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

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

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

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

36)     </ul>

37) 

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

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

45)     <li><a href="#CompileTorWindows">How do I compile Tor under
46) Windows?</a></li>
47)     <li><a href="#VirusFalsePositives">Why does my Tor executable appear
48) to

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

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

52)     </ul>

53) 

54)     <p>Tor Browser Bundle:</p>
55)     <ul>

56) 

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

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

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

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

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

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

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

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

71)     <li><a href="#TBBOtherBrowser">I want to use Chrome/IE/Opera/etc
72)     with Tor.</a></li>
73)     <li><a href="#TBBCloseBrowser">I want to leave Tor Browser Bundle
74)     running but close the browser.</a></li>
75) 

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

77) tells

78)     me I have spyware installed.</a></li>
79)     <li><a href="#GmailWarning">Gmail warns me that my account may have
80)     been compromised.</a></li>
81)     </ul>
82) 
83)     <p>Advanced Tor usage:</p>

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

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

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

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

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

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

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

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

98)     </ul>

99) 

100)     <p>Running a Tor relay:</p>
101)     <ul>

102)     <li><a href="#RelayFlexible">How stable does my relay need to
103) be?</a></li>
104)     <li><a href="#ExitPolicies">I'd run a relay, but I don't want to
105) deal

106)     with abuse issues.</a></li>
107)     <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
108)     relay?</a></li>

109)     <li><a href="#MultipleRelays">I want to run more than one
110) relay.</a></li>
111)     <li><a href="#RelayMemory">Why is my Tor relay using so much
112) memory?</a></li>

113)     <li><a href="#WhyNotNamed">Why is my Tor relay not named?</a></li>

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

116)     </ul>

117) 

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

119) 

120)     <p>Anonymity and Security:</p>
121)     <ul>

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

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

125)     </ul>

126) 

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

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

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

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

136)     </ul>

137) 

138)     <p>Abuse:</p>

139)     <ul>

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

142)     <li><a href="#RespondISP">How do I respond to my ISP about my exit
143)     relay?</a></li>
144)     </ul>

145) 

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

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

149) 

150)     <hr>

151) 

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

153) 

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

156) 

157)     <p>
158)     The name "Tor" can refer to several different components.
159)     </p>

160) 

161)     <p>

162)     The Tor software is a program you can run on your computer that
163) helps keep
164)     you safe on the Internet. Tor protects you by bouncing your
165) communications

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

167)     the world: it prevents somebody watching your Internet connection
168) from

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

170)     from learning your physical location. This set of volunteer relays
171) is
172)     called the Tor network. You can read more about how Tor works on the
173) <a

174)     href="<page about/overview>">overview page</a>.
175)     </p>

176) 

177)     <p>

178)     The Tor Project is a non-profit (charity) organization that
179) maintains

180)     and develops the Tor software.
181)     </p>

182) 

183)     <hr>

184) 

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

186)     <h3><a class="anchor" href="#Torisdifferent">How is Tor different
187) from other proxies?</a></h3>
188)     <p>
189)     A typical proxy provider sets up a server somewhere on the Internet
190) and
191) allows you to use it to relay your traffic.  This creates a simple, easy
192) to
193) maintain architecture.  The users all enter and leave through the same
194) server.
195) The provider may charge for use of the proxy, or fund their costs
196) through
197) advertisements on the server.  In the simplest configuration, you don't
198) have to
199) install anything.  You just have to point your browser at their proxy
200) server.
201) Simple proxy providers are fine solutions if you do not want protections
202) for
203) your privacy and anonymity online and you trust the provider from doing
204) bad
205) things.  Some simple proxy providers use SSL to secure your connection
206) to them.
207) This may protect you against local eavesdroppers, such as those at a
208) cafe with

209) free wifi Internet.
210)     </p>
211)     <p>

212)     Simple proxy providers also create a single point of failure.  The
213) provider
214) knows who you are and where you browse on the Internet.  They can see
215) your
216) traffic as it passes through their server.  In some cases, they can even
217) see

218) inside your

219) encrypted traffic as they relay it to your banking site or to ecommerce
220) stores.

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

222) watching your traffic, injecting their own advertisements into your
223) traffic

224) stream, and recording your personal details.

225)     </p>
226)     <p>

227)     Tor passes your traffic through at least 3 different servers before
228) sending
229) it on to the destination. Because there's a separate layer of encryption
230) for
231) each of the three relays, Tor does not modify, or even know, what you
232) are
233) sending into it.  It merely relays your traffic, completely encrypted
234) through
235) the Tor network and has it pop out somewhere else in the world,
236) completely
237) intact.  The Tor client is required because we assume you trust your
238) local
239) computer.  The Tor client manages the encryption and the path chosen
240) through
241) the network.  The relays located all over the world merely pass
242) encrypted

243) packets between themselves.</p>

244)     <p>
245)     <dl>

246)     <dt>Doesn't the first server see who I am?</dt><dd>Possibly. A bad
247) first of
248) three servers can see encrypted Tor traffic coming from your computer.
249) It
250) still doesn't know who you are and what you are doing over Tor.  It
251) merely sees
252) "This IP address is using Tor".  Tor is not illegal anywhere in the
253) world, so
254) using Tor by itself is fine.  You are still protected from this node
255) figuring

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

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

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

262) e-commerce website, or encrypted mail connections, etc, it will only
263) know the
264) destination.  It won't be able to see the data inside the traffic
265) stream.  You

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

268)     </dl>
269)     </p>

270) 

271)     <hr>

272) 

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

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

276) 

277)     <p>

278)     There are two pieces to "Torifying" a program: connection-level
279) anonymity
280)     and application-level anonymity. Connection-level anonymity focuses
281) on
282)     making sure the application's Internet connections get sent through
283) Tor.

284)     This step is normally done by configuring
285)     the program to use your Tor client as a "socks" proxy, but there are

286)     other ways to do it too. For application-level anonymity, you need
287) to
288)     make sure that the information the application sends out doesn't
289) hurt
290)     your privacy. (Even if the connections are being routed through Tor,
291) you
292)     still don't want to include sensitive information like your name.)
293) This

294)     second step needs to be done on a program-by-program basis, which is
295)     why we don't yet recommend very many programs for safe use with Tor.
296)     </p>

297) 

298)     <p>
299)     Most of our work so far has focused on the Firefox web browser. The

300)     bundles on the <a href="<page download/download>">download page</a>
301) automatically

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

303)     extension</a> if you have Firefox installed. As of version 1.2.0,
304)     Torbutton now takes care of a lot of the connection-level and
305)     application-level worries.
306)     </p>

307) 

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

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

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

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

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

319) 

320)     <hr>

321) 

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

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

325) 

326)     <p>
327)     Because Tor is the onion routing network. When we were starting the
328)     new next-generation design and implementation of onion routing in
329)     2001-2002, we would tell people we were working on onion routing,
330)     and they would say "Neat. Which one?" Even if onion routing has
331)     become a standard household term, Tor was born out of the actual <a
332)     href="http://www.onion-router.net/">onion routing project</a> run by
333)     the Naval Research Lab.
334)     </p>

335) 

336)     <p>
337)     (It's also got a fine translation from German and Turkish.)
338)     </p>

339) 

340)     <p>

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

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

344)     spot people who haven't read any of our website (and have instead
345) learned
346)     everything they know about Tor from news articles) by the fact that
347) they

348)     spell it wrong.
349)     </p>

350) 

351)     <hr>

352) 

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

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

356) 

357)     <p>

358)     There is absolutely no backdoor in Tor. Nobody has asked us to put
359) one
360)     in, and we know some smart lawyers who say that it's unlikely that
361) anybody

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

365) 

366)     <p>
367)     We think that putting a backdoor in Tor would be tremendously

368)     irresponsible to our users, and a bad precedent for security
369) software

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

374) 

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

378)     computers, or something like that. Tor is open source, and you
379) should
380)     always check the source (or at least the diffs since the last
381) release)

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

388) 

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

391)     anonymity. We periodically find and fix anonymity-related bugs, so
392) make

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

395) 

396)     <hr>

397) 

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

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

401) 

402)     <p>
403)     Yes.
404)     </p>

405) 

406)     <p>

407)     The Tor software is <a href="https://www.fsf.org/">free
408) software</a>. This
409)     means we give you the rights to redistribute the Tor software,
410) either
411)     modified or unmodified, either for a fee or gratis. You don't have
412) to

413)     ask us for specific permission.
414)     </p>

415) 

416)     <p>

417)     However, if you want to redistribute the Tor software you must
418) follow our

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

420)     Essentially this means that you need to include our LICENSE file
421) along

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

424) 

425)     <p>

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

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

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

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

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

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

441)     </p>

442) 

443)     <p>

444)     Also, you should make sure not to confuse your readers about what
445) Tor is,
446)     who makes it, and what properties it provides (and doesn't provide).
447) See
448)     our <a href="<page docs/trademark-faq>">trademark FAQ</a> for
449) details.

450)     </p>

451) 

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

455)     changes. So if you distribute a particular version of the Tor
456) software, it
457)     may not be supported — or even work — six months later.
458) This

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

461) 

462)     <hr>

463) 

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

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

467) 

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

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

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

473)     <li>Read through the <a

474) 
475) href="https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk">
476) tor-talk

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

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

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

481)     <li>Send an email to <a

482) 
483) href="mailto:help@rt.torproject.org">help@rt.torproject.org</a>.</li>
484)     <li>If all else fails, try <a href="<page about/contact>">contacting
485) us</a> directly.</li>

486)     </ol>

487) 

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

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

491) 

492)     <hr>

493) 

494)     <a id="Forum"></a>
495)     <h3><a class="anchor" href="#Forum">Is there a Tor forum?</a></h3>
496) 
497)     <p>Not yet, but we're working on it. Most forum software is
498)     a disaster to maintain and keep secure, and at the same time
499)     too many of the Tor developers are spread too thin to be able

500)     to contribute enough to a forum.

501)     </p>
502) 
503)     <hr>
504) 

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

507) 

508)     <p>
509)     There are many reasons why the Tor network is currently slow.
510)     </p>

511) 

512)     <p>

513)     Before we answer, though, you should realize that Tor is never going
514) to
515)     be blazing fast. Your traffic is bouncing through volunteers'
516) computers
517)     in various parts of the world, and some bottlenecks and network
518) latency

519)     will always be present. You shouldn't expect to see university-style
520)     bandwidth through Tor.
521)     </p>

522) 

523)     <p>

524)     But that doesn't mean that it can't be improved. The current Tor
525) network
526)     is quite small compared to the number of people trying to use it,
527) and
528)     many of these users don't understand or care that Tor can't
529) currently

530)     handle file-sharing traffic load.
531)     </p>

532) 

533)     <p>
534)     For the much more in-depth answer, see <a

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

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

538)     to go with it.
539)     </p>

540) 

541)     <p>
542)     What can you do to help?
543)     </p>

544) 

545)     <ul>

546) 

547)     <li>

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

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

554) 

555)     <li>

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

558)     especially need people to help make it easier to configure your Tor
559)     as a relay. Also, we need help with clear simple documentation to
560)     walk people through setting it up.
561)     </li>

562) 

563)     <li>

564)     There are some bottlenecks in the current Tor network. Help us
565) design
566)     experiments to track down and demonstrate where the problems are,
567) and

568)     then we can focus better on fixing them.
569)     </li>

570) 

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

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

577)     get to spend more time on it.
578)     </li>

579) 

580)     <li>

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

585)     getinvolved/volunteer>">look at our volunteer page</a>.
586)     </li>

587) 

588)     <li>

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

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

592)     competition's websites discreetly, or to connect back to the home
593) servers
594)     when on the road without revealing affiliations? If your
595) organization has
596)     an interest in keeping the Tor network working, please contact them
597) about
598)     supporting Tor. Without sponsors, Tor is going to become even
599) slower.

600)     </li>

601) 

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

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

606)     cause</a>. It adds up!
607)     </li>

608) 

609)     </ul>

610) 

611)     <hr>

612) 

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

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

616) 

617)     <p>

618)     The Tor network's <a

619) 
620) href="https://metrics.torproject.org/network.html#networksize">several

621)     thousand</a> relays push <a
622)     href="https://metrics.torproject.org/network.html#bandwidth">over
623)     1GB per second on average</a>. We have <a

624) 
625) href="https://metrics.torproject.org/users.html#direct-users">several

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

628)     </p>

629) 

630)     <p>

631)     There are six main development/maintenance pushes that need
632) attention:

633)     </p>

634) 

635)     <ul>

636) 

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

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

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

644) 

645)     <li>

646)     User support: With this many users, a lot of people are asking
647) questions
648)     all the time, offering to help out with things, and so on. We need
649) good
650)     clean docs, and we need to spend some effort coordinating
651) volunteers.

652)     </li>

653) 

654)     <li>

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

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

658)     reminders to upgrade, and so on. The network itself is a commons,
659) and
660)     somebody needs to spend some energy making sure the relay operators
661) stay
662)     happy. We also need to work on stability on some platforms —
663) e.g.,

664)     Tor relays have problems on Win XP currently.

665)     </li>

666) 

667)     <li>

668)     Usability: Beyond documentation, we also need to work on usability
669) of the
670)     software itself. This includes installers, clean GUIs, easy
671) configuration
672)     to interface with other applications, and generally automating all
673) of
674)     the difficult and confusing steps inside Tor. We've got a start on
675) this
676)     with the <a href="<page projects/vidalia>">Vidalia GUI</a>, but much
677) more work

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

680) 

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

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

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

688) 

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

694)     critical <a href="<page getinvolved/volunteer>#Research">Tor
695) research questions</a>
696)     that will help us figure out how to make Tor secure against the
697) variety of
698)     attacks out there. Of course, there are more research questions
699) waiting

700)     behind these.
701)     </li>

702) 

703)     </ul>

704) 

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

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

709)     can keep up</a>.

710)     Now would be an excellent time to add a few more developers to the
711) effort

712)     so we can continue to grow the network.
713)     </p>

714) 

715)     <p>
716)     We are also excited about tackling related problems, such as
717)     censorship-resistance.
718)     </p>

719) 

720)     <p>

721)     We are proud to have <a href="<page about/sponsors>">sponsorship and
722) support</a>
723)     from the Omidyar Network, the International Broadcasting Bureau,
724) Bell
725)     Security Solutions, the Electronic Frontier Foundation, several
726) government

727)     agencies and research groups, and hundreds of private contributors.
728)     </p>

729) 

730)     <p>

731)     However, this support is not enough to keep Tor abreast of changes
732) in the
733)     Internet privacy landscape. Please <a href="<page
734) donate/donate>">donate</a>
735)     to the project, or <a href="<page about/contact>">contact</a> our
736) executive

737)     director for information on making grants or major donations.
738)     </p>

739) 

740)     <hr>
741) 

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

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

745) 

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

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

748)     <hr>

749) 

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

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

754)     <pre>

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

756)     The serial number is:

757) 06:DE:97:E5:1D:C3:9D:C2:64:8D:AC:72:DD:41:01:FC
758)     The SHA-1 fingerprint is: 1f9d306e8bfccfcb03981a71a27a9f5d1e0876ce

759)     The SHA-256 fingerprint is:

760) 3613d2b22a750094760c41ad19db52a4f05bdea80172e2578761ad967f7ed9aa

761) 

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

763)     The serial number is: 00:EF:A3
764)     The SHA-1 fingerprint is: 50af43db8438e67f305a3257d8ef198e8c42f13f

765)     </pre>

766)     </p>
767)     <hr>
768) 

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

770)     <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall
771) Tor?</a></h3>
772) 
773)     <p>
774)     Tor Browser does not install itself in the classic sense of
775) applications. You just simply delete the folder or directory named "Tor
776) Browser" and it is removed from your system.
777)     </p>

778) 

779)     <p>

780)     If this is not related to Tor Browser, uninstallation depends
781) entirely on how you installed it and which operating system you
782)     have. If you installed a package, then hopefully your package has a
783) way to
784)     uninstall itself. The Windows packages include uninstallers. The
785) proper way to
786)     completely remove Tor, Vidalia, and Torbutton for Firefox on any
787) version of Windows is as follows:

788)     </p>

789) 

790)     <ol>

791)     <li>In your taskbar, right click on Vidalia (the green onion or the
792) black head)

793)     and choose exit.</li>

794)     <li>Right click on the taskbar to bring up TaskManager. Look for
795) tor.exe in the
796)     Process List. If it's running, right click and choose End
797) Process.</li>
798)     <li>Click the Start button, go to Programs, go to Vidalia, choose
799) Uninstall.
800)     This will remove the Vidalia bundle, which includes Tor.</li>
801)     <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select
802) Torbutton.

803)     Click the Uninstall button.</li>
804)     </ol>

805) 

806)     <p>
807)     If you do not follow these steps (for example by trying to uninstall

808)     Vidalia and Tor while they are still running), you will need to
809)     reboot and manually remove the directory "Program Files\Vidalia
810) Bundle".

811)     </p>

812) 

813)     <p>
814)     For Mac OS X, follow the <a
815)     href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.
816)     </p>

817) 

818)     <p>

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

823)     be pretty easy to notice things there.
824)     </p>

825) 

826)     <hr>

827) 

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

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

831) 

832)     <p>

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

835)     exactly the one that we intended you to get.
836)     </p>

837) 

838)     <p>
839)     Please read the <a

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

842)     </p>

843) 

844) <hr>
845) 
846) <a id="GetTor"></a>
847) <h3><a class="anchor" href="#GetTor">Your website is blocked in my
848) country. How do I download Tor?</a></h3>
849) 
850) <p>
851) Some government or corporate firewalls censor connections to Tor's
852) website. In those cases, you have three options. First, get it from

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

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

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

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

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

861) in the body of the email, it will reply with instructions. Note that
862) only a few webmail providers are supported, since they need to be able
863) to receive very large attachments.
864) </p>
865) 
866) <p>

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

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

871) </p>
872) 
873) <hr>

874) 

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

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

878) 

879)     <p>

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

882)     tor-win32-mingw-creation.txt</a>.
883)     </p>

884) 

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

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

889)     download/download>">download page</a>.)
890)     </p>

891) 

892)     <hr>

893) 

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

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

897) 

898)     <p>

899)     Sometimes, overzealous Windows virus and spyware detectors trigger
900) on some
901)     parts of the Tor Windows binary. Our best guess is that these are
902) false
903)     positives — after all, the anti-virus and anti-spyware
904) business is just a
905)     guessing game anyway. You should contact your vendor and explain
906) that you have
907)     a program that seems to be triggering false positives. Or pick a
908) better vendor.

909)     </p>

910) 

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

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

915)     href="#CompileTorWindows">recompile it yourself</a>.
916)     </p>

917) 

918)     <hr>

919) 

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

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

923) 

924)     <p>

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

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

928)     Bundle</a>.

929)     </p>

930) 
931) <hr>
932) 

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

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

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

937) 
938) <p>

939) YouTube and similar sites require third party browser plugins such as Flash.
940) Plugins operate independently from Firefox and can perform
941) activity on your computer that ruins your anonymity. This includes
942) but is not limited to: <a href="http://decloak.net">completely disregarding
943) proxy settings</a>, querying your <a
944) href="http://forums.sun.com/thread.jspa?threadID=5162138&amp;messageID=9618376">local
945) IP address</a>, and <a
946) href="http://epic.org/privacy/cookies/flash.html">storing their own
947) cookies</a>. It is possible to use a LiveCD solution such as
948) or <a href="https://tails.boum.org/">The Amnesic Incognito Live System</a> that creates a
949) secure, transparent proxy to protect you from proxy bypass, however issues
950) with local IP address discovery and Flash cookies still remain.  </p>
951) 
952) <p>

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

955) find HTML5 videos.
956) </p>
957) 

958) <hr>
959) 

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

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

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

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

964) 
965) <p>

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

967) on port 9150.

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

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

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

973) </p>
974) 
975) <hr>
976) 
977) <a id="TBBPolipo"></a>
978) <h3><a class="anchor" href="#TBBPolipo">I need an HTTP proxy. Where did
979) Polipo go?</a></h3>
980) 
981) <p>
982) In the past, Tor bundles included an HTTP proxy like Privoxy or Polipo,
983) solely to work around a bug in Firefox that was finally fixed in Firefox
984) 6. Now you don't need a separate HTTP proxy to use Tor, and in fact
985) leaving it out makes you safer because Torbutton has better control over
986) Firefox's interaction with websites.
987) </p>
988) 
989) <p>
990) If you are trying to use some external application with Tor, step zero

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

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

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

994) proxy on port 9050 on Windows, or <a href="#TBBSocksPort">see above</a>
995) for OSX and Linux.
996) </p>
997) 
998) <p>

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

1000) href="http://www.privoxy.org/">privoxy</a>.
1001) However, please realize that this approach is not recommended for novice
1002) users. Privoxy has an <a
1003) href="http://www.privoxy.org/faq/misc.html#TOR">example
1004) configuration</a> of Tor and Privoxy.

1005) </p>
1006) 
1007) <hr>
1008) 

1009) <a id="TBBOtherExtensions"></a>
1010) <h3><a class="anchor" href="#TBBOtherExtensions">Can I install other
1011) Firefox extensions?</a></h3>
1012) 
1013) <p>
1014) Yes. Just install them like normal. But be sure to avoid extensions like

1015) Foxyproxy that screw up your proxy settings. Also, avoid
1016) privacy-invasive

1017) extensions (for example, pretty much anything with the word Toolbar in
1018) its name).
1019) </p>
1020) 

1021) <p>

1022) Generally, extensions that require registration, and/or provide
1023) additional information about websites you are visiting, should be

1024) suspect.
1025) </p>
1026) 
1027) <p>
1028) Extensions you might like include
1029)  <a href="https://addons.mozilla.org/firefox/addon/953">RefControl</a> (referer spoofing),
1030)  <a href="https://addons.mozilla.org/firefox/addon/1474">SafeCache</a>,
1031)  <a href="https://addons.mozilla.org/en-US/firefox/addon/6623">Better Privacy</a>,
1032)  <a href="https://addons.mozilla.org/firefox/addon/1865">AdBlock Plus</a> (EasyPrivacy+EasyList),
1033)  <a href="https://addons.mozilla.org/firefox/addon/82">Cookie Culler</a>,
1034)  <a href="https://addons.mozilla.org/en-US/firefox/addon/9727/">Request Policy</a> and
1035)  <a href="https://addons.mozilla.org/en-US/firefox/addon/certificate-patrol/">Certificate Patrol</a>.

1036) </p>

1037) 

1038) <hr>
1039) 

1040) <a id="TBBJavaScriptEnabled"></a>

1041) <h3><a class="anchor" href="#TBBJavaScriptEnabled">Why is NoScript
1042) configured to allow JavaScript by default in the Tor Browser Bundle?
1043) Isn't that unsafe?</a></h3>

1044) 
1045) <p>
1046) We configure NoScript to allow JavaScript by default in the Tor
1047) Browser Bundle because many websites will not work with JavaScript
1048) disabled.  Most users would give up on Tor entirely if a website
1049) they want to use requires JavaScript, because they would not know
1050) how to allow a website to use JavaScript (or that enabling
1051) JavaScript might make a website work).
1052) </p>
1053) 
1054) <hr>
1055) 
1056) <a id="TBBCanIBlockJS"></a>

1057) <h3><a class="anchor" href="#CanIBlockJS">I'm an expert!  (No, really!)
1058) Can I configure NoScript to block JavaScript by default?</a></h3>

1059) 
1060) <p>
1061) You can configure your copies of Tor Browser Bundle however you want
1062) to.  However, we recommend that even users who know how to use
1063) NoScript leave JavaScript enabled if possible, because a website or
1064) exit node can easily distinguish users who disable JavaScript from
1065) users who use Tor Browser bundle with its default settings (thus
1066) users who disable JavaScript are less anonymous).
1067) </p>
1068) 
1069) <p>
1070) Disabling JavaScript by default, then allowing a few websites to run
1071) scripts, is especially bad for your anonymity: the set of websites
1072) which you allow to run scripts is very likely to <em>uniquely</em>
1073) identify your browser.
1074) </p>
1075) 
1076) <hr>
1077) 

1078) <a id="TBBOtherBrowser"></a>
1079) <h3><a class="anchor" href="#TBBOtherBrowser">I want to use
1080) Chrome/IE/Opera/etc with Tor.</a></h3>
1081) 
1082) <p>
1083) Unfortunately, Torbutton only works with Firefox right now, and without
1084) <a href="https://www.torproject.org/torbutton/en/design/">Torbutton's
1085) extensive privacy fixes</a> there are many ways for websites or other

1086) attackers to recognize you, track you back to your IP address, and so
1087) on.

1088) In short, using any browser besides Tor Browser Bundle with Tor is a
1089) really bad idea.
1090) </p>
1091) 
1092) <p>
1093) We're working with the Chrome team to <a

1094) href="https://blog.torproject.org/blog/google-chrome-incognito-mode-tor-
1095) and-fingerprinting">fix
1096) some bugs and missing APIs in Chrome</a> so it will be possible to write
1097) a
1098) Torbutton for Chrome. No support for any other browser is on the
1099) horizon.

1100) </p>
1101) 
1102) <hr>
1103) 
1104) <a id="TBBCloseBrowser"></a>

1105) <h3><a class="anchor" href="#TBBCloseBrowser">I want to leave Tor
1106) Browser

1107) Bundle running but close the browser.</a></h3>
1108) 
1109) <p>
1110) We're working on a way to make this possible on all platforms. Please
1111) be patient.
1112) </p>
1113) 
1114) <hr>
1115) 

1116) <a id="GoogleCAPTCHA"></a>
1117) <h3><a class="anchor" href="#GoogleCAPTCHA">Google makes me solve a
1118) CAPTCHA or tells me I have spyware installed.</a></h3>

1119) 
1120) <p>
1121) This is a known and intermittent problem; it does not mean that Google
1122) considers Tor to be spyware.
1123) </p>
1124) 
1125) <p>

1126) When you use Tor, you are sending queries through exit relays that are
1127) also

1128) shared by thousands of other users. Tor users typically see this message

1129) when many Tor users are querying Google in a short period of time.
1130) Google

1131) interprets the high volume of traffic from a single IP address (the exit
1132) relay you happened to pick) as somebody trying to "crawl" their website,
1133) so it slows down traffic from that IP address for a short time.
1134) </p>
1135) <p>
1136) An alternate explanation is that Google tries to detect certain
1137) kinds of spyware or viruses that send distinctive queries to Google
1138) Search. It notes the IP addresses from which those queries are received
1139) (not realizing that they are Tor exit relays), and tries to warn any
1140) connections coming from those IP addresses that recent queries indicate
1141) an infection.
1142) </p>
1143) 
1144) <p>

1145) To our knowledge, Google is not doing anything intentionally
1146) specifically

1147) to deter or block Tor use. The error message about an infected machine
1148) should clear up again after a short time.
1149) </p>
1150) 
1151) <p>
1152) Torbutton 1.2.5 (released in mid 2010) detects Google captchas and can
1153) automatically redirect you to a more Tor-friendly search engine such as

1154) DuckDuckGo, ixquick, or Bing.

1155) </p>
1156) 
1157) <hr />
1158) 
1159) <a id="GmailWarning"></a>

1160) <h3><a class="anchor" href="#GmailWarning">Gmail warns me that my
1161) account

1162) may have been compromised.</a></h3>

1163) 
1164) <p>
1165) Sometimes, after you've used Gmail over Tor, Google presents a
1166) pop-up notification that your account may have been compromised.
1167) The notification window lists a series of IP addresses and locations
1168) throughout the world recently used to access your account.
1169) </p>
1170) 
1171) <p>
1172) In general this is a false alarm: Google saw a bunch of logins from

1173) different places, as a result of running the service via Tor, and
1174) decided

1175) it was a good idea to confirm the account was being accessed by it's
1176) rightful owner.
1177) </p>
1178) 
1179) <p>
1180) Even though this may be a biproduct of using the service via tor,
1181) that doesn't mean you can entirely ignore the warning. It is
1182) <i>probably</i> a false positive, but it might not be since it is
1183) possible for someone to hijack your Google cookie.
1184) </p>
1185) 
1186) <p>
1187) Cookie hijacking is possible by either physical access to your computer
1188) or by watching your network traffic.  In theory only physical access
1189) should compromise your system because Gmail and similar services
1190) should only send the cookie over an SSL link. In practice, alas, it's <a

1191) href="http://fscked.org/blog/fully-automated-active-https-cookie-
1192) hijacking">

1193) way more complex than that</a>.
1194) </p>
1195) 
1196) <p>
1197) And if somebody <i>did</i> steal your google cookie, they might end
1198) up logging in from unusual places (though of course they also might
1199) not). So the summary is that since you're using Tor, this security
1200) measure that Google uses isn't so useful for you, because it's full of
1201) false positives. You'll have to use other approaches, like seeing if
1202) anything looks weird on the account, or looking at the timestamps for
1203) recent logins and wondering if you actually logged in at those times.
1204) </p>
1205) 
1206) <hr>
1207) 

1208) <a id="torrc"></a>

1209) <h3><a class="anchor" href="#torrc">I'm supposed to "edit my torrc".
1210) What does that mean?</a></h3>

1211) 
1212) <p>
1213) Tor installs a text file called torrc that contains configuration
1214) instructions for how your Tor program should behave. The default
1215) configuration should work fine for most Tor users. Users of Vidalia can
1216) make common changes through the Vidalia interface &mdash; only advanced
1217) users should need to modify their torrc file directly.
1218) </p>

1219) <p>

1220) Tor Browser Bundle users should edit your torrc through Vidalia. Open
1221) the
1222) Vidalia Control Panel. Choose Settings. Choose Advanced. Click the
1223) button

1224) labelled "Edit current torrc". Remember to make sure the checkbox for
1225) "Save Settings." is checked. Hit the Ok button and you are done.
1226) </p>

1227) <p>

1228) Otherwise, you will need to edit the file manually.

1229) The location of your torrc file depends on the way you installed Tor:
1230) </p>
1231) <ul>

1232) <li>If you installed Tor Browser Bundle, look for
1233) <code>Data/Tor/torrc</code> inside your Tor Browser Bundle directory.
1234) </li>

1235) <li>On Windows, if you installed a Tor bundle with Vidalia, you can
1236) find your torrc file in the Start menu under Programs -&gt; Vidalia
1237) Bundle -&gt; Tor, or you can find it by hand in <code>\Documents and
1238) Settings\<i>username</i>\Application Data\Vidalia\torrc</code>. If you
1239) installed Tor without Vidalia, you can find your torrc in the Start
1240) menu under Programs -&gt; Tor, or manually in either <code>\Documents
1241) and Settings\Application Data\tor\torrc</code> or <code>\Documents and
1242) Settings\<i>username</i>\Application Data\tor\torrc</code>.
1243) </li>
1244) <li>On OS X, if you use Vidalia, edit
1245) <code>~/.vidalia/torrc</code>. Otherwise, open your favorite text editor
1246) and load <code>/Library/Tor/torrc</code>.
1247) </li>
1248) <li>On Unix, if you installed a pre-built package, look for
1249) <code>/etc/tor/torrc</code> or <code>/etc/torrc</code> or consult your
1250) package's documentation.
1251) </li>
1252) <li>Finally, if you installed from source, you may not have a torrc
1253) installed yet: look in <code>/usr/local/etc/</code> and note that you

1254) may need to manually copy <code>torrc.sample</code> to
1255) <code>torrc</code>.

1256) </li>
1257) </ul>
1258) 
1259) <p>
1260) If you use Vidalia, be sure to exit both Tor and Vidalia before you edit

1261) your torrc file manually. Otherwise Vidalia might overwrite your
1262) changes.

1263) </p>
1264) 
1265) <p>
1266) Once you've changed your torrc, you will need to restart Tor for the
1267) changes to take effect. (For advanced users on OS X and Unix, note that

1268) you actually only need to send Tor a HUP signal, not actually restart
1269) it.)

1270) </p>
1271) 
1272) <p>
1273) For other configuration options you can use, look at the <a href="<page
1274) docs/tor-manual>">Tor manual page</a>. Remember, all lines beginning
1275) with # in torrc are treated as comments and have no effect on Tor's
1276) configuration.
1277) </p>
1278) 
1279) <hr>
1280) 

1281) <a id="Logs"></a>

1282) <h3><a class="anchor" href="#Logs">How do I set up logging, or see Tor's
1283) logs?</a></h3>

1284) 
1285) <p>

1286) If you installed a Tor bundle that includes Vidalia, then Vidalia has a

1287) window called "Message Log" that will show you Tor's log messages. Click
1288) on "Advanced" to see more details. You can click on "Settings" to change
1289) your log verbosity or save the messages to a file. You're all set.

1290) </p>
1291) 
1292) <p>
1293) If you're not using Vidalia, you'll have to go find the log files by

1294) hand. Here are some likely places for your logs to be:

1295) </p>
1296) 
1297) <ul>
1298) <li>On OS X, Debian, Red Hat, etc, the logs are in /var/log/tor/
1299) </li>

1300) <li>On Windows, there are no default log files currently. If you enable
1301) logs in your torrc file, they default to <code>\username\Application
1302) Data\tor\log\</code> or <code>\Application Data\tor\log\</code>
1303) </li>
1304) <li>If you compiled Tor from source, by default your Tor logs to <a
1305) href="http://en.wikipedia.org/wiki/Standard_streams">"stdout"</a>
1306) at log-level notice. If you enable logs in your torrc file, they
1307) default to <code>/usr/local/var/log/tor/</code>.

1308) </li>
1309) </ul>
1310) 
1311) <p>

1312) To change your logging setup by hand, <a href="#torrc">edit your
1313) torrc</a>

1314) and find the section (near the top of the file) which contains the
1315) following line:

1316) </p>
1317) 
1318) <pre>

1319) \## Logs go to stdout at level "notice" unless redirected by something
1320) \## else, like one of the below lines.

1321) </pre>

1322) 
1323) <p>

1324) For example, if you want Tor to send complete debug, info, notice, warn,

1325) and err level messages to a file, append the following line to the end
1326) of the section:
1327) </p>
1328) 
1329) <pre>
1330) Log debug file c:/program files/tor/debug.log
1331) </pre>
1332) 
1333) <p>

1334) Replace <code>c:/program files/tor/debug.log</code> with a directory
1335) and filename for your Tor log.

1336) </p>
1337) 
1338) <hr>
1339) 

1340) <a id="DoesntWork"></a>

1341) <h3><a class="anchor" href="#DoesntWork">I installed Tor but it's not
1342) working.</a></h3>

1343) 
1344) <p>

1345) Once you've got the Tor bundle up and running, the first question to
1346) ask is whether your Tor client is able to establish a circuit.

1347) </p>
1348) 
1349) <p>If Tor can establish a circuit, the onion icon in

1350) Vidalia will turn green (and if you're running Tor Browser Bundle, it
1351) will
1352) automatically launch a browser for you). You can also check in the
1353) Vidalia

1354) Control Panel to make sure it says "Connected to the Tor
1355) network!" under Status. For those not using Vidalia, check your <a

1356) href="#Logs">Tor logs</a> for

1357) a line saying that Tor "has successfully opened a circuit. Looks like
1358) client functionality is working."
1359) </p>
1360) 
1361) <p>
1362) If Tor can't establish a circuit, here are some hints:
1363) </p>
1364) 
1365) <ol>
1366) <li>Are you sure Tor is running? If you're using Vidalia, you may have
1367) to click on the onion and select "Start" to launch Tor.</li>
1368) <li>Check your system clock. If it's more than a few hours off, Tor will

1369) refuse to build circuits. For Microsoft Windows users, synchronize your
1370) clock under the clock -> Internet time tab. In addition, correct the

1371) day and date under the 'Date & Time' Tab. Also make sure your time
1372) zone is correct.</li>

1373) <li>Is your Internet connection <a href="#FirewallPorts">firewalled
1374) by port</a>, or do you normally need to use a <a

1375) href="<wikifaq>#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</
1376) a>?

1377) </li>

1378) <li>Are you running programs like Norton Internet Security or SELinux
1379) that

1380) block certain connections, even though you don't realize they do? They
1381) could be preventing Tor from making network connections.</li>
1382) <li>Are you in China, or behind a restrictive corporate network firewall
1383) that blocks the public Tor relays? If so, you should learn about <a

1384) href="<page docs/bridges>">Tor bridges</a>.</li>

1385) <li>Check your <a href="#Logs">Tor logs</a>. Do they give you any hints
1386) about what's going wrong?</li>

1387) </ol>
1388) 
1389) <hr />
1390) 
1391) <a id="VidaliaPassword"></a>

1392) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for a
1393) password at start.</a></h3>

1394) 
1395) <p>
1396) Vidalia interacts with the Tor software via Tor's "control port". The
1397) control port lets Vidalia receive status updates from Tor, request a new
1398) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
1399) Vidalia sets a random password for Tor's control port to prevent other
1400) applications from also connecting to the control port and potentially
1401) compromising your anonymity.
1402) </p>
1403) 
1404) <p>
1405) Usually this process of generating and setting a random control password
1406) happens in the background. There are three common situations, though,
1407) where Vidalia may prompt you for a password:
1408) </p>
1409) 
1410) <ol>
1411) <li>You're already running Vidalia and Tor. For example, this situation
1412) can happen if you installed the Vidalia bundle and now you're trying to
1413) run the Tor Browser Bundle. In that case, you'll need to close the old
1414) Vidalia and Tor before you can run this one.
1415) </li>
1416) <li>Vidalia crashed, but left Tor running with the last known random
1417) password. After you restart Vidalia, it generates a new random password,

1418) but Vidalia can't talk to Tor, because the random passwords are
1419) different.

1420) <br />

1421) If the dialog that prompts you for a control password has a Reset
1422) button,

1423) you can click the button and Vidalia will restart Tor with a new random
1424) control password.
1425) <br />
1426) If you do not see a Reset button, or if Vidalia is unable to restart
1427) Tor for you, you can still fix the problem manually. Simply go into your
1428) process or task manager, and terminate the Tor process. Then use Vidalia
1429) to restart Tor and all will work again.
1430) </li>
1431) <li>You had previously set Tor to run as a Windows NT service. When Tor
1432) is set to
1433) run as a service, it starts up when the system boots. If you configured
1434) Tor to start as a service through Vidalia, a random password was set
1435) and saved in Tor. When you reboot, Tor starts up and uses the random
1436) password it saved. You login and start up Vidalia. Vidalia attempts to
1437) talk to the already running Tor. Vidalia generates a random password,
1438) but it is different than the saved password in the Tor service.
1439) <br />
1440) You need to reconfigure Tor to not be a service. See the FAQ entry on

1441) <a href="<wikifaq>#HowdoIrunmyTorrelayasanNTservice">running Tor as a
1442) Windows NT service</a>

1443) for more information on how to remove the Tor service.
1444) </li>
1445) </ol>
1446) 

1447)     <hr>

1448) 

1449)     <a id="ChooseEntryExit"></a>

1450)     <h3><a class="anchor" href="#ChooseEntryExit">Can I control which
1451) nodes (or country) are used for entry/exit?</a></h3>

1452) 

1453)     <p>

1454)     Yes. You can set preferred entry and exit nodes as well as
1455)     inform Tor which nodes you do not want to use.

1456)     The following options can be added to your config file <a
1457)     href="#torrc">"torrc"</a> or specified on the command line:

1458)     </p>
1459)     <dl>
1460)       <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>

1461)         <dd>A list of preferred nodes to use for the first hop in the
1462) circuit, if possible.

1463)         </dd>
1464)       <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>

1465)         <dd>A list of preferred nodes to use for the last hop in the
1466) circuit, if possible.

1467)         </dd>
1468)       <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>

1469)         <dd>A list of nodes to never use when building a circuit.

1470)         </dd>
1471)       <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>

1472)         <dd>A list of nodes to never use when picking an exit.

1473)             Nodes listed in <tt>ExcludeNodes</tt> are automatically in
1474) this list.

1475)         </dd>
1476)     </dl>
1477)     <p>

1478)     <em>We recommend you do not use these</em>

1479)     — they are intended for testing and may disappear in future
1480) versions.

1481)     You get the best security that Tor can provide when you leave the
1482)     route selection to Tor; overriding the entry / exit nodes can mess
1483)     up your anonymity in ways we don't understand.

1484)     </p>
1485)     <p>

1486)     Note also that not every circuit is used to deliver traffic outside of the Tor network. It is normal to see non-exit circuits (such as those used to connect to hidden services, those that do directory fetches, those used for relay reachability self-tests, and so on) that end at a non-exit node. To keep a node from being used entirely, see <tt>ExcludeNodes</tt> and <tt>StrictNodes</tt> in the <a href="<page docs/tor-manual>">manual</a>.

1487)     </p>
1488)     <p>

1489)     Instead of <tt>$fingerprint</tt> you can also specify a <a

1490) 
1491) href="https://secure.wikimedia.org/wikipedia/en/wiki/ISO_3166-1_alpha-2"
1492) >2

1493)     letter ISO3166 country code</a> in curly braces (for example <tt>{de}</tt>),

1494)     or an ip address pattern (for example 255.254.0.0/8), or a node
1495)     nickname. Make sure there are no spaces between the commas and the
1496)     list items.

1497)     </p>
1498)     <p>

1499)     If you want to access a service directly through Tor's Socks
1500) interface

1501)     (eg. using ssh via connect.c), another option is to set up an

1502)     internal mapping in your configuration file using
1503) <tt>MapAddress</tt>.

1504)     See the manual page for details.
1505)     </p>

1506) 

1507)     <hr>

1508) 

1509) <a id="FirewallPorts"></a>

1510) <h3><a class="anchor" href="#FirewallPorts">My firewall only allows a
1511) few outgoing ports.</a></h3>

1512) 
1513) <p>
1514) If your firewall works by blocking ports, then you can tell Tor to only

1515) use the ports that your firewall permits by adding "FascistFirewall 1"
1516) to

1517) your <a href="<page docs/faq>#torrc">torrc

1518) configuration file</a>, or by clicking "My firewall only lets me connect
1519) to certain ports" in Vidalia's Network Settings window.
1520) </p>
1521) 
1522) <p>
1523) By default, when you set this Tor assumes that your firewall allows only
1524) port 80 and port 443 (HTTP and HTTPS respectively). You can select a
1525) different set of ports with the FirewallPorts torrc option.
1526) </p>
1527) 
1528) <p>
1529) If you want to be more fine-grained with your controls, you can also
1530) use the ReachableAddresses config options, e.g.:
1531) </p>
1532) 
1533) <pre>
1534)   ReachableDirAddresses *:80
1535)   ReachableORAddresses *:443
1536) </pre>
1537) 
1538) <hr>

1539) 

1540)     <a id="RelayFlexible"></a>

1541)     <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
1542) need to be?</a></h3>

1543) 

1544)     <p>
1545)     We aim to make setting up a Tor relay easy and convenient:
1546)     </p>

1547) 

1548)     <ul>
1549)     <li>Tor has built-in support for <a

1550)     href="<wikifaq>#WhatbandwidthshapingoptionsareavailabletoTorrelays">

1551)     rate limiting</a>. Further, if you have a fast
1552)     link but want to limit the number of bytes per
1553)     day (or week or month) that you donate, check out the <a

1554) 
1555) href="<wikifaq>#HowcanIlimitthetotalamountofbandwidthusedbymyTorrelay">
1556) hibernation

1557)     feature</a>.
1558)     </li>

1559)     <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a>
1560) that
1561)     specifies what sort of outbound connections are allowed or refused
1562) from
1563)     that relay. If you are uncomfortable allowing people to exit from
1564) your
1565)     relay, you can set it up to only allow connections to other Tor
1566) relays.

1567)     </li>
1568)     <li>It's fine if the relay goes offline sometimes. The directories
1569)     notice this quickly and stop advertising the relay. Just try to make
1570)     sure it's not too often, since connections using the relay when it
1571)     disconnects will break.
1572)     </li>
1573)     <li>We can handle relays with dynamic IPs just fine &mdash; simply
1574)     leave the Address config option blank, and Tor will try to guess.
1575)     </li>
1576)     <li>If your relay is behind a NAT and it doesn't know its public
1577)     IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

1578)     forwarding. Forwarding TCP connections is system dependent but

1579)     <a href="<wikifaq>#ImbehindaNATFirewall">this FAQ entry</a>

1580)     offers some examples on how to do this.
1581)     </li>
1582)     <li>Your relay will passively estimate and advertise its recent

1583)     bandwidth capacity, so high-bandwidth relays will attract more users
1584) than
1585)     low-bandwidth ones. Therefore having low-bandwidth relays is useful
1586) too.

1587)     </li>
1588)     </ul>

1589) 

1590)     <hr>

1591) 

1592)     <a id="RunARelayBut"></a>
1593)     <a id="ExitPolicies"></a>

1594)     <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I
1595) don't want to deal with abuse issues.</a></h3>

1596) 

1597)     <p>
1598)     Great. That's exactly why we implemented exit policies.
1599)     </p>

1600) 

1601)     <p>
1602)     Each Tor relay has an exit policy that specifies what sort of

1603)     outbound connections are allowed or refused from that relay. The
1604) exit

1605)     policies are propagated to Tor clients via the directory, so clients
1606)     will automatically avoid picking exit relays that would refuse to
1607)     exit to their intended destination. This way each relay can decide
1608)     the services, hosts, and networks he wants to allow connections to,

1609)     based on abuse potential and his own situation. Read the FAQ entry
1610) on
1611)     <a href="<page docs/faq-abuse>#TypicalAbuses">issues you might
1612) encounter</a>

1613)     if you use the default exit policy, and then read Mike Perry's

1614)     <a href="<blog>tips-running-exit-node-minimal-harassment">tips

1615)     for running an exit node with minimal harassment</a>.
1616)     </p>

1617) 

1618)     <p>

1619)     The default exit policy allows access to many popular services

1620)     (e.g. web browsing), but <a
1621) href="<wikifaq>#Istherealistofdefaultexitports">restricts</a>

1622)     some due to abuse potential (e.g. mail) and some since
1623)     the Tor network can't handle the load (e.g. default
1624)     file-sharing ports). You can change your exit policy

1625)     using Vidalia's "Sharing" tab, or by manually editing your

1626)     <a href="<page docs/faq>#torrc">torrc</a>

1627)     file. If you want to avoid most if not all abuse potential, set it
1628) to
1629)     "reject *:*" (or un-check all the boxes in Vidalia). This setting
1630) means
1631)     that your relay will be used for relaying traffic inside the Tor
1632) network,

1633)     but not for connections to external websites or other services.
1634)     </p>

1635) 

1636)     <p>

1637)     If you do allow any exit connections, make sure name resolution
1638) works

1639)     (that is, your computer can resolve Internet addresses correctly).

1640)     If there are any resources that your computer can't reach (for
1641) example,

1642)     you are behind a restrictive firewall or content filter), please

1643)     explicitly reject them in your exit policy — otherwise Tor
1644) users

1645)     will be impacted too.
1646)     </p>

1647) 

1648)     <hr>

1649) 

1650)     <a id="RelayOrBridge"></a>

1651)     <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal
1652) relay or bridge relay?</a></h3>

1653) 

1654)     <p><a href="<page docs/bridges>">Bridge relays</a> (or "bridges" for
1655) short)
1656)     are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't

1657)     listed in the public Tor directory.

1658)     That means that ISPs or governments trying to block access to the

1659)     Tor network can't simply block all bridges.

1660)     </p>

1661) 

1662)     <p>Being a normal relay vs being a bridge relay is almost the same
1663)     configuration: it's just a matter of whether your relay is listed

1664)     publicly or not.

1665)     </p>

1666) 

1667)     <p>

1668)     So bridges are useful a) for Tor users in oppressive regimes,

1669)     and b) for people who want an extra layer of security

1670)     because they're worried somebody will recognize that it's a public
1671)     Tor relay IP address they're contacting.

1672)     </p>

1673) 

1674)     <p>
1675)     Several countries, including China and Iran, have found ways to

1676)     detect and block connections to Tor bridges.

1677)     <a href="<page projects/obfsproxy>">Obfsproxy</a> bridges address

1678)     this by adding another layer of obfuscation.

1679)     </p>
1680) 

1681)     <p>So should you run a normal relay or bridge relay? If you have
1682) lots

1683)     of bandwidth, you should definitely run a normal relay.
1684)     If you're willing

1685)     to <a href="#ExitPolicies">be an exit</a>, you should definitely
1686)     run a normal relay, since we need more exits. If you can't be an
1687)     exit and only have a little bit of bandwidth, be a bridge. Thanks
1688)     for volunteering!

1689)     </p>

1690) 

1691)     <hr>

1692) 

1693) <a id="MultipleRelays"></a>

1694) <h3><a class="anchor" href="#MultipleRelays">I want to run more than one
1695) relay.</a></h3>

1696) 
1697) <p>
1698) Great. If you want to run several relays to donate more to the network,
1699) we're happy with that. But please don't run more than a few dozen on
1700) the same network, since part of the goal of the Tor network is dispersal
1701) and diversity.
1702) </p>
1703) 
1704) <p>
1705) If you do decide to run more than one relay, please set the "MyFamily"

1706) config option in the <a href="#torrc">torrc</a> of each relay, listing
1707) all the relays (comma-separated) that are under your control:

1708) </p>
1709) 
1710) <pre>
1711)     MyFamily $fingerprint1,$fingerprint2,$fingerprint3
1712) </pre>
1713) 
1714) <p>
1715) where each fingerprint is the 40 character identity fingerprint (without

1716) spaces). You can also list them by nickname, but fingerprint is safer.
1717) Be

1718) sure to prefix the digest strings with a dollar sign ('$') so that the
1719) digest is not confused with a nickname in the config file.
1720) </p>
1721) 
1722) <p>
1723) That way clients will know to avoid using more than one of your relays
1724) in a single circuit. You should set MyFamily if you have administrative
1725) control of the computers or of their network, even if they're not all in
1726) the same geographic location.
1727) </p>
1728) 
1729)     <hr>
1730) 

1731)     <a id="RelayMemory"></a>

1732)     <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using
1733) so much memory?</a></h3>

1734) 

1735)     <p>If your Tor relay is using more memory than you'd like, here are
1736) some

1737)     tips for reducing its footprint:
1738)     </p>

1739) 

1740)     <ol>
1741)     <li>If you're on Linux, you may be encountering memory fragmentation

1742)     bugs in glibc's malloc implementation. That is, when Tor releases
1743) memory
1744)     back to the system, the pieces of memory are fragmented so they're
1745) hard
1746)     to reuse. The Tor tarball ships with OpenBSD's malloc
1747) implementation,
1748)     which doesn't have as many fragmentation bugs (but the tradeoff is
1749) higher
1750)     CPU load). You can tell Tor to use this malloc implementation
1751) instead:

1752)     <tt>./configure --enable-openbsd-malloc</tt></li>

1753) 

1754)     <li>If you're running a fast relay, meaning you have many TLS
1755) connections

1756)     open, you are probably losing a lot of memory to OpenSSL's internal
1757)     buffers (38KB+ per socket). We've patched OpenSSL to <a

1758) 
1759) href="https://lists.torproject.org/pipermail/tor-dev/2008-June/001519.
1760) html">release

1761)     unused buffer memory more aggressively</a>. If you update to OpenSSL

1762)     1.0.0 or newer, Tor's build process will automatically recognize and
1763) use

1764)     this feature.</li>

1765) 

1766)     <li>If you're running on Solaris, OpenBSD, NetBSD, or
1767)     old FreeBSD, Tor is probably forking separate processes
1768)     rather than using threads. Consider switching to a <a

1769)     href="<wikifaq>#WhydoesntmyWindowsorotherOSTorrelayrunwell">better

1770)     operating system</a>.</li>

1771) 

1772)     <li>If you still can't handle the memory load, consider reducing the

1773)     amount of bandwidth your relay advertises. Advertising less
1774) bandwidth

1775)     means you will attract fewer users, so your relay shouldn't grow
1776)     as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1777)     page.</li>

1778) 

1779)     </ol>

1780) 

1781)     <p>

1782)     All of this said, fast Tor relays do use a lot of ram. It is not
1783) unusual

1784)     for a fast exit relay to use 500-1000 MB of memory.
1785)     </p>

1786) 

1787)     <hr>

1788) 

1789)     <a id="WhyNotNamed"></a>

1790)     <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not
1791) named?</a></h3>

1792) 

1793)     <p>

1794)     We currently use these metrics to determine if your relay should be
1795) named:<br>

1796)     </p>
1797)     <ul>

1798)     <li>The name is not currently mapped to a different key. Existing
1799) mappings

1800)     are removed after 6 months of inactivity from a relay.</li>
1801)     <li>The relay must have been around for at least two weeks.</li>

1802)     <li>No other router may have wanted the same name in the past
1803) month.</li>

1804)     </ul>

1805) 

1806)     <hr>

1807) 

1808)     <a id="RelayDonations"></a>

1809)     <h3><a class="anchor" href="#RelayDonations">Can I donate for a
1810)     relay rather than run my own?</a></h3>

1811) 
1812)     <p>

1813)     Sure! We recommend these non-profit charities that are happy to turn

1814)     your donations into better speed and anonymity for the Tor network:
1815)     </p>
1816)     <ul>
1817)     <li><a href="https://www.torservers.net/">torservers.net</a>
1818)     is a German charitable non-profit that runs a wide variety of

1819)     exit relays worldwide. They also like donations of bandwidth from
1820)     ISPs.</li>

1821)     <li><a

1822) href="https://www.noisebridge.net/wiki/Noisebridge_Tor">Noisebridge</a>

1823)     is a US-based 501(c)(3) non-profit that collects donations and turns

1824)     them into more US-based exit relay capacity.</li>
1825)     <li><a href="https://nos-oignons.net/">Nos Oignons</a> is a French
1826)     charitable non-profit that runs fast exit relays in France.</li>

1827)     </ul>
1828) 
1829)     <p>
1830)     These organizations are not the same as <a href="<page
1831)     donate/donate>">The Tor Project, Inc</a>, but we consider that a

1832)     good thing. They're both run by nice people who are part of the
1833)     Tor community.

1834)     </p>
1835) 
1836)     <p>
1837)     Note that there can be a tradeoff here between anonymity and

1838)     performance. The Tor network's anonymity comes in part from
1839) diversity,

1840)     so if you are in a position to run your own relay, you will be

1841)     improving Tor's anonymity more than by donating. At the same time
1842)     though, economies

1843)     of scale for bandwidth mean that combining many small donations into

1844)     several larger relays is more efficient at improving network

1845)     performance. Improving anonymity and improving performance are both
1846)     worthwhile goals, so however you can help is great!
1847)     </p>
1848) 
1849)     <hr>
1850) 

1851)     <a id="KeyManagement"></a>

1852)     <h3><a class="anchor" href="#KeyManagement">Tell me about all the
1853) keys Tor uses.</a></h3>

1854) 

1855)     <p>
1856)     Tor uses a variety of different keys, with three goals in mind: 1)
1857)     encryption to ensure privacy of data within the Tor network, 2)
1858)     authentication so clients know they're

1859)     talking to the relays they meant to talk to, and 3) signatures to
1860) make

1861)     sure all clients know the same set of relays.
1862)     </p>

1863) 

1864)     <p>

1865)     <b>Encryption</b>: first, all connections in Tor use TLS link
1866) encryption,

1867)     so observers can't look inside to see which circuit a given cell is

1868)     intended for. Further, the Tor client establishes an ephemeral
1869) encryption

1870)     key with each relay in the circuit; these extra layers of encryption
1871)     mean that only the exit relay can read

1872)     the cells. Both sides discard the circuit key when the circuit ends,

1873)     so logging traffic and then breaking into the relay to discover the
1874) key

1875)     won't work.
1876)     </p>

1877) 

1878)     <p>
1879)     <b>Authentication</b>:
1880)     Every Tor relay has a public decryption key called the "onion key".

1881)     Each relay rotates its onion key once a week.

1882)     When the Tor client establishes circuits, at each step it <a

1883) 
1884) href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands

1885)     that the Tor relay prove knowledge of its onion key</a>. That way
1886)     the first node in the path can't just spoof the rest of the path.

1887)     Because the Tor client chooses the path, it can make sure to get
1888)     Tor's "distributed trust" property: no single relay in the path can
1889)     know about both the client and what the client is doing.

1890)     </p>

1891) 

1892)     <p>
1893)     <b>Coordination</b>:

1894)     How do clients know what the relays are, and how do they know that
1895) they
1896)     have the right keys for them? Each relay has a long-term public
1897) signing
1898)     key called the "identity key". Each directory authority additionally
1899) has a

1900)     "directory signing key". The directory authorities <a

1901)     href="<specblob>dir-spec.txt">provide a signed list</a>

1902)     of all the known relays, and in that list are a set of certificates
1903) from
1904)     each relay (self-signed by their identity key) specifying their
1905) keys,
1906)     locations, exit policies, and so on. So unless the adversary can
1907) control

1908)     a majority of the directory authorities (as of 2012 there are 8

1909)     directory authorities), he can't trick the Tor client into using
1910)     other Tor relays.

1911)     </p>

1912) 

1913)     <p>

1914)     How do clients know what the directory authorities are? The Tor
1915) software
1916)     comes with a built-in list of location and public key for each
1917) directory
1918)     authority. So the only way to trick users into using a fake Tor
1919) network

1920)     is to give them a specially modified version of the software.
1921)     </p>

1922) 

1923)     <p>
1924)     How do users know they've got the right software? When we distribute
1925)     the source code or a package, we digitally sign it with <a
1926)     href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a
1927)     href="<page docs/verifying-signatures>">instructions
1928)     on how to check Tor's signatures</a>.
1929)     </p>

1930) 

1931)     <p>

1932)     In order to be certain that it's really signed by us, you need to
1933) have
1934)     met us in person and gotten a copy of our GPG key fingerprint, or
1935) you
1936)     need to know somebody who has. If you're concerned about an attack
1937) on
1938)     this level, we recommend you get involved with the security
1939) community

1940)     and start meeting people.
1941)     </p>

1942) 

1943)     <hr>

1944) 

1945) <a id="EntryGuards"></a>

1946) <h3><a class="anchor" href="#EntryGuards">What are Entry
1947) Guards?</a></h3>

1948) 
1949) <p>
1950) Tor (like all current practical low-latency anonymity designs) fails
1951) when the attacker can see both ends of the communications channel. For

1952) example, suppose the attacker controls or watches the Tor relay you
1953) choose
1954) to enter the network, and also controls or watches the website you
1955) visit. In

1956) this case, the research community knows no practical low-latency design
1957) that can reliably stop the attacker from correlating volume and timing
1958) information on the two sides.
1959) </p>
1960) 
1961) <p>
1962) So, what should we do? Suppose the attacker controls, or can observe,

1963) <i>C</i> relays. Suppose there are <i>N</i> relays total. If you select
1964) new entry and exit relays each time you use the network, the attacker
1965) will be able to correlate all traffic you send with probability
1966) <i>(c/n)<sup>2</sup></i>. But profiling is, for most users, as bad
1967) as being traced all the time: they want to do something often without
1968) an attacker noticing, and the attacker noticing once is as bad as the

1969) attacker noticing more often. Thus, choosing many random entries and
1970) exits

1971) gives the user no chance of escaping profiling by this kind of attacker.

1972) </p>
1973) 
1974) <p>

1975) The solution is "entry guards": each Tor client selects a few relays at
1976) random

1977) to use as entry points, and uses only those relays for her first hop. If
1978) those relays are not controlled or observed, the attacker can't win,
1979) ever, and the user is secure. If those relays <i>are</i> observed or
1980) controlled by the attacker, the attacker sees a larger <i>fraction</i>

1981) of the user's traffic — but still the user is no more profiled
1982) than

1983) before. Thus, the user has some chance (on the order of <i>(n-c)/n</i>)
1984) of avoiding profiling, whereas she had none before.

1985) </p>
1986) 
1987) <p>

1988) You can read more at <a href="http://freehaven.net/anonbib/#wright02">An
1989) Analysis of the Degradation of Anonymous Protocols</a>, <a
1990) href="http://freehaven.net/anonbib/#wright03">Defending Anonymous
1991) Communication Against Passive Logging Attacks</a>, and especially
1992) <a href="http://freehaven.net/anonbib/#hs-attack06">Locating Hidden
1993) Servers</a>.

1994) </p>
1995) 
1996) <p>
1997) Restricting your entry nodes may also help against attackers who want
1998) to run a few Tor nodes and easily enumerate all of the Tor user IP
1999) addresses. (Even though they can't learn what destinations the users
2000) are talking to, they still might be able to do bad things with just a

2001) list of users.) However, that feature won't really become useful until
2002) we move to a "directory guard" design as well.

2003) </p>
2004) 
2005)     <hr>
2006) 

2007)     <a id="EverybodyARelay"></a>

2008)     <h3><a class="anchor" href="#EverybodyARelay">You should make every
2009) Tor user be a relay.</a></h3>

2010) 

2011)     <p>
2012)     Requiring every Tor user to be a relay would help with scaling the

2013)     network to handle all our users, and <a
2014)     href="<wikifaq>#DoIgetbetteranonymityifIrunarelay">running a Tor

2015)     relay may help your anonymity</a>. However, many Tor users cannot be
2016) good
2017)     relays &mdash; for example, some Tor clients operate from behind
2018) restrictive
2019)     firewalls, connect via modem, or otherwise aren't in a position
2020) where they

2021)     can relay traffic. Providing service to these clients is a critical

2022)     part of providing effective anonymity for everyone, since many Tor
2023) users
2024)     are subject to these or similar constraints and including these
2025) clients

2026)     increases the size of the anonymity set.
2027)     </p>

2028) 

2029)     <p>

2030)     That said, we do want to encourage Tor users to run relays, so what
2031) we
2032)     really want to do is simplify the process of setting up and
2033) maintaining
2034)     a relay. We've made a lot of progress with easy configuration in the
2035) past
2036)     few years: Vidalia has an easy relay configuration interface, and
2037) supports
2038)     uPnP too. Tor is good at automatically detecting whether it's
2039) reachable and

2040)     how much bandwidth it can offer.
2041)     </p>

2042) 

2043)     <p>

2044)     There are five steps we need to address before we can do this
2045) though:

2046)     </p>

2047) 

2048)     <p>
2049)     First, we need to make Tor stable as a relay on all common
2050)     operating systems. The main remaining platform is Windows,

2051)     and we're mostly there. See Section 4.1 of <a

2052) 
2053) href="https://www.torproject.org/press/2008-12-19-roadmap-press-release"
2054) >our

2055)     development roadmap</a>.
2056)     </p>

2057) 

2058)     <p>
2059)     Second, we still need to get better at automatically estimating
2060)     the right amount of bandwidth to allow. See item #7 on the

2061)     <a href="<page getinvolved/volunteer>#Research">research section of
2062) the

2063)     volunteer page</a>: "Tor doesn't work very well when relays
2064)     have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

2065)     href="<page docs/faq>#TransportIPnotTCP">switching

2066)     to UDP transport</a> is the simplest answer here &mdash; which alas
2067) is

2068)     not a very simple answer at all.
2069)     </p>

2070) 

2071)     <p>
2072)     Third, we need to work on scalability, both of the network (how to
2073)     stop requiring that all Tor relays be able to connect to all Tor
2074)     relays) and of the directory (how to stop requiring that all Tor
2075)     users know about all Tor relays). Changes like this can have large
2076)     impact on potential and actual anonymity. See Section 5 of the <a
2077)     href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper
2078)     for details. Again, UDP transport would help here.
2079)     </p>

2080) 

2081)     <p>
2082)     Fourth, we need to better understand the risks from
2083)     letting the attacker send traffic through your relay while
2084)     you're also initiating your own anonymized traffic. <a
2085)     href="http://freehaven.net/anonbib/#back01">Three</a> <a
2086)     href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
2087)     <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
2088)     describe ways to identify the relays in a circuit by running traffic

2089)     through candidate relays and looking for dips in the traffic while
2090) the
2091)     circuit is active. These clogging attacks are not that scary in the
2092) Tor
2093)     context so long as relays are never clients too. But if we're trying
2094) to
2095)     encourage more clients to turn on relay functionality too (whether
2096) as
2097)     <a href="<page docs/bridges>">bridge relays</a> or as normal
2098) relays), then
2099)     we need to understand this threat better and learn how to mitigate
2100) it.
2101)     </p>
2102) 
2103)     <p>
2104)     Fifth, we might need some sort of incentive scheme to encourage
2105) people
2106)     to relay traffic for others, and/or to become exit nodes. Here are
2107) our

2108)     <a href="<blog>two-incentive-designs-tor">current

2109)     thoughts on Tor incentives</a>.
2110)     </p>

2111) 

2112)     <p>
2113)     Please help on all of these!
2114)     </p>

2115) 

2116) <hr>
2117) 
2118) <a id="TransportIPnotTCP"></a>

2119) <h3><a class="anchor" href="#TransportIPnotTCP">You should transport all
2120) IP packets, not just TCP packets.</a></h3>

2121) 
2122) <p>

2123) This would be handy, because it would make Tor better able to handle
2124) new protocols like VoIP, it could solve the whole need to socksify
2125) applications, and it would solve the fact that exit relays need to

2126) allocate a lot of file descriptors to hold open all the exit
2127) connections.

2128) </p>
2129) 
2130) <p>

2131) We're heading in this direction: see <a
2132) href="https://trac.torproject.org/projects/tor/ticket/1855">this trac
2133) ticket</a> for directions we should investigate. Some of the hard
2134) problems are:

2135) </p>
2136) 

2137) <ol>

2138) <li>IP packets reveal OS characteristics. We would still need to do
2139) IP-level packet normalization, to stop things like TCP fingerprinting
2140) attacks. Given the diversity and complexity of TCP stacks, along with <a

2141) href="<wikifaq>#DoesTorresistremotephysicaldevicefingerprinting">device

2142) fingerprinting attacks</a>, it looks like our best bet is shipping our
2143) own user-space TCP stack.

2144) </li>

2145) <li>Application-level streams still need scrubbing. We will still need
2146) user-side applications like Torbutton. So it won't become just a matter
2147) of capturing packets and anonymizing them at the IP layer.

2148) </li>
2149) <li>Certain protocols will still leak information. For example, we must
2150) rewrite DNS requests so they are delivered to an unlinkable DNS server
2151) rather than the DNS server at a user's ISP; thus, we must understand
2152) the protocols we are transporting.
2153) </li>
2154) <li><a

2155) href="http://crypto.stanford.edu/~nagendra/projects/dtls/dtls.html">DTLS
2156) </a>

2157) (datagram TLS) basically has no users, and IPsec sure is big. Once we've
2158) picked a transport mechanism, we need to design a new end-to-end Tor
2159) protocol for avoiding tagging attacks and other potential anonymity and
2160) integrity issues now that we allow drops, resends, et cetera.

2161) </li>
2162) <li>Exit policies for arbitrary IP packets mean building a secure
2163) IDS. Our node operators tell us that exit policies are one of the main
2164) reasons they're willing to run Tor. Adding an Intrusion Detection System
2165) to handle exit policies would increase the security complexity of Tor,

2166) and would likely not work anyway, as evidenced by the entire field of
2167) IDS

2168) and counter-IDS papers. Many potential abuse issues are resolved by the
2169) fact that Tor only transports valid TCP streams (as opposed to arbitrary
2170) IP including malformed packets and IP floods), so exit policies become
2171) even <i>more</i> important as we become able to transport IP packets. We
2172) also need to compactly describe exit policies in the Tor directory,

2173) so clients can predict which nodes will allow their packets to exit
2174) —

2175) and clients need to predict all the packets they will want to send in
2176) a session before picking their exit node!
2177) </li>

2178) <li>The Tor-internal name spaces would need to be redesigned. We support
2179) hidden service ".onion" addresses by intercepting the addresses when
2180) they are passed to the Tor client. Doing so at the IP level will require
2181) a more complex interface between Tor and the local DNS resolver.

2182) </li>

2183) </ol>
2184) 
2185) <hr>
2186) 
2187) <a id="HideExits"></a>
2188) <h3><a class="anchor" href="#HideExits">You should hide the list of Tor
2189) relays, so people can't block the exits.</a></h3>
2190) 
2191) <p>
2192) There are a few reasons we don't:
2193) </p>
2194) 
2195) <ol>
2196) <li>We can't help but make the information available, since Tor clients
2197) need to use it to pick their paths. So if the "blockers" want it, they
2198) can get it anyway. Further, even if we didn't tell clients about the
2199) list of relays directly, somebody could still make a lot of connections
2200) through Tor to a test site and build a list of the addresses they see.
2201) </li>
2202) 

2203) <li>If people want to block us, we believe that they should be allowed
2204) to

2205) do so.  Obviously, we would prefer for everybody to allow Tor users to
2206) connect to them, but people have the right to decide who their services

2207) should allow connections from, and if they want to block anonymous
2208) users,

2209) they can.
2210) </li>
2211) 
2212) <li>Being blockable also has tactical advantages: it may be a persuasive

2213) response to website maintainers who feel threatened by Tor. Giving them
2214) the option may inspire them to <a href="<page docs/faq-abuse>#Bans">stop
2215) and think</a> about whether they really want to eliminate private access
2216) to their system, and if not, what other options they might have. The
2217) time they might otherwise have spent blocking Tor, they may instead
2218) spend rethinking their overall approach to privacy and anonymity.

2219) </li>

2220) </ol>
2221) 

2222)     <hr>

2223) 

2224)     <a id="Criminals"></a>

2225)     <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals
2226) to do bad things?</a></h3>

2227) 

2228)     <p>
2229)     For the answer to this question and others, please see our <a
2230)     href="<page docs/faq-abuse>">Tor Abuse FAQ</a>.
2231)     </p>

2232) 

2233)     <hr>

2234) 

2235)     <a id="RespondISP"></a>

2236)     <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP
2237) about my exit relay?</a></h3>

2238) 

2239)     <p>
2240)     A collection of templates for successfully responding to ISPs is <a

2241)     href="<wiki>doc/TorAbuseTemplates">collected

2242)     here</a>.
2243)     </p>

2244) 

2245)     <hr>

2246) 

2247)   </div>
2248)   <!-- END MAINCOL -->
2249)   <div id = "sidecol">
2250) #include "side.wmi"
2251) #include "info.wmi"
2252)   </div>
2253)   <!-- END SIDECOL -->
2254) </div>
2255) <!-- END CONTENT -->

2256) #include <foot.wmi>