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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 for other browsers?</a></li>

81)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
82)     running but close the browser.</a></li>
83) 

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

85) tells

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

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

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

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

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

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

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

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

102)     <li><a href="#TorCrash">My Tor keeps crashing.</a></li>

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

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

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

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

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

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

119)     </ul>

120) 

121)     <p>Running a Tor relay:</p>
122)     <ul>

123) 
124)     <li><a href="#HowDoIDecide">How do I decide if I should run a relay?
125)     </a></li>

126)     <li><a href="#WhyIsntMyRelayBeingUsedMore">Why isn't my relay being 
127)     used more?</a></li>
128)     <li><a href="#HighCapacityConnection">How can I get Tor to fully 
129)     make use of my high capacity connection?</a></li>

130)     <li><a href="#RelayFlexible">How stable does my relay need to
131) be?</a></li>
132)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to
133) deal

134)     with abuse issues.</a></li>
135)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
136)     relay?</a></li>

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

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

141)     <li><a href="#NTService">How do I run my Tor relay as an NT service?
142)     </a></li>
143)     <li><a href="#VirtualServer">Can I run a Tor relay from my virtual server 
144)     account?</a></li>

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

147)     <li><a href="#RelayMemory">Why is my Tor relay using so much memory?
148)     </a></li>
149)     <li><a href="#BetterAnonymity">Do I get better anonymity if I run a relay?
150)     </a></li>

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

153)     </ul>

154) 

155)     <p>Tor hidden services:</p>
156)     <ul>
157)     <li><a href="#AccessHiddenServices">How do I access hidden services?</a></li>
158)     <li><a href="#ProvideAHiddenService">How do I provide a hidden service</a></li>
159)     </ul>

160) 

161)     <p>Development</p>
162)     <ul>
163)     <li><a href="#WhoIsResponsible">Who is responsible for Tor?</a></li>
164)     <li><a href="#VersionNumbers">What do these weird version numbers 
165)     mean?</a></li>
166)     <li><a href="#PrivateTorNetwork">How do I set up my own private
167)     Tor network?</a></li>
168)     <li><a href="#UseTorWithJava">How can I make my Java program use the 
169)     Tor network?</a></li>
170)     <li><a href="#WhatIsLibevent">What is Libevent?</a></li>
171)     <li><a href="#MyNewFeature">What do I need to do to get a new feature 
172)     into Tor?</a></li>
173)     </ul>
174) 

175)     <p>Anonymity and Security:</p>
176)     <ul>

177)     <li><a href="#WhatProtectionsDoesTorProvide">What protections does Tor 
178)     provide?</a></li>
179)     <li><a href="#CanExitNodesEavesdrop">Can exit nodes eavesdrop on 
180)     communications? Isn't that bad? </a></li>
181)     <li><a href="#ExitEnclaving">What is Exit Enclaving?</a></li>

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

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

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

186)     <li><a href="#CellSize">Tor uses hundreds of bytes for every IRC line. I 
187)     can't afford that!</a></li>
188)     <li><a href="#OutboundConnections">Why does netstat show these outbound 
189)     connections?</a></li>
190)     <li><a href="#PowerfulBlockers">What about powerful blocking mechanisms
191)     </a></li>
192)     <li><a href="#RemotePhysicalDeviceFingerprinting">Does Tor resist 
193)     "remote physical device fingerprinting"?</a></li>

194)     <li><a href="#VPN">What's safer, Tor or a VPN?</a></li>
195)     <li><a href="#Proxychains">Aren't 10 proxies (proxychains) better than 
196)     Tor with only 3 hops?</a></li>

197)     <li><a href="#AttacksOnOnionRouting">What attacks remain against onion 
198)     routing?</a></li>

199)     </ul>

200) 

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

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

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

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

210)     <li><a href="#ChoosePathLength">You should let people choose their path 
211)     length.</a></li>
212)     <li><a href="#SplitEachConnection">You should split each connection over 
213)     many paths.</a></li>
214)     <li><a href="#UnallocatedNetBlocks">Your default exit policy should block 
215)     unallocated net blocks too.</a></li>
216)     <li><a href="#BlockWebsites">Exit policies should be able to block 
217)     websites, not just IP addresses.</a></li>
218)     <li><a href="#BlockContent">You should change Tor to prevent users from 
219)     posting certain content.</a></li>

220)     <li><a href="#SendPadding">You should send padding so it's more secure.
221)     </a></li>
222)     <li><a href="#Steganography">You should use steganography to hide Tor 
223)     traffic.</a></li>

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

225)     </ul>

226) 

227)     <p>Abuse:</p>

228)     <ul>

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

231)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
232)     relay?</a></li>

233)     <li><a href="#HelpPoliceOrLawyers">I have questions about
234)    a Tor IP address for a legal case.</a></li>

235)     </ul>

236) 

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

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

240) 

241)     <hr>

242) 

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

244) 

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

247) 

248)     <p>
249)     The name "Tor" can refer to several different components.
250)     </p>

251) 

252)     <p>

253)     The Tor software is a program you can run on your computer that
254) helps keep
255)     you safe on the Internet. Tor protects you by bouncing your
256) communications

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

258)     the world: it prevents somebody watching your Internet connection
259) from

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

261)     from learning your physical location. This set of volunteer relays
262) is
263)     called the Tor network. You can read more about how Tor works on the
264) <a

265)     href="<page about/overview>">overview page</a>.
266)     </p>

267) 

268)     <p>

269)     The Tor Project is a non-profit (charity) organization that
270) maintains

271)     and develops the Tor software.
272)     </p>

273) 

274)     <hr>

275) 

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

277)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different
278) from other proxies?</a></h3>
279)     <p>
280)     A typical proxy provider sets up a server somewhere on the Internet
281) and
282) allows you to use it to relay your traffic.  This creates a simple, easy
283) to
284) maintain architecture.  The users all enter and leave through the same
285) server.
286) The provider may charge for use of the proxy, or fund their costs
287) through
288) advertisements on the server.  In the simplest configuration, you don't
289) have to
290) install anything.  You just have to point your browser at their proxy
291) server.
292) Simple proxy providers are fine solutions if you do not want protections
293) for
294) your privacy and anonymity online and you trust the provider from doing
295) bad
296) things.  Some simple proxy providers use SSL to secure your connection
297) to them.
298) This may protect you against local eavesdroppers, such as those at a
299) cafe with

300) free wifi Internet.
301)     </p>
302)     <p>

303)     Simple proxy providers also create a single point of failure.  The
304) provider
305) knows who you are and where you browse on the Internet.  They can see
306) your
307) traffic as it passes through their server.  In some cases, they can even
308) see

309) inside your

310) encrypted traffic as they relay it to your banking site or to ecommerce
311) stores.

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

313) watching your traffic, injecting their own advertisements into your
314) traffic

315) stream, and recording your personal details.

316)     </p>
317)     <p>

318)     Tor passes your traffic through at least 3 different servers before
319) sending
320) it on to the destination. Because there's a separate layer of encryption
321) for
322) each of the three relays, Tor does not modify, or even know, what you
323) are
324) sending into it.  It merely relays your traffic, completely encrypted
325) through
326) the Tor network and has it pop out somewhere else in the world,
327) completely
328) intact.  The Tor client is required because we assume you trust your
329) local
330) computer.  The Tor client manages the encryption and the path chosen
331) through
332) the network.  The relays located all over the world merely pass
333) encrypted

334) packets between themselves.</p>

335)     <p>
336)     <dl>

337)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad
338) first of
339) three servers can see encrypted Tor traffic coming from your computer.
340) It
341) still doesn't know who you are and what you are doing over Tor.  It
342) merely sees
343) "This IP address is using Tor".  Tor is not illegal anywhere in the
344) world, so
345) using Tor by itself is fine.  You are still protected from this node
346) figuring

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

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

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

353) e-commerce website, or encrypted mail connections, etc, it will only
354) know the
355) destination.  It won't be able to see the data inside the traffic
356) stream.  You

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

359)     </dl>
360)     </p>

361) 

362)     <hr>

363) 

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

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

367) 

368)     <p>

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

373)     </p>
374)     <p>
375)     There are plenty of other programs you can use with Tor,
376)     but we haven't researched the application-level anonymity

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

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

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

380)     specific applications</a>.

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

383) 

384)     <hr>

385) 

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

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

389) 

390)     <p>
391)     Because Tor is the onion routing network. When we were starting the
392)     new next-generation design and implementation of onion routing in
393)     2001-2002, we would tell people we were working on onion routing,
394)     and they would say "Neat. Which one?" Even if onion routing has
395)     become a standard household term, Tor was born out of the actual <a
396)     href="http://www.onion-router.net/">onion routing project</a> run by
397)     the Naval Research Lab.
398)     </p>

399) 

400)     <p>
401)     (It's also got a fine translation from German and Turkish.)
402)     </p>

403) 

404)     <p>

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

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

408)     spot people who haven't read any of our website (and have instead
409) learned
410)     everything they know about Tor from news articles) by the fact that
411) they

412)     spell it wrong.
413)     </p>

414) 

415)     <hr>

416) 

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

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

420) 

421)     <p>

422)     There is absolutely no backdoor in Tor. Nobody has asked us to put
423) one
424)     in, and we know some smart lawyers who say that it's unlikely that
425) anybody

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

429) 

430)     <p>
431)     We think that putting a backdoor in Tor would be tremendously

432)     irresponsible to our users, and a bad precedent for security
433) software

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

438) 

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

442)     computers, or something like that. Tor is open source, and you
443) should
444)     always check the source (or at least the diffs since the last
445) release)

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

452) 

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

455)     anonymity. We periodically find and fix anonymity-related bugs, so
456) make

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

459) 

460)     <hr>

461) 

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

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

465) 

466)     <p>
467)     Yes.
468)     </p>

469) 

470)     <p>

471)     The Tor software is <a href="https://www.fsf.org/">free
472) software</a>. This
473)     means we give you the rights to redistribute the Tor software,
474) either
475)     modified or unmodified, either for a fee or gratis. You don't have
476) to

477)     ask us for specific permission.
478)     </p>

479) 

480)     <p>

481)     However, if you want to redistribute the Tor software you must
482) follow our

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

484)     Essentially this means that you need to include our LICENSE file
485) along

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

488) 

489)     <p>

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

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

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

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

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

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

505)     </p>

506) 

507)     <p>

508)     Also, you should make sure not to confuse your readers about what
509) Tor is,
510)     who makes it, and what properties it provides (and doesn't provide).
511) See
512)     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for
513) details.

514)     </p>

515) 

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

519)     changes. So if you distribute a particular version of the Tor
520) software, it
521)     may not be supported — or even work — six months later.
522) This

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

525) 

526)     <hr>

527) 

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

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

531) 

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

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

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

537)     <li>Read through the <a

538) 
539) href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
540) tor-talk

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

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

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

545)     <li>Send an email to <a

546) 
547) href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
548)     <li>If all else fails, try <a href="<page about/contact>">contacting
549) us</a> directly.</li>

550)     </ol>

551) 

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

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

555) 

556)     <hr>

557) 

558)     <a id="Forum"></a>
559)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
560) 

561)     <p>We have a <a href="https://tor.stackexchange.com/">StackExchange 

562)     page</a> that is currently in public beta.

563)     </p>
564) 
565)     <hr>
566) 

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

569) 

570)     <p>
571)     There are many reasons why the Tor network is currently slow.
572)     </p>

573) 

574)     <p>

575)     Before we answer, though, you should realize that Tor is never going
576) to
577)     be blazing fast. Your traffic is bouncing through volunteers'
578) computers
579)     in various parts of the world, and some bottlenecks and network
580) latency

581)     will always be present. You shouldn't expect to see university-style
582)     bandwidth through Tor.
583)     </p>

584) 

585)     <p>

586)     But that doesn't mean that it can't be improved. The current Tor
587) network
588)     is quite small compared to the number of people trying to use it,
589) and
590)     many of these users don't understand or care that Tor can't
591) currently

592)     handle file-sharing traffic load.
593)     </p>

594) 

595)     <p>
596)     For the much more in-depth answer, see <a

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

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

600)     to go with it.
601)     </p>

602) 

603)     <p>
604)     What can you do to help?
605)     </p>

606) 

607)     <ul>

608) 

609)     <li>

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

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

616) 

617)     <li>

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

620)     especially need people to help make it easier to configure your Tor
621)     as a relay. Also, we need help with clear simple documentation to
622)     walk people through setting it up.
623)     </li>

624) 

625)     <li>

626)     There are some bottlenecks in the current Tor network. Help us
627) design
628)     experiments to track down and demonstrate where the problems are,
629) and

630)     then we can focus better on fixing them.
631)     </li>

632) 

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

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

639)     get to spend more time on it.
640)     </li>

641) 

642)     <li>

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

647)     getinvolved/volunteer>">look at our volunteer page</a>.
648)     </li>

649) 

650)     <li>

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

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

654)     competition's websites discreetly, or to connect back to the home
655) servers
656)     when on the road without revealing affiliations? If your
657) organization has
658)     an interest in keeping the Tor network working, please contact them
659) about
660)     supporting Tor. Without sponsors, Tor is going to become even
661) slower.

662)     </li>

663) 

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

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

668)     cause</a>. It adds up!
669)     </li>

670) 

671)     </ul>

672) 

673)     <hr>

674) 

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

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

678) 
679)     <p>

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

686)     </p>
687) 
688)     <hr>
689) 

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

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

693) 

694)     <p>

695)     The Tor network's <a

696) 
697) href="https://metrics.torproject.org/network.html#networksize">several

698)     thousand</a> relays push <a
699)     href="https://metrics.torproject.org/network.html#bandwidth">over
700)     1GB per second on average</a>. We have <a

701) 
702) href="https://metrics.torproject.org/users.html#direct-users">several

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

705)     </p>

706) 

707)     <p>

708)     There are six main development/maintenance pushes that need
709) attention:

710)     </p>

711) 

712)     <ul>

713) 

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

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

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

721) 

722)     <li>

723)     User support: With this many users, a lot of people are asking
724) questions
725)     all the time, offering to help out with things, and so on. We need
726) good
727)     clean docs, and we need to spend some effort coordinating
728) volunteers.

729)     </li>

730) 

731)     <li>

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

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

735)     reminders to upgrade, and so on. The network itself is a commons,
736) and
737)     somebody needs to spend some energy making sure the relay operators
738) stay
739)     happy. We also need to work on stability on some platforms —
740) e.g.,

741)     Tor relays have problems on Win XP currently.

742)     </li>

743) 

744)     <li>

745)     Usability: Beyond documentation, we also need to work on usability
746) of the
747)     software itself. This includes installers, clean GUIs, easy
748) configuration
749)     to interface with other applications, and generally automating all
750) of
751)     the difficult and confusing steps inside Tor. We've got a start on
752) this
753)     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much
754) more work

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

757) 

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

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

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

765) 

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

771)     critical <a href="<page getinvolved/volunteer>#Research">Tor
772) research questions</a>
773)     that will help us figure out how to make Tor secure against the
774) variety of
775)     attacks out there. Of course, there are more research questions
776) waiting

777)     behind these.
778)     </li>

779) 

780)     </ul>

781) 

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

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

786)     can keep up</a>.

787)     Now would be an excellent time to add a few more developers to the
788) effort

789)     so we can continue to grow the network.
790)     </p>

791) 

792)     <p>
793)     We are also excited about tackling related problems, such as
794)     censorship-resistance.
795)     </p>

796) 

797)     <p>

798)     We are proud to have <a href="<page about/sponsors>">sponsorship and
799) support</a>
800)     from the Omidyar Network, the International Broadcasting Bureau,
801) Bell
802)     Security Solutions, the Electronic Frontier Foundation, several
803) government

804)     agencies and research groups, and hundreds of private contributors.
805)     </p>

806) 

807)     <p>

808)     However, this support is not enough to keep Tor abreast of changes
809) in the
810)     Internet privacy landscape. Please <a href="<page
811) donate/donate>">donate</a>
812)     to the project, or <a href="<page about/contact>">contact</a> our
813) executive

814)     director for information on making grants or major donations.
815)     </p>

816) 

817)     <hr>
818) 

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

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

822) 
823)     <p>

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

828)     </p>
829)     <p>

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

837)     </p>
838)     <p>

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

841)     </p>
842)     <p>

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

848)     </p>
849)     
850)     <hr>
851)     
852)     <a id="IsItWorking"></a>

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

855) 
856)     <p>

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

860)     </p>
861)     <p>

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

868)     </p>
869)     <p>

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

873)     </p>
874)     <p>

875)     If you are behind a NAT or firewall, though, your IP address will be 
876)     within the range of 10.XXX.XXX.XXX, 192.168.XXX.XXX, or 172.16.XXX.XXX - 
877)     172.31.XXX.XXX, which is not your public IP address. In this case, you 
878)     should check your IP address with one of the sites above without using 
879)     Tor, and then check again using Tor to see whether your IP address has 
880)     changed. 

881)     </p>
882)     
883)     <hr>
884)     
885)     <a id="FTP"></a>
886)     <h3><a class="anchor" href="#FTP">How do I use my browser for ftp with Tor?
887)     </a></h3>
888) 

889)     <p>
890)     Use the Tor Browser Bundle. If you want a separate application for an 
891)     ftp client, we've heard good things about  FileZilla for Windows. You can 
892)     configure it to point to Tor as a "socks4a" proxy on "localhost" port 
893)     "9050". 
894)     </p>

895)     <hr>
896)     

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

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

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

900) 

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

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

904)     <hr>

905) 

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

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

909)     <p>

910)     <pre>

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

912)     The serial number is:

913) 06:DE:97:E5:1D:C3:9D:C2:64:8D:AC:72:DD:41:01:FC
914)     The SHA-1 fingerprint is: 1f9d306e8bfccfcb03981a71a27a9f5d1e0876ce

915)     The SHA-256 fingerprint is:

916) 3613d2b22a750094760c41ad19db52a4f05bdea80172e2578761ad967f7ed9aa

917) 

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

919)     The serial number is: 00:EF:A3
920)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

921)     </pre>

922)     </p>
923)     <hr>
924) 

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

926)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
927) Tor?</a></h3>
928) 
929)     <p>
930)     Tor Browser does not install itself in the classic sense of
931) applications. You just simply delete the folder or directory named "Tor
932) Browser" and it is removed from your system.
933)     </p>

934) 

935)     <p>

936)     If this is not related to Tor Browser, uninstallation depends
937) entirely on how you installed it and which operating system you
938)     have. If you installed a package, then hopefully your package has a
939) way to

940)     uninstall itself. The Windows packages include uninstallers. 

941)     </p>

942) 

943)     <p>
944)     For Mac OS X, follow the <a
945)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
946)     </p>

947) 

948)     <p>

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

953)     be pretty easy to notice things there.
954)     </p>

955) 

956)     <hr>

957) 

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

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

961) 

962)     <p>

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

965)     exactly the one that we intended you to get.
966)     </p>

967) 

968)     <p>
969)     Please read the <a

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

972)     </p>

973) 

974) <hr>
975) 
976) <a id="GetTor"></a>
977) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
978) country. How do I download Tor?</a></h3>
979) 
980) <p>
981) Some government or corporate firewalls censor connections to Tor's
982) website. In those cases, you have three options. First, get it from

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

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

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

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

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

991) in the body of the email, it will reply with instructions. Note that
992) only a few webmail providers are supported, since they need to be able
993) to receive very large attachments.
994) </p>
995) 
996) <p>

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

999) of any package you download, especially when you get it from somewhere
1000) other than our official HTTPS website.

1001) </p>
1002) 
1003) <hr>

1004) 

1005)     <a id="CompileTorWindows"></a>

1006)     <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor
1007) under Windows?</a></h3>

1008) 

1009)     <p>

1010)     Try following the steps at <a
1011) href="<gitblob>doc/tor-win32-mingw-creation.txt">

1012)     tor-win32-mingw-creation.txt</a>.
1013)     </p>

1014) 

1015)     <p>
1016)     (Note that you don't need to compile Tor yourself in order to use

1017)     it. Most people just use the packages available on the <a
1018) href="<page

1019)     download/download>">download page</a>.)
1020)     </p>

1021) 

1022)     <hr>

1023) 

1024)     <a id="VirusFalsePositives"></a>

1025)     <h3><a class="anchor" href="#VirusFalsePositives">Why does my Tor
1026) executable appear to have a virus or spyware?</a></h3>

1027) 

1028)     <p>

1029)     Sometimes, overzealous Windows virus and spyware detectors trigger
1030) on some
1031)     parts of the Tor Windows binary. Our best guess is that these are
1032) false
1033)     positives — after all, the anti-virus and anti-spyware
1034) business is just a
1035)     guessing game anyway. You should contact your vendor and explain
1036) that you have
1037)     a program that seems to be triggering false positives. Or pick a
1038) better vendor.

1039)     </p>

1040) 

1041)     <p>
1042)     In the meantime, we encourage you to not just take our word for

1043)     it. Our job is to provide the source; if you're concerned, please do
1044) <a

1045)     href="#CompileTorWindows">recompile it yourself</a>.
1046)     </p>

1047) 

1048)     <hr>

1049) 

1050)     <a id="LiveCD"></a>

1051)     <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other
1052) bundle that includes Tor?</a></h3>

1053) 

1054)     <p>

1055)     Yes.  Use <a href="https://tails.boum.org/">The Amnesic Incognito

1056)     Live System</a> or <a href="<page projects/torbrowser>">the Tor
1057) Browser

1058)     Bundle</a>.

1059)     </p>

1060) 
1061) <hr>
1062) 

1063) <a id="TBBFlash"></a>

1064) <h3><a class="anchor" href="#TBBFlash">Why can't I view videos on
1065) YouTube

1066) and other Flash-based sites?</a></h3>

1067) 
1068) <p>

1069) YouTube and similar sites require third party browser plugins such as Flash.
1070) Plugins operate independently from Firefox and can perform
1071) activity on your computer that ruins your anonymity. This includes
1072) but is not limited to: <a href="http://decloak.net">completely disregarding
1073) proxy settings</a>, querying your <a

1074) href="http://forums.sun.com/thread.jspa?threadID=5162138&messageID=9618376">
1075) local IP address</a>, and <a

1076) href="http://epic.org/privacy/cookies/flash.html">storing their own
1077) cookies</a>. It is possible to use a LiveCD solution such as

1078) or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> 
1079) that creates a secure, transparent proxy to protect you from proxy bypass, 
1080) however issues with local IP address discovery and Flash cookies still remain. 
1081) </p>

1082) 
1083) <p>

1084) <a href="https://www.youtube.com/html5">YouTube offers experimental HTML5 video
1085) support</a> for many of their videos. You can use their Advanced Search to

1086) find HTML5 videos.
1087) </p>
1088) 

1089) <hr>
1090) 

1091) <a id="Ubuntu"></a>
1092) <h3><a class="anchor" href="#Ubuntu">
1093) I'm using Ubuntu and I can't start Tor Browser</a></h3>
1094) <p>

1095) Ubuntu prevents its users from executing shell scripts by clicking them, 
1096) even when the file permissions are set correctly. For now you need to 
1097) start the Tor Browser from the command line by running </p>

1098) <pre>
1099) ./start-tor-browser
1100) </pre>
1101) <p>
1102) from inside the Tor Browser directory.
1103) </p>
1104) 
1105) <hr>
1106) 

1107) <a id="TBBSocksPort"></a>

1108) <h3><a class="anchor" href="#TBBSocksPort">

1109) I want to run another application through the Tor launched by Tor

1110) Browser Bundle.</a></h3>

1111) 
1112) <p>

1113) Typically Tor listens for Socks connections on port 9050. TBB listens

1114) on port 9150.

1115) The goal is to avoid conflicting with a "system" Tor install,

1116) so you can run a system Tor and TBB at the same time. We're <a
1117) href="https://trac.torproject.org/projects/tor/ticket/3948">working on
1118) a feature</a> where Tor will try the usual ports first and then back

1119) off to a random choice if they're already in use.

1120) </p>
1121) 
1122) <hr>
1123) 
1124) <a id="TBBPolipo"></a>
1125) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
1126) Polipo go?</a></h3>
1127) 
1128) <p>
1129) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
1130) solely to work around a bug in Firefox that was finally fixed in Firefox
1131) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
1132) leaving it out makes you safer because Torbutton has better control over
1133) Firefox's interaction with websites.
1134) </p>
1135) 
1136) <p>
1137) If you are trying to use some external application with Tor, step zero

1138) should be to <a href="<page download/download>#warning">reread the set

1139) of warnings</a> for ways you can screw up. Step one should be to try

1140) to use a Socks proxy rather than an http proxy — Tor runs a Socks

1141) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
1142) for OSX and Linux.
1143) </p>
1144) 
1145) <p>

1146) If that fails, feel free to install <a

1147) href="http://www.privoxy.org/">privoxy</a>.
1148) However, please realize that this approach is not recommended for novice
1149) users. Privoxy has an <a
1150) href="http://www.privoxy.org/faq/misc.html#TOR">example
1151) configuration</a> of Tor and Privoxy.

1152) </p>
1153) 
1154) <hr>
1155) 

1156) <a id="TBBOtherExtensions"></a>
1157) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
1158) Firefox extensions?</a></h3>
1159) 
1160) <p>

1161) The Tor Browser is free software, so there is nothing preventing you from 
1162) modifying it any way you like. However, we do not recommend installing any 
1163) additional Firefox add-ons with the Tor Browser Bundle. Add-ons can break 
1164) your anonymity in a number of ways, including browser fingerprinting and 
1165) bypassing proxy settings.

1166) </p>

1167) <p>

1168) Some people have suggested we include ad-blocking software or 
1169) anti-tracking software with the Tor Browser Bundle. Right now, we do not 
1170) think that's such a good idea. The Tor Browser Bundle aims to provide 
1171) sufficient privacy that additional add-ons to stop ads and trackers are 
1172) not necessary. Using add-ons like these may cause some sites to break, which 
1173) <a href="https://www.torproject.org/projects/torbrowser/design/#philosophy">
1174) we don't want to do</a>. Additionally, maintaining a list of "bad" sites that 
1175) should be black-listed provides another opportunity to uniquely fingerprint 
1176) users. 

1177) </p>

1178) 

1179) <hr>
1180) 

1181) <a id="TBBJavaScriptEnabled"></a>

1182) <a id="TBBCanIBlockJS"></a>

1183) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
1184) configured to allow JavaScript by default in the Tor Browser Bundle?
1185) Isn't that unsafe?</a></h3>

1186) 
1187) <p>
1188) We configure NoScript to allow JavaScript by default in the Tor
1189) Browser Bundle because many websites will not work with JavaScript
1190) disabled.  Most users would give up on Tor entirely if a website
1191) they want to use requires JavaScript, because they would not know
1192) how to allow a website to use JavaScript (or that enabling
1193) JavaScript might make a website work).
1194) </p>
1195) 

1196) <p>
1197) There's a tradeoff here. On the one hand, we should leave
1198) JavaScript enabled by default so websites work the way
1199) users expect. On the other hand, we should disable JavaScript
1200) by default to better protect against browser vulnerabilities (<a

1201) href="https://blog.torproject.org/blog/tor-security-advisory-old-tor-browser-bundles-vulnerable">
1202) not just a theoretical concern!</a>). But there's a third issue: websites

1203) can easily determine whether you have allowed JavaScript for them,
1204) and if you disable JavaScript by default but then allow a few websites
1205) to run scripts (the way most people use NoScript), then your choice of
1206) whitelisted websites acts as a sort of cookie that makes you recognizable
1207) (and distinguishable), thus harming your anonymity.
1208) </p>

1209) 
1210) <p>

1211) Ultimately, we want the default Tor bundles to use
1212) a combination of firewalls (like the iptables rules
1213) in <a href="https://tails.boum.org/">Tails</a>) and <a
1214) href="https://trac.torproject.org/projects/tor/ticket/7680">sandboxes</a>
1215) to make JavaScript not so scary. In
1216) the shorter term, TBB 3.0 will hopefully <a
1217) href="https://trac.torproject.org/projects/tor/ticket/9387">allow users
1218) to choose their JavaScript settings more easily</a> &mdash; but the
1219) partitioning concern will remain.

1220) </p>
1221) 
1222) <p>

1223) Until we get there, feel free to leave JavaScript on or off depending
1224) on your security, anonymity, and usability priorities.

1225) </p>
1226) 
1227) <hr>
1228) 

1229) <a id="TBBOtherBrowser"></a>
1230) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
1231) Chrome/IE/Opera/etc with Tor.</a></h3>
1232) 
1233) <p>
1234) Unfortunately, Torbutton only works with Firefox right now, and without
1235) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
1236) extensive privacy fixes</a> there are many ways for websites or other

1237) attackers to recognize you, track you back to your IP address, and so
1238) on.

1239) In short, using any browser besides Tor Browser Bundle with Tor is a
1240) really bad idea.
1241) </p>
1242) 
1243) <p>
1244) We're working with the Chrome team to <a

1245) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-
1246) and-fingerprinting">fix
1247) some bugs and missing APIs in Chrome</a> so it will be possible to write
1248) a
1249) Torbutton for Chrome. No support for any other browser is on the
1250) horizon.

1251) </p>
1252) 
1253) <hr>
1254) 

1255) <a id="TorbuttonOtherBrowser"></a>

1256) <h3><a class="anchor" href="TorbuttonOtherBrowser">
1257) Will ​Torbutton be available for other browsers?</a></h3>

1258) 
1259) <p>

1260)  We don't support IE, Opera or Safari and never plan to. There are too many ways that your privacy can go wrong with those browsers, and because of their closed design it is really hard for us to do anything to change these privacy problems.

1261) </p>
1262) <p>

1263) We are working with the Chrome people to modify Chrome's internals so that we can eventually support it. But for now, Firefox is the only safe choice. 

1264) </p>
1265) 

1266) <hr>

1267) 

1268) <a id="TBBCloseBrowser"></a>

1269) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor
1270) Browser

1271) Bundle running but close the browser.</a></h3>
1272) 
1273) <p>
1274) We're working on a way to make this possible on all platforms. Please
1275) be patient.
1276) </p>
1277) 
1278) <hr>
1279) 

1280) <a id="GoogleCAPTCHA"></a>
1281) <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
1282) CAPTCHA or tells me I have spyware installed.</a></h3>

1283) 
1284) <p>
1285) This is a known and intermittent problem; it does not mean that Google
1286) considers Tor to be spyware.
1287) </p>
1288) 
1289) <p>

1290) When you use Tor, you are sending queries through exit relays that are
1291) also

1292) shared by thousands of other users. Tor users typically see this message

1293) when many Tor users are querying Google in a short period of time.
1294) Google

1295) interprets the high volume of traffic from a single IP address (the exit
1296) relay you happened to pick) as somebody trying to "crawl" their website,
1297) so it slows down traffic from that IP address for a short time.
1298) </p>
1299) <p>
1300) An alternate explanation is that Google tries to detect certain
1301) kinds of spyware or viruses that send distinctive queries to Google
1302) Search. It notes the IP addresses from which those queries are received
1303) (not realizing that they are Tor exit relays), and tries to warn any
1304) connections coming from those IP addresses that recent queries indicate
1305) an infection.
1306) </p>
1307) 
1308) <p>

1309) To our knowledge, Google is not doing anything intentionally
1310) specifically

1311) to deter or block Tor use. The error message about an infected machine
1312) should clear up again after a short time.
1313) </p>
1314) 
1315) <p>
1316) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1317) automatically redirect you to a more Tor-friendly search engine such as

1318) DuckDuckGo, ixquick, or Bing.

1319) </p>
1320) 
1321) <hr />
1322) 

1323) <a id="ForeignLanguages"></a>
1324) <h3><a class="anchor" href="#ForeignLanguages">
1325) Why does Google show up in foreign languages?</a></h3>
1326) 
1327) <p>

1328)  Google uses "geolocation" to determine where in the world you are, so it 
1329)  can give you a personalized experience. This includes using the language 
1330)  it thinks you prefer, and it also includes giving you different results 
1331)  on your queries.

1332) </p>
1333) <p>

1334) If you really want to see Google in English you can click the link that 
1335) provides that. But we consider this a feature with Tor, not a bug --- the 
1336) Internet is not flat, and it in fact does look different depending on 
1337) where you are. This feature reminds people of this fact. The easy way to 
1338) avoid this "feature" is to use 
1339) <a href="https://google.com/ncr">https://google.com/ncr</a>.

1340) </p>
1341) <p>

1342) Note that Google search URLs take name/value pairs as arguments and one 
1343) of those names is "hl". If you set "hl" to "en" then Google will return 
1344) search results in English regardless of what Google server you have been 
1345) sent to. On a query this looks like: 
1346) </p>
1347) <pre>https://encrypted.google.com/search?q=online%20anonymity&hl=en

1348) </pre>

1349) <p>

1350) Another method is to simply use your country code for accessing Google. 
1351) This can be google.be, google.de, google.us and so on. 

1352) </p>
1353) <hr />

1354) <a id="GmailWarning"></a>

1355) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my

1356) account may have been compromised.</a></h3>

1357) 
1358) <p>
1359) Sometimes, after you've used Gmail over Tor, Google presents a
1360) pop-up notification that your account may have been compromised.
1361) The notification window lists a series of IP addresses and locations
1362) throughout the world recently used to access your account.
1363) </p>
1364) 
1365) <p>
1366) In general this is a false alarm: Google saw a bunch of logins from

1367) different places, as a result of running the service via Tor, and
1368) decided

1369) it was a good idea to confirm the account was being accessed by it's
1370) rightful owner.
1371) </p>
1372) 
1373) <p>
1374) Even though this may be a biproduct of using the service via tor,
1375) that doesn't mean you can entirely ignore the warning. It is
1376) <i>probably</i> a false positive, but it might not be since it is
1377) possible for someone to hijack your Google cookie.
1378) </p>
1379) 
1380) <p>
1381) Cookie hijacking is possible by either physical access to your computer
1382) or by watching your network traffic.  In theory only physical access
1383) should compromise your system because Gmail and similar services
1384) should only send the cookie over an SSL link. In practice, alas, it's <a

1385) href="http://fscked.org/blog/fully-automated-active-https-cookie-
1386) hijacking">

1387) way more complex than that</a>.
1388) </p>
1389) 
1390) <p>
1391) And if somebody <i>did</i> steal your google cookie, they might end
1392) up logging in from unusual places (though of course they also might
1393) not). So the summary is that since you're using Tor, this security
1394) measure that Google uses isn't so useful for you, because it's full of
1395) false positives. You'll have to use other approaches, like seeing if
1396) anything looks weird on the account, or looking at the timestamps for
1397) recent logins and wondering if you actually logged in at those times.
1398) </p>
1399) 
1400) <hr>
1401) 

1402) <a id="torrc"></a>

1403) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
1404) What does that mean?</a></h3>

1405) 
1406) <p>
1407) Tor installs a text file called torrc that contains configuration
1408) instructions for how your Tor program should behave. The default
1409) configuration should work fine for most Tor users. Users of Vidalia can
1410) make common changes through the Vidalia interface &mdash; only advanced
1411) users should need to modify their torrc file directly.
1412) </p>

1413) <p>

1414) Tor Browser Bundle users should edit your torrc through Vidalia. Open
1415) the
1416) Vidalia Control Panel. Choose Settings. Choose Advanced. Click the
1417) button

1418) labelled "Edit current torrc". Remember to make sure the checkbox for
1419) "Save Settings." is checked. Hit the Ok button and you are done.
1420) </p>

1421) <p>

1422) Otherwise, you will need to edit the file manually.

1423) The location of your torrc file depends on the way you installed Tor:
1424) </p>
1425) <ul>

1426) <li>If you installed Tor Browser Bundle, look for
1427) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
1428) </li>

1429) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
1430) find your torrc file in the Start menu under Programs -&gt; Vidalia
1431) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
1432) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
1433) installed Tor without Vidalia, you can find your torrc in the Start
1434) menu under Programs -&gt; Tor, or manually in either <code>\Documents
1435) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
1436) Settings\<i>username</i>\Application Data\tor\torrc</code>.
1437) </li>
1438) <li>On OS X, if you use Vidalia, edit
1439) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
1440) and load <code>/Library/Tor/torrc</code>.
1441) </li>
1442) <li>On Unix, if you installed a pre-built package, look for
1443) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
1444) package's documentation.
1445) </li>
1446) <li>Finally, if you installed from source, you may not have a torrc
1447) installed yet: look in <code>/usr/local/etc/</code> and note that you

1448) may need to manually copy <code>torrc.sample</code> to
1449) <code>torrc</code>.

1450) </li>
1451) </ul>
1452) 
1453) <p>
1454) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit

1455) your torrc file manually. Otherwise Vidalia might overwrite your
1456) changes.

1457) </p>
1458) 
1459) <p>
1460) Once you've changed your torrc, you will need to restart Tor for the
1461) changes to take effect. (For advanced users on OS X and Unix, note that

1462) you actually only need to send Tor a HUP signal, not actually restart
1463) it.)

1464) </p>
1465) 
1466) <p>
1467) For other configuration options you can use, look at the <a href="<page
1468) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1469) with # in torrc are treated as comments and have no effect on Tor's
1470) configuration.
1471) </p>
1472) 
1473) <hr>
1474) 

1475) <a id="Logs"></a>

1476) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
1477) logs?</a></h3>

1478) 
1479) <p>

1480) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1481) window called "Message Log" that will show you Tor's log messages. Click
1482) on "Advanced" to see more details. You can click on "Settings" to change
1483) your log verbosity or save the messages to a file. You're all set.

1484) </p>
1485) 
1486) <p>
1487) If you're not using Vidalia, you'll have to go find the log files by

1488) hand. Here are some likely places for your logs to be:

1489) </p>
1490) 
1491) <ul>
1492) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1493) </li>

1494) <li>On Windows, there are no default log files currently. If you enable
1495) logs in your torrc file, they default to <code>\username\Application
1496) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1497) </li>
1498) <li>If you compiled Tor from source, by default your Tor logs to <a
1499) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1500) at log-level notice. If you enable logs in your torrc file, they
1501) default to <code>/usr/local/var/log/tor/</code>.

1502) </li>
1503) </ul>
1504) 
1505) <p>

1506) To change your logging setup by hand, <a href="#torrc">edit your
1507) torrc</a>

1508) and find the section (near the top of the file) which contains the
1509) following line:

1510) </p>
1511) 
1512) <pre>

1513) \## Logs go to stdout at level "notice" unless redirected by something
1514) \## else, like one of the below lines.

1515) </pre>

1516) 
1517) <p>

1518) For example, if you want Tor to send complete debug, info, notice, warn,

1519) and err level messages to a file, append the following line to the end
1520) of the section:
1521) </p>
1522) 
1523) <pre>
1524) Log debug file c:/program files/tor/debug.log
1525) </pre>
1526) 
1527) <p>

1528) Replace <code>c:/program files/tor/debug.log</code> with a directory
1529) and filename for your Tor log.

1530) </p>
1531) 
1532) <hr>
1533) 

1534) 
1535) <a id="LogLevel"></a>
1536) <h3><a class="anchor" href="#LogLevel">What log level should I use?</a></h3>
1537) 
1538) <p>

1539) There are five log levels (also called "log severities") you might see in 
1540) Tor's logs:

1541) </p>
1542) 
1543) <ul>

1544)     <li>"err": something bad just happened, and we can't recover. Tor will 
1545)     exit.</li>
1546)     <li>"warn": something bad happened, but we're still running. The bad 
1547)     thing might be a bug in the code, some other Tor process doing something 
1548)     unexpected, etc. The operator should examine the message and try to 
1549)     correct the problem.</li>

1550)     <li>"notice": something the operator will want to know about.</li>

1551)     <li>"info": something happened (maybe bad, maybe ok), but there's 
1552)     nothing you need to (or can) do about it.</li>

1553)     <li>"debug": for everything louder than info. It is quite loud indeed.</li> 
1554) </ul>
1555) 
1556) <p>

1557) Alas, some of the warn messages are hard for ordinary users to correct -- the 
1558) developers are slowly making progress at making Tor automatically react 
1559) correctly for each situation.

1560) </p>
1561) 
1562) <p>

1563) We recommend running at the default, which is "notice". You will hear about 
1564) important things, and you won't hear about unimportant things.

1565) </p>
1566) 
1567) <p>

1568) Tor relays in particular should avoid logging at info or debug in normal 
1569) operation, since they might end up recording sensitive information in 
1570) their logs. 

1571) </p>
1572) 

1573) <hr>
1574) 

1575) <a id="DoesntWork"></a>

1576) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
1577) working.</a></h3>

1578) 
1579) <p>

1580) Once you've got the Tor bundle up and running, the first question to
1581) ask is whether your Tor client is able to establish a circuit.

1582) </p>
1583) 
1584) <p>If Tor can establish a circuit, the onion icon in

1585) Vidalia will turn green (and if you're running Tor Browser Bundle, it
1586) will
1587) automatically launch a browser for you). You can also check in the
1588) Vidalia

1589) Control Panel to make sure it says "Connected to the Tor
1590) network!" under Status. For those not using Vidalia, check your <a

1591) href="#Logs">Tor logs</a> for

1592) a line saying that Tor "has successfully opened a circuit. Looks like
1593) client functionality is working."
1594) </p>
1595) 
1596) <p>
1597) If Tor can't establish a circuit, here are some hints:
1598) </p>
1599) 
1600) <ol>
1601) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1602) to click on the onion and select "Start" to launch Tor.</li>
1603) <li>Check your system clock. If it's more than a few hours off, Tor will

1604) refuse to build circuits. For Microsoft Windows users, synchronize your
1605) clock under the clock -> Internet time tab. In addition, correct the

1606) day and date under the 'Date & Time' Tab. Also make sure your time
1607) zone is correct.</li>

1608) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1609) by port</a>, or do you normally need to use a <a

1610) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</a>?

1611) </li>

1612) <li>Are you running programs like Norton Internet Security or SELinux
1613) that

1614) block certain connections, even though you don't realize they do? They
1615) could be preventing Tor from making network connections.</li>
1616) <li>Are you in China, or behind a restrictive corporate network firewall
1617) that blocks the public Tor relays? If so, you should learn about <a

1618) href="<page docs/bridges>">Tor bridges</a>.</li>

1619) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1620) about what's going wrong?</li>

1621) </ol>
1622) 
1623) <hr />
1624) 

1625) <a id="TorCrash"></a>
1626) <h3><a class="anchor" href="#TorCrash">My Tor keeps crashing.</a></h3>
1627) <p>
1628)  We want to hear from you! There are supposed to be zero crash bugs in Tor. 
1629)  This FAQ entry describes the best way for you to be helpful to us. But even 
1630)  if you can't work out all the details, we still want to hear about it, so 
1631)  we can help you track it down. 
1632) </p>
1633) <p>
1634) First, make sure you're using the latest version of Tor (either the latest 
1635) stable or the latest development version). 
1636) </p>
1637) <p>
1638) Second, make sure your version of libevent is new enough. We recommend at 
1639) least libevent 1.3a. 
1640) </p>
1641) <p>
1642) Third, see if there's already an entry for your bug in the <a 
1643) href="https://bugs.torproject.org/">Tor bugtracker</a>. If so, 
1644) check if there are any new details that you can add. 
1645) </p>
1646) <p>
1647) Fourth, is the crash repeatable? Can you cause the crash? Can 
1648) you isolate some of the circumstances or config options that 
1649) make it happen? How quickly or often does the bug show up? 
1650) Can you check if it happens with other versions of Tor, for 
1651) example the latest stable release? 
1652) </p>
1653) <p>
1654) Fifth, what sort of crash do you get? 
1655) </p>
1656) <ul>
1657) <li>
1658) Does your Tor log include an "assert failure"? If so, please 
1659) tell us that line, since it helps us figure out what's going on. 
1660) Tell us the previous couple of log messages as well, especially 
1661) if they seem important. 
1662) </li>
1663) <li>
1664) If it says "Segmentation fault - core dumped" then you need to 
1665) do a bit more to track it down. Look for a file like "core" or 
1666) "tor.core" or "core.12345" in your current directory, or in your 
1667) Data Directory. If it's there, run "gdb tor core" and then "bt", 
1668) and include the output. If you can't find a core, run "ulimit -c 
1669) unlimited", restart Tor, and try to make it crash again. (This core 
1670) thing will only work on Unix -- alas, tracking down bugs on Windows 
1671) is harder. If you're on Windows, can you get somebody to duplicate 
1672) your bug on Unix?)
1673) </li>
1674) <li>
1675) If Tor simply vanishes mysteriously, it probably is a segmentation 
1676) fault but you're running Tor in the background (as a daemon) so you 
1677) won't notice. Go look at the end of your log file, and look for a 
1678) core file as above. If you don't find any good hints, you should 
1679) consider running Tor in the foreground (from a shell) so you can 
1680) see how it dies. Warning: if you switch to running Tor in the foreground, 
1681) you might start using a different torrc file, with a different default 
1682) Data Directory; see the <a href="#UpgradeOrMove">relay-upgrade FAQ entry</a> 
1683) for details. 
1684) </li>
1685) <li>
1686) If it's still vanishing mysteriously, perhaps something else is killing it? 
1687) Do you have resource limits (ulimits) configured that kill off processes 
1688) sometimes? (This is especially common on OpenBSD.) On Linux, try running 
1689) "dmesg" to see if the out-of-memory killer removed your process. (Tor will 
1690) exit cleanly if it notices that it's run out of memory, but in some cases 
1691) it might not have time to notice.) In very rare circumstances, hardware 
1692) problems could also be the culprit. 
1693) </li>
1694) </ul>
1695) <p>
1696) Sixth, if the above ideas don't point out the bug, consider increasing your 
1697) log level to "loglevel debug". You can look at the log-configuration FAQ 
1698) entry for instructions on what to put in your torrc file. If it usually 
1699) takes a long time for the crash to show up, you will want to reserve a whole 
1700) lot of disk space for the debug log. Alternatively, you could just send 
1701) debug-level logs to the screen (it's called "stdout" in the torrc), and then 
1702) when it crashes you'll see the last couple of log lines it had printed. 
1703) (Note that running with verbose logging like this will slow Tor down 
1704) considerably, and note also that it's generally not a good idea security-wise 
1705) to keep logs like this sitting around.) 
1706) </p>
1707) 
1708) <hr />
1709) 

1710) <a id="VidaliaPassword"></a>

1711) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a
1712) password at start.</a></h3>

1713) 
1714) <p>
1715) Vidalia interacts with the Tor software via Tor's "control port". The
1716) control port lets Vidalia receive status updates from Tor, request a new
1717) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1718) Vidalia sets a random password for Tor's control port to prevent other
1719) applications from also connecting to the control port and potentially
1720) compromising your anonymity.
1721) </p>
1722) 
1723) <p>
1724) Usually this process of generating and setting a random control password
1725) happens in the background. There are three common situations, though,
1726) where Vidalia may prompt you for a password:
1727) </p>
1728) 
1729) <ol>
1730) <li>You're already running Vidalia and Tor. For example, this situation
1731) can happen if you installed the Vidalia bundle and now you're trying to
1732) run the Tor Browser Bundle. In that case, you'll need to close the old
1733) Vidalia and Tor before you can run this one.
1734) </li>
1735) <li>Vidalia crashed, but left Tor running with the last known random
1736) password. After you restart Vidalia, it generates a new random password,

1737) but Vidalia can't talk to Tor, because the random passwords are
1738) different.

1739) <br />

1740) If the dialog that prompts you for a control password has a Reset
1741) button,

1742) you can click the button and Vidalia will restart Tor with a new random
1743) control password.
1744) <br />
1745) If you do not see a Reset button, or if Vidalia is unable to restart
1746) Tor for you, you can still fix the problem manually. Simply go into your
1747) process or task manager, and terminate the Tor process. Then use Vidalia
1748) to restart Tor and all will work again.
1749) </li>
1750) <li>You had previously set Tor to run as a Windows NT service. When Tor
1751) is set to
1752) run as a service, it starts up when the system boots. If you configured
1753) Tor to start as a service through Vidalia, a random password was set
1754) and saved in Tor. When you reboot, Tor starts up and uses the random
1755) password it saved. You login and start up Vidalia. Vidalia attempts to
1756) talk to the already running Tor. Vidalia generates a random password,
1757) but it is different than the saved password in the Tor service.
1758) <br />
1759) You need to reconfigure Tor to not be a service. See the FAQ entry on

1760) <a href="#NTservice">running Tor as a

1761) Windows NT service</a>

1762) for more information on how to remove the Tor service.
1763) </li>
1764) </ol>
1765) 

1766)     <hr>

1767) 

1768)     <a id="ChooseEntryExit"></a>

1769)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
1770) nodes (or country) are used for entry/exit?</a></h3>

1771) 

1772)     <p>

1773)     Yes. You can set preferred entry and exit nodes as well as
1774)     inform Tor which nodes you do not want to use.

1775)     The following options can be added to your config file <a
1776)     href="#torrc">"torrc"</a> or specified on the command line:

1777)     </p>
1778)     <dl>
1779)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

1780)         <dd>A list of preferred nodes to use for the first hop in the
1781) circuit, if possible.

1782)         </dd>
1783)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1784)         <dd>A list of preferred nodes to use for the last hop in the
1785) circuit, if possible.

1786)         </dd>
1787)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1788)         <dd>A list of nodes to never use when building a circuit.

1789)         </dd>
1790)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1791)         <dd>A list of nodes to never use when picking an exit.

1792)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
1793) this list.

1794)         </dd>
1795)     </dl>
1796)     <p>

1797)     <em>We recommend you do not use these</em>

1798)     — they are intended for testing and may disappear in future
1799) versions.

1800)     You get the best security that Tor can provide when you leave the
1801)     route selection to Tor; overriding the entry / exit nodes can mess
1802)     up your anonymity in ways we don't understand.

1803)     </p>
1804)     <p>

1805)     Note also that not every circuit is used to deliver traffic outside of 
1806)     the Tor network. It is normal to see non-exit circuits (such as those 
1807)     used to connect to hidden services, those that do directory fetches, 
1808)     those used for relay reachability self-tests, and so on) that end at 
1809)     a non-exit node. To keep a node from being used entirely, see 
1810)     <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the 
1811)     <a href="<page docs/tor-manual>">manual</a>.

1812)     </p>
1813)     <p>

1814)     Instead of <tt>$fingerprint</tt> you can also specify a <a

1815) 
1816) href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
1817) >2

1818)     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

1819)     or an ip address pattern (for example 255.254.0.0/8), or a node
1820)     nickname. Make sure there are no spaces between the commas and the
1821)     list items.

1822)     </p>
1823)     <p>

1824)     If you want to access a service directly through Tor's Socks
1825) interface

1826)     (eg. using ssh via connect.c), another option is to set up an

1827)     internal mapping in your configuration file using
1828) <tt>MapAddress</tt>.

1829)     See the manual page for details.
1830)     </p>

1831) 

1832)     <hr>

1833) 

1834) <a id="FirewallPorts"></a>

1835) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1836) few outgoing ports.</a></h3>

1837) 
1838) <p>
1839) If your firewall works by blocking ports, then you can tell Tor to only

1840) use the ports that your firewall permits by adding "FascistFirewall 1"
1841) to

1842) your <a href="<page docs/faq>#torrc">torrc

1843) configuration file</a>, or by clicking "My firewall only lets me connect
1844) to certain ports" in Vidalia's Network Settings window.
1845) </p>
1846) 
1847) <p>
1848) By default, when you set this Tor assumes that your firewall allows only
1849) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1850) different set of ports with the FirewallPorts torrc option.
1851) </p>
1852) 
1853) <p>
1854) If you want to be more fine-grained with your controls, you can also
1855) use the ReachableAddresses config options, e.g.:
1856) </p>
1857) 
1858) <pre>
1859)   ReachableDirAddresses *:80
1860)   ReachableORAddresses *:443
1861) </pre>
1862) 
1863) <hr>

1864) 

1865)     <a id="ExitPorts"></a>

1866)     <h3><a class="anchor" href="#ExitPorts">Is there a list of default exit 
1867)     ports?</a></h3>

1868)     <p>

1869) The default open ports are listed below but keep in mind that, any port or 
1870) ports can be opened by the relay operator by configuring it in torrc or 
1871) modifying the source code. But the default according to src/or/policies.c 
1872) from the source code release tor-0.2.4.16-rc is: 

1873)     </p>
1874)     <pre>
1875)   reject 0.0.0.0/8
1876)   reject 169.254.0.0/16
1877)   reject 127.0.0.0/8
1878)   reject 192.168.0.0/16
1879)   reject 10.0.0.0/8
1880)   reject 172.16.0.0/12
1881)   reject *:25
1882)   reject *:119
1883)   reject *:135-139
1884)   reject *:445
1885)   reject *:563
1886)   reject *:1214
1887)   reject *:4661-4666
1888)   reject *:6346-6429
1889)   reject *:6699
1890)   reject *:6881-6999
1891)   accept *:*
1892)     </pre>
1893)     <p>

1894)     A relay will block access to its own IP address, as well local network 
1895)     IP addresses. A relay always blocks itself by default. This prevents 
1896)     Tor users from accidentally accessing any of the exit operator's local 
1897)     services. 
1898)     </p>
1899) 
1900)     <hr>
1901) 
1902)     <a id="SocksAndDNS"></a>
1903)     <h3><a class="anchor" href="#SocksAndDNS">How do I check if my application that uses 
1904)     SOCKS is leaking DNS requests?</a></h3>
1905) 
1906)     <p>
1907)     These are two steps you need to take here. The first is to make sure 
1908)     that it's using the correct variant of the SOCKS protocol, and the 
1909)     second is to make sure that there aren't other leaks. 
1910)     </p>
1911) 
1912)     <p>
1913)     Step one: add "TestSocks 1" to your torrc file, and then watch your 
1914)     logs as you use your application. Tor will then log, for each SOCKS 
1915)     connection, whether it was using a 'good' variant or a 'bad' one. 
1916)     (If you want to automatically disable all 'bad' variants, set 
1917)     "SafeSocks 1" in your <a href="#torrc">torrc</a> file.) 
1918)     </p>
1919) 
1920)     <p>
1921)     Step two: even if your application is using the correct variant of 
1922)     the SOCKS protocol, there is still a risk that it could be leaking 
1923)     DNS queries. This problem happens in Firefox extensions that resolve 
1924)     the destination hostname themselves, for example to show you its IP 
1925)     address, what country it's in, etc. These applications may use a safe 
1926)     SOCKS variant when actually making connections, but they still do DNS 
1927)     resolves locally. If you suspect your application might behave like 
1928)     this, you should use a network sniffer like <a 
1929)     href="https://www.wireshark.org/">Wireshark</a> and look for 
1930)     suspicious outbound DNS requests. I'm afraid the details of how to look 
1931)     for these problems are beyond the scope of a FAQ entry though -- find 
1932)     a friend to help if you have problems. 

1933)     </p>
1934) 
1935)     <hr>
1936) 

1937)     <a id="HowDoIDecide"></a>
1938)     <h3><a class="anchor" href="#HowDoIDecide">How do I decide if I should 
1939)     run a relay?</a></h3>
1940)     <p>
1941)     We're looking for people with reasonably reliable Internet connections, 
1942)     that have at least 20 kilobytes/second each way. If that's you, please 
1943)     consider <a href="https://www.torproject.org/docs/tor-relay-debian">helping 
1944)     out</a>. 
1945)     </p>
1946)     
1947)     <hr>
1948)     
1949)     <a id="WhyIsntMyRelayBeingUsedMore"></a>
1950)     <h3><a class="anchor" href="#WhyIsntMyRelayBeingUsedMore">Why isn't my 
1951)     relay being used more?</a></h3>
1952)     <p>
1953)     If your relay is relatively new then give it time. Tor decides which 
1954)     relays it uses heuristically based on reports from Bandwidth 
1955)     Authorities. These authorities take measurements of your relay's 
1956)     capacity and, over time, directs more traffic there until it reaches 
1957)     an optimal load. The lifecycle of a new relay is explained in more 
1958)     depth in <a href="https://blog.torproject.org/blog/lifecycle-of-a-new-relay">
1959)     this blog post</a>.
1960)     </p>
1961)     <p>
1962)     If you've been running a relay for a while and still having issues 
1963)     then try asking on the <a href=
1964)     "https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-relays/">
1965)     tor-relays list</a>. 
1966)     </p>
1967)     
1968)     <hr>
1969) 

1970)     <a id="HighCapacityConnection"></a>    
1971)     <h3><a class="anchor" href="#HighCapacityConnection">How can I get Tor to fully 
1972)     make use of my high capacity connection?</a></h3>
1973)     
1974)     <p>
1975)     See <a href="http://archives.seul.org/or/relays/Aug-2010/msg00034.html">this 
1976)     tor-relays thread</a>.
1977)     </p>
1978)     
1979)     <hr>    
1980)     

1981)     <a id="RelayFlexible"></a>

1982)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1983) need to be?</a></h3>

1984) 

1985)     <p>
1986)     We aim to make setting up a Tor relay easy and convenient:
1987)     </p>

1988) 

1989)     <ul>
1990)     <li>Tor has built-in support for <a

1991)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1992)     rate limiting</a>. Further, if you have a fast
1993)     link but want to limit the number of bytes per
1994)     day (or week or month) that you donate, check out the <a

1995) 
1996) href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">
1997) hibernation

1998)     feature</a>.
1999)     </li>

2000)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
2001) that
2002)     specifies what sort of outbound connections are allowed or refused
2003) from
2004)     that relay. If you are uncomfortable allowing people to exit from
2005) your
2006)     relay, you can set it up to only allow connections to other Tor
2007) relays.

2008)     </li>
2009)     <li>It's fine if the relay goes offline sometimes. The directories
2010)     notice this quickly and stop advertising the relay. Just try to make
2011)     sure it's not too often, since connections using the relay when it
2012)     disconnects will break.
2013)     </li>
2014)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
2015)     leave the Address config option blank, and Tor will try to guess.
2016)     </li>
2017)     <li>If your relay is behind a NAT and it doesn't know its public
2018)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

2019)     forwarding. Forwarding TCP connections is system dependent but

2020)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

2021)     offers some examples on how to do this.
2022)     </li>
2023)     <li>Your relay will passively estimate and advertise its recent

2024)     bandwidth capacity, so high-bandwidth relays will attract more users
2025) than
2026)     low-bandwidth ones. Therefore having low-bandwidth relays is useful
2027) too.

2028)     </li>
2029)     </ul>

2030) 

2031)     <hr>

2032) 

2033)     <a id="ExitPolicies"></a>

2034)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
2035) don't want to deal with abuse issues.</a></h3>

2036) 

2037)     <p>
2038)     Great. That's exactly why we implemented exit policies.
2039)     </p>

2040) 

2041)     <p>
2042)     Each Tor relay has an exit policy that specifies what sort of

2043)     outbound connections are allowed or refused from that relay. The
2044) exit

2045)     policies are propagated to Tor clients via the directory, so clients
2046)     will automatically avoid picking exit relays that would refuse to
2047)     exit to their intended destination. This way each relay can decide
2048)     the services, hosts, and networks he wants to allow connections to,

2049)     based on abuse potential and his own situation. Read the FAQ entry
2050) on
2051)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
2052) encounter</a>

2053)     if you use the default exit policy, and then read Mike Perry's

2054)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

2055)     for running an exit node with minimal harassment</a>.
2056)     </p>

2057) 

2058)     <p>

2059)     The default exit policy allows access to many popular services

2060)     (e.g. web browsing), but <a
2061) href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

2062)     some due to abuse potential (e.g. mail) and some since
2063)     the Tor network can't handle the load (e.g. default
2064)     file-sharing ports). You can change your exit policy

2065)     using Vidalia's "Sharing" tab, or by manually editing your

2066)     <a href="<page docs/faq>#torrc">torrc</a>

2067)     file. If you want to avoid most if not all abuse potential, set it
2068) to
2069)     "reject *:*" (or un-check all the boxes in Vidalia). This setting
2070) means
2071)     that your relay will be used for relaying traffic inside the Tor
2072) network,

2073)     but not for connections to external websites or other services.
2074)     </p>

2075) 

2076)     <p>

2077)     If you do allow any exit connections, make sure name resolution
2078) works

2079)     (that is, your computer can resolve Internet addresses correctly).

2080)     If there are any resources that your computer can't reach (for
2081) example,

2082)     you are behind a restrictive firewall or content filter), please

2083)     explicitly reject them in your exit policy — otherwise Tor
2084) users

2085)     will be impacted too.
2086)     </p>

2087) 

2088)     <hr>

2089) 

2090)     <a id="DifferentComputer"></a>

2091)     <h3><a class="anchor" href="#DifferentComputer">I want to run my 
2092)     Tor client on a different computer than my applications.</a></h3>

2093)     <p>

2094)     By default, your Tor client only listens for applications that 
2095)     connect from localhost. Connections from other computers are 
2096)     refused. If you want to torify applications on different computers 
2097)     than the Tor client, you should edit your torrc to define 
2098)     SocksListenAddress 0.0.0.0 g and then restart (or hup) Tor. If you 
2099)     want to get more advanced, you can configure your Tor client on a 
2100)     firewall to bind to your internal IP but not your external IP.  

2101)     </p>
2102) 
2103)     <hr>
2104) 
2105)     <a id="ServerClient"></a>

2106)     <h3><a class="anchor" href="#ServerClient">Can I install Tor on a 
2107)     central server, and have my clients connect to it?</a></h3>
2108)     <p>
2109)      Yes. Tor can be configured as a client or a relay on another 
2110)      machine, and allow other machines to be able to connect to it 
2111)      for anonymity. This is most useful in an environment where many 
2112)      computers want a gateway of anonymity to the rest of the world. 
2113)      However, be forwarned that with this configuration, anyone within 
2114)      your private network (existing between you and the Tor 
2115)      client/relay) can see what traffic you are sending in clear text. 
2116)      The anonymity doesn't start until you get to the Tor relay. 
2117)      Because of this, if you are the controller of your domain and you 
2118)      know everything's locked down, you will be OK, but this configuration 
2119)      may not be suitable for large private networks where security is 
2120)      key all around.
2121)     </p>
2122)     <p>
2123) Configuration is simple, editing your torrc file's SocksListenAddress 
2124) according to the following examples:

2125)     </p>
2126)     <pre>

2127) 
2128)   #This provides local interface access only, 
2129)   #needs SocksPort to be greater than 0
2130)   SocksListenAddress 127.0.0.1 
2131) 
2132)   #This provides access to Tor on a specified interface
2133)   SocksListenAddress 192.168.x.x:9100 
2134) 
2135)   #Accept from all interfaces
2136)   SocksListenAddress 0.0.0.0:9100
2137)    </pre>

2138)     <p>

2139) You can state multiple listen addresses, in the case that you are 
2140) part of several networks or subnets.

2141)     </p>
2142)     <pre>
2143)   SocksListenAddress 192.168.x.x:9100 #eth0
2144)   SocksListenAddress 10.x.x.x:9100 #eth1
2145)     </pre>
2146)     <p>

2147) After this, your clients on their respective networks/subnets would specify 
2148) a socks proxy with the address and port you specified SocksListenAddress 
2149) to be. 

2150)     </p>
2151)     <p>

2152) Please note that the SocksPort configuration option gives the port ONLY for 
2153) localhost (127.0.0.1). When setting up your SocksListenAddress(es), you need 
2154) to give the port with the address, as shown above.

2155)     <p>

2156) If you are interested in forcing all outgoing data through the central Tor 
2157) client/relay, instead of the server only being an optional proxy, you may find 
2158) the program iptables (for *nix) useful. 

2159)     </p>
2160) 
2161)     <hr>
2162) 

2163)     <a id="JoinTheNetwork"></a>

2164)     <h3><a class="anchor" href="#JoinTheNetwork">So I can just configure a 
2165)     nickname and ORPort and join the network?</a></h3>

2166) 
2167)     <p>

2168)      Yes. You can join the network and be a useful relay just by configuring 
2169)      your Tor to be a relay and making sure it's reachable from the outside.

2170)     </p>
2171)     <p>
2172) 30 Seconds to a Tor Relay:
2173)     </p>
2174)     <ul><li>
2175)     Configure a Nickname: 
2176)     </li></ul>
2177)     <pre>
2178) Nickname ididnteditheconfig
2179)     </pre>

2180)     <ul><li>

2181)     Configure ORPort: 

2182)     </li></ul>

2183)     <pre>
2184) ORPort 9001
2185)     </pre>

2186)     <ul><li>

2187)     Configure Contact Info: 

2188)     </li></ul>

2189) 
2190)     <pre>
2191) ContactInfo human@…

2192)     </pre>
2193)     <ul><li>

2194)     Start Tor. Watch the log file for a log entry that states: "Self-testing 
2195)     indicates your ORPort is reachable from the outside. Excellent. Publishing 
2196)     server descriptor."

2197)     </li></ul>

2198) 
2199)     <hr />

2200) 

2201)     <a id="RelayOrBridge"></a>

2202)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
2203) relay or bridge relay?</a></h3>

2204) 

2205)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
2206) short)
2207)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

2208)     listed in the public Tor directory.

2209)     That means that ISPs or governments trying to block access to the

2210)     Tor network can't simply block all bridges.

2211)     </p>

2212) 

2213)     <p>Being a normal relay vs being a bridge relay is almost the same
2214)     configuration: it's just a matter of whether your relay is listed

2215)     publicly or not.

2216)     </p>

2217) 

2218)     <p>

2219)     So bridges are useful a) for Tor users in oppressive regimes,

2220)     and b) for people who want an extra layer of security

2221)     because they're worried somebody will recognize that it's a public
2222)     Tor relay IP address they're contacting.

2223)     </p>

2224) 

2225)     <p>
2226)     Several countries, including China and Iran, have found ways to

2227)     detect and block connections to Tor bridges.

2228)     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

2229)     this by adding another layer of obfuscation.

2230)     </p>
2231) 

2232)     <p>So should you run a normal relay or bridge relay? If you have
2233) lots

2234)     of bandwidth, you should definitely run a normal relay.
2235)     If you're willing

2236)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
2237)     run a normal relay, since we need more exits. If you can't be an
2238)     exit and only have a little bit of bandwidth, be a bridge. Thanks
2239)     for volunteering!

2240)     </p>

2241) 

2242)     <hr>

2243) 

2244) <a id="UpgradeOrMove"></a>

2245) <h3><a class="anchor" href="#UpgradeOrMove">I want to upgrade/move my relay. 
2246) How do I keep the same key?</a></h3>

2247) 
2248) <p>

2249)  When upgrading your Tor relay, or running it on a different computer, 
2250)  the important part is to keep the same nickname (defined in your torrc 
2251)  file) and the same identity key (stored in "keys/secret_id_key" in 
2252)  your DataDirectory).

2253) </p>
2254) <p>

2255) This means that if you're upgrading your Tor relay and you keep the same 
2256) torrc and the same DataDirectory, then the upgrade should just work and 
2257) your relay will keep using the same key. If you need to pick a new 
2258) DataDirectory, be sure to copy your old keys/secret_id_key over. 

2259) </p>
2260) 
2261)     <hr>
2262) 
2263) <a id="NTService"></a>

2264) <h3><a class="anchor" href="#NTService">How do I run my Tor relay as an NT 
2265) service?</a></h3>

2266) 
2267) <p>

2268)  You can run Tor as a service on all versions of Windows except Windows 
2269)  95/98/ME. This way you can run a Tor relay without needing to always have 
2270)  Vidalia running.

2271) </p>
2272) <p>

2273) If you've already configured your Tor to be a relay, please note that when 
2274) you enable Tor as a service, it will use a different DatagDirectory, and 
2275) thus will generate a different key. If you want to keep using the old key, 
2276) see the Upgrading your Tor relay FAQ entry for how to restore the old 
2277) identity key.

2278) </p>
2279) <p>
2280) To install Tor as a service, you can simply run:
2281) </p>
2282) <pre>
2283) tor --service install
2284) </pre>
2285) <p>

2286) A service called Tor Win32 Service will be installed and started. This 
2287) service will also automatically start every time Windows boots, unless 
2288) you change the Start-up type. An easy way to check the status of Tor, 
2289) start or stop the service, and change the start-up type is by running 
2290) services.msc and finding the Tor service in the list of currently 
2291) installed services.

2292) </p>
2293) <p>

2294) Optionally, you can specify additional options for the Tor service using 
2295) the -options argument. For example, if you want Tor to use C:\tor\torrc, 
2296) instead of the default torrc, and open a control port on port 9151, you 
2297) would run:

2298) </p>
2299) <pre>
2300) tor --service install -options -f C:\tor\torrc ControlPort 9151
2301) </pre>
2302) <p>
2303) You can also start or stop the Tor service from the command line by typing:
2304) </p>
2305) <pre>
2306)  tor --service start
2307) </pre>
2308) <p>
2309) or
2310) </p>
2311) <pre>
2312)  tor --service stop
2313) </pre>
2314) <p>
2315) To remove the Tor service, you can run the following command:
2316) </p>
2317) <pre>
2318) tor --service remove
2319) </pre>
2320) <p>

2321) If you are running Tor as a service and you want to uninstall Tor entirely, 
2322) be sure to run the service removal command (shown above) first before 
2323) running the uninstaller from "Add/Remove Programs". The uninstaller is 
2324) currently not capable of removing the active service.

2325) </p>
2326) 
2327) <hr>
2328) 
2329) <a id="VirtualServer"></a>

2330) <h3><a class="anchor" href="#VirtualServer">Can I run a Tor relay from my 
2331) virtual server account?</a></h3>

2332) 
2333) <p>

2334) Some ISPs are selling "vserver" accounts that provide what they call a 
2335) virtual server -- you can't actually interact with the hardware, and 
2336) they can artificially limit certain resources such as the number of file 
2337) descriptors you can open at once. Competent vserver admins are able to 
2338) configure your server to not hit these limits. For example, in SWSoft's 
2339) Virtuozzo, investigate /proc/user_beancounters. Look for "failcnt" in 
2340) tcpsndbuf, tcprecvbuf, numothersock, and othersockbuf. Ask for these to 
2341) be increased accordingly. Some users have seen settings work well as follows: 

2342) <p>

2343) <table border="1">

2344) <tr>
2345) <td>
2346) <i>resource</i>
2347) </td>
2348) <td>
2349) <i>held</i>
2350) </td>
2351) <td>
2352) <i>maxheld</i>
2353) </td>
2354) <td>
2355) <i>barrier</i>
2356) </td>
2357) <td>
2358) <i>limit</i>
2359) </td>
2360) <td>
2361) <i>failcnt</i>
2362) </td>
2363) </tr>
2364) <tr>
2365) <td>
2366) tcpsndbuf
2367) </td>
2368) <td>
2369) 46620
2370) </td>
2371) <td>
2372) 48840
2373) </td>
2374) <td>
2375) 3440640
2376) </td>
2377) <td>
2378) 5406720
2379) </td>
2380) <td>
2381) 0
2382) </td>
2383) </tr>
2384) <tr>
2385) <td>
2386) tcprcvbuf
2387) </td>
2388) <td>
2389) 0
2390) </td>
2391) <td>
2392) 2220
2393) </td>
2394) <td>
2395) 3440640
2396) </td>
2397) <td>
2398) 5406720
2399) </td>
2400) <td>
2401) 0
2402) </td>
2403) </tr>
2404) <tr>
2405) <td>
2406) othersockbuf
2407) </td>
2408) <td>
2409) 243516
2410) </td>
2411) <td>
2412) 260072
2413) </td>
2414) <td>
2415) 2252160
2416) </td>
2417) <td>
2418) 4194304
2419) </td>
2420) <td>
2421) 0
2422) </td>
2423) </tr>
2424) <tr>
2425) <td>
2426) numothersock
2427) </td>
2428) <td>
2429) 151
2430) </td>
2431) <td>
2432) 153
2433) </td>
2434) <td>
2435) 720
2436) </td>
2437) <td>
2438) 720
2439) </td>
2440) <td>
2441) 0
2442) </td>
2443) </tr>
2444) </table>
2445) <p>
2446)  Xen, Virtual Box and VMware virtual servers have no such limits normally.
2447) </p>
2448) <p>

2449) If the vserver admin will not increase system limits another option is 
2450) to reduce the memory allocated to the send and receive buffers on TCP 
2451) connections Tor uses. An experimental feature to constrain socket buffers 
2452) has recently been added. If your version of Tor supports it, set 
2453) "ConstrainedSockets 1" in your configuration. See the tor man page for 
2454) additional details about this option.

2455) </p>
2456) <p>

2457) Unfortunately, since Tor currently requires you to be able to connect to 
2458) all the other Tor relays, we need you to be able to use at least 1024 file 
2459) descriptors. This means we can't make use of Tor relays that are crippled 
2460) in this way.

2461) </p>
2462) <p>

2463) We hope to fix this in the future, once we know how to build a Tor network 
2464) with restricted topologies -- that is, where each node connects to only a 
2465) few other nodes. But this is still a long way off.

2466) </p>
2467) 

2468) <hr>
2469) 

2470) <a id="MultipleRelays"></a>

2471) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
2472) relay.</a></h3>

2473) 
2474) <p>
2475) Great. If you want to run several relays to donate more to the network,
2476) we're happy with that. But please don't run more than a few dozen on
2477) the same network, since part of the goal of the Tor network is dispersal
2478) and diversity.
2479) </p>
2480) 
2481) <p>
2482) If you do decide to run more than one relay, please set the "MyFamily"

2483) config option in the <a href="#torrc">torrc</a> of each relay, listing
2484) all the relays (comma-separated) that are under your control:

2485) </p>
2486) 
2487) <pre>
2488)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
2489) </pre>
2490) 
2491) <p>
2492) where each fingerprint is the 40 character identity fingerprint (without

2493) spaces). You can also list them by nickname, but fingerprint is safer.
2494) Be

2495) sure to prefix the digest strings with a dollar sign ('$') so that the
2496) digest is not confused with a nickname in the config file.
2497) </p>
2498) 
2499) <p>
2500) That way clients will know to avoid using more than one of your relays
2501) in a single circuit. You should set MyFamily if you have administrative
2502) control of the computers or of their network, even if they're not all in
2503) the same geographic location.
2504) </p>
2505) 
2506)     <hr>
2507) 

2508)     <a id="WrongIP"></a>

2509)     <h3><a class="anchor" href="#WrongIP">My relay is picking the wrong 
2510)     IP address.</a></h3>

2511)     <p>

2512)  Tor guesses its IP address by asking the computer for its hostname, and 
2513)  then resolving that hostname. Often people have old entries in their 
2514)  /etc/hosts file that point to old IP addresses.

2515)     </p>
2516)     <p>

2517) If that doesn't fix it, you should use the "Address" config option to 
2518) specify the IP you want it to pick. If your computer is behind a NAT and 
2519) it only has an internal IP address, see the following FAQ entry on <a 
2520) href="https://www.torproject.org/docs/faq.html.en#RelayFlexible">dynamic 
2521) IP addresses</a>.

2522)     </p>
2523)     <p>

2524) Also, if you have many addresses, you might also want to set 
2525) "OutboundBindAddress" so external connections come from the IP you intend 
2526) to present to the world. 

2527)     </p>
2528) 
2529)     <hr>
2530) 
2531)     <a id="BehindANAT"></a>
2532)     <h3><a class="anchor" href="#BehindANAT">I'm behind a NAT/Firewall.</a></h3>
2533) 
2534)     <p>

2535) See <a>​http://portforward.com/</a> for directions on how to port forward with 
2536) your NAT/router device.

2537) </p>
2538) <p>

2539) If your relay is running on a internal net you need to setup port forwarding. 
2540) Forwarding TCP connections is system dependent but the firewalled-clients FAQ 
2541) entry offers some examples on how to do this.

2542) </p>
2543) <p>

2544) Also, here's an example of how you would do this on GNU/Linux if you're using 
2545) iptables:

2546) </p>
2547) <pre>
2548) /sbin/iptables -A INPUT -i eth0 -p tcp --destination-port 9001 -j ACCEPT
2549) </pre>
2550) <p>

2551) You may have to change "eth0" if you have a different external interface 
2552) (the one connected to the Internet). Chances are you have only one (except 
2553) the loopback) so it shouldn't be too hard to figure out. 

2554)     </p>
2555)     <hr>
2556) 

2557)     <a id="RelayMemory"></a>

2558)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
2559) so much memory?</a></h3>

2560) 

2561)     <p>If your Tor relay is using more memory than you'd like, here are
2562) some

2563)     tips for reducing its footprint:
2564)     </p>

2565) 

2566)     <ol>
2567)     <li>If you're on Linux, you may be encountering memory fragmentation

2568)     bugs in glibc's malloc implementation. That is, when Tor releases
2569) memory
2570)     back to the system, the pieces of memory are fragmented so they're
2571) hard
2572)     to reuse. The Tor tarball ships with OpenBSD's malloc
2573) implementation,
2574)     which doesn't have as many fragmentation bugs (but the tradeoff is
2575) higher
2576)     CPU load). You can tell Tor to use this malloc implementation
2577) instead:

2578)     <tt>./configure --enable-openbsd-malloc</tt></li>

2579) 

2580)     <li>If you're running a fast relay, meaning you have many TLS
2581) connections

2582)     open, you are probably losing a lot of memory to OpenSSL's internal
2583)     buffers (38KB+ per socket). We've patched OpenSSL to <a

2584) 
2585) href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.
2586) html">release

2587)     unused buffer memory more aggressively</a>. If you update to OpenSSL

2588)     1.0.0 or newer, Tor's build process will automatically recognize and
2589) use

2590)     this feature.</li>

2591) 

2592)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
2593)     old FreeBSD, Tor is probably forking separate processes
2594)     rather than using threads. Consider switching to a <a
2595)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better
2596)     operating system</a>.</li>

2597) 

2598)     <li>If you still can't handle the memory load, consider reducing the

2599)     amount of bandwidth your relay advertises. Advertising less
2600) bandwidth

2601)     means you will attract fewer users, so your relay shouldn't grow
2602)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
2603)     page.</li>

2604) 

2605)     </ol>

2606) 

2607)     <p>

2608)     All of this said, fast Tor relays do use a lot of ram. It is not
2609) unusual

2610)     for a fast exit relay to use 500-1000 MB of memory.
2611)     </p>

2612) 

2613)     <hr>

2614) 

2615)     <a id="BetterAnonymity"></a>

2616)     <h3><a class="anchor" href="#BetterAnonymity">Do I get better anonymity 
2617)     if I run a relay?</a></h3>

2618) 

2619)     <p>

2620) Yes, you do get better anonymity against some attacks.
2621)     </p>
2622)     <p>

2623) The simplest example is an attacker who owns a small number of Tor relays. 
2624) He will see a connection from you, but he won't be able to know whether 
2625) the connection originated at your computer or was relayed from somebody else.

2626)     </p>
2627)     <p>

2628) There are some cases where it doesn't seem to help: if an attacker can 
2629) watch all of your incoming and outgoing traffic, then it's easy for him 
2630) to learn which connections were relayed and which started at you. (In 
2631) this case he still doesn't know your destinations unless he is watching 
2632) them too, but you're no better off than if you were an ordinary client.)

2633)     </p>
2634)     <p>

2635) There are also some downsides to running a Tor relay. First, while we 
2636) only have a few hundred relays, the fact that you're running one might 
2637) signal to an attacker that you place a high value on your anonymity. 
2638) Second, there are some more esoteric attacks that are not as 
2639) well-understood or well-tested that involve making use of the knowledge 
2640) that you're running a relay -- for example, an attacker may be able to 
2641) "observe" whether you're sending traffic even if he can't actually watch 
2642) your network, by relaying traffic through your Tor relay and noticing 
2643) changes in traffic timing.

2644)     </p>
2645)     <p>

2646) It is an open research question whether the benefits outweigh the risks. 
2647) A lot of that depends on the attacks you are most worried about. For 
2648) most users, we think it's a smart move. 

2649)     </p>

2650) 

2651)     <hr>

2652) 

2653)     <a id="RelayDonations"></a>

2654)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
2655)     relay rather than run my own?</a></h3>

2656) 
2657)     <p>

2658)     Sure! We recommend these non-profit charities that are happy to turn

2659)     your donations into better speed and anonymity for the Tor network:
2660)     </p>
2661)     <ul>
2662)     <li><a href="https://www.torservers.net/">torservers.net</a>
2663)     is a German charitable non-profit that runs a wide variety of

2664)     exit relays worldwide. They also like donations of bandwidth from
2665)     ISPs.</li>

2666)     <li><a

2667) href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

2668)     is a US-based 501(c)(3) non-profit that collects donations and turns

2669)     them into more US-based exit relay capacity.</li>
2670)     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
2671)     charitable non-profit that runs fast exit relays in France.</li>

2672)     </ul>
2673) 
2674)     <p>
2675)     These organizations are not the same as <a href="<page
2676)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

2677)     good thing. They're both run by nice people who are part of the
2678)     Tor community.

2679)     </p>
2680) 
2681)     <p>
2682)     Note that there can be a tradeoff here between anonymity and

2683)     performance. The Tor network's anonymity comes in part from
2684) diversity,

2685)     so if you are in a position to run your own relay, you will be

2686)     improving Tor's anonymity more than by donating. At the same time
2687)     though, economies

2688)     of scale for bandwidth mean that combining many small donations into

2689)     several larger relays is more efficient at improving network

2690)     performance. Improving anonymity and improving performance are both
2691)     worthwhile goals, so however you can help is great!
2692)     </p>
2693) 
2694)     <hr>
2695) 

2696)     <a id="AccessHiddenServices"></a>
2697)     <h3><a class="anchor" href="#AccessHiddenServices">How do I access 
2698)     hidden services?</a></h3>
2699)     
2700)     <p>
2701)     Tor hidden services are named with a special top-level domain (TLD) 
2702)     name in DNS: .onion. Since the .onion TLD is not recognized by the 
2703)     official root DNS servers on the Internet, your application will not 
2704)     get the response it needs to locate the service. Currently, the Tor 
2705)     directory server provides this look-up service; and thus the look-up 
2706)     request must get to the Tor network. 
2707)     </p>
2708) 
2709) <p>
2710)  Therefore, your application <b>needs</b> to pass the .onion hostname to 
2711)  Tor directly. You can't try to resolve it to an IP address, since there 
2712)  <i>is</i> no corresponding IP address: the server is hidden, after all! 
2713) </p>
2714)     
2715)     <p>
2716)     So, how do you make your application pass the hostname directly to Tor? 
2717)     You can't use SOCKS 4, since SOCKS 4 proxies require an IP from the 
2718)     client (a web browser is an example of a SOCKS client). Even though 
2719)     SOCKS 5 can accept either an IP or a hostname, most applications 
2720)     supporting SOCKS 5 try to resolve the name before passing it to the 
2721)     SOCKS proxy. SOCKS 4a, however, always accepts a hostname: You'll need 
2722)     to use SOCKS 4a. 
2723)     </p>
2724)     
2725)     <p>
2726)     Some applications, such as the browsers Mozilla Firefox and Apple's 
2727)     Safari, support sending DNS queries to Tor's SOCKS 5 proxy. Most web 
2728)     browsers don't support SOCKS 4a very well, though. The workaround is 
2729)     to point your web browser at an HTTP proxy, and tell the HTTP proxy 
2730)     to speak to Tor with SOCKS 4a. We recommend Polipo as your HTTP proxy.
2731)     </p>
2732)     
2733)     <p>
2734)     For applications that do not support HTTP proxy, and so cannot use 
2735)     Polipo, <a href="http://www.freecap.ru/eng/">FreeCap</a> is an 
2736)     alternative. When using FreeCap set proxy protocol  to SOCKS 5 and under 
2737)     settings set DNS name resolving to remote. This 
2738)     will allow you to use almost any program with Tor without leaking DNS 
2739)     lookups and allow those same programs to access hidden services. 
2740)     </p>
2741)     
2742)     <p>
2743)     See also the <a href="#SocksAndDNS">question on DNS</a>. 
2744)     </p>    
2745)     
2746)     <hr>
2747) 
2748)     <a id="ProvideAHiddenService"></a>
2749)     <h3><a class="anchor" href="#ProvideAHiddenService">How do I provide a 
2750)     hidden service?</a></h3>
2751)     
2752)     <p>

2753)     See the <a href="https://www.torproject.org/docs/tor-hidden-service.html.en">

2754)     official hidden service configuration instructions</a>.
2755)     </p>
2756) 
2757)     <hr>
2758)     

2759)     <a id="WhoIsResponsible"></a>
2760)     <h3><a class="anchor" href="#WhoIsResponsible">Who is responsible 
2761)     for Tor?</a></h3>
2762) 
2763)     <p>
2764)     <a href="http://www.freehaven.net/~arma/cv.html">Roger Dingledine</a> and 
2765)     <a href="http://www.wangafu.net/~nickm/">Nick Mathewson</a> are the main 
2766)     developers of Tor. You can read more at 
2767)     <a href="https://www.torproject.org/about/corepeople">Tor's People 
2768)     page</a>. 
2769)     </p>
2770) 
2771)     <hr>
2772) 
2773)     <a id="VersionNumbers"></a>
2774)     <h3><a class="anchor" href="#VersionNumbers">What do these weird 
2775)     version numbers mean?</a></h3>
2776) 
2777)     <p>
2778)     Versions of Tor before 0.1.0 used a strange and hard-to-explain version scheme. Let's forget about those.
2779)     </p>
2780)     <p>
2781)     Starting with 0.1.0, versions all look like this: 
2782)     MAJOR.MINOR.MICRO(.PATCHLEVEL)(-TAG). The stuff in parenthesis is 
2783)     optional. MAJOR, MINOR, MICRO, and PATCHLEVEL are all numbers. Only one 
2784)     release is ever made with any given set of these version numbers. The 
2785)     TAG lets you know how stable we think the release is: "alpha" is pretty 
2786)     unstable; "rc" is a release candidate; and no tag at all means that we 
2787)     have a final release. If the tag ends with "-cvs", you're looking at 
2788)     a development snapshot that came after a given release. 
2789)     </p>
2790)     <p>
2791)     So for example, we might start a development branch with (say) 
2792)     0.1.1.1-alpha. The patchlevel increments consistently as the status 
2793)     tag changes, for example, as in: 0.1.1.2-alpha, 0.1.1.3-alpha, 
2794)     0.1.1.4-rc, 0.1.1.5-rc, etc. Eventually, we would release 0.1.1.6. 
2795)     The next stable release would be 0.1.1.7.
2796)     </p>
2797)     <p>
2798)     Why do we do it like this? Because every release has a unique 
2799)     version number, it is easy for tools like package manager to tell 
2800)     which release is newer than another. The tag makes it easy for users 
2801)     to tell how stable the release is likely to be. 
2802)     </p>
2803) 
2804)     <hr>
2805) 
2806)     <a id="PrivateTorNetwork"></a>
2807)     <h3><a class="anchor" href="#PrivateTorNetwork">How do I set up my 
2808)     own private Tor network?</a></h3>
2809)     
2810)     <p>
2811)     If you want to experiment locally with your own network, or you're 
2812)     cut off from the Internet and want to be able to mess with Tor still, 
2813)     then you may want to set up your own separate Tor network. 
2814)     </p>
2815)     <p>
2816)     To set up your own Tor network, you need to run your own authoritative 
2817)     directory servers, and your clients and relays must be configured so 
2818)     they know about your directory servers rather than the default public 
2819)     ones. 
2820)     </p>
2821)     <p>
2822)     Apart from the somewhat tedious method of manually configuring a couple 
2823)     of directory authorities, relays and clients there are two separate 
2824)     tools that could help. One is Chutney, the other is Shadow. 
2825)     </p>
2826)     <p>
2827)     <a href="https://gitweb.torproject.org/chutney.git">Chutney</a> is a 
2828)     tool for configuring, controlling and running tests on a 
2829)     testing Tor network. It requires that you have Tor and Python (2.5 or 
2830)     later) installed on your system. You can use Chutney to create a testing
2831)     network by generating Tor configuration files (torrc) and necssary keys 
2832)     (for the directory authorities). Then you can let Chutney start your Tor
2833)     authorities, relays and clients and wait for the network to bootstrap.
2834)     Finally, you can have Chutney run tests on your network to see which 
2835)     things work and which do not. Chutney is typically used for running a 
2836)     testing network with about 10 instances of Tor. Every instance of Tor 
2837)     binds to one or two ports on localhost (127.0.0.1) and all Tor 
2838)     communication is done over the loopback interface. The <a 
2839)     href="https://gitweb.torproject.org/chutney.git/blob/HEAD:/README">Chutney 
2840)     README</a> is a good starting point for getting it up and running. 
2841)     </p>
2842)     <p>
2843)     <a href="https://github.com/shadow/shadow">Shadow</a> is a network 
2844)     simulator that can run Tor through its Scallion plug-in. Although 
2845)     it's typically used for running load and performance tests on 
2846)     substantially larger Tor test networks than what's feasible with 
2847)     Chutney, it also makes for an excellent debugging tool since you can 
2848)     run completely deterministic experiments. A large Shadow network is on 
2849)     the size of thousands of instances of Tor, and you can run experiments 
2850)     out of the box using one of Shadow's several included scallion experiment 
2851)     configurations. Shadow can be run on any linux machine without root, 
2852)     and can also run on EC2 using a pre-configured image. Also, Shadow 
2853)     controls the time of the simulation with the effect that 
2854)     time-consuming tests can be done more efficiently than in an 
2855)     ordinary testing network. The <a 
2856)     href="https://github.com/shadow/shadow/wiki">Shadow wiki</a> and 
2857)     <a href="http://shadow.github.io/">Shadow website</a> are 
2858)     good places to get started. 
2859)     </p>
2860) 
2861)     <hr>
2862) 
2863)     <a id="UseTorInJava"></a>
2864)     <h3><a class="anchor" href="UseTorInJava">How can I make my Java 
2865)     program use the Tor Network?</a></h3>
2866) 
2867)     <p>
2868)     The newest versions of Java now have SOCKS4/5 support built in. 
2869)     Unfortunately, the SOCKS interface is not very well documented and 
2870)     may still leak your DNS lookups. The safest way to use Tor is to 
2871)     interface the SOCKS protocol directly or go through an application-level 
2872)     proxy that speaks SOCKS4a. For an example and libraries that implement 
2873)     the SOCKS4a connection, go to Joe Foley's TorLib in the <a 
2874)     href="http://web.mit.edu/foley/www/TinFoil/">TinFoil Project</a>. 
2875)     </p>
2876) 
2877)     <p>
2878)     A fully Java implementation of the Tor client is now available as <a 
2879)     href="http://www.subgraph.com/orchid.html">Orchid</a>. We still consider 
2880)     Orchid to be experimental, so use with care. 
2881)     </p>
2882) 
2883)     <hr>
2884) 
2885) 
2886)     <a id="WhatIsLibevent"></a>
2887)     <h3><a class="anchor" href="#WhatIsLibevent">What is Libevent?</a></h3>
2888)     
2889)     <p>
2890)     When you want to deal with a bunch of net connections at once, you 
2891)     have a few options: 
2892)     </p>
2893)     <p>
2894)     One is multithreading: you have a separate micro-program inside the 
2895)     main program for each net connection that reads and writes to the 
2896)     connection as needed.This, performance-wise, sucks. 
2897)     </p>
2898)     <p>
2899)     Another is asynchronous network programming: you have a single main 
2900)     program that finds out when various net connections are ready to 
2901)     read/write, and acts accordingly.
2902)     </p>
2903)     <p>
2904)     The problem is that the oldest ways to find out when net connections 
2905)     are ready to read/write, suck. And the newest ways are finally fast, 
2906)     but are not available on all platforms. 
2907)     </p>
2908)     <p>
2909)     This is where Libevent comes in and wraps all these ways to find 
2910)     out whether net connections are ready to read/write, so that Tor 
2911)     (and other programs) can use the fastest one that your platform 
2912)     supports, but can still work on older platforms (these methods are 
2913)     all different depending on the platorm) So Libevent presents a 
2914)     consistent and fast interface to select, poll, kqueue, epoll, 
2915)     /dev/poll, and windows select. 
2916)     </p>
2917)     <p>
2918)     However, On the the Win32 platform (by Microsoft) the only good 
2919)     way to do fast IO on windows with hundreds of sockets is using 
2920)     overlapped IO, which is grossly unlike every other BSD sockets 
2921)     interface. 
2922)     </p>
2923)     <p>Libevent has <a href="http://www.monkey.org/~provos/libevent/">its 
2924)     own website</a>.
2925)     </p>
2926)     <hr>
2927) 
2928)     <a id="MyNewFeature"></a>
2929)     <h3><a class="anchor" href="#MyNewFeature">What do I need to do to get 
2930)     a new feature into Tor?</a></h3>
2931)     
2932)     <p>
2933)     For a new feature to go into Tor, it needs to be designed (explain what 
2934)     you think Tor should do), argued to be secure (explain why it's better 
2935)     or at least as good as what Tor does now), specified (explained at the 
2936)     byte level at approximately the level of detail in tor-spec.txt), and 
2937)     implemented (done in software). 
2938)     </p>
2939) 
2940)     <p>
2941)     You probably shouldn't count on other people doing all of these steps 
2942)     for you: people who are skilled enough to do this stuff generally 
2943)     have their own favorite feature requests.
2944)     </p>
2945) 
2946)     <hr>
2947) 

2948)     <a id="WhatProtectionsDoesTorProvide"></a>
2949)     <h3><a class="anchor" href="#WhatProtectionsDoesTorProvide">What 
2950)     protections does Tor provide?</a></h3>
2951)     
2952)     <p>

2953)     Internet communication is based on a store-and-forward model that 
2954)     can be understood in analogy to postal mail: Data is transmitted in 
2955)     blocks called IP datagrams or packets. Every packet includes a source 
2956)     IP address (of the sender) and a destination IP address (of the 
2957)     receiver), just as ordinary letters contain postal addresses of sender 
2958)     and receiver. The way from sender to receiver involves multiple hops of 
2959)     routers, where each router inspects the destination IP address and 
2960)     forwards the packet closer to its destination. Thus, every router 
2961)     between sender and receiver learns that the sender is communicating 
2962)     with the receiver. In particular, your local ISP is in the position to 
2963)     build a complete profile of your Internet usage. In addition, every 
2964)     server in the Internet that can see any of the packets can profile your 
2965)     behaviour. 

2966)     </p>
2967)     
2968)     <p>
2969)     The aim of Tor is to improve your privacy by sending your traffic through 
2970)     a series of proxies. Your communication is encrypted in multiple layers 
2971)     and routed via multiple hops through the Tor network to the final 
2972)     receiver. More details on this process can be found in the <a 
2973)     href="https://www.torproject.org/about/overview">Tor overview</a>. 
2974)     Note that all your local ISP can observe now is that you are 
2975)     communicating with Tor nodes. Similarly, servers in the Internet just 
2976)     see that they are being contacted by Tor nodes.
2977)     </p>
2978)     
2979)     <p>
2980)     Generally speaking, Tor aims to solve three privacy problems: 
2981)     </p>
2982)     
2983)     <p>
2984)     First, Tor prevents websites and other services from learning 
2985)     your location, which they can use to build databases about your 
2986)     habits and interests. With Tor, your Internet connections don't 
2987)     give you away by default -- now you can have the ability to choose, 
2988)     for each connection, how much information to reveal. 
2989)     </p>
2990)     
2991)     <p>
2992)     Second, Tor prevents people watching your traffic locally (such as 
2993)     your ISP) from learning what information you're fetching and where 
2994)     you're fetching it from. It also stops them from deciding what you're 
2995)     allowed to learn and publish -- if you can get to any part of the Tor 
2996)     network, you can reach any site on the Internet.     
2997)     </p>
2998) 
2999)     <p>
3000)     Third, Tor routes your connection through more than one Tor relay 
3001)     so no single relay can learn what you're up to. Because these relays 
3002)     are run by different individuals or organizations, distributing trust 
3003)     provides more security than the old <a href="#Torisdifferent">one hop proxy
3004)     </a> approach. 
3005)     </p>
3006)     
3007)     <p>
3008)     Note, however, that there are situations where Tor fails to solve these 
3009)     privacy problems entirely: see the entry below on <a 
3010)     href="#AttacksOnOnionRouting">remaining attacks</a>.    
3011)     </p>
3012)     
3013)     <hr>
3014)     
3015)     <a id="CanExitNodesEavesdrop"></a>
3016)     <h3><a class="anchor" href="#CanExitNodesEavesdrop">Can exit nodes eavesdrop 
3017)     on communications? Isn't that bad?</a></h3>
3018)     
3019)     <p>
3020)     Yes, the guy running the exit node can read the bytes that come in and 
3021)     out there. Tor anonymizes the origin of your traffic, and it makes sure 
3022)     to encrypt everything inside the Tor network, but it does not magically 
3023)     encrypt all traffic throughout the Internet. 
3024)     </p>
3025)     
3026)     <p>
3027)     This is why you should always use end-to-end encryption such as SSL for 
3028)     sensitive Internet connections. (The corollary to this answer is that if 
3029)     you are worried about somebody intercepting your traffic and you're 
3030)     *not* using end-to-end encryption at the application layer, then something 
3031)     has already gone wrong and you shouldn't be thinking that Tor is the problem.) 
3032)     </p>
3033)     
3034)     <p>
3035)     Tor does provide a partial solution in a very specific situation, though. 
3036)     When you make a connection to a destination that also runs a Tor relay, 
3037)     Tor will automatically extend your circuit so you exit from that circuit. 
3038)     So for example if Indymedia ran a Tor relay on the same IP address as 
3039)     their website, people using Tor to get to the Indymedia website would 
3040)     automatically exit from their Tor relay, thus getting *better* encryption 
3041)     and authentication properties than just browsing there the normal way. 
3042)     </p>
3043) 
3044)     <p>
3045)     We'd like to make it still work even if the service is nearby the Tor 
3046)     relay but not on the same IP address. But there are a variety of 
3047)     technical problems we need to overcome first (the main one being "how 
3048)     does the Tor client learn which relays are associated with which 
3049)     websites in a decentralized yet non-gamable way?"). 
3050)     </p>
3051)             
3052)     <hr>
3053)     
3054)     <a id="ExitEnclaving"></a>
3055)     <h3><a class="anchor" href="#ExitEnclaving">What is Exit Enclaving?</a></h3>
3056) 
3057)     <p>
3058)     When a machine that runs a Tor relay also runs a public service, such as 
3059)     a webserver, you can configure Tor to offer Exit Enclaving to that 
3060)     service. Running an Exit Enclave for all of your services you wish to 
3061)     be accessible via Tor provides your users the assurance that they will 
3062)     exit through your server, rather than exiting from a randomly selected 
3063)     exit node that could be watched. Normally, a tor circuit would end at 
3064)     an exit node and then that node would make a connection to your service. 
3065)     Anyone watching that exit node could see the connection to your service, 
3066)     and be able to snoop on the contents if it were an unencrypted 
3067)     connection. If you run an Exit Enclave for your service, then the exit 
3068)     from the Tor network happens on the machine that runs your service, 
3069)     rather than on an untrusted random node. This works when Tor clients 
3070)     wishing to connect to this public service extend their their circuit 
3071)     to exit from the Tor relay running on that same host. For example, if 
3072)     the server at 1.2.3.4 runs a web server on port 80 and also acts as a 
3073)     Tor relay configured for Exit Enclaving, then Tor clients wishing to 
3074)     connect to the webserver will extend their circuit a fourth hop to exit 
3075)     to port 80 on the Tor relay running on 1.2.3.4. 
3076)     </p>
3077)     <p>
3078)     Exit Enclaving is disabled by default to prevent attackers from 
3079)     exploiting trust relationships with locally bound services. For 
3080)     example, often 127.0.0.1 will run services that are not designed to 
3081)     be shared with the entire world. Sometimes these services will also 
3082)     be bound to the public IP address, but will only allow connections if 
3083)     the source address is something trusted, such as 127.0.0.1. 
3084)     </p>
3085)     <p>
3086)     As a result of possible trust issues, relay operators must configure 
3087)     their exit policy to allow connections to themselves, but they should 
3088)     do so only when they are certain that this is a feature that they would 
3089)     like. Once certain, turning off the ExitPolicyRejectPrivate option will 
3090)     enable Exit Enclaving. An example configuration would be as follows: 
3091)     </p>
3092)     <pre>
3093)     ExitPolicy accept 1.2.3.4:80
3094)     ExitPolicy reject 127.0.0.1/8
3095)     ExitPolicyRejectPrivate 0
3096)     </pre>
3097)     <p>
3098)     This option should be used with care as it may expose internal network 
3099)     blocks that are not meant to be accessible from the outside world or 
3100)     the Tor network. Please tailor your ExitPolicy to reflect all netblocks 
3101)     that you want to prohibit access. 
3102)     </p>
3103)     <p>
3104)     This option should be used with care as it may expose internal network 
3105)     blocks that are not meant to be accessible from the outside world or 
3106)     the Tor network. Please tailor your ExitPolicy to reflect all netblocks 
3107)     that you want to prohibit access. 
3108)     </p>
3109)     <p>
3110)     While useful, this behavior may go away in the future because it is 
3111)     imperfect. A great idea but not such a great implementation. 
3112)     </p>
3113) 
3114)     <hr>
3115)     

3116)     <a id="KeyManagement"></a>

3117)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the
3118) keys Tor uses.</a></h3>

3119) 

3120)     <p>
3121)     Tor uses a variety of different keys, with three goals in mind: 1)
3122)     encryption to ensure privacy of data within the Tor network, 2)
3123)     authentication so clients know they're

3124)     talking to the relays they meant to talk to, and 3) signatures to
3125) make

3126)     sure all clients know the same set of relays.
3127)     </p>

3128) 

3129)     <p>

3130)     <b>Encryption</b>: first, all connections in Tor use TLS link
3131) encryption,

3132)     so observers can't look inside to see which circuit a given cell is

3133)     intended for. Further, the Tor client establishes an ephemeral
3134) encryption

3135)     key with each relay in the circuit; these extra layers of encryption
3136)     mean that only the exit relay can read