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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
21) proxies?</a></li>

22)     <li><a href="#CompatibleApplications">What programs can I use with
23)     Tor?</a></li>
24)     <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
25)     <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>

26)     <li><a href="#DistributingTor">Can I distribute Tor?</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="#FileSharing">How can I share files anonymously through Tor?
31)     </a></li>
32)     <li><a href="#OutboundPorts">Do I have to open all these outbound ports 
33)     on my firewall?</a></li>

34)     <li><a href="#Funding">What would The Tor Project do with more
35)     funding?</a></li>

36)     <li><a href="#IsItWorking">How can I tell if Tor is working, and that my 
37)     connections really are anonymized?</a></li>

38)     <li><a href="#FTP">How do I use my browser for ftp with Tor?</a></li>

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

41)     <li><a href="#SSLcertfingerprint">What are your SSL certificate

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

43)     </ul>

44) 

45)     <p>Compilation and Installation:</p>
46)     <ul>
47)     <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>
48)     <li><a href="#PGPSigs">What are these "sig" files on the download
49)     page?</a></li>

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

52)     <li><a href="#CompileTorWindows">How do I compile Tor under
53) Windows?</a></li>
54)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear
55) to

56)     have a virus or spyware?</a></li>

57)     <li><a href="#LiveCD">Is there a LiveCD or other bundle that
58) includes Tor?</a></li>

59)     </ul>

60) 

61)     <p>Tor Browser Bundle:</p>
62)     <ul>

63) 

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

66)     <li><a href="#Ubuntu">I'm using Ubuntu and I can't start Tor Browser
67)     </a></li>

68)     <li><a href="#TBBSocksPort">I want to

69)     run another application through the Tor launched by Tor Browser

70)     Bundle.</a></li>

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

73)     <li><a href="#TBBOtherExtensions">Can I install other Firefox

74)     extensions? Which extensions should I avoid using?</a></li>

75)     <li><a href="#TBBJavaScriptEnabled">Why is NoScript configured to
76) allow JavaScript by default in the Tor Browser Bundle?  Isn't that
77) unsafe?</a></li>

78)     <li><a href="#TBBOtherBrowser">I want to use Chrome/IE/Opera/etc
79)     with Tor.</a></li>

80)     <li><a href="#TorbuttonOtherBrowser">Will Torbutton be available 
81)     for other browsers?</a></li>
82)     <li><a href="#NoDataScrubbing">Does Tor remove personal information 
83)     from the data my application sends?</a></li>

84)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
85)     running but close the browser.</a></li>
86) 

87)     <li><a href="#GoogleCAPTCHA">Google makes me solve a CAPTCHA or

88) tells

89)     me I have spyware installed.</a></li>

90)     <li><a href="#ForeignLanguages">Why does Google show up in foreign 
91)     languages?</li></a>

92)     <li><a href="#GmailWarning">Gmail warns me that my account may have
93)     been compromised.</a></li>
94)     </ul>
95) 
96)     <p>Advanced Tor usage:</p>

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

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

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

102)     <li><a href="#LogLevel">What log level should I use?</a></li>

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

105)     <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at
106)     start.</a></li>

107)     <li><a href="#ChooseEntryExit">Can I control which nodes (or
108) country)

109)     are used for entry/exit?</a></li>

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

112)     <li><a href="#ExitPorts">Is there a list of default exit ports?</a></li>

113)     <li><a href="#SocksAndDNS">How do I check if my application that uses 
114)     SOCKS is leaking DNS requests?</a></li>
115)     <li><a href="#DifferentComputer">I want to run my Tor client on a 
116)     different computer than my applications.</a></li>
117)     <li><a href="#ServerClient">Can I install Tor on a central server, and 
118)     have my clients connect to it?</a></li>
119)     <li><a href="#JoinTheNetwork">So I can just configure a nickname and 
120)     ORPort and join the network?</a></li>

121)     </ul>

122) 

123)     <p>Running a Tor relay:</p>
124)     <ul>

125)     

126)     <li><a href="#RelayFlexible">How stable does my relay need to
127) be?</a></li>
128)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to
129) deal

130)     with abuse issues.</a></li>
131)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
132)     relay?</a></li>

133)     <li><a href="#UpgradeOrMove">I want to upgrade/move my relay. How do I 
134)     keep the same key?</a></li>

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

137)     <li><a href="#NTService">How do I run my Tor relay as an NT service?
138)     </a></li>
139)     <li><a href="#VirtualServer">Can I run a Tor relay from my virtual server 
140)     account?</a></li>

141)     <li><a href="#WrongIP">My relay is picking the wrong IP address.</a></li>
142)     <li><a href="#BehindANAT">I'm behind a NAT/Firewall</a></li>

143)     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?
144)     </a></li>
145)     <li><a href="#BetterAnonymity">Do I get better anonymity if I run a relay?
146)     </a></li>

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

149)     </ul>

150) 

151)     <p>Tor hidden services:</p>
152)     <ul>
153)     <li><a href="#AccessHiddenServices">How do I access hidden services?</a></li>
154)     <li><a href="#ProvideAHiddenService">How do I provide a hidden service</a></li>
155)     </ul>

156) 

157)     <p>Anonymity and Security:</p>
158)     <ul>

159)     <li><a href="#KeyManagement">Tell me about all the keys Tor
160) uses.</a></li>

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

162)     <li><a href="#ChangePaths">How often does Tor change its paths?</a></li>

163)     <li><a href="#CellSize">Tor uses hundreds of bytes for every IRC line. I 
164)     can't afford that!</a></li>
165)     <li><a href="#OutboundConnections">Why does netstat show these outbound 
166)     connections?</a></li>
167)     <li><a href="#PowerfulBlockers">What about powerful blocking mechanisms
168)     </a></li>
169)     <li><a href="#RemotePhysicalDeviceFingerprinting">Does Tor resist 
170)     "remote physical device fingerprinting"?</a></li>
171)     <li><a href="#AttacksOnOnionRouting">What attacks remain against onion 
172)     routing?</a></li>

173)     </ul>

174) 

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

179)     <li><a href="#TransportIPnotTCP">You should transport all IP
180) packets,

181)     not just TCP packets.</a></li>

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

184)     <li><a href="#ChoosePathLength">You should let people choose their path 
185)     length.</a></li>
186)     <li><a href="#SplitEachConnection">You should split each connection over 
187)     many paths.</a></li>
188)     <li><a href="#UnallocatedNetBlocks">Your default exit policy should block 
189)     unallocated net blocks too.</a></li>
190)     <li><a href="#BlockWebsites">Exit policies should be able to block 
191)     websites, not just IP addresses.</a></li>
192)     <li><a href="#BlockContent">You should change Tor to prevent users from 
193)     posting certain content.</a></li>

194)     <li><a href="#IPv6">Tor should support IPv6.</a></li>

195)     </ul>

196) 

197)     <p>Abuse:</p>

198)     <ul>

199)     <li><a href="#Criminals">Doesn't Tor enable criminals to do bad
200) things?</a></li>

201)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
202)     relay?</a></li>
203)     </ul>

204) 

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

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

208) 

209)     <hr>

210) 

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

212) 

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

215) 

216)     <p>
217)     The name "Tor" can refer to several different components.
218)     </p>

219) 

220)     <p>

221)     The Tor software is a program you can run on your computer that
222) helps keep
223)     you safe on the Internet. Tor protects you by bouncing your
224) communications

225)     around a distributed network of relays run by volunteers all around

226)     the world: it prevents somebody watching your Internet connection
227) from

228)     learning what sites you visit, and it prevents the sites you visit

229)     from learning your physical location. This set of volunteer relays
230) is
231)     called the Tor network. You can read more about how Tor works on the
232) <a

233)     href="<page about/overview>">overview page</a>.
234)     </p>

235) 

236)     <p>

237)     The Tor Project is a non-profit (charity) organization that
238) maintains

239)     and develops the Tor software.
240)     </p>

241) 

242)     <hr>

243) 

244)     <a id="Torisdifferent"></a>

245)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different
246) from other proxies?</a></h3>
247)     <p>
248)     A typical proxy provider sets up a server somewhere on the Internet
249) and
250) allows you to use it to relay your traffic.  This creates a simple, easy
251) to
252) maintain architecture.  The users all enter and leave through the same
253) server.
254) The provider may charge for use of the proxy, or fund their costs
255) through
256) advertisements on the server.  In the simplest configuration, you don't
257) have to
258) install anything.  You just have to point your browser at their proxy
259) server.
260) Simple proxy providers are fine solutions if you do not want protections
261) for
262) your privacy and anonymity online and you trust the provider from doing
263) bad
264) things.  Some simple proxy providers use SSL to secure your connection
265) to them.
266) This may protect you against local eavesdroppers, such as those at a
267) cafe with

268) free wifi Internet.
269)     </p>
270)     <p>

271)     Simple proxy providers also create a single point of failure.  The
272) provider
273) knows who you are and where you browse on the Internet.  They can see
274) your
275) traffic as it passes through their server.  In some cases, they can even
276) see

277) inside your

278) encrypted traffic as they relay it to your banking site or to ecommerce
279) stores.

280) You have to trust the provider isn't doing any number of things, such as

281) watching your traffic, injecting their own advertisements into your
282) traffic

283) stream, and recording your personal details.

284)     </p>
285)     <p>

286)     Tor passes your traffic through at least 3 different servers before
287) sending
288) it on to the destination. Because there's a separate layer of encryption
289) for
290) each of the three relays, Tor does not modify, or even know, what you
291) are
292) sending into it.  It merely relays your traffic, completely encrypted
293) through
294) the Tor network and has it pop out somewhere else in the world,
295) completely
296) intact.  The Tor client is required because we assume you trust your
297) local
298) computer.  The Tor client manages the encryption and the path chosen
299) through
300) the network.  The relays located all over the world merely pass
301) encrypted

302) packets between themselves.</p>

303)     <p>
304)     <dl>

305)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad
306) first of
307) three servers can see encrypted Tor traffic coming from your computer.
308) It
309) still doesn't know who you are and what you are doing over Tor.  It
310) merely sees
311) "This IP address is using Tor".  Tor is not illegal anywhere in the
312) world, so
313) using Tor by itself is fine.  You are still protected from this node
314) figuring

315) out who you are and where you are going on the Internet.</dd>

316)     <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad
317) third
318) of three servers can see the traffic you sent into Tor.  It won't know
319) who sent

320) this traffic.  If you're using encryption, such as visiting a bank or

321) e-commerce website, or encrypted mail connections, etc, it will only
322) know the
323) destination.  It won't be able to see the data inside the traffic
324) stream.  You

325) are still protected from this node figuring out who you are and if using
326) encryption, what data you're sending to the destination.</dd>

327)     </dl>
328)     </p>

329) 

330)     <hr>

331) 

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

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

335) 

336)     <p>

337)     If you want to use Tor with a web browser, we provide the Tor Browser 
338)     Bundle, which includes everything you need to browse the web safely using 
339)     Tor. If you want to use another web browser with Tor, see <a 
340)     href="#TBBOtherBrowser">Other web browsers</a>. 

341)     </p>
342)     <p>
343)     There are plenty of other programs you can use with Tor,
344)     but we haven't researched the application-level anonymity

345)     issues on all of them well enough to be able to recommend a safe

346)     configuration. Our wiki has a list of instructions for <a

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

348)     specific applications</a>.

349)     Please add to these lists and help us keep them accurate!
350)     </p>

351) 

352)     <hr>

353) 

354)     <a id="WhyCalledTor"></a>

355)     <h3><a class="anchor" href="#WhyCalledTor">Why is it called
356) Tor?</a></h3>

357) 

358)     <p>
359)     Because Tor is the onion routing network. When we were starting the
360)     new next-generation design and implementation of onion routing in
361)     2001-2002, we would tell people we were working on onion routing,
362)     and they would say "Neat. Which one?" Even if onion routing has
363)     become a standard household term, Tor was born out of the actual <a
364)     href="http://www.onion-router.net/">onion routing project</a> run by
365)     the Naval Research Lab.
366)     </p>

367) 

368)     <p>
369)     (It's also got a fine translation from German and Turkish.)
370)     </p>

371) 

372)     <p>

373)     Note: even though it originally came from an acronym, Tor is not
374) spelled

375)     "TOR". Only the first letter is capitalized. In fact, we can usually

376)     spot people who haven't read any of our website (and have instead
377) learned
378)     everything they know about Tor from news articles) by the fact that
379) they

380)     spell it wrong.
381)     </p>

382) 

383)     <hr>

384) 

385)     <a id="Backdoor"></a>

386)     <h3><a class="anchor" href="#Backdoor">Is there a backdoor in
387) Tor?</a></h3>

388) 

389)     <p>

390)     There is absolutely no backdoor in Tor. Nobody has asked us to put
391) one
392)     in, and we know some smart lawyers who say that it's unlikely that
393) anybody

394)     will try to make us add one in our jurisdiction (U.S.). If they do
395)     ask us, we will fight them, and (the lawyers say) probably win.
396)     </p>

397) 

398)     <p>
399)     We think that putting a backdoor in Tor would be tremendously

400)     irresponsible to our users, and a bad precedent for security
401) software

402)     in general. If we ever put a deliberate backdoor in our security
403)     software, it would ruin our professional reputations. Nobody would
404)     trust our software ever again — for excellent reason!
405)     </p>

406) 

407)     <p>
408)     But that said, there are still plenty of subtle attacks
409)     people might try. Somebody might impersonate us, or break into our

410)     computers, or something like that. Tor is open source, and you
411) should
412)     always check the source (or at least the diffs since the last
413) release)

414)     for suspicious things. If we (or the distributors) don't give you
415)     source, that's a sure sign something funny might be going on. You
416)     should also check the <a href="<page docs/verifying-signatures>">PGP
417)     signatures</a> on the releases, to make sure nobody messed with the
418)     distribution sites.
419)     </p>

420) 

421)     <p>
422)     Also, there might be accidental bugs in Tor that could affect your

423)     anonymity. We periodically find and fix anonymity-related bugs, so
424) make

425)     sure you keep your Tor versions up-to-date.
426)     </p>

427) 

428)     <hr>

429) 

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

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

433) 

434)     <p>
435)     Yes.
436)     </p>

437) 

438)     <p>

439)     The Tor software is <a href="https://www.fsf.org/">free
440) software</a>. This
441)     means we give you the rights to redistribute the Tor software,
442) either
443)     modified or unmodified, either for a fee or gratis. You don't have
444) to

445)     ask us for specific permission.
446)     </p>

447) 

448)     <p>

449)     However, if you want to redistribute the Tor software you must
450) follow our

451)     <a href="<gitblob>LICENSE">LICENSE</a>.

452)     Essentially this means that you need to include our LICENSE file
453) along

454)     with whatever part of the Tor software you're distributing.
455)     </p>

456) 

457)     <p>

458)     Most people who ask us this question don't want to distribute just
459) the

460)     Tor software, though. They want to distribute the <a

461)     href="<page projects/torbrowser>">Tor Browser</a>. This includes <a

462)     href="https://www.mozilla.org/en-US/firefox/all-aurora.html">Mozilla
463)     Aurora</a> and <a href="<page projects/vidalia>">Vidalia</a>.

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

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

473)     </p>

474) 

475)     <p>

476)     Also, you should make sure not to confuse your readers about what
477) Tor is,
478)     who makes it, and what properties it provides (and doesn't provide).
479) See
480)     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for
481) details.

482)     </p>

483) 

484)     <p>
485)     Lastly, you should realize that we release new versions of the
486)     Tor software frequently, and sometimes we make backward incompatible

487)     changes. So if you distribute a particular version of the Tor
488) software, it
489)     may not be supported — or even work — six months later.
490) This

491)     is a fact of life for all security software under heavy development.
492)     </p>

493) 

494)     <hr>

495) 

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

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

499) 

500)     <p>Your best bet is to first try the following:</p>

501)     <ol>
502)     <li>Read through this <a href="<page docs/faq>">FAQ</a>.</li>

503)     <li>Read through the <a href="<page
504) docs/documentation>">documentation</a>.</li>

505)     <li>Read through the <a

506) 
507) href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
508) tor-talk

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

510)     <li>Join our <a href="ircs://irc.torproject.org#tor">irc channel</a>
511) and

512)     state the issue and wait for help.</li>

513)     <li>Send an email to <a

514) 
515) href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
516)     <li>If all else fails, try <a href="<page about/contact>">contacting
517) us</a> directly.</li>

518)     </ol>

519) 

520)     <p>If you find your answer, please stick around on the IRC channel
521) or the

522)     mailing list to help others who were once in your position.</p>

523) 

524)     <hr>

525) 

526)     <a id="Forum"></a>
527)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
528) 
529)     <p>Not yet, but we're working on it. Most forum software is
530)     a disaster to maintain and keep secure, and at the same time
531)     too many of the Tor developers are spread too thin to be able

532)     to contribute enough to a forum.

533)     </p>
534) 
535)     <hr>
536) 

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

539) 

540)     <p>
541)     There are many reasons why the Tor network is currently slow.
542)     </p>

543) 

544)     <p>

545)     Before we answer, though, you should realize that Tor is never going
546) to
547)     be blazing fast. Your traffic is bouncing through volunteers'
548) computers
549)     in various parts of the world, and some bottlenecks and network
550) latency

551)     will always be present. You shouldn't expect to see university-style
552)     bandwidth through Tor.
553)     </p>

554) 

555)     <p>

556)     But that doesn't mean that it can't be improved. The current Tor
557) network
558)     is quite small compared to the number of people trying to use it,
559) and
560)     many of these users don't understand or care that Tor can't
561) currently

562)     handle file-sharing traffic load.
563)     </p>

564) 

565)     <p>
566)     For the much more in-depth answer, see <a

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

568)     post on the topic</a>, which includes both a detailed PDF and a
569) video

570)     to go with it.
571)     </p>

572) 

573)     <p>
574)     What can you do to help?
575)     </p>

576) 

577)     <ul>

578) 

579)     <li>

580)     <a href="<page docs/tor-doc-relay>">Configure your Tor to relay
581) traffic
582)     for others</a>. Help make the Tor network large enough that we can
583) handle

584)     all the users who want privacy and security on the Internet.
585)     </li>

586) 

587)     <li>

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

590)     especially need people to help make it easier to configure your Tor
591)     as a relay. Also, we need help with clear simple documentation to
592)     walk people through setting it up.
593)     </li>

594) 

595)     <li>

596)     There are some bottlenecks in the current Tor network. Help us
597) design
598)     experiments to track down and demonstrate where the problems are,
599) and

600)     then we can focus better on fixing them.
601)     </li>

602) 

603)     <li>
604)     Tor needs some architectural changes too. One important change is to

605)     start providing <a href="#EverybodyARelay">better service to people
606) who
607)     relay traffic</a>. We're working on this, and we'll finish faster if
608) we

609)     get to spend more time on it.
610)     </li>

611) 

612)     <li>

613)     Help do other things so we can do the hard stuff. Please take a
614) moment
615)     to figure out what your skills and interests are, and then <a
616) href="<page

617)     getinvolved/volunteer>">look at our volunteer page</a>.
618)     </li>

619) 

620)     <li>

621)     Help find sponsors for Tor. Do you work at a company or government
622) agency

623)     that uses Tor or has a use for Internet privacy, e.g. to browse the

624)     competition's websites discreetly, or to connect back to the home
625) servers
626)     when on the road without revealing affiliations? If your
627) organization has
628)     an interest in keeping the Tor network working, please contact them
629) about
630)     supporting Tor. Without sponsors, Tor is going to become even
631) slower.

632)     </li>

633) 

634)     <li>
635)     If you can't help out with any of the above, you can still help out

636)     individually by <a href="<page donate/donate>">donating a bit of
637) money to the

638)     cause</a>. It adds up!
639)     </li>

640) 

641)     </ul>

642) 

643)     <hr>

644) 

645)     <a id="FileSharing"></a>

646)     <h3><a class="anchor" href="#FileSharing">How can I share files 
647)     anonymously through Tor?</a></h3>

648) 
649)     <p>

650)     File sharing (peer-to-peer/P2P) is widely unwanted in the Tor network, 
651)     and exit nodes are configured to block file sharing traffic by default. 
652)     Tor is not really designed for it, and file sharing through Tor slows 
653)     down everyone's browsing. Also, Bittorrent over Tor <a 
654)     href="https://blog.torproject.org/blog/bittorrent-over-tor-isnt-good-idea">
655)     is not anonymous</a>!

656)     </p>
657) 
658)     <hr>
659) 

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

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

663) 

664)     <p>

665)     The Tor network's <a

666) 
667) href="https://metrics.torproject.org/network.html#networksize">several

668)     thousand</a> relays push <a
669)     href="https://metrics.torproject.org/network.html#bandwidth">over
670)     1GB per second on average</a>. We have <a

671) 
672) href="https://metrics.torproject.org/users.html#direct-users">several

673)     hundred thousand daily users</a>. But the Tor network is not yet
674)     self-sustaining.

675)     </p>

676) 

677)     <p>

678)     There are six main development/maintenance pushes that need
679) attention:

680)     </p>

681) 

682)     <ul>

683) 

684)     <li>
685)     Scalability: We need to keep scaling and decentralizing the Tor
686)     architecture so it can handle thousands of relays and millions of

687)     users. The upcoming stable release is a major improvement, but
688) there's

689)     lots more to be done next in terms of keeping Tor fast and stable.
690)     </li>

691) 

692)     <li>

693)     User support: With this many users, a lot of people are asking
694) questions
695)     all the time, offering to help out with things, and so on. We need
696) good
697)     clean docs, and we need to spend some effort coordinating
698) volunteers.

699)     </li>

700) 

701)     <li>

702)     Relay support: the Tor network is run by volunteers, but they still
703) need

704)     attention with prompt bug fixes, explanations when things go wrong,

705)     reminders to upgrade, and so on. The network itself is a commons,
706) and
707)     somebody needs to spend some energy making sure the relay operators
708) stay
709)     happy. We also need to work on stability on some platforms —
710) e.g.,

711)     Tor relays have problems on Win XP currently.

712)     </li>

713) 

714)     <li>

715)     Usability: Beyond documentation, we also need to work on usability
716) of the
717)     software itself. This includes installers, clean GUIs, easy
718) configuration
719)     to interface with other applications, and generally automating all
720) of
721)     the difficult and confusing steps inside Tor. We've got a start on
722) this
723)     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much
724) more work

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

727) 

728)     <li>
729)     Incentives: We need to work on ways to encourage people to configure
730)     their Tors as relays and exit nodes rather than just clients.

731)     <a href="#EverybodyARelay">We need to make it easy to become a
732) relay,

733)     and we need to give people incentives to do it.</a>
734)     </li>

735) 

736)     <li>
737)     Research: The anonymous communications field is full
738)     of surprises and gotchas. In our copious free time, we
739)     also help run top anonymity and privacy conferences like <a
740)     href="http://petsymposium.org/">PETS</a>. We've identified a set of

741)     critical <a href="<page getinvolved/volunteer>#Research">Tor
742) research questions</a>
743)     that will help us figure out how to make Tor secure against the
744) variety of
745)     attacks out there. Of course, there are more research questions
746) waiting

747)     behind these.
748)     </li>

749) 

750)     </ul>

751) 

752)     <p>
753)     We're continuing to move forward on all of these, but at this rate

754)     <a href="#WhySlow">the Tor network is growing faster than the
755) developers

756)     can keep up</a>.

757)     Now would be an excellent time to add a few more developers to the
758) effort

759)     so we can continue to grow the network.
760)     </p>

761) 

762)     <p>
763)     We are also excited about tackling related problems, such as
764)     censorship-resistance.
765)     </p>

766) 

767)     <p>

768)     We are proud to have <a href="<page about/sponsors>">sponsorship and
769) support</a>
770)     from the Omidyar Network, the International Broadcasting Bureau,
771) Bell
772)     Security Solutions, the Electronic Frontier Foundation, several
773) government

774)     agencies and research groups, and hundreds of private contributors.
775)     </p>

776) 

777)     <p>

778)     However, this support is not enough to keep Tor abreast of changes
779) in the
780)     Internet privacy landscape. Please <a href="<page
781) donate/donate>">donate</a>
782)     to the project, or <a href="<page about/contact>">contact</a> our
783) executive

784)     director for information on making grants or major donations.
785)     </p>

786) 

787)     <hr>
788) 

789)      <a id="OutboundPorts"></a>

790)     <h3><a class="anchor" href="#OutboundPorts">Do I have to open all these 
791)     outbound ports on my firewall?</a></h3>

792) 
793)     <p>

794)     Tor may attempt to connect to any port that is advertised in the 
795)     directory as an ORPort (for making Tor connections) or a DirPort (for 
796)     fetching updates to the directory). There are a variety of these ports, 
797)     but many of them are running on 80, 443, 9001, and 9030.

798)     </p>
799)     <p>

800)     So as a client, you could probably get away with opening only those four 
801)     ports. Since Tor does all its connections in the background, it will retry 
802)     ones that fail, and hopefully you'll never have to know that it failed, as 
803)     long as it finds a working one often enough. However, to get the most 
804)     diversity in your entry nodes -- and thus the most security -- as well as 
805)     the most robustness in your connectivity, you'll want to let it connect 
806)     to all of them.

807)     </p>
808)     <p>

809)     If you really need to connect to only a small set of ports, see the FAQ 
810)     entry on firewalled ports.

811)     </p>
812)     <p>

813)     Note that if you're running Tor as a relay, you must allow outgoing 
814)     connections to every other relay and to anywhere your exit policy 
815)     advertises that you allow. The cleanest way to do that is simply to allow 
816)     all outgoing connections at your firewall. If you don't, clients will try 
817)     to use these connections and things won't work. 

818)     </p>
819)     
820)     <hr>
821)     
822)     <a id="IsItWorking"></a>

823)     <h3><a class="anchor" href="#IsItWorking">How can I tell if Tor is 
824)     working, and that my connections really are anonymized?</a></h3>

825) 
826)     <p>

827)     There are sites you can visit that will tell you if you appear to be 
828)     coming through the Tor network. Try the <a href="https://check.torproject.org">
829)     Tor Check</a> site and see whether it thinks you are using Tor or not.

830)     </p>
831)     <p>

832)     If that site is down, you can still test, but it will involve more effort. 
833)     Sites like <a href="http://ipid.shat.net">http://ipid.shat.net</a> and 
834)     <a href="http://www.showmyip.com/">http://www.showmyip.com/</a> will tell 
835)     you what your IP address appears to be, but you'll need to know your 
836)     current IP address so you can compare and decide whether you're using Tor 
837)     correctly.

838)     </p>
839)     <p>

840)     To learn your IP address on OS X, Linux, BSD, etc, run "ifconfig". On 
841)     Windows, go to the Start menu, click Run and enter "cmd". At the command 
842)     prompt, enter "ipconfig /a".

843)     </p>
844)     <p>

845)     If you are behind a NAT or firewall, though, your IP address will be 
846)     within the range of 10.XXX.XXX.XXX, 192.168.XXX.XXX, or 172.16.XXX.XXX - 
847)     172.31.XXX.XXX, which is not your public IP address. In this case, you 
848)     should check your IP address with one of the sites above without using 
849)     Tor, and then check again using Tor to see whether your IP address has 
850)     changed. 

851)     </p>
852)     
853)     <hr>
854)     
855)     <a id="FTP"></a>
856)     <h3><a class="anchor" href="#FTP">How do I use my browser for ftp with Tor?
857)     </a></h3>
858) 

859)     <p>
860)     Use the Tor Browser Bundle. If you want a separate application for an 
861)     ftp client, we've heard good things about  FileZilla for Windows. You can 
862)     configure it to point to Tor as a "socks4a" proxy on "localhost" port 
863)     "9050". 
864)     </p>

865)     <hr>
866)     

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

868)     <h3><a class="anchor" href="#Metrics">How many people use Tor? How

869)     many relays or exit nodes are there?</a></h3>

870) 

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

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

874)     <hr>

875) 

876)     <a id="SSLcertfingerprint"></a>

877)     <h3><a class="anchor" href="#SSLcertfingerprint">What are the SSL 
878)     certificate fingerprints for Tor's various websites?</a></h3>

879)     <p>

880)     <pre>

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

882)     The serial number is:

883) 06:DE:97:E5:1D:C3:9D:C2:64:8D:AC:72:DD:41:01:FC
884)     The SHA-1 fingerprint is: 1f9d306e8bfccfcb03981a71a27a9f5d1e0876ce

885)     The SHA-256 fingerprint is:

886) 3613d2b22a750094760c41ad19db52a4f05bdea80172e2578761ad967f7ed9aa

887) 

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

889)     The serial number is: 00:EF:A3
890)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

891)     </pre>

892)     </p>
893)     <hr>
894) 

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

896)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
897) Tor?</a></h3>
898) 
899)     <p>
900)     Tor Browser does not install itself in the classic sense of
901) applications. You just simply delete the folder or directory named "Tor
902) Browser" and it is removed from your system.
903)     </p>

904) 

905)     <p>

906)     If this is not related to Tor Browser, uninstallation depends
907) entirely on how you installed it and which operating system you
908)     have. If you installed a package, then hopefully your package has a
909) way to

910)     uninstall itself. The Windows packages include uninstallers. 

911)     </p>

912) 

913)     <p>
914)     For Mac OS X, follow the <a
915)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
916)     </p>

917) 

918)     <p>

919)     If you installed by source, I'm afraid there is no easy uninstall
920) method. But
921)     on the bright side, by default it only installs into /usr/local/ and
922) it should

923)     be pretty easy to notice things there.
924)     </p>

925) 

926)     <hr>

927) 

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

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

931) 

932)     <p>

933)     These are PGP signatures, so you can verify that the file you've
934) downloaded is

935)     exactly the one that we intended you to get.
936)     </p>

937) 

938)     <p>
939)     Please read the <a

940)     href="<page docs/verifying-signatures>">verifying signatures</a>
941) page for details.

942)     </p>

943) 

944) <hr>
945) 
946) <a id="GetTor"></a>
947) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
948) country. How do I download Tor?</a></h3>
949) 
950) <p>
951) Some government or corporate firewalls censor connections to Tor's
952) website. In those cases, you have three options. First, get it from

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

954) Bundle</a> fits nicely on a USB key. Second, find the <a

955) href="https://encrypted.google.com/search?q=tor+mirrors">google
956) cache</a>

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

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

961) in the body of the email, it will reply with instructions. Note that
962) only a few webmail providers are supported, since they need to be able
963) to receive very large attachments.
964) </p>
965) 
966) <p>

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

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

971) </p>
972) 
973) <hr>

974) 

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

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

978) 

979)     <p>

980)     Try following the steps at <a
981) href="<gitblob>doc/tor-win32-mingw-creation.txt">

982)     tor-win32-mingw-creation.txt</a>.
983)     </p>

984) 

985)     <p>
986)     (Note that you don't need to compile Tor yourself in order to use

987)     it. Most people just use the packages available on the <a
988) href="<page

989)     download/download>">download page</a>.)
990)     </p>

991) 

992)     <hr>

993) 

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

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

997) 

998)     <p>

999)     Sometimes, overzealous Windows virus and spyware detectors trigger
1000) on some
1001)     parts of the Tor Windows binary. Our best guess is that these are
1002) false
1003)     positives — after all, the anti-virus and anti-spyware
1004) business is just a
1005)     guessing game anyway. You should contact your vendor and explain
1006) that you have
1007)     a program that seems to be triggering false positives. Or pick a
1008) better vendor.

1009)     </p>

1010) 

1011)     <p>
1012)     In the meantime, we encourage you to not just take our word for

1013)     it. Our job is to provide the source; if you're concerned, please do
1014) <a

1015)     href="#CompileTorWindows">recompile it yourself</a>.
1016)     </p>

1017) 

1018)     <hr>

1019) 

1020)     <a id="LiveCD"></a>

1021)     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other
1022) bundle that includes Tor?</a></h3>

1023) 

1024)     <p>

1025)     Yes.  Use <a href="https://tails.boum.org/">The Amnesic Incognito

1026)     Live System</a> or <a href="<page projects/torbrowser>">the Tor
1027) Browser

1028)     Bundle</a>.

1029)     </p>

1030) 
1031) <hr>
1032) 

1033) <a id="TBBFlash"></a>

1034) <h3><a class="anchor" href="#TBBFlash">Why can't I view videos on
1035) YouTube

1036) and other Flash-based sites?</a></h3>

1037) 
1038) <p>

1039) YouTube and similar sites require third party browser plugins such as Flash.
1040) Plugins operate independently from Firefox and can perform
1041) activity on your computer that ruins your anonymity. This includes
1042) but is not limited to: <a href="http://decloak.net">completely disregarding
1043) proxy settings</a>, querying your <a

1044) href="http://forums.sun.com/thread.jspa?threadID=5162138&messageID=9618376">
1045) local IP address</a>, and <a

1046) href="http://epic.org/privacy/cookies/flash.html">storing their own
1047) cookies</a>. It is possible to use a LiveCD solution such as

1048) or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> 
1049) that creates a secure, transparent proxy to protect you from proxy bypass, 
1050) however issues with local IP address discovery and Flash cookies still remain. 
1051) </p>

1052) 
1053) <p>

1054) <a href="https://www.youtube.com/html5">YouTube offers experimental HTML5 video
1055) support</a> for many of their videos. You can use their Advanced Search to

1056) find HTML5 videos.
1057) </p>
1058) 

1059) <hr>
1060) 

1061) <a id="Ubuntu"></a>
1062) <h3><a class="anchor" href="#Ubuntu">
1063) I'm using Ubuntu and I can't start Tor Browser</a></h3>
1064) <p>

1065) Ubuntu prevents its users from executing shell scripts by clicking them, 
1066) even when the file permissions are set correctly. For now you need to 
1067) start the Tor Browser from the command line by running </p>

1068) <pre>
1069) ./start-tor-browser
1070) </pre>
1071) <p>
1072) from inside the Tor Browser directory.
1073) </p>
1074) 
1075) <hr>
1076) 

1077) <a id="TBBSocksPort"></a>

1078) <h3><a class="anchor" href="#TBBSocksPort">

1079) I want to run another application through the Tor launched by Tor

1080) Browser Bundle.</a></h3>

1081) 
1082) <p>

1083) Typically Tor listens for Socks connections on port 9050. TBB listens

1084) on port 9150.

1085) The goal is to avoid conflicting with a "system" Tor install,

1086) so you can run a system Tor and TBB at the same time. We're <a
1087) href="https://trac.torproject.org/projects/tor/ticket/3948">working on
1088) a feature</a> where Tor will try the usual ports first and then back

1089) off to a random choice if they're already in use.

1090) </p>
1091) 
1092) <hr>
1093) 
1094) <a id="TBBPolipo"></a>
1095) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
1096) Polipo go?</a></h3>
1097) 
1098) <p>
1099) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
1100) solely to work around a bug in Firefox that was finally fixed in Firefox
1101) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
1102) leaving it out makes you safer because Torbutton has better control over
1103) Firefox's interaction with websites.
1104) </p>
1105) 
1106) <p>
1107) If you are trying to use some external application with Tor, step zero

1108) should be to <a href="<page download/download>#warning">reread the set

1109) of warnings</a> for ways you can screw up. Step one should be to try

1110) to use a Socks proxy rather than an http proxy — Tor runs a Socks

1111) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
1112) for OSX and Linux.
1113) </p>
1114) 
1115) <p>

1116) If that fails, feel free to install <a

1117) href="http://www.privoxy.org/">privoxy</a>.
1118) However, please realize that this approach is not recommended for novice
1119) users. Privoxy has an <a
1120) href="http://www.privoxy.org/faq/misc.html#TOR">example
1121) configuration</a> of Tor and Privoxy.

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

1126) <a id="TBBOtherExtensions"></a>
1127) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
1128) Firefox extensions?</a></h3>
1129) 
1130) <p>

1131) The Tor Browser is free software, so there is nothing preventing you from 
1132) modifying it any way you like. However, we do not recommend installing any 
1133) additional Firefox add-ons with the Tor Browser Bundle. Add-ons can break 
1134) your anonymity in a number of ways, including browser fingerprinting and 
1135) bypassing proxy settings.

1136) </p>

1137) <p>

1138) Some people have suggested we include ad-blocking software or 
1139) anti-tracking software with the Tor Browser Bundle. Right now, we do not 
1140) think that's such a good idea. The Tor Browser Bundle aims to provide 
1141) sufficient privacy that additional add-ons to stop ads and trackers are 
1142) not necessary. Using add-ons like these may cause some sites to break, which 
1143) <a href="https://www.torproject.org/projects/torbrowser/design/#philosophy">
1144) we don't want to do</a>. Additionally, maintaining a list of "bad" sites that 
1145) should be black-listed provides another opportunity to uniquely fingerprint 
1146) users. 

1147) </p>

1148) 

1149) <hr>
1150) 

1151) <a id="TBBJavaScriptEnabled"></a>

1152) <a id="TBBCanIBlockJS"></a>

1153) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
1154) configured to allow JavaScript by default in the Tor Browser Bundle?
1155) Isn't that unsafe?</a></h3>

1156) 
1157) <p>
1158) We configure NoScript to allow JavaScript by default in the Tor
1159) Browser Bundle because many websites will not work with JavaScript
1160) disabled.  Most users would give up on Tor entirely if a website
1161) they want to use requires JavaScript, because they would not know
1162) how to allow a website to use JavaScript (or that enabling
1163) JavaScript might make a website work).
1164) </p>
1165) 

1166) <p>
1167) There's a tradeoff here. On the one hand, we should leave
1168) JavaScript enabled by default so websites work the way
1169) users expect. On the other hand, we should disable JavaScript
1170) by default to better protect against browser vulnerabilities (<a

1171) href="https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable">
1172) not just a theoretical concern!</a>). But there's a third issue: websites

1173) can easily determine whether you have allowed JavaScript for them,
1174) and if you disable JavaScript by default but then allow a few websites
1175) to run scripts (the way most people use NoScript), then your choice of
1176) whitelisted websites acts as a sort of cookie that makes you recognizable
1177) (and distinguishable), thus harming your anonymity.
1178) </p>

1179) 
1180) <p>

1181) Ultimately, we want the default Tor bundles to use
1182) a combination of firewalls (like the iptables rules
1183) in <a href="https://tails.boum.org/">Tails</a>) and <a
1184) href="https://trac.torproject.org/projects/tor/ticket/7680">sandboxes</a>
1185) to make JavaScript not so scary. In
1186) the shorter term, TBB 3.0 will hopefully <a
1187) href="https://trac.torproject.org/projects/tor/ticket/9387">allow users
1188) to choose their JavaScript settings more easily</a> &mdash; but the
1189) partitioning concern will remain.

1190) </p>
1191) 
1192) <p>

1193) Until we get there, feel free to leave JavaScript on or off depending
1194) on your security, anonymity, and usability priorities.

1195) </p>
1196) 
1197) <hr>
1198) 

1199) <a id="TBBOtherBrowser"></a>
1200) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
1201) Chrome/IE/Opera/etc with Tor.</a></h3>
1202) 
1203) <p>
1204) Unfortunately, Torbutton only works with Firefox right now, and without
1205) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
1206) extensive privacy fixes</a> there are many ways for websites or other

1207) attackers to recognize you, track you back to your IP address, and so
1208) on.

1209) In short, using any browser besides Tor Browser Bundle with Tor is a
1210) really bad idea.
1211) </p>
1212) 
1213) <p>
1214) We're working with the Chrome team to <a

1215) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-
1216) and-fingerprinting">fix
1217) some bugs and missing APIs in Chrome</a> so it will be possible to write
1218) a
1219) Torbutton for Chrome. No support for any other browser is on the
1220) horizon.

1221) </p>
1222) 
1223) <hr>
1224) 

1225) <a id="TorbuttonOtherBrowser"></a>
1226) <h3><a class="anchor" href="#TorbuttonOtherBrowser">
1227) Will Torbutton be available for other browsers?</a></h3>
1228) 
1229) <p>
1230)  We don't support IE, Opera or Safari and never plan to. There are too many 
1231)  ways that your privacy can go wrong with those browsers, and because of 
1232)  their closed design it is really hard for us to do anything to change these 
1233)  privacy problems.
1234) </p>
1235) <p>
1236) We are working with the Chrome people to modify Chrome's internals so that 
1237) we can eventually support it. But for now, Firefox is the only safe choice. 
1238) </p>
1239) 
1240) <hr>
1241) 
1242) <a id="NoDataScrubbing"></a>
1243) <h3><a class="anchor" href="#NoDataScrubbing">
1244) Does Tor remove personal information from the data my application sends?
1245) </a></h3>
1246) <p>
1247) No, it doesn't. You need to use a separate program that understands your 
1248) application and protocol and knows how to clean or "scrub" the data it 
1249) sends. Privoxy is an example of this for web browsing. But note that even 
1250) Privoxy won't protect you completely: you may still fall victim to viruses, 
1251) Java Script attacks, etc; and Privoxy can't do anything about text that you 
1252) type into forms. Be careful and be smart. 
1253) </p>
1254) 
1255) </hr>
1256) 

1257) <a id="TBBCloseBrowser"></a>

1258) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor
1259) Browser

1260) Bundle running but close the browser.</a></h3>
1261) 
1262) <p>
1263) We're working on a way to make this possible on all platforms. Please
1264) be patient.
1265) </p>
1266) 
1267) <hr>
1268) 

1269) <a id="GoogleCAPTCHA"></a>
1270) <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
1271) CAPTCHA or tells me I have spyware installed.</a></h3>

1272) 
1273) <p>
1274) This is a known and intermittent problem; it does not mean that Google
1275) considers Tor to be spyware.
1276) </p>
1277) 
1278) <p>

1279) When you use Tor, you are sending queries through exit relays that are
1280) also

1281) shared by thousands of other users. Tor users typically see this message

1282) when many Tor users are querying Google in a short period of time.
1283) Google

1284) interprets the high volume of traffic from a single IP address (the exit
1285) relay you happened to pick) as somebody trying to "crawl" their website,
1286) so it slows down traffic from that IP address for a short time.
1287) </p>
1288) <p>
1289) An alternate explanation is that Google tries to detect certain
1290) kinds of spyware or viruses that send distinctive queries to Google
1291) Search. It notes the IP addresses from which those queries are received
1292) (not realizing that they are Tor exit relays), and tries to warn any
1293) connections coming from those IP addresses that recent queries indicate
1294) an infection.
1295) </p>
1296) 
1297) <p>

1298) To our knowledge, Google is not doing anything intentionally
1299) specifically

1300) to deter or block Tor use. The error message about an infected machine
1301) should clear up again after a short time.
1302) </p>
1303) 
1304) <p>
1305) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1306) automatically redirect you to a more Tor-friendly search engine such as

1307) DuckDuckGo, ixquick, or Bing.

1308) </p>
1309) 
1310) <hr />
1311) 

1312) <a id="ForeignLanguages"></a>
1313) <h3><a class="anchor" href="#ForeignLanguages">
1314) Why does Google show up in foreign languages?</a></h3>
1315) 
1316) <p>

1317)  Google uses "geolocation" to determine where in the world you are, so it 
1318)  can give you a personalized experience. This includes using the language 
1319)  it thinks you prefer, and it also includes giving you different results 
1320)  on your queries.

1321) </p>
1322) <p>

1323) If you really want to see Google in English you can click the link that 
1324) provides that. But we consider this a feature with Tor, not a bug --- the 
1325) Internet is not flat, and it in fact does look different depending on 
1326) where you are. This feature reminds people of this fact. The easy way to 
1327) avoid this "feature" is to use 
1328) <a href="https://google.com/ncr">https://google.com/ncr</a>.

1329) </p>
1330) <p>

1331) Note that Google search URLs take name/value pairs as arguments and one 
1332) of those names is "hl". If you set "hl" to "en" then Google will return 
1333) search results in English regardless of what Google server you have been 
1334) sent to. On a query this looks like: 
1335) </p>
1336) <pre>https://encrypted.google.com/search?q=online%20anonymity&hl=en

1337) </pre>

1338) <p>

1339) Another method is to simply use your country code for accessing Google. 
1340) This can be google.be, google.de, google.us and so on. 

1341) </p>
1342) <hr />

1343) <a id="GmailWarning"></a>

1344) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my

1345) account may have been compromised.</a></h3>

1346) 
1347) <p>
1348) Sometimes, after you've used Gmail over Tor, Google presents a
1349) pop-up notification that your account may have been compromised.
1350) The notification window lists a series of IP addresses and locations
1351) throughout the world recently used to access your account.
1352) </p>
1353) 
1354) <p>
1355) In general this is a false alarm: Google saw a bunch of logins from

1356) different places, as a result of running the service via Tor, and
1357) decided

1358) it was a good idea to confirm the account was being accessed by it's
1359) rightful owner.
1360) </p>
1361) 
1362) <p>
1363) Even though this may be a biproduct of using the service via tor,
1364) that doesn't mean you can entirely ignore the warning. It is
1365) <i>probably</i> a false positive, but it might not be since it is
1366) possible for someone to hijack your Google cookie.
1367) </p>
1368) 
1369) <p>
1370) Cookie hijacking is possible by either physical access to your computer
1371) or by watching your network traffic.  In theory only physical access
1372) should compromise your system because Gmail and similar services
1373) should only send the cookie over an SSL link. In practice, alas, it's <a

1374) href="http://fscked.org/blog/fully-automated-active-https-cookie-
1375) hijacking">

1376) way more complex than that</a>.
1377) </p>
1378) 
1379) <p>
1380) And if somebody <i>did</i> steal your google cookie, they might end
1381) up logging in from unusual places (though of course they also might
1382) not). So the summary is that since you're using Tor, this security
1383) measure that Google uses isn't so useful for you, because it's full of
1384) false positives. You'll have to use other approaches, like seeing if
1385) anything looks weird on the account, or looking at the timestamps for
1386) recent logins and wondering if you actually logged in at those times.
1387) </p>
1388) 
1389) <hr>
1390) 

1391) <a id="torrc"></a>

1392) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
1393) What does that mean?</a></h3>

1394) 
1395) <p>
1396) Tor installs a text file called torrc that contains configuration
1397) instructions for how your Tor program should behave. The default
1398) configuration should work fine for most Tor users. Users of Vidalia can
1399) make common changes through the Vidalia interface &mdash; only advanced
1400) users should need to modify their torrc file directly.
1401) </p>

1402) <p>

1403) Tor Browser Bundle users should edit your torrc through Vidalia. Open
1404) the
1405) Vidalia Control Panel. Choose Settings. Choose Advanced. Click the
1406) button

1407) labelled "Edit current torrc". Remember to make sure the checkbox for
1408) "Save Settings." is checked. Hit the Ok button and you are done.
1409) </p>

1410) <p>

1411) Otherwise, you will need to edit the file manually.

1412) The location of your torrc file depends on the way you installed Tor:
1413) </p>
1414) <ul>

1415) <li>If you installed Tor Browser Bundle, look for
1416) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
1417) </li>

1418) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
1419) find your torrc file in the Start menu under Programs -&gt; Vidalia
1420) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
1421) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
1422) installed Tor without Vidalia, you can find your torrc in the Start
1423) menu under Programs -&gt; Tor, or manually in either <code>\Documents
1424) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
1425) Settings\<i>username</i>\Application Data\tor\torrc</code>.
1426) </li>
1427) <li>On OS X, if you use Vidalia, edit
1428) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
1429) and load <code>/Library/Tor/torrc</code>.
1430) </li>
1431) <li>On Unix, if you installed a pre-built package, look for
1432) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
1433) package's documentation.
1434) </li>
1435) <li>Finally, if you installed from source, you may not have a torrc
1436) installed yet: look in <code>/usr/local/etc/</code> and note that you

1437) may need to manually copy <code>torrc.sample</code> to
1438) <code>torrc</code>.

1439) </li>
1440) </ul>
1441) 
1442) <p>
1443) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit

1444) your torrc file manually. Otherwise Vidalia might overwrite your
1445) changes.

1446) </p>
1447) 
1448) <p>
1449) Once you've changed your torrc, you will need to restart Tor for the
1450) changes to take effect. (For advanced users on OS X and Unix, note that

1451) you actually only need to send Tor a HUP signal, not actually restart
1452) it.)

1453) </p>
1454) 
1455) <p>
1456) For other configuration options you can use, look at the <a href="<page
1457) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1458) with # in torrc are treated as comments and have no effect on Tor's
1459) configuration.
1460) </p>
1461) 
1462) <hr>
1463) 

1464) <a id="Logs"></a>

1465) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
1466) logs?</a></h3>

1467) 
1468) <p>

1469) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1470) window called "Message Log" that will show you Tor's log messages. Click
1471) on "Advanced" to see more details. You can click on "Settings" to change
1472) your log verbosity or save the messages to a file. You're all set.

1473) </p>
1474) 
1475) <p>
1476) If you're not using Vidalia, you'll have to go find the log files by

1477) hand. Here are some likely places for your logs to be:

1478) </p>
1479) 
1480) <ul>
1481) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1482) </li>

1483) <li>On Windows, there are no default log files currently. If you enable
1484) logs in your torrc file, they default to <code>\username\Application
1485) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1486) </li>
1487) <li>If you compiled Tor from source, by default your Tor logs to <a
1488) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1489) at log-level notice. If you enable logs in your torrc file, they
1490) default to <code>/usr/local/var/log/tor/</code>.

1491) </li>
1492) </ul>
1493) 
1494) <p>

1495) To change your logging setup by hand, <a href="#torrc">edit your
1496) torrc</a>

1497) and find the section (near the top of the file) which contains the
1498) following line:

1499) </p>
1500) 
1501) <pre>

1502) \## Logs go to stdout at level "notice" unless redirected by something
1503) \## else, like one of the below lines.

1504) </pre>

1505) 
1506) <p>

1507) For example, if you want Tor to send complete debug, info, notice, warn,

1508) and err level messages to a file, append the following line to the end
1509) of the section:
1510) </p>
1511) 
1512) <pre>
1513) Log debug file c:/program files/tor/debug.log
1514) </pre>
1515) 
1516) <p>

1517) Replace <code>c:/program files/tor/debug.log</code> with a directory
1518) and filename for your Tor log.

1519) </p>
1520) 
1521) <hr>
1522) 

1523) 
1524) <a id="LogLevel"></a>
1525) <h3><a class="anchor" href="#LogLevel">What log level should I use?</a></h3>
1526) 
1527) <p>

1528) There are five log levels (also called "log severities") you might see in 
1529) Tor's logs:

1530) </p>
1531) 
1532) <ul>

1533)     <li>"err": something bad just happened, and we can't recover. Tor will 
1534)     exit.</li>
1535)     <li>"warn": something bad happened, but we're still running. The bad 
1536)     thing might be a bug in the code, some other Tor process doing something 
1537)     unexpected, etc. The operator should examine the message and try to 
1538)     correct the problem.</li>

1539)     <li>"notice": something the operator will want to know about.</li>

1540)     <li>"info": something happened (maybe bad, maybe ok), but there's 
1541)     nothing you need to (or can) do about it.</li>

1542)     <li>"debug": for everything louder than info. It is quite loud indeed.</li> 
1543) </ul>
1544) 
1545) <p>

1546) Alas, some of the warn messages are hard for ordinary users to correct -- the 
1547) developers are slowly making progress at making Tor automatically react 
1548) correctly for each situation.

1549) </p>
1550) 
1551) <p>

1552) We recommend running at the default, which is "notice". You will hear about 
1553) important things, and you won't hear about unimportant things.

1554) </p>
1555) 
1556) <p>

1557) Tor relays in particular should avoid logging at info or debug in normal 
1558) operation, since they might end up recording sensitive information in 
1559) their logs. 

1560) </p>
1561) 

1562) <hr>
1563) 

1564) <a id="DoesntWork"></a>

1565) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
1566) working.</a></h3>

1567) 
1568) <p>

1569) Once you've got the Tor bundle up and running, the first question to
1570) ask is whether your Tor client is able to establish a circuit.

1571) </p>
1572) 
1573) <p>If Tor can establish a circuit, the onion icon in

1574) Vidalia will turn green (and if you're running Tor Browser Bundle, it
1575) will
1576) automatically launch a browser for you). You can also check in the
1577) Vidalia

1578) Control Panel to make sure it says "Connected to the Tor
1579) network!" under Status. For those not using Vidalia, check your <a

1580) href="#Logs">Tor logs</a> for

1581) a line saying that Tor "has successfully opened a circuit. Looks like
1582) client functionality is working."
1583) </p>
1584) 
1585) <p>
1586) If Tor can't establish a circuit, here are some hints:
1587) </p>
1588) 
1589) <ol>
1590) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1591) to click on the onion and select "Start" to launch Tor.</li>
1592) <li>Check your system clock. If it's more than a few hours off, Tor will

1593) refuse to build circuits. For Microsoft Windows users, synchronize your
1594) clock under the clock -> Internet time tab. In addition, correct the

1595) day and date under the 'Date & Time' Tab. Also make sure your time
1596) zone is correct.</li>

1597) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1598) by port</a>, or do you normally need to use a <a

1599) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</a>?

1600) </li>

1601) <li>Are you running programs like Norton Internet Security or SELinux
1602) that

1603) block certain connections, even though you don't realize they do? They
1604) could be preventing Tor from making network connections.</li>
1605) <li>Are you in China, or behind a restrictive corporate network firewall
1606) that blocks the public Tor relays? If so, you should learn about <a

1607) href="<page docs/bridges>">Tor bridges</a>.</li>

1608) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1609) about what's going wrong?</li>

1610) </ol>
1611) 
1612) <hr />
1613) 
1614) <a id="VidaliaPassword"></a>

1615) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a
1616) password at start.</a></h3>

1617) 
1618) <p>
1619) Vidalia interacts with the Tor software via Tor's "control port". The
1620) control port lets Vidalia receive status updates from Tor, request a new
1621) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1622) Vidalia sets a random password for Tor's control port to prevent other
1623) applications from also connecting to the control port and potentially
1624) compromising your anonymity.
1625) </p>
1626) 
1627) <p>
1628) Usually this process of generating and setting a random control password
1629) happens in the background. There are three common situations, though,
1630) where Vidalia may prompt you for a password:
1631) </p>
1632) 
1633) <ol>
1634) <li>You're already running Vidalia and Tor. For example, this situation
1635) can happen if you installed the Vidalia bundle and now you're trying to
1636) run the Tor Browser Bundle. In that case, you'll need to close the old
1637) Vidalia and Tor before you can run this one.
1638) </li>
1639) <li>Vidalia crashed, but left Tor running with the last known random
1640) password. After you restart Vidalia, it generates a new random password,

1641) but Vidalia can't talk to Tor, because the random passwords are
1642) different.

1643) <br />

1644) If the dialog that prompts you for a control password has a Reset
1645) button,

1646) you can click the button and Vidalia will restart Tor with a new random
1647) control password.
1648) <br />
1649) If you do not see a Reset button, or if Vidalia is unable to restart
1650) Tor for you, you can still fix the problem manually. Simply go into your
1651) process or task manager, and terminate the Tor process. Then use Vidalia
1652) to restart Tor and all will work again.
1653) </li>
1654) <li>You had previously set Tor to run as a Windows NT service. When Tor
1655) is set to
1656) run as a service, it starts up when the system boots. If you configured
1657) Tor to start as a service through Vidalia, a random password was set
1658) and saved in Tor. When you reboot, Tor starts up and uses the random
1659) password it saved. You login and start up Vidalia. Vidalia attempts to
1660) talk to the already running Tor. Vidalia generates a random password,
1661) but it is different than the saved password in the Tor service.
1662) <br />
1663) You need to reconfigure Tor to not be a service. See the FAQ entry on

1664) <a href="#NTservice">running Tor as a

1665) Windows NT service</a>

1666) for more information on how to remove the Tor service.
1667) </li>
1668) </ol>
1669) 

1670)     <hr>

1671) 

1672)     <a id="ChooseEntryExit"></a>

1673)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
1674) nodes (or country) are used for entry/exit?</a></h3>

1675) 

1676)     <p>

1677)     Yes. You can set preferred entry and exit nodes as well as
1678)     inform Tor which nodes you do not want to use.

1679)     The following options can be added to your config file <a
1680)     href="#torrc">"torrc"</a> or specified on the command line:

1681)     </p>
1682)     <dl>
1683)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

1684)         <dd>A list of preferred nodes to use for the first hop in the
1685) circuit, if possible.

1686)         </dd>
1687)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1688)         <dd>A list of preferred nodes to use for the last hop in the
1689) circuit, if possible.

1690)         </dd>
1691)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1692)         <dd>A list of nodes to never use when building a circuit.

1693)         </dd>
1694)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1695)         <dd>A list of nodes to never use when picking an exit.

1696)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
1697) this list.

1698)         </dd>
1699)     </dl>
1700)     <p>

1701)     <em>We recommend you do not use these</em>

1702)     — they are intended for testing and may disappear in future
1703) versions.

1704)     You get the best security that Tor can provide when you leave the
1705)     route selection to Tor; overriding the entry / exit nodes can mess
1706)     up your anonymity in ways we don't understand.

1707)     </p>
1708)     <p>

1709)     Note also that not every circuit is used to deliver traffic outside of 
1710)     the Tor network. It is normal to see non-exit circuits (such as those 
1711)     used to connect to hidden services, those that do directory fetches, 
1712)     those used for relay reachability self-tests, and so on) that end at 
1713)     a non-exit node. To keep a node from being used entirely, see 
1714)     <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the 
1715)     <a href="<page docs/tor-manual>">manual</a>.

1716)     </p>
1717)     <p>

1718)     Instead of <tt>$fingerprint</tt> you can also specify a <a

1719) 
1720) href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
1721) >2

1722)     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

1723)     or an ip address pattern (for example 255.254.0.0/8), or a node
1724)     nickname. Make sure there are no spaces between the commas and the
1725)     list items.

1726)     </p>
1727)     <p>

1728)     If you want to access a service directly through Tor's Socks
1729) interface

1730)     (eg. using ssh via connect.c), another option is to set up an

1731)     internal mapping in your configuration file using
1732) <tt>MapAddress</tt>.

1733)     See the manual page for details.
1734)     </p>

1735) 

1736)     <hr>

1737) 

1738) <a id="FirewallPorts"></a>

1739) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1740) few outgoing ports.</a></h3>

1741) 
1742) <p>
1743) If your firewall works by blocking ports, then you can tell Tor to only

1744) use the ports that your firewall permits by adding "FascistFirewall 1"
1745) to

1746) your <a href="<page docs/faq>#torrc">torrc

1747) configuration file</a>, or by clicking "My firewall only lets me connect
1748) to certain ports" in Vidalia's Network Settings window.
1749) </p>
1750) 
1751) <p>
1752) By default, when you set this Tor assumes that your firewall allows only
1753) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1754) different set of ports with the FirewallPorts torrc option.
1755) </p>
1756) 
1757) <p>
1758) If you want to be more fine-grained with your controls, you can also
1759) use the ReachableAddresses config options, e.g.:
1760) </p>
1761) 
1762) <pre>
1763)   ReachableDirAddresses *:80
1764)   ReachableORAddresses *:443
1765) </pre>
1766) 
1767) <hr>

1768) 

1769)     <a id="ExitPorts"></a>

1770)     <h3><a class="anchor" href="#ExitPorts">Is there a list of default exit 
1771)     ports?</a></h3>

1772)     <p>

1773) The default open ports are listed below but keep in mind that, any port or 
1774) ports can be opened by the relay operator by configuring it in torrc or 
1775) modifying the source code. But the default according to src/or/policies.c 
1776) from the source code release tor-0.2.4.16-rc is: 

1777)     </p>
1778)     <pre>
1779)   reject 0.0.0.0/8
1780)   reject 169.254.0.0/16
1781)   reject 127.0.0.0/8
1782)   reject 192.168.0.0/16
1783)   reject 10.0.0.0/8
1784)   reject 172.16.0.0/12
1785)   reject *:25
1786)   reject *:119
1787)   reject *:135-139
1788)   reject *:445
1789)   reject *:563
1790)   reject *:1214
1791)   reject *:4661-4666
1792)   reject *:6346-6429
1793)   reject *:6699
1794)   reject *:6881-6999
1795)   accept *:*
1796)     </pre>
1797)     <p>

1798)     A relay will block access to its own IP address, as well local network 
1799)     IP addresses. A relay always blocks itself by default. This prevents 
1800)     Tor users from accidentally accessing any of the exit operator's local 
1801)     services. 
1802)     </p>
1803) 
1804)     <hr>
1805) 
1806)     <a id="SocksAndDNS"></a>
1807)     <h3><a class="anchor" href="#SocksAndDNS">How do I check if my application that uses 
1808)     SOCKS is leaking DNS requests?</a></h3>
1809) 
1810)     <p>
1811)     These are two steps you need to take here. The first is to make sure 
1812)     that it's using the correct variant of the SOCKS protocol, and the 
1813)     second is to make sure that there aren't other leaks. 
1814)     </p>
1815) 
1816)     <p>
1817)     Step one: add "TestSocks 1" to your torrc file, and then watch your 
1818)     logs as you use your application. Tor will then log, for each SOCKS 
1819)     connection, whether it was using a 'good' variant or a 'bad' one. 
1820)     (If you want to automatically disable all 'bad' variants, set 
1821)     "SafeSocks 1" in your <a href="#torrc">torrc</a> file.) 
1822)     </p>
1823) 
1824)     <p>
1825)     Step two: even if your application is using the correct variant of 
1826)     the SOCKS protocol, there is still a risk that it could be leaking 
1827)     DNS queries. This problem happens in Firefox extensions that resolve 
1828)     the destination hostname themselves, for example to show you its IP 
1829)     address, what country it's in, etc. These applications may use a safe 
1830)     SOCKS variant when actually making connections, but they still do DNS 
1831)     resolves locally. If you suspect your application might behave like 
1832)     this, you should use a network sniffer like <a 
1833)     href="https://www.wireshark.org/">Wireshark</a> and look for 
1834)     suspicious outbound DNS requests. I'm afraid the details of how to look 
1835)     for these problems are beyond the scope of a FAQ entry though -- find 
1836)     a friend to help if you have problems. 

1837)     </p>
1838) 
1839)     <hr>
1840) 

1841)     <a id="RelayFlexible"></a>

1842)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1843) need to be?</a></h3>

1844) 

1845)     <p>
1846)     We aim to make setting up a Tor relay easy and convenient:
1847)     </p>

1848) 

1849)     <ul>
1850)     <li>Tor has built-in support for <a

1851)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1852)     rate limiting</a>. Further, if you have a fast
1853)     link but want to limit the number of bytes per
1854)     day (or week or month) that you donate, check out the <a

1855) 
1856) href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">
1857) hibernation

1858)     feature</a>.
1859)     </li>

1860)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
1861) that
1862)     specifies what sort of outbound connections are allowed or refused
1863) from
1864)     that relay. If you are uncomfortable allowing people to exit from
1865) your
1866)     relay, you can set it up to only allow connections to other Tor
1867) relays.

1868)     </li>
1869)     <li>It's fine if the relay goes offline sometimes. The directories
1870)     notice this quickly and stop advertising the relay. Just try to make
1871)     sure it's not too often, since connections using the relay when it
1872)     disconnects will break.
1873)     </li>
1874)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1875)     leave the Address config option blank, and Tor will try to guess.
1876)     </li>
1877)     <li>If your relay is behind a NAT and it doesn't know its public
1878)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1879)     forwarding. Forwarding TCP connections is system dependent but

1880)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1881)     offers some examples on how to do this.
1882)     </li>
1883)     <li>Your relay will passively estimate and advertise its recent

1884)     bandwidth capacity, so high-bandwidth relays will attract more users
1885) than
1886)     low-bandwidth ones. Therefore having low-bandwidth relays is useful
1887) too.

1888)     </li>
1889)     </ul>

1890) 

1891)     <hr>

1892) 

1893)     <a id="ExitPolicies"></a>

1894)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
1895) don't want to deal with abuse issues.</a></h3>

1896) 

1897)     <p>
1898)     Great. That's exactly why we implemented exit policies.
1899)     </p>

1900) 

1901)     <p>
1902)     Each Tor relay has an exit policy that specifies what sort of

1903)     outbound connections are allowed or refused from that relay. The
1904) exit

1905)     policies are propagated to Tor clients via the directory, so clients
1906)     will automatically avoid picking exit relays that would refuse to
1907)     exit to their intended destination. This way each relay can decide
1908)     the services, hosts, and networks he wants to allow connections to,

1909)     based on abuse potential and his own situation. Read the FAQ entry
1910) on
1911)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
1912) encounter</a>

1913)     if you use the default exit policy, and then read Mike Perry's

1914)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1915)     for running an exit node with minimal harassment</a>.
1916)     </p>

1917) 

1918)     <p>

1919)     The default exit policy allows access to many popular services

1920)     (e.g. web browsing), but <a
1921) href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1922)     some due to abuse potential (e.g. mail) and some since
1923)     the Tor network can't handle the load (e.g. default
1924)     file-sharing ports). You can change your exit policy

1925)     using Vidalia's "Sharing" tab, or by manually editing your

1926)     <a href="<page docs/faq>#torrc">torrc</a>

1927)     file. If you want to avoid most if not all abuse potential, set it
1928) to
1929)     "reject *:*" (or un-check all the boxes in Vidalia). This setting
1930) means
1931)     that your relay will be used for relaying traffic inside the Tor
1932) network,

1933)     but not for connections to external websites or other services.
1934)     </p>

1935) 

1936)     <p>

1937)     If you do allow any exit connections, make sure name resolution
1938) works

1939)     (that is, your computer can resolve Internet addresses correctly).

1940)     If there are any resources that your computer can't reach (for
1941) example,

1942)     you are behind a restrictive firewall or content filter), please

1943)     explicitly reject them in your exit policy — otherwise Tor
1944) users

1945)     will be impacted too.
1946)     </p>

1947) 

1948)     <hr>

1949) 

1950)     <a id="DifferentComputer"></a>

1951)     <h3><a class="anchor" href="#DifferentComputer">I want to run my 
1952)     Tor client on a different computer than my applications.</a></h3>

1953)     <p>

1954)     By default, your Tor client only listens for applications that 
1955)     connect from localhost. Connections from other computers are 
1956)     refused. If you want to torify applications on different computers 
1957)     than the Tor client, you should edit your torrc to define 
1958)     SocksListenAddress 0.0.0.0 g and then restart (or hup) Tor. If you 
1959)     want to get more advanced, you can configure your Tor client on a 
1960)     firewall to bind to your internal IP but not your external IP.  

1961)     </p>
1962) 
1963)     <hr>
1964) 
1965)     <a id="ServerClient"></a>

1966)     <h3><a class="anchor" href="#ServerClient">Can I install Tor on a 
1967)     central server, and have my clients connect to it?</a></h3>
1968)     <p>
1969)      Yes. Tor can be configured as a client or a relay on another 
1970)      machine, and allow other machines to be able to connect to it 
1971)      for anonymity. This is most useful in an environment where many 
1972)      computers want a gateway of anonymity to the rest of the world. 
1973)      However, be forwarned that with this configuration, anyone within 
1974)      your private network (existing between you and the Tor 
1975)      client/relay) can see what traffic you are sending in clear text. 
1976)      The anonymity doesn't start until you get to the Tor relay. 
1977)      Because of this, if you are the controller of your domain and you 
1978)      know everything's locked down, you will be OK, but this configuration 
1979)      may not be suitable for large private networks where security is 
1980)      key all around.
1981)     </p>
1982)     <p>
1983) Configuration is simple, editing your torrc file's SocksListenAddress 
1984) according to the following examples:

1985)     </p>
1986)     <pre>

1987) 
1988)   #This provides local interface access only, 
1989)   #needs SocksPort to be greater than 0
1990)   SocksListenAddress 127.0.0.1 
1991) 
1992)   #This provides access to Tor on a specified interface
1993)   SocksListenAddress 192.168.x.x:9100 
1994) 
1995)   #Accept from all interfaces
1996)   SocksListenAddress 0.0.0.0:9100
1997)    </pre>

1998)     <p>

1999) You can state multiple listen addresses, in the case that you are 
2000) part of several networks or subnets.

2001)     </p>
2002)     <pre>
2003)   SocksListenAddress 192.168.x.x:9100 #eth0
2004)   SocksListenAddress 10.x.x.x:9100 #eth1
2005)     </pre>
2006)     <p>

2007) After this, your clients on their respective networks/subnets would specify 
2008) a socks proxy with the address and port you specified SocksListenAddress 
2009) to be. 

2010)     </p>
2011)     <p>

2012) Please note that the SocksPort configuration option gives the port ONLY for 
2013) localhost (127.0.0.1). When setting up your SocksListenAddress(es), you need 
2014) to give the port with the address, as shown above.

2015)     <p>

2016) If you are interested in forcing all outgoing data through the central Tor 
2017) client/relay, instead of the server only being an optional proxy, you may find 
2018) the program iptables (for *nix) useful. 

2019)     </p>
2020) 
2021)     <hr>
2022) 

2023)     <a id="JoinTheNetwork"></a>

2024)     <h3><a class="anchor" href="#JoinTheNetwork">So I can just configure a 
2025)     nickname and ORPort and join the network?</a></h3>

2026) 
2027)     <p>

2028)      Yes. You can join the network and be a useful relay just by configuring 
2029)      your Tor to be a relay and making sure it's reachable from the outside.

2030)     </p>
2031)     <p>
2032) 30 Seconds to a Tor Relay:
2033)     </p>
2034)     <ul><li>
2035)     Configure a Nickname: 
2036)     </li></ul>
2037)     <pre>
2038) Nickname ididnteditheconfig
2039)     </pre>

2040)     <ul><li>

2041)     Configure ORPort: 

2042)     </li></ul>

2043)     <pre>
2044) ORPort 9001
2045)     </pre>

2046)     <ul><li>

2047)     Configure Contact Info: 

2048)     </li></ul>

2049) 
2050)     <pre>
2051) ContactInfo human@…

2052)     </pre>
2053)     <ul><li>

2054)     Start Tor. Watch the log file for a log entry that states: "Self-testing 
2055)     indicates your ORPort is reachable from the outside. Excellent. Publishing 
2056)     server descriptor."

2057)     </li></ul>

2058) 
2059)     <hr />

2060) 

2061)     <a id="RelayOrBridge"></a>

2062)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
2063) relay or bridge relay?</a></h3>

2064) 

2065)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
2066) short)
2067)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

2068)     listed in the public Tor directory.

2069)     That means that ISPs or governments trying to block access to the

2070)     Tor network can't simply block all bridges.

2071)     </p>

2072) 

2073)     <p>Being a normal relay vs being a bridge relay is almost the same
2074)     configuration: it's just a matter of whether your relay is listed

2075)     publicly or not.

2076)     </p>

2077) 

2078)     <p>

2079)     So bridges are useful a) for Tor users in oppressive regimes,

2080)     and b) for people who want an extra layer of security

2081)     because they're worried somebody will recognize that it's a public
2082)     Tor relay IP address they're contacting.

2083)     </p>

2084) 

2085)     <p>
2086)     Several countries, including China and Iran, have found ways to

2087)     detect and block connections to Tor bridges.

2088)     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

2089)     this by adding another layer of obfuscation.

2090)     </p>
2091) 

2092)     <p>So should you run a normal relay or bridge relay? If you have
2093) lots

2094)     of bandwidth, you should definitely run a normal relay.
2095)     If you're willing

2096)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
2097)     run a normal relay, since we need more exits. If you can't be an
2098)     exit and only have a little bit of bandwidth, be a bridge. Thanks
2099)     for volunteering!

2100)     </p>

2101) 

2102)     <hr>

2103) 

2104) <a id="UpgradeOrMove"></a>

2105) <h3><a class="anchor" href="#UpgradeOrMove">I want to upgrade/move my relay. 
2106) How do I keep the same key?</a></h3>

2107) 
2108) <p>

2109)  When upgrading your Tor relay, or running it on a different computer, 
2110)  the important part is to keep the same nickname (defined in your torrc 
2111)  file) and the same identity key (stored in "keys/secret_id_key" in 
2112)  your DataDirectory).

2113) </p>
2114) <p>

2115) This means that if you're upgrading your Tor relay and you keep the same 
2116) torrc and the same DataDirectory, then the upgrade should just work and 
2117) your relay will keep using the same key. If you need to pick a new 
2118) DataDirectory, be sure to copy your old keys/secret_id_key over. 

2119) </p>
2120) 
2121)     <hr>
2122) 
2123) <a id="NTService"></a>

2124) <h3><a class="anchor" href="#NTService">How do I run my Tor relay as an NT 
2125) service?</a></h3>

2126) 
2127) <p>

2128)  You can run Tor as a service on all versions of Windows except Windows 
2129)  95/98/ME. This way you can run a Tor relay without needing to always have 
2130)  Vidalia running.

2131) </p>
2132) <p>

2133) If you've already configured your Tor to be a relay, please note that when 
2134) you enable Tor as a service, it will use a different DatagDirectory, and 
2135) thus will generate a different key. If you want to keep using the old key, 
2136) see the Upgrading your Tor relay FAQ entry for how to restore the old 
2137) identity key.

2138) </p>
2139) <p>
2140) To install Tor as a service, you can simply run:
2141) </p>
2142) <pre>
2143) tor --service install
2144) </pre>
2145) <p>

2146) A service called Tor Win32 Service will be installed and started. This 
2147) service will also automatically start every time Windows boots, unless 
2148) you change the Start-up type. An easy way to check the status of Tor, 
2149) start or stop the service, and change the start-up type is by running 
2150) services.msc and finding the Tor service in the list of currently 
2151) installed services.

2152) </p>
2153) <p>

2154) Optionally, you can specify additional options for the Tor service using 
2155) the -options argument. For example, if you want Tor to use C:\tor\torrc, 
2156) instead of the default torrc, and open a control port on port 9151, you 
2157) would run:

2158) </p>
2159) <pre>
2160) tor --service install -options -f C:\tor\torrc ControlPort 9151
2161) </pre>
2162) <p>
2163) You can also start or stop the Tor service from the command line by typing:
2164) </p>
2165) <pre>
2166)  tor --service start
2167) </pre>
2168) <p>
2169) or
2170) </p>
2171) <pre>
2172)  tor --service stop
2173) </pre>
2174) <p>
2175) To remove the Tor service, you can run the following command:
2176) </p>
2177) <pre>
2178) tor --service remove
2179) </pre>
2180) <p>

2181) If you are running Tor as a service and you want to uninstall Tor entirely, 
2182) be sure to run the service removal command (shown above) first before 
2183) running the uninstaller from "Add/Remove Programs". The uninstaller is 
2184) currently not capable of removing the active service.

2185) </p>
2186) 
2187) <hr>
2188) 
2189) <a id="VirtualServer"></a>

2190) <h3><a class="anchor" href="#VirtualServer">Can I run a Tor relay from my 
2191) virtual server account?</a></h3>

2192) 
2193) <p>

2194) Some ISPs are selling "vserver" accounts that provide what they call a 
2195) virtual server -- you can't actually interact with the hardware, and 
2196) they can artificially limit certain resources such as the number of file 
2197) descriptors you can open at once. Competent vserver admins are able to 
2198) configure your server to not hit these limits. For example, in SWSoft's 
2199) Virtuozzo, investigate /proc/user_beancounters. Look for "failcnt" in 
2200) tcpsndbuf, tcprecvbuf, numothersock, and othersockbuf. Ask for these to 
2201) be increased accordingly. Some users have seen settings work well as follows: 

2202) <p>

2203) <table border="1">

2204) <tr>
2205) <td>
2206) <i>resource</i>
2207) </td>
2208) <td>
2209) <i>held</i>
2210) </td>
2211) <td>
2212) <i>maxheld</i>
2213) </td>
2214) <td>
2215) <i>barrier</i>
2216) </td>
2217) <td>
2218) <i>limit</i>
2219) </td>
2220) <td>
2221) <i>failcnt</i>
2222) </td>
2223) </tr>
2224) <tr>
2225) <td>
2226) tcpsndbuf
2227) </td>
2228) <td>
2229) 46620
2230) </td>
2231) <td>
2232) 48840
2233) </td>
2234) <td>
2235) 3440640
2236) </td>
2237) <td>
2238) 5406720
2239) </td>
2240) <td>
2241) 0
2242) </td>
2243) </tr>
2244) <tr>
2245) <td>
2246) tcprcvbuf
2247) </td>
2248) <td>
2249) 0
2250) </td>
2251) <td>
2252) 2220
2253) </td>
2254) <td>
2255) 3440640
2256) </td>
2257) <td>
2258) 5406720
2259) </td>
2260) <td>
2261) 0
2262) </td>
2263) </tr>
2264) <tr>
2265) <td>
2266) othersockbuf
2267) </td>
2268) <td>
2269) 243516
2270) </td>
2271) <td>
2272) 260072
2273) </td>
2274) <td>
2275) 2252160
2276) </td>
2277) <td>
2278) 4194304
2279) </td>
2280) <td>
2281) 0
2282) </td>
2283) </tr>
2284) <tr>
2285) <td>
2286) numothersock
2287) </td>
2288) <td>
2289) 151
2290) </td>
2291) <td>
2292) 153
2293) </td>
2294) <td>
2295) 720
2296) </td>
2297) <td>
2298) 720
2299) </td>
2300) <td>
2301) 0
2302) </td>
2303) </tr>
2304) </table>
2305) <p>
2306)  Xen, Virtual Box and VMware virtual servers have no such limits normally.
2307) </p>
2308) <p>

2309) If the vserver admin will not increase system limits another option is 
2310) to reduce the memory allocated to the send and receive buffers on TCP 
2311) connections Tor uses. An experimental feature to constrain socket buffers 
2312) has recently been added. If your version of Tor supports it, set 
2313) "ConstrainedSockets 1" in your configuration. See the tor man page for 
2314) additional details about this option.

2315) </p>
2316) <p>

2317) Unfortunately, since Tor currently requires you to be able to connect to 
2318) all the other Tor relays, we need you to be able to use at least 1024 file 
2319) descriptors. This means we can't make use of Tor relays that are crippled 
2320) in this way.

2321) </p>
2322) <p>

2323) We hope to fix this in the future, once we know how to build a Tor network 
2324) with restricted topologies -- that is, where each node connects to only a 
2325) few other nodes. But this is still a long way off.

2326) </p>
2327) 

2328) <hr>
2329) 

2330) <a id="MultipleRelays"></a>

2331) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
2332) relay.</a></h3>

2333) 
2334) <p>
2335) Great. If you want to run several relays to donate more to the network,
2336) we're happy with that. But please don't run more than a few dozen on
2337) the same network, since part of the goal of the Tor network is dispersal
2338) and diversity.
2339) </p>
2340) 
2341) <p>
2342) If you do decide to run more than one relay, please set the "MyFamily"

2343) config option in the <a href="#torrc">torrc</a> of each relay, listing
2344) all the relays (comma-separated) that are under your control:

2345) </p>
2346) 
2347) <pre>
2348)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
2349) </pre>
2350) 
2351) <p>
2352) where each fingerprint is the 40 character identity fingerprint (without

2353) spaces). You can also list them by nickname, but fingerprint is safer.
2354) Be

2355) sure to prefix the digest strings with a dollar sign ('$') so that the
2356) digest is not confused with a nickname in the config file.
2357) </p>
2358) 
2359) <p>
2360) That way clients will know to avoid using more than one of your relays
2361) in a single circuit. You should set MyFamily if you have administrative
2362) control of the computers or of their network, even if they're not all in
2363) the same geographic location.
2364) </p>
2365) 
2366)     <hr>
2367) 

2368)     <a id="WrongIP"></a>

2369)     <h3><a class="anchor" href="#WrongIP">My relay is picking the wrong 
2370)     IP address.</a></h3>

2371)     <p>

2372)  Tor guesses its IP address by asking the computer for its hostname, and 
2373)  then resolving that hostname. Often people have old entries in their 
2374)  /etc/hosts file that point to old IP addresses.

2375)     </p>
2376)     <p>

2377) If that doesn't fix it, you should use the "Address" config option to 
2378) specify the IP you want it to pick. If your computer is behind a NAT and 
2379) it only has an internal IP address, see the following FAQ entry on <a 
2380) href="https://www.torproject.org/docs/faq.html.en#RelayFlexible">dynamic 
2381) IP addresses</a>.

2382)     </p>
2383)     <p>

2384) Also, if you have many addresses, you might also want to set 
2385) "OutboundBindAddress" so external connections come from the IP you intend 
2386) to present to the world. 

2387)     </p>
2388) 
2389)     <hr>
2390) 
2391)     <a id="BehindANAT"></a>
2392)     <h3><a class="anchor" href="#BehindANAT">I'm behind a NAT/Firewall.</a></h3>
2393) 
2394)     <p>

2395) See <a>​http://portforward.com/</a> for directions on how to port forward with 
2396) your NAT/router device.

2397) </p>
2398) <p>

2399) If your relay is running on a internal net you need to setup port forwarding. 
2400) Forwarding TCP connections is system dependent but the firewalled-clients FAQ 
2401) entry offers some examples on how to do this.

2402) </p>
2403) <p>

2404) Also, here's an example of how you would do this on GNU/Linux if you're using 
2405) iptables:

2406) </p>
2407) <pre>
2408) /sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 9001 -j ACCEPT
2409) </pre>
2410) <p>

2411) You may have to change "eth0" if you have a different external interface 
2412) (the one connected to the Internet). Chances are you have only one (except 
2413) the loopback) so it shouldn't be too hard to figure out. 

2414)     </p>
2415)     <hr>
2416) 

2417)     <a id="RelayMemory"></a>

2418)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
2419) so much memory?</a></h3>

2420) 

2421)     <p>If your Tor relay is using more memory than you'd like, here are
2422) some

2423)     tips for reducing its footprint:
2424)     </p>

2425) 

2426)     <ol>
2427)     <li>If you're on Linux, you may be encountering memory fragmentation

2428)     bugs in glibc's malloc implementation. That is, when Tor releases
2429) memory
2430)     back to the system, the pieces of memory are fragmented so they're
2431) hard
2432)     to reuse. The Tor tarball ships with OpenBSD's malloc
2433) implementation,
2434)     which doesn't have as many fragmentation bugs (but the tradeoff is
2435) higher
2436)     CPU load). You can tell Tor to use this malloc implementation
2437) instead:

2438)     <tt>./configure --enable-openbsd-malloc</tt></li>

2439) 

2440)     <li>If you're running a fast relay, meaning you have many TLS
2441) connections

2442)     open, you are probably losing a lot of memory to OpenSSL's internal
2443)     buffers (38KB+ per socket). We've patched OpenSSL to <a

2444) 
2445) href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.
2446) html">release

2447)     unused buffer memory more aggressively</a>. If you update to OpenSSL

2448)     1.0.0 or newer, Tor's build process will automatically recognize and
2449) use

2450)     this feature.</li>

2451) 

2452)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
2453)     old FreeBSD, Tor is probably forking separate processes
2454)     rather than using threads. Consider switching to a <a
2455)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better
2456)     operating system</a>.</li>

2457) 

2458)     <li>If you still can't handle the memory load, consider reducing the

2459)     amount of bandwidth your relay advertises. Advertising less
2460) bandwidth

2461)     means you will attract fewer users, so your relay shouldn't grow
2462)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
2463)     page.</li>

2464) 

2465)     </ol>

2466) 

2467)     <p>

2468)     All of this said, fast Tor relays do use a lot of ram. It is not
2469) unusual

2470)     for a fast exit relay to use 500-1000 MB of memory.
2471)     </p>

2472) 

2473)     <hr>

2474) 

2475)     <a id="BetterAnonymity"></a>

2476)     <h3><a class="anchor" href="#BetterAnonymity">Do I get better anonymity 
2477)     if I run a relay?</a></h3>

2478) 

2479)     <p>

2480) Yes, you do get better anonymity against some attacks.
2481)     </p>
2482)     <p>

2483) The simplest example is an attacker who owns a small number of Tor relays. 
2484) He will see a connection from you, but he won't be able to know whether 
2485) the connection originated at your computer or was relayed from somebody else.

2486)     </p>
2487)     <p>

2488) There are some cases where it doesn't seem to help: if an attacker can 
2489) watch all of your incoming and outgoing traffic, then it's easy for him 
2490) to learn which connections were relayed and which started at you. (In 
2491) this case he still doesn't know your destinations unless he is watching 
2492) them too, but you're no better off than if you were an ordinary client.)

2493)     </p>
2494)     <p>

2495) There are also some downsides to running a Tor relay. First, while we 
2496) only have a few hundred relays, the fact that you're running one might 
2497) signal to an attacker that you place a high value on your anonymity. 
2498) Second, there are some more esoteric attacks that are not as 
2499) well-understood or well-tested that involve making use of the knowledge 
2500) that you're running a relay -- for example, an attacker may be able to 
2501) "observe" whether you're sending traffic even if he can't actually watch 
2502) your network, by relaying traffic through your Tor relay and noticing 
2503) changes in traffic timing.

2504)     </p>
2505)     <p>

2506) It is an open research question whether the benefits outweigh the risks. 
2507) A lot of that depends on the attacks you are most worried about. For 
2508) most users, we think it's a smart move. 

2509)     </p>

2510) 

2511)     <hr>

2512) 

2513)     <a id="RelayDonations"></a>

2514)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
2515)     relay rather than run my own?</a></h3>

2516) 
2517)     <p>

2518)     Sure! We recommend these non-profit charities that are happy to turn

2519)     your donations into better speed and anonymity for the Tor network:
2520)     </p>
2521)     <ul>
2522)     <li><a href="https://www.torservers.net/">torservers.net</a>
2523)     is a German charitable non-profit that runs a wide variety of

2524)     exit relays worldwide. They also like donations of bandwidth from
2525)     ISPs.</li>

2526)     <li><a

2527) href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

2528)     is a US-based 501(c)(3) non-profit that collects donations and turns

2529)     them into more US-based exit relay capacity.</li>
2530)     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
2531)     charitable non-profit that runs fast exit relays in France.</li>

2532)     </ul>
2533) 
2534)     <p>
2535)     These organizations are not the same as <a href="<page
2536)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

2537)     good thing. They're both run by nice people who are part of the
2538)     Tor community.

2539)     </p>
2540) 
2541)     <p>
2542)     Note that there can be a tradeoff here between anonymity and

2543)     performance. The Tor network's anonymity comes in part from
2544) diversity,

2545)     so if you are in a position to run your own relay, you will be

2546)     improving Tor's anonymity more than by donating. At the same time
2547)     though, economies

2548)     of scale for bandwidth mean that combining many small donations into

2549)     several larger relays is more efficient at improving network

2550)     performance. Improving anonymity and improving performance are both
2551)     worthwhile goals, so however you can help is great!
2552)     </p>
2553) 
2554)     <hr>
2555) 

2556)     <a id="AccessHiddenServices"></a>
2557)     <h3><a class="anchor" href="#AccessHiddenServices">How do I access 
2558)     hidden services?</a></h3>
2559)     
2560)     <p>
2561)     Tor hidden services are named with a special top-level domain (TLD) 
2562)     name in DNS: .onion. Since the .onion TLD is not recognized by the 
2563)     official root DNS servers on the Internet, your application will not 
2564)     get the response it needs to locate the service. Currently, the Tor 
2565)     directory server provides this look-up service; and thus the look-up 
2566)     request must get to the Tor network. 
2567)     </p>
2568) 
2569) <p>
2570)  Therefore, your application <b>needs</b> to pass the .onion hostname to 
2571)  Tor directly. You can't try to resolve it to an IP address, since there 
2572)  <i>is</i> no corresponding IP address: the server is hidden, after all! 
2573) </p>
2574)     
2575)     <p>
2576)     So, how do you make your application pass the hostname directly to Tor? 
2577)     You can't use SOCKS 4, since SOCKS 4 proxies require an IP from the 
2578)     client (a web browser is an example of a SOCKS client). Even though 
2579)     SOCKS 5 can accept either an IP or a hostname, most applications 
2580)     supporting SOCKS 5 try to resolve the name before passing it to the 
2581)     SOCKS proxy. SOCKS 4a, however, always accepts a hostname: You'll need 
2582)     to use SOCKS 4a. 
2583)     </p>
2584)     
2585)     <p>
2586)     Some applications, such as the browsers Mozilla Firefox and Apple's 
2587)     Safari, support sending DNS queries to Tor's SOCKS 5 proxy. Most web 
2588)     browsers don't support SOCKS 4a very well, though. The workaround is 
2589)     to point your web browser at an HTTP proxy, and tell the HTTP proxy 
2590)     to speak to Tor with SOCKS 4a. We recommend Polipo as your HTTP proxy.
2591)     </p>
2592)     
2593)     <p>
2594)     For applications that do not support HTTP proxy, and so cannot use 
2595)     Polipo, <a href="http://www.freecap.ru/eng/">FreeCap</a> is an 
2596)     alternative. When using FreeCap set proxy protocol  to SOCKS 5 and under 
2597)     settings set DNS name resolving to remote. This 
2598)     will allow you to use almost any program with Tor without leaking DNS 
2599)     lookups and allow those same programs to access hidden services. 
2600)     </p>
2601)     
2602)     <p>
2603)     See also the <a href="#SocksAndDNS">question on DNS</a>. 
2604)     </p>    
2605)     
2606)     <hr>
2607) 
2608)     <a id="ProvideAHiddenService"></a>
2609)     <h3><a class="anchor" href="#ProvideAHiddenService">How do I provide a 
2610)     hidden service?</a></h3>
2611)     
2612)     <p>
2613)     See the ​<a href="https://www.torproject.org/docs/tor-hidden-service.html.en">
2614)     official hidden service configuration instructions</a>.
2615)     </p>
2616) 
2617)     <hr>
2618)     

2619)     <a id="KeyManagement"></a>

2620)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the
2621) keys Tor uses.</a></h3>

2622) 

2623)     <p>
2624)     Tor uses a variety of different keys, with three goals in mind: 1)
2625)     encryption to ensure privacy of data within the Tor network, 2)
2626)     authentication so clients know they're

2627)     talking to the relays they meant to talk to, and 3) signatures to
2628) make

2629)     sure all clients know the same set of relays.
2630)     </p>

2631) 

2632)     <p>

2633)     <b>Encryption</b>: first, all connections in Tor use TLS link
2634) encryption,

2635)     so observers can't look inside to see which circuit a given cell is

2636)     intended for. Further, the Tor client establishes an ephemeral
2637) encryption

2638)     key with each relay in the circuit; these extra layers of encryption
2639)     mean that only the exit relay can read

2640)     the cells. Both sides discard the circuit key when the circuit ends,

2641)     so logging traffic and then breaking into the relay to discover the

2642)     key won't work.

2643)     </p>

2644) 

2645)     <p>
2646)     <b>Authentication</b>:
2647)     Every Tor relay has a public decryption key called the "onion key".

2648)     Each relay rotates its onion key once a week.

2649)     When the Tor client establishes circuits, at each step it <a

2650) 
2651) href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands

2652)     that the Tor relay prove knowledge of its onion key</a>. That way
2653)     the first node in the path can't just spoof the rest of the path.

2654)     Because the Tor client chooses the path, it can make sure to get
2655)     Tor's "distributed trust" property: no single relay in the path can
2656)     know about both the client and what the client is doing.

2657)     </p>

2658) 

2659)     <p>
2660)     <b>Coordination</b>:

2661)     How do clients know what the relays are, and how do they know that
2662) they
2663)     have the right keys for them? Each relay has a long-term public
2664) signing
2665)     key called the "identity key". Each directory authority additionally
2666) has a

2667)     "directory signing key". The directory authorities <a

2668)     href="<specblob>dir-spec.txt">provide a signed list</a>

2669)     of all the known relays, and in that list are a set of certificates
2670) from
2671)     each relay (self-signed by their identity key) specifying their
2672) keys,
2673)     locations, exit policies, and so on. So unless the adversary can
2674) control

2675)     a majority of the directory authorities (as of 2012 there are 8

2676)     directory authorities), he can't trick the Tor client into using
2677)     other Tor relays.

2678)     </p>

2679) 

2680)     <p>

2681)     How do clients know what the directory authorities are? The Tor
2682) software
2683)     comes with a built-in list of location and public key for each
2684) directory
2685)     authority. So the only way to trick users into using a fake Tor
2686) network

2687)     is to give them a specially modified version of the software.
2688)     </p>

2689) 

2690)     <p>
2691)     How do users know they've got the right software? When we distribute
2692)     the source code or a package, we digitally sign it with <a
2693)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
2694)     href="<page docs/verifying-signatures>">instructions
2695)     on how to check Tor's signatures</a>.
2696)     </p>

2697)