do, your Tor connections will stop working
1263)     if all of the nodes you have specified become unreachable.
1264)     See the <a href="<page docs/documentation>#NeatLinks">Tor status pages</a>

1265)     for some nodes you might pick.
1266)     </p>
1267)     <p>

1268)     Instead of <tt>$fingerprint</tt> you can also specify a <a
1269)     href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2">2
1270)     letter ISO3166 country code</a> in curly braces (for example {de}),
1271)     or an ip address pattern (for example 255.254.0.0/8), or a node
1272)     nickname. Make sure there are no spaces between the commas and the
1273)     list items.

1274)     </p>
1275)     <p>

1276)     If you want to access a service directly through Tor's Socks interface

1277)     (eg. using ssh via connect.c), another option is to set up an
1278)     internal mapping in your configuration file using <tt>MapAddress</tt>.

1279)     See the manual page for details.
1280)     </p>

1281) 

1282)     <hr>

1283) 

1284) <a id="FirewallPorts"></a>

1285) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a few outgoing ports.</a></h3>

1286) 
1287) <p>
1288) If your firewall works by blocking ports, then you can tell Tor to only
1289) use the ports that your firewall permits by adding "FascistFirewall 1" to

1290) your <a href="<page docs/faq>#torrc">torrc

1291) configuration file</a>, or by clicking "My firewall only lets me connect
1292) to certain ports" in Vidalia's Network Settings window.
1293) </p>
1294) 
1295) <p>
1296) By default, when you set this Tor assumes that your firewall allows only
1297) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1298) different set of ports with the FirewallPorts torrc option.
1299) </p>
1300) 
1301) <p>
1302) If you want to be more fine-grained with your controls, you can also
1303) use the ReachableAddresses config options, e.g.:
1304) </p>
1305) 
1306) <pre>
1307)   ReachableDirAddresses *:80
1308)   ReachableORAddresses *:443
1309) </pre>
1310) 
1311) <hr>

1312) 

1313)     <a id="RelayFlexible"></a>

1314)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay need to be?</a></h3>

1315) 

1316)     <p>
1317)     We aim to make setting up a Tor relay easy and convenient:
1318)     </p>

1319) 

1320)     <ul>
1321)     <li>Tor has built-in support for <a

1322)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1323)     rate limiting</a>. Further, if you have a fast
1324)     link but want to limit the number of bytes per
1325)     day (or week or month) that you donate, check out the <a

1326)     href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">hibernation

1327)     feature</a>.
1328)     </li>
1329)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
1330)     specifies what sort of outbound connections are allowed or refused from
1331)     that relay. If you are uncomfortable allowing people to exit from your
1332)     relay, you can set it up to only allow connections to other Tor relays.
1333)     </li>
1334)     <li>It's fine if the relay goes offline sometimes. The directories
1335)     notice this quickly and stop advertising the relay. Just try to make
1336)     sure it's not too often, since connections using the relay when it
1337)     disconnects will break.
1338)     </li>
1339)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1340)     leave the Address config option blank, and Tor will try to guess.
1341)     </li>
1342)     <li>If your relay is behind a NAT and it doesn't know its public
1343)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1344)     forwarding. Forwarding TCP connections is system dependent but

1345)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1346)     offers some examples on how to do this.
1347)     </li>
1348)     <li>Your relay will passively estimate and advertise its recent
1349)     bandwidth capacity, so high-bandwidth relays will attract more users than
1350)     low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
1351)     </li>
1352)     </ul>

1353) 

1354)     <hr>

1355) 

1356)     <a id="RunARelayBut"></a>
1357)     <a id="ExitPolicies"></a>

1358)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't want to deal with abuse issues.</a></h3>

1359) 

1360)     <p>
1361)     Great. That's exactly why we implemented exit policies.
1362)     </p>

1363) 

1364)     <p>
1365)     Each Tor relay has an exit policy that specifies what sort of
1366)     outbound connections are allowed or refused from that relay. The exit
1367)     policies are propagated to Tor clients via the directory, so clients
1368)     will automatically avoid picking exit relays that would refuse to
1369)     exit to their intended destination. This way each relay can decide
1370)     the services, hosts, and networks he wants to allow connections to,

1371)     based on abuse potential and his own situation. Read the FAQ entry on
1372)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might encounter</a>
1373)     if you use the default exit policy, and then read Mike Perry's

1374)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1375)     for running an exit node with minimal harassment</a>.
1376)     </p>

1377) 

1378)     <p>

1379)     The default exit policy allows access to many popular services

1380)     (e.g. web browsing), but <a href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1381)     some due to abuse potential (e.g. mail) and some since
1382)     the Tor network can't handle the load (e.g. default
1383)     file-sharing ports). You can change your exit policy

1384)     using Vidalia's "Sharing" tab, or by manually editing your

1385)     <a href="<page docs/faq>#torrc">torrc</a>

1386)     file. If you want to avoid most if not all abuse potential, set it to
1387)     "reject *:*" (or un-check all the boxes in Vidalia). This setting means
1388)     that your relay will be used for relaying traffic inside the Tor network,
1389)     but not for connections to external websites or other services.
1390)     </p>

1391) 

1392)     <p>
1393)     If you do allow any exit connections, make sure name resolution works
1394)     (that is, your computer can resolve Internet addresses correctly).
1395)     If there are any resources that your computer can't reach (for example,
1396)     you are behind a restrictive firewall or content filter), please
1397)     explicitly reject them in your exit policy &mdash; otherwise Tor users
1398)     will be impacted too.
1399)     </p>

1400) 

1401)     <hr>

1402) 

1403)     <a id="RelayOrBridge"></a>

1404)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay or bridge relay?</a></h3>

1405) 

1406)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for short)
1407)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
1408)     in the main Tor directory. That means
1409)     that even an ISP or government trying to filter connections to the Tor
1410)     network probably won't be able to block all the bridges.
1411)     </p>

1412) 

1413)     <p>Being a normal relay vs being a bridge relay is almost the same
1414)     configuration: it's just a matter of whether your relay is listed
1415)     publically or not.
1416)     </p>

1417) 

1418)     <p>Right now, China is the main place in the world that filters
1419)     connections to the Tor network. So bridges are useful a) for users in
1420)     China, b) as a backup measure in case the Tor network gets blocked in
1421)     more places, and c) for people who want an extra layer of security
1422)     because they're worried somebody will recognize that it's a public
1423)     Tor relay IP address they're contacting.

1424)     </p>

1425) 

1426)     <p>So should you run a normal relay or bridge relay? If you have lots
1427)     of bandwidth, you should definitely run a normal relay &mdash; the
1428)     average bridge doesn't see much load these days. If you're willing
1429)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
1430)     run a normal relay, since we need more exits. If you can't be an
1431)     exit and only have a little bit of bandwidth, be a bridge. Thanks
1432)     for volunteering!

1433)     </p>

1434) 

1435)     <hr>

1436) 

1437) <a id="MultipleRelays"></a>
1438) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one relay.</a></h3>

1439) 
1440) <p>
1441) Great. If you want to run several relays to donate more to the network,
1442) we're happy with that. But please don't run more than a few dozen on
1443) the same network, since part of the goal of the Tor network is dispersal
1444) and diversity.
1445) </p>
1446) 
1447) <p>
1448) If you do decide to run more than one relay, please set the "MyFamily"

1449) config option in the <a href="#torrc">torrc</a> of each relay, listing
1450) all the relays (comma-separated) that are under your control:

1451) </p>
1452) 
1453) <pre>
1454)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
1455) </pre>
1456) 
1457) <p>
1458) where each fingerprint is the 40 character identity fingerprint (without
1459) spaces). You can also list them by nickname, but fingerprint is safer. Be
1460) sure to prefix the digest strings with a dollar sign ('$') so that the
1461) digest is not confused with a nickname in the config file.
1462) </p>
1463) 
1464) <p>
1465) That way clients will know to avoid using more than one of your relays
1466) in a single circuit. You should set MyFamily if you have administrative
1467) control of the computers or of their network, even if they're not all in
1468) the same geographic location.
1469) </p>
1470) 
1471)     <hr>
1472) 

1473)     <a id="RelayMemory"></a>

1474)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so much memory?</a></h3>

1475) 

1476)     <p>If your Tor relay is using more memory than you'd like, here are some
1477)     tips for reducing its footprint:
1478)     </p>

1479) 

1480)     <ol>
1481)     <li>If you're on Linux, you may be encountering memory fragmentation
1482)     bugs in glibc's malloc implementation. That is, when Tor releases memory
1483)     back to the system, the pieces of memory are fragmented so they're hard
1484)     to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
1485)     which doesn't have as many fragmentation bugs (but the tradeoff is higher
1486)     CPU load). You can tell Tor to use this malloc implementation instead:
1487)     <tt>./configure --enable-openbsd-malloc</tt></li>

1488) 

1489)     <li>If you're running a fast relay, meaning you have many TLS connections
1490)     open, you are probably losing a lot of memory to OpenSSL's internal
1491)     buffers (38KB+ per socket). We've patched OpenSSL to <a

1492)     href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.html">release

1493)     unused buffer memory more aggressively</a>. If you update to OpenSSL

1494)     1.0.0 or newer, Tor's build process will automatically recognize and use

1495)     this feature.</li>

1496) 

1497)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1498)     old FreeBSD, Tor is probably forking separate processes
1499)     rather than using threads. Consider switching to a <a

1500)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better

1501)     operating system</a>.</li>

1502) 

1503)     <li>If you still can't handle the memory load, consider reducing the
1504)     amount of bandwidth your relay advertises. Advertising less bandwidth
1505)     means you will attract fewer users, so your relay shouldn't grow
1506)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1507)     page.</li>

1508) 

1509)     </ol>

1510) 

1511)     <p>
1512)     All of this said, fast Tor relays do use a lot of ram. It is not unusual
1513)     for a fast exit relay to use 500-1000 MB of memory.
1514)     </p>

1515) 

1516)     <hr>

1517) 

1518)     <a id="WhyNotNamed"></a>

1519)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not named?</a></h3>

1520) 

1521)     <p>

1522)     We currently use these metrics to determine if your relay should be named:<br>

1523)     </p>
1524)     <ul>
1525)     <li>The name is not currently mapped to a different key. Existing mappings
1526)     are removed after 6 months of inactivity from a relay.</li>
1527)     <li>The relay must have been around for at least two weeks.</li>
1528)     <li>No other router may have wanted the same name in the past month.</li>
1529)     </ul>

1530) 

1531)     <hr>

1532) 

1533)     <a id="RelayDonations"></a>

1534)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
1535)     relay rather than run my own?</a></h3>

1536) 
1537)     <p>
1538)     Sure! We recommend two non-profit charities that are happy to turn
1539)     your donations into better speed and anonymity for the Tor network:
1540)     </p>
1541)     <ul>
1542)     <li><a href="https://www.torservers.net/">torservers.net</a>
1543)     is a German charitable non-profit that runs a wide variety of

1544)     exit relays. They also like donations of bandwidth from ISPs.</li>

1545)     <li><a
1546)     href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>
1547)     is a US-based 501(c)(3) non-profit that collects donations and turns
1548)     them into more exit relay capacity.</li>
1549)     </ul>
1550) 
1551)     <p>
1552)     These organizations are not the same as <a href="<page
1553)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

1554)     good thing. They're both run by nice people who are part of the
1555)     Tor community.

1556)     </p>
1557) 
1558)     <p>
1559)     Note that there can be a tradeoff here between anonymity and
1560)     performance. The Tor network's anonymity comes in part from diversity,
1561)     so if you are in a position to run your own relay, you will be

1562)     improving Tor's anonymity more than by donating. At the same time
1563)     though, economies

1564)     of scale for bandwidth mean that combining many small donations into

1565)     several larger relays is more efficient at improving network

1566)     performance. Improving anonymity and improving performance are both
1567)     worthwhile goals, so however you can help is great!
1568)     </p>
1569) 
1570)     <hr>
1571) 

1572)     <a id="KeyManagement"></a>

1573)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys Tor uses.</a></h3>

1574) 

1575)     <p>
1576)     Tor uses a variety of different keys, with three goals in mind: 1)
1577)     encryption to ensure privacy of data within the Tor network, 2)
1578)     authentication so clients know they're
1579)     talking to the relays they meant to talk to, and 3) signatures to make
1580)     sure all clients know the same set of relays.
1581)     </p>

1582) 

1583)     <p>
1584)     <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
1585)     so observers can't look inside to see which circuit a given cell is
1586)     intended for. Further, the Tor client establishes an ephemeral encryption

1587)     key with each relay in the circuit; these extra layers of encryption
1588)     mean that only the exit relay can read

1589)     the cells. Both sides discard the circuit key when the circuit ends,
1590)     so logging traffic and then breaking into the relay to discover the key
1591)     won't work.
1592)     </p>

1593) 

1594)     <p>
1595)     <b>Authentication</b>:
1596)     Every Tor relay has a public decryption key called the "onion key".

1597)     Each relay rotates its onion key once a week.

1598)     When the Tor client establishes circuits, at each step it <a
1599)     href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands
1600)     that the Tor relay prove knowledge of its onion key</a>. That way
1601)     the first node in the path can't just spoof the rest of the path.

1602)     Because the Tor client chooses the path, it can make sure to get
1603)     Tor's "distributed trust" property: no single relay in the path can
1604)     know about both the client and what the client is doing.

1605)     </p>

1606) 

1607)     <p>
1608)     <b>Coordination</b>:
1609)     How do clients know what the relays are, and how do they know that they
1610)     have the right keys for them? Each relay has a long-term public signing
1611)     key called the "identity key". Each directory authority additionally has a
1612)     "directory signing key". The directory authorities <a

1613)     href="<specblob>dir-spec.txt">provide a signed list</a>

1614)     of all the known relays, and in that list are a set of certificates from
1615)     each relay (self-signed by their identity key) specifying their keys,
1616)     locations, exit policies, and so on. So unless the adversary can control

1617)     a majority of the directory authorities (as of 2012 there are 8

1618)     directory authorities), he can't trick the Tor client into using
1619)     other Tor relays.

1620)     </p>

1621) 

1622)     <p>
1623)     How do clients know what the directory authorities are? The Tor software
1624)     comes with a built-in list of location and public key for each directory
1625)     authority. So the only way to trick users into using a fake Tor network
1626)     is to give them a specially modified version of the software.
1627)     </p>

1628) 

1629)     <p>
1630)     How do users know they've got the right software? When we distribute
1631)     the source code or a package, we digitally sign it with <a
1632)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
1633)     href="<page docs/verifying-signatures>">instructions
1634)     on how to check Tor's signatures</a>.
1635)     </p>

1636) 

1637)     <p>
1638)     In order to be certain that it's really signed by us, you need to have
1639)     met us in person and gotten a copy of our GPG key fingerprint, or you
1640)     need to know somebody who has. If you're concerned about an attack on
1641)     this level, we recommend you get involved with the security community
1642)     and start meeting people.
1643)     </p>

1644) 

1645)     <hr>

1646) 

1647) <a id="EntryGuards"></a>
1648) <h3><a class="anchor" href="#EntryGuards">What are Entry Guards?</a></h3>
1649) 
1650) <p>
1651) Tor (like all current practical low-latency anonymity designs) fails
1652) when the attacker can see both ends of the communications channel. For

1653) example, suppose the attacker controls or watches the Tor relay you choose
1654) to enter the network, and also controls or watches the website you visit. In

1655) this case, the research community knows no practical low-latency design
1656) that can reliably stop the attacker from correlating volume and timing
1657) information on the two sides.
1658) </p>
1659) 
1660) <p>
1661) So, what should we do? Suppose the attacker controls, or can observe,

1662) <i>C</i> relays. Suppose there are <i>N</i> relays total. If you select
1663) new entry and exit relays each time you use the network, the attacker
1664) will be able to correlate all traffic you send with probability
1665) <i>(c/n)<sup>2</sup></i>. But profiling is, for most users, as bad
1666) as being traced all the time: they want to do something often without
1667) an attacker noticing, and the attacker noticing once is as bad as the
1668) attacker noticing more often. Thus, choosing many random entries and exits
1669) gives the user no chance of escaping profiling by this kind of attacker.

1670) </p>
1671) 
1672) <p>

1673) The solution is "entry guards": each Tor client selects a few relays at random

1674) to use as entry points, and uses only those relays for her first hop. If
1675) those relays are not controlled or observed, the attacker can't win,
1676) ever, and the user is secure. If those relays <i>are</i> observed or
1677) controlled by the attacker, the attacker sees a larger <i>fraction</i>
1678) of the user's traffic &mdash; but still the user is no more profiled than
1679) before. Thus, the user has some chance (on the order of <i>(n-c)/n</i>)
1680) of avoiding profiling, whereas she had none before.

1681) </p>
1682) 
1683) <p>

1684) You can read more at <a href="http://freehaven.net/anonbib/#wright02">An
1685) Analysis of the Degradation of Anonymous Protocols</a>, <a
1686) href="http://freehaven.net/anonbib/#wright03">Defending Anonymous
1687) Communication Against Passive Logging Attacks</a>, and especially
1688) <a href="http://freehaven.net/anonbib/#hs-attack06">Locating Hidden
1689) Servers</a>.

1690) </p>
1691) 
1692) <p>
1693) Restricting your entry nodes may also help against attackers who want
1694) to run a few Tor nodes and easily enumerate all of the Tor user IP
1695) addresses. (Even though they can't learn what destinations the users
1696) are talking to, they still might be able to do bad things with just a

1697) list of users.) However, that feature won't really become useful until
1698) we move to a "directory guard" design as well.

1699) </p>
1700) 
1701)     <hr>
1702) 

1703)     <a id="EverybodyARelay"></a>

1704)     <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor user be a relay.</a></h3>

1705) 

1706)     <p>
1707)     Requiring every Tor user to be a relay would help with scaling the

1708)     network to handle all our users, and <a
1709)     href="<wikifaq>#DoIgetbetteranonymityifIrunarelay">running a Tor

1710)     relay may help your anonymity</a>. However, many Tor users cannot be good
1711)     relays &mdash; for example, some Tor clients operate from behind restrictive
1712)     firewalls, connect via modem, or otherwise aren't in a position where they
1713)     can relay traffic. Providing service to these clients is a critical
1714)     part of providing effective anonymity for everyone, since many Tor users
1715)     are subject to these or similar constraints and including these clients
1716)     increases the size of the anonymity set.
1717)     </p>

1718) 

1719)     <p>
1720)     That said, we do want to encourage Tor users to run relays, so what we
1721)     really want to do is simplify the process of setting up and maintaining
1722)     a relay. We've made a lot of progress with easy configuration in the past
1723)     few years: Vidalia has an easy relay configuration interface, and supports
1724)     uPnP too. Tor is good at automatically detecting whether it's reachable and
1725)     how much bandwidth it can offer.
1726)     </p>

1727) 

1728)     <p>
1729)     There are five steps we need to address before we can do this though:
1730)     </p>

1731) 

1732)     <p>
1733)     First, we need to make Tor stable as a relay on all common
1734)     operating systems. The main remaining platform is Windows,

1735)     and we're mostly there. See Section 4.1 of <a

1736)     href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
1737)     development roadmap</a>.
1738)     </p>

1739) 

1740)     <p>
1741)     Second, we still need to get better at automatically estimating
1742)     the right amount of bandwidth to allow. See item #7 on the
1743)     <a href="<page getinvolved/volunteer>#Research">research section of the
1744)     volunteer page</a>: "Tor doesn't work very well when relays
1745)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

1746)     href="<page docs/faq>#TransportIPnotTCP">switching

1747)     to UDP transport</a> is the simplest answer here &mdash; which alas is
1748)     not a very simple answer at all.
1749)     </p>

1750) 

1751)     <p>
1752)     Third, we need to work on scalability, both of the network (how to
1753)     stop requiring that all Tor relays be able to connect to all Tor
1754)     relays) and of the directory (how to stop requiring that all Tor
1755)     users know about all Tor relays). Changes like this can have large
1756)     impact on potential and actual anonymity. See Section 5 of the <a
1757)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
1758)     for details. Again, UDP transport would help here.
1759)     </p>

1760) 

1761)     <p>
1762)     Fourth, we need to better understand the risks from
1763)     letting the attacker send traffic through your relay while
1764)     you're also initiating your own anonymized traffic. <a
1765)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
1766)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
1767)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
1768)     describe ways to identify the relays in a circuit by running traffic
1769)     through candidate relays and looking for dips in the traffic while the
1770)     circuit is active. These clogging attacks are not that scary in the Tor
1771)     context so long as relays are never clients too. But if we're trying to
1772)     encourage more clients to turn on relay functionality too (whether as
1773)     <a href="<page docs/bridges>">bridge relays</a> or as normal relays), then
1774)     we need to understand this threat better and learn how to mitigate it.
1775)     </p>

1776) 

1777)     <p>
1778)     Fifth, we might need some sort of incentive scheme to encourage people
1779)     to relay traffic for others, and/or to become exit nodes. Here are our

1780)     <a href="<blog>two-incentive-designs-tor">current

1781)     thoughts on Tor incentives</a>.
1782)     </p>

1783) 

1784)     <p>
1785)     Please help on all of these!
1786)     </p>

1787) 

1788) <hr>
1789) 
1790) <a id="TransportIPnotTCP"></a>

1791) <h3><a class="anchor" href="#TransportIPnotTCP">You should transport all IP packets, not just TCP packets.</a></h3>

1792) 
1793) <p>

1794) This would be handy, because it would make Tor better able to handle
1795) new protocols like VoIP, it could solve the whole need to socksify
1796) applications, and it would solve the fact that exit relays need to
1797) allocate a lot of file descriptors to hold open all the exit connections.

1798) </p>
1799) 
1800) <p>

1801) We're heading in this direction: see <a
1802) href="https://trac.torproject.org/projects/tor/ticket/1855">this trac
1803) ticket</a> for directions we should investigate. Some of the hard
1804) problems are:

1805) </p>
1806) 

1807) <ol>

1808) <li>IP packets reveal OS characteristics. We would still need to do
1809) IP-level packet normalization, to stop things like TCP fingerprinting
1810) attacks. Given the diversity and complexity of TCP stacks, along with <a

1811) href="<wikifaq>#DoesTorresistremotephysicaldevicefingerprinting">device

1812) fingerprinting attacks</a>, it looks like our best bet is shipping our
1813) own user-space TCP stack.

1814) </li>

1815) <li>Application-level streams still need scrubbing. We will still need
1816) user-side applications like Torbutton. So it won't become just a matter
1817) of capturing packets and anonymizing them at the IP layer.

1818) </li>
1819) <li>Certain protocols will still leak information. For example, we must
1820) rewrite DNS requests so they are delivered to an unlinkable DNS server
1821) rather than the DNS server at a user's ISP; thus, we must understand
1822) the protocols we are transporting.
1823) </li>
1824) <li><a
1825) href="http://crypto.stanford.edu/~nagendra/projects/dtls/dtls.html">DTLS</a>

1826) (datagram TLS) basically has no users, and IPsec sure is big. Once we've
1827) picked a transport mechanism, we need to design a new end-to-end Tor
1828) protocol for avoiding tagging attacks and other potential anonymity and
1829) integrity issues now that we allow drops, resends, et cetera.

1830) </li>
1831) <li>Exit policies for arbitrary IP packets mean building a secure
1832) IDS. Our node operators tell us that exit policies are one of the main
1833) reasons they're willing to run Tor. Adding an Intrusion Detection System
1834) to handle exit policies would increase the security complexity of Tor,
1835) and would likely not work anyway, as evidenced by the entire field of IDS
1836) and counter-IDS papers. Many potential abuse issues are resolved by the
1837) fact that Tor only transports valid TCP streams (as opposed to arbitrary
1838) IP including malformed packets and IP floods), so exit policies become
1839) even <i>more</i> important as we become able to transport IP packets. We
1840) also need to compactly describe exit policies in the Tor directory,
1841) so clients can predict which nodes will allow their packets to exit &mdash;
1842) and clients need to predict all the packets they will want to send in
1843) a session before picking their exit node!
1844) </li>

1845) <li>The Tor-internal name spaces would need to be redesigned. We support
1846) hidden service ".onion" addresses by intercepting the addresses when
1847) they are passed to the Tor client. Doing so at the IP level will require
1848) a more complex interface between Tor and the local DNS resolver.

1849) </li>

1850) </ol>
1851) 
1852) <hr>
1853) 
1854) <a id="HideExits"></a>
1855) <h3><a class="anchor" href="#HideExits">You should hide the list of Tor
1856) relays, so people can't block the exits.</a></h3>
1857) 
1858) <p>
1859) There are a few reasons we don't:
1860) </p>
1861) 
1862) <ol>
1863) <li>We can't help but make the information available, since Tor clients
1864) need to use it to pick their paths. So if the "blockers" want it, they
1865) can get it anyway. Further, even if we didn't tell clients about the
1866) list of relays directly, somebody could still make a lot of connections
1867) through Tor to a test site and build a list of the addresses they see.
1868) </li>
1869) 
1870) <li>If people want to block us, we believe that they should be allowed to
1871) do so.  Obviously, we would prefer for everybody to allow Tor users to
1872) connect to them, but people have the right to decide who their services
1873) should allow connections from, and if they want to block anonymous users,
1874) they can.
1875) </li>
1876) 
1877) <li>Being blockable also has tactical advantages: it may be a persuasive

1878) response to website maintainers who feel threatened by Tor. Giving them
1879) the option may inspire them to <a href="<page docs/faq-abuse>#Bans">stop
1880) and think</a> about whether they really want to eliminate private access
1881) to their system, and if not, what other options they might have. The
1882) time they might otherwise have spent blocking Tor, they may instead
1883) spend rethinking their overall approach to privacy and anonymity.

1884) </li>

1885) </ol>
1886) 

1887)     <hr>

1888) 

1889)     <a id="Criminals"></a>

1890)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></h3>

1891) 

1892)     <p>
1893)     For the answer to this question and others, please see our <a
1894)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
1895)     </p>

1896) 

1897)     <hr>

1898) 

1899)     <a id="RespondISP"></a>

1900)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my exit relay?</a></h3>

1901) 

1902)     <p>
1903)     A collection of templates for successfully responding to ISPs is <a

1904)     href="<wiki>doc/TorAbuseTemplates">collected

1905)     here</a>.
1906)     </p>

1907) 

1908)     <hr>

1909) 

1910)   </div>
1911)   <!-- END MAINCOL -->
1912)   <div id = "sidecol">
1913) #include "side.wmi"
1914) #include "info.wmi"
1915)   </div>
1916)   <!-- END SIDECOL -->
1917) </div>
1918) <!-- END CONTENT -->