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5) #include "head.wmi" TITLE="Tor FAQ" CHARSET="UTF-8"

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7) <div class="main-column">
8) 
9) <!-- PUT CONTENT AFTER THIS TAG -->
10) 

11) <h2>Tor FAQ</h2>
12) <hr />

13) 

14) <p>General questions:</p>

15) <ul>

16) <li><a href="#WhatIsTor">What is Tor?</a></li>

17) <li><a href="#Torisdifferent">How is Tor different from other proxies?</a></li>

18) <li><a href="#CompatibleApplications">What programs can I use with
19) Tor?</a></li>
20) <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
21) <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
22) <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
23) CD?</a></li>
24) <li><a href="#SupportMail">How can I get an answer to my
25) Tor support mail?</a></li>
26) <li><a href="#WhySlow">Why is Tor so slow?</a></li>
27) <li><a href="#Funding">What would The Tor Project do with more
28) funding?</a></li>

29) </ul>
30) 

31) <p>Compilation and Installation:</p>

32) <ul>
33) <li><a href="#HowUninstallTor">How do I uninstall Tor?</a></li>

34) <li><a href="#PGPSigs">What are these "sig" files on the download
35) page?</a></li>

36) <li><a href="#CompileTorWindows">How do I compile Tor under Windows?</a></li>

37) <li><a href="#VirusFalsePositives">Why does my Tor executable appear to
38) have a virus or spyware?</a></li>

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

40) </ul>

41) 
42) <p>Running Tor:</p>
43) 
44) <p>Running a Tor client:</p>

45) <ul>

46) <li><a href="#DoesntWork">I installed Tor and Polipo but it's not working.</a></li>
47) <li><a href="#VidaliaPassword">Tor/Vidalia prompts for a password at start.</a></li>

48) <li><a href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></li>
49) </ul>

50) 
51) <p>Running a Tor relay:</p>

52) <ul>

53) <li><a href="#RelayFlexible">How stable does my relay need to be?</a></li>

54) <li><a href="#ExitPolicies">I'd run a relay, but I don't want to deal

55) with abuse issues.</a></li>

56) <li><a href="#RelayOrBridge">Should I be a normal relay or bridge
57) relay?</a></li>

58) <li><a href="#RelayMemory">Why is my Tor relay using so much memory?</a></li>

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

60) </ul>

61) 
62) <p>Running a Tor hidden service:</p>
63) 

64) <p>Anonymity and Security:</p>
65) <ul>

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

67) </ul>
68) 

69) <p>Alternate designs that we don't do (yet):</p>
70) <ul>
71) <li><a href="#EverybodyARelay">You should make every Tor user be a
72) relay.</a></li>
73) </ul>
74) 

75) <p>Abuse</p>
76) <ul>
77) <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
78) <li><a href="#RespondISP">How do I respond to my ISP about my exit
79) relay?</a></li>
80) </ul>
81) 

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

83) href="<wiki>TorFAQ">wiki

84) FAQ</a> for now.</p>
85) 

86) <hr />
87) 
88) <a id="General"></a>
89) 

90) <a id="WhatIsTor"></a>
91) <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
92) 
93) <p>
94) The name "Tor" can refer to several different components.
95) </p>
96) 
97) <p>
98) The Tor software is a program you can run on your computer that helps keep
99) you safe on the Internet. Tor protects you by bouncing your communications
100) around a distributed network of relays run by volunteers all around
101) the world: it prevents somebody watching your Internet connection from
102) learning what sites you visit, and it prevents the sites you visit
103) from learning your physical location. This set of volunteer relays is
104) called the Tor network. You can read more about how Tor works on the <a
105) href="<page overview>">overview page</a>.
106) </p>
107) 
108) <p>
109) The Tor Project is a non-profit (charity) organization that maintains

110) and develops the Tor software.

111) </p>
112) 

113) <hr />
114) 

115) <a id="Torisdifferent"></a>
116) <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
117) <p>
118) A typical proxy provider sets up a server somewhere on the Internet and allows you to use it to relay your traffic.  This creates a simple, easy to maintain architecture.  The users all enter and leave through the same server.  The provider may charge for use of the proxy, or fund their costs through advertisements on the server.  In the simplest configuration, you don't have to install anything.  You just have to point your browser at their proxy server.  Simple proxy providers are fine solutions if you do not want protections for your privacy and anonymity online and you trust the provider from doing bad things.  Some simple proxy providers use SSL to secure your connection to them.  This may protect you against local eavesdroppers, such as those at a cafe with free wifi Internet.
119) </p>
120) <p>
121) Simple proxy providers also create a single point of failure.  The provider knows who you are and where you browse on the Internet.  They can see your traffic as it passes through their server.  In some cases, they can see your encrypted traffic as they relay it to your banking site or to ecommerce stores.  You have to trust the provider isn't doing any number of things, such as watching your traffic, injecting their own advertisements into your traffic stream, and isn't recording your personal details.
122) </p>
123) <p>
124) Tor passes your traffic through at least 3 different servers before sending it on to the destination.  Tor does not modify, or even know, what you are sending into it.  It merely relays your traffic, completely encrypted through the Tor network and has it pop out somewhere else in the world, completely intact.  The Tor client is required because we assume you trust your local computer.  The Tor client manages the encryption and the path chosen through the network.  The relays located all over the world merely pass encrypted packets between themselves.</p>
125) <p>

126) <dl>

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

128) <dt>Can't the third server see my traffic?</dt><dd>Possibly.  A bad third of three servers can see the traffic you sent into Tor.  It won't know who sent this traffic.  If you're using encryption, such as visiting a bank or e-commerce website, or encrypted mail connections, etc, it will only know the destination.  It won't be able to see the data inside the traffic stream.  You are still protected from this node figuring out who you are and if using encryption, what data you're sending to the destination.</dd>

129) </dl>

130) </p>
131) 

132) <hr />
133) 

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

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

137) 
138) <p>
139) There are two pieces to "Torifying" a program: connection-level anonymity
140) and application-level anonymity. Connection-level anonymity focuses on

141) making sure the application's Internet connections get sent through Tor.
142) This step is normally done by configuring

143) the program to use your Tor client as a "socks" proxy, but there are
144) other ways to do it too. For application-level anonymity, you need to
145) make sure that the information the application sends out doesn't hurt
146) your privacy. (Even if the connections are being routed through Tor, you
147) still don't want to include sensitive information like your name.) This
148) second step needs to be done on a program-by-program basis, which is
149) why we don't yet recommend very many programs for safe use with Tor.

150) </p>
151) 
152) <p>

153) Most of our work so far has focused on the Firefox web browser. The
154) bundles on the <a href="<page download>">download page</a> automatically
155) install the <a href="<page torbutton/index>">Torbutton Firefox
156) extension</a> if you have Firefox installed. As of version 1.2.0,
157) Torbutton now takes care of a lot of the connection-level and
158) application-level worries.

159) </p>
160) 
161) <p>

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

166) href="<wiki>TorifyHOWTO">Torifying

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

168) href="<wiki>SupportPrograms">list

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

171) </p>
172) 

173) <hr />
174) 

175) <a id="WhyCalledTor"></a>
176) <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
177) 
178) <p>

179) Because Tor is the onion routing network. When we were starting the
180) new next-generation design and implementation of onion routing in
181) 2001-2002, we would tell people we were working on onion routing,
182) and they would say "Neat. Which one?" Even if onion routing has
183) become a standard household term, Tor was born out of the actual <a
184) href="http://www.onion-router.net/">onion routing project</a> run by
185) the Naval Research Lab.

186) </p>
187) 
188) <p>

189) (It's also got a fine translation from German and Turkish.)

190) </p>
191) 
192) <p>

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

194) "TOR". Only the first letter is capitalized. In fact, we can usually
195) spot people who haven't read any of our website (and have instead learned
196) everything they know about Tor from news articles) by the fact that they
197) spell it wrong.

198) </p>
199) 

200) <hr />
201) 

202) <a id="Backdoor"></a>
203) <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
204) 
205) <p>

206) There is absolutely no backdoor in Tor. Nobody has asked us to put one

207) in, and we know some smart lawyers who say that it's unlikely that anybody

208) will try to make us add one in our jurisdiction (U.S.). If they do

209) ask us, we will fight them, and (the lawyers say) probably win.
210) </p>
211) 
212) <p>
213) We think that putting a backdoor in Tor would be tremendously
214) irresponsible to our users, and a bad precedent for security software

215) in general. If we ever put a deliberate backdoor in our security
216) software, it would ruin our professional reputations. Nobody would

217) trust our software ever again — for excellent reason!
218) </p>
219) 
220) <p>
221) But that said, there are still plenty of subtle attacks

222) people might try. Somebody might impersonate us, or break into our
223) computers, or something like that. Tor is open source, and you should

224) always check the source (or at least the diffs since the last release)

225) for suspicious things. If we (or the distributors) don't give you

226) source, that's a sure sign something funny might be going on. You

227) should also check the <a href="<page verifying-signatures>">PGP

228) signatures</a> on the releases, to make sure nobody messed with the
229) distribution sites.

230) </p>
231) 
232) <p>
233) Also, there might be accidental bugs in Tor that could affect your

234) anonymity. We periodically find and fix anonymity-related bugs, so make
235) sure you keep your Tor versions up-to-date.

236) </p>
237) 

238) <hr />
239) 

240) <a id="DistributingTor"></a>
241) <h3><a class="anchor" href="#DistributingTor">Can I distribute Tor on

242) my magazine's CD?</a></h3>

243) 
244) <p>
245) Yes.
246) </p>
247) 
248) <p>

249) The Tor software is <a href="https://www.fsf.org/">free software</a>. This

250) means we give you the rights to redistribute the Tor software, either
251) modified or unmodified, either for a fee or gratis. You don't have to
252) ask us for specific permission.
253) </p>
254) 
255) <p>
256) However, if you want to redistribute the Tor software you must follow our

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

258) Essentially this means that you need to include our LICENSE file along
259) with whatever part of the Tor software you're distributing.
260) </p>
261) 
262) <p>
263) Most people who ask us this question don't want to distribute just the
264) Tor software, though. They want to distribute the Tor bundles, which

265) typically include <a href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a>

266) and <a href="<page vidalia/index>">Vidalia</a>.

267) You will need to follow the licenses for those programs
268) as well. Both of them are distributed under the <a

269) href="https://www.fsf.org/licensing/licenses/gpl.html">GNU General

270) Public License</a>. The simplest way to obey their licenses is to
271) include the source code for these programs everywhere you include
272) the bundles themselves. Look for "source" packages on the <a

273) href="<page vidalia/index>">Vidalia page</a> and the <a

274) href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo

275) download page</a>.
276) </p>
277) 
278) <p>

279) Also, you should make sure not to confuse your readers about what Tor is,

280) who makes it, and what properties it provides (and doesn't provide). See
281) our <a href="<page trademark-faq>">trademark FAQ</a> for details.
282) </p>
283) 
284) <p>
285) Lastly, you should realize that we release new versions of the
286) Tor software frequently, and sometimes we make backward incompatible
287) changes. So if you distribute a particular version of the Tor software, it
288) may not be supported &mdash; or even work &mdash; six months later. This
289) is a fact of life for all security software under heavy development.
290) </p>
291) 

292) <hr />
293) 

294) <a id="SupportMail"></a>
295) <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
296) Tor support mail?</a></h3>
297) 
298) <p>
299) Many people send the Tor developers mail privately, or send mail to

300) our internal <a href="<page contact>">lists</a>, with questions about their

301) specific setup — they can't get their firewall working right,

302) they can't configure Polipo correctly, or so on. Sometimes our

303) volunteers can answer these mails, but typically they need to spend
304) most of their time on development tasks that will benefit more people.
305) This is especially true if your question is already covered in the <a

306) href="<page documentation>">documentation</a> or on this FAQ.

307) </p>
308) 
309) <p>
310) So if we don't answer your mail, first check the <a href="<page
311) documentation>">documentation</a> page, along with this FAQ,
312) to make sure your question isn't already answered.  Then read <a
313) href="http://www.catb.org/~esr/faqs/smart-questions.html">"How to ask
314) questions the smart way"</a>. If this doesn't help you, note that we
315) have <a href="<page documentation>#Support">an IRC channel</a> where you
316) can ask your questions (but if they are still open-ended, ill-formed,
317) or not about Tor, you likely won't get much help there either). Lastly,
318) people on the <a href="<page documentation>#MailingLists">or-talk
319) mailing list</a> may be able to provide some hints for you, if
320) others have experienced your problems too. Be sure to look over <a
321) href="http://archives.seul.org/or/talk/">the archives</a> first.
322) </p>
323) 
324) <p>
325) Another strategy is to <a href="<page docs/tor-doc-relay>">run a Tor
326) relay for a while</a>, and/or <a href="<page donate>">donate money</a>
327) <a href="<page volunteer>">or time</a> to the effort. We're more likely
328) to pay attention to people who have demonstrated interest and commitment
329) to giving back to the Tor community.
330) </p>
331) 
332) <p>

333) If you find your answer, please stick around on the IRC channel or the

334) mailing list and answer questions from others.
335) </p>
336) 

337) <hr />
338) 

339) <a id="WhySlow"></a>
340) <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
341) 
342) <p>
343) There are many reasons why the Tor network is currently slow.
344) </p>
345) 
346) <p>
347) Before we answer, though, you should realize that Tor is never going to
348) be blazing fast. Your traffic is bouncing through volunteers' computers
349) in various parts of the world, and some bottlenecks and network latency
350) will always be present. You shouldn't expect to see university-style
351) bandwidth through Tor.
352) </p>
353) 
354) <p>
355) But that doesn't mean that it can't be improved. The current Tor network
356) is quite small compared to the number of people trying to use it, and
357) many of these users don't understand or care that Tor can't currently
358) handle file-sharing traffic load.
359) </p>
360) 

361) <p>
362) For the much more in-depth answer, see <a

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

364) post on the topic</a>, which includes both a detailed PDF and a video
365) to go with it.
366) </p>
367) 

368) <p>
369) What can you do to help?
370) </p>
371) 
372) <ul>
373) 
374) <li>
375) <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
376) for others</a>. Help make the Tor network large enough that we can handle
377) all the users who want privacy and security on the Internet.
378) </li>
379) 
380) <li>
381) <a href="<page gui/index>">Help us make Tor more usable</a>. We
382) especially need people to help make it easier to configure your Tor
383) as a relay. Also, we need help with clear simple documentation to
384) walk people through setting it up.
385) </li>
386) 
387) <li>
388) There are some bottlenecks in the current Tor network. Help us design
389) experiments to track down and demonstrate where the problems are, and
390) then we can focus better on fixing them.
391) </li>
392) 
393) <li>
394) There are some steps that individuals
395) can take to improve their Tor performance. <a

396) href="<wiki>FireFoxTorPerf">You

397) can configure your Firefox to handle Tor better</a>, <a
398) href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
399) Polipo with Tor</a>, or you can try <a href="<page download>">upgrading
400) to the latest version of Tor</a>.  If this works well, please help by
401) documenting what you did, and letting us know about it.
402) </li>
403) 
404) <li>
405) Tor needs some architectural changes too. One important change is to

406) start providing <a href="#EverybodyARelay">better service to people who
407) relay traffic</a>. We're working on this, and we'll finish faster if we
408) get to spend more time on it.

409) </li>
410) 
411) <li>
412) Help do other things so we can do the hard stuff. Please take a moment
413) to figure out what your skills and interests are, and then <a href="<page
414) volunteer>">look at our volunteer page</a>.
415) </li>
416) 
417) <li>
418) Help find sponsors for Tor. Do you work at a company or government agency
419) that uses Tor or has a use for Internet privacy, e.g. to browse the
420) competition's websites discreetly, or to connect back to the home servers
421) when on the road without revealing affiliations? If your organization has
422) an interest in keeping the Tor network working, please contact them about
423) supporting Tor. Without sponsors, Tor is going to become even slower.
424) </li>
425) 
426) <li>
427) If you can't help out with any of the above, you can still help out
428) individually by <a href="<page donate>">donating a bit of money to the
429) cause</a>. It adds up!
430) </li>
431) 
432) </ul>
433) 

434) <hr />
435) 

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

437) <h3><a class="anchor" href="#Funding">What would The Tor Project do with

438) more funding?</a></h3>
439) 
440) <p>

441) We have about 1800 relays right now, pushing over 150 MB/s average

442) traffic. We have several hundred thousand active users. But the Tor
443) network is not yet self-sustaining.
444) </p>
445) 
446) <p>
447) There are six main development/maintenance pushes that need attention:
448) </p>
449) 
450) <ul>
451) 
452) <li>
453) Scalability: We need to keep scaling and decentralizing the Tor
454) architecture so it can handle thousands of relays and millions of
455) users. The upcoming stable release is a major improvement, but there's
456) lots more to be done next in terms of keeping Tor fast and stable.
457) </li>
458) 
459) <li>
460) User support: With this many users, a lot of people are asking questions
461) all the time, offering to help out with things, and so on. We need good
462) clean docs, and we need to spend some effort coordinating volunteers.
463) </li>
464) 
465) <li>
466) Relay support: the Tor network is run by volunteers, but they still need
467) attention with prompt bug fixes, explanations when things go wrong,
468) reminders to upgrade, and so on. The network itself is a commons, and
469) somebody needs to spend some energy making sure the relay operators stay
470) happy. We also need to work on <a href="#RelayOS">stability</a> on some
471) platforms &mdash; e.g., Tor relays have problems on Win XP currently.
472) </li>
473) 
474) <li>
475) Usability: Beyond documentation, we also need to work on usability of the
476) software itself. This includes installers, clean GUIs, easy configuration
477) to interface with other applications, and generally automating all of
478) the difficult and confusing steps inside Tor. We've got a start on this
479) with the <a href="<page gui/index>">GUI Contest</a>, but much more work
480) remains &mdash; usability for privacy software has never been easy.
481) </li>
482) 
483) <li>
484) Incentives: We need to work on ways to encourage people to configure
485) their Tors as relays and exit nodes rather than just clients.
486) <a href="#EverybodyARelay">We need to make it easy to become a relay,
487) and we need to give people incentives to do it.</a>
488) </li>
489) 
490) <li>
491) Research: The anonymous communications field is full
492) of surprises and gotchas. In our copious free time, we
493) also help run top anonymity and privacy conferences like <a
494) href="http://petsymposium.org/">PETS</a>. We've identified a set of
495) critical <a href="<page volunteer>#Research">Tor research questions</a>
496) that will help us figure out how to make Tor secure against the variety of
497) attacks out there. Of course, there are more research questions waiting
498) behind these.
499) </li>
500) 
501) </ul>
502) 
503) <p>
504) We're continuing to move forward on all of these, but at this rate
505) <a href="#WhySlow">the Tor network is growing faster than the developers
506) can keep up</a>.
507) Now would be an excellent time to add a few more developers to the effort
508) so we can continue to grow the network.
509) </p>
510) 
511) <p>
512) We are also excited about tackling related problems, such as
513) censorship-resistance.
514) </p>
515) 
516) <p>
517) We are proud to have <a href="<page sponsors>">sponsorship and support</a>
518) from the Omidyar Network, the International Broadcasting Bureau, Bell
519) Security Solutions, the Electronic Frontier Foundation, several government
520) agencies and research groups, and hundreds of private contributors.
521) </p>
522) 
523) <p>
524) However, this support is not enough to keep Tor abreast of changes in the
525) Internet privacy landscape. Please <a href="<page donate>">donate</a>
526) to the project, or <a href="<page contact>">contact</a> our executive
527) director for information on making grants or major donations.
528) </p>
529) 
530) <hr />
531) 

532) <a id="HowUninstallTor"></a>
533) <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
534) 
535) <p>
536) This depends entirely on how you installed it and which operating system you
537) have. If you installed a package, then hopefully your package has a way to

538) uninstall itself. The Windows packages include uninstallers. The proper way to

539) completely remove Tor, Vidalia, Torbutton for Firefox, and Polipo on any

540) version of Windows is as follows:
541) </p>
542) 
543) <ol>
544) <li>In your taskbar, right click on Vidalia (the green onion or the black head)
545) and choose exit.</li>
546) <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
547) Process List. If it's running, right click and choose End Process.</li>
548) <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.

549) This will remove the Vidalia bundle, which includes Tor and Polipo.</li>

550) <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
551) Click the Uninstall button.</li>

552) </ol>

553) 
554) <p>

555) If you do not follow these steps (for example by trying to uninstall

556) Vidalia, Tor, and Polipo while they are still running), you will need to

557) reboot and manually remove the directory "Program Files\Vidalia Bundle".

558) </p>
559) 
560) <p>
561) For Mac OS X, follow the <a

562) href="<page docs/tor-doc-osx>#uninstall">uninstall directions</a>.

563) </p>
564) 
565) <p>
566) If you installed by source, I'm afraid there is no easy uninstall method. But
567) on the bright side, by default it only installs into /usr/local/ and it should
568) be pretty easy to notice things there.
569) </p>
570) 
571) <hr />
572) 

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

576) 
577) <p>
578) These are PGP signatures, so you can verify that the file you've downloaded is
579) exactly the one that we intended you to get.
580) </p>
581) 
582) <p>
583) Please read the <a

584) href="<page verifying-signatures>">verifying signatures</a> page for details.

585) </p>
586) 
587) <hr />
588) 
589) <a id="CompileTorWindows"></a>
590) <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
591) Windows?</a></h3>
592) 
593) <p>

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

596) </p>
597) 

598) <p>
599) (Note that you don't need to compile Tor yourself in order to use
600) it. Most people just use the packages available on the <a href="<page
601) download>">download page</a>.)
602) </p>
603) 

604) <hr />
605) 

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

609) 
610) <p>
611) Sometimes, overzealous Windows virus and spyware detectors trigger on some
612) parts of the Tor Windows binary. Our best guess is that these are false

613) positives — after all, the anti-virus and anti-spyware business is just a

614) guessing game anyway. You should contact your vendor and explain that you have
615) a program that seems to be triggering false positives. Or pick a better vendor.
616) </p>
617) 
618) <p>

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

622) </p>
623) 
624) <hr />
625) 
626) <a id="LiveCD"></a>
627) <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
628) includes Tor?</a></h3>
629) 
630) <p>
631) There isn't any official LiveCD at this point. We're still trying to find good
632) solutions and trying to understand the security and anonymity implications of
633) the various options. In the mean time, feel free to check out the list below
634) and use your best judgement:
635) </p>
636) 
637) <p>

638) LiveCDs:

639) </p>
640) 
641) <ol>

642) <li><a href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
643) System</a> is a Live System aimed at preserving your privacy and
644) anonymity:

645) <ul>
646) <li> All outgoing connections to the Internet are forced to go through
647) the Tor network.</li>
648) <li> No trace is left on local storage devices unless explicitely asked.</li>
649) <li> It includes Firefox, Tor, Torbutton, Vidalia graphical Tor
650) controller, Pidgin Instant Messaging client, and lots of other
651) software.</li>
652) <li> It's based upon Debian gnu/linux and comes with the GNOME desktop
653) environment.</li>
654) </ul>

655) <li><a href="http://tork.sourceforge.net/wiki/index.php/LiveCD">TorK LiveCD</a>
656) is Knoppix-based with an emphasis on user-friendliness. You can work
657) anonymously or non-anonymously while TorK tries to keep you informed of the
658) consequences of your activity. The TorK LiveCD is experimental, so the aim is
659) to provide regular releases through 2007 and beyond.</li>

660) <li><a href="http://mandalka.name/privatix/">Privatix LiveCD/USB</a> is a
661) debian based live-system including tor, firefox and torbutton which can save
662) bookmarks and other settings or data on an encrypted usb-key</li>

663) </li>

664) </ol>
665) 
666) <p>
667) Windows bundles:
668) </p>
669) 
670) <ol>

671) <li><a href="<page torbrowser/index>">Tor Browser Bundle</a>

672) for Windows comes with a pre-configured web browser and is self contained
673) so you can run it from a USB stick.</li>
674) <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
675) running in VMWare that sits between your Windows computer and the Internet,
676) making sure that your Internet traffic is scrubbed and anonymized.</li>

677) </ol>
678) 
679) <p>
680) Not currently maintained as far as we know:
681) </p>
682) 
683) <ol>

684) <li>Polippix / Privatlivets Fred is a Danish Knoppix-based LiveCD with Tor
685) and utilities to encrypt IP-telephony. <a href="http://polippix.org/">Info and
686) download</a>.</li>

687) <li>ELE is a Linux LiveCD which is focused on privacy related
688) software. It includes Tor and you can download it at
689) <a
690) href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
691) <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
692) than Linux for maximum security. It was designed to be anonymous and secure
693) from the ground up, and thus has some features and limitations not found in
694) other LiveCDs (Tor related or otherwise). You can obtain more information and

695) download Anonym.OS from <a href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>

696) <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most

697) recent KNOPPIX release. It comes preconfigured with Privoxy, Tor and Polipo. You can

698) get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
699) Website</a>.</li>
700) </ol>
701) 

702) <p>
703) Please contact us if you know any others.
704) </p>
705) 

706) <hr />
707) 

708) <a id="DoesntWork"></a>
709) <h3><a class="anchor" href="#DoesntWork">I installed Tor and Polipo but
710) it's not working.</a></h3>
711) 
712) <p>
713) Are you sure Tor and Polipo are both running? If you're using Vidalia,
714) you may have to click on the onion and select "Start" to launch Tor.
715) </p>
716) 
717) <p>
718) Did you configure your web browser to http proxy to port 8118? Most people
719) should do this simply by installing Torbutton and making sure it says
720) "Tor enabled" at the bottom.
721) </p>
722) 
723) <p>
724) If you are using Firefox and would like to use Tor via the Torbutton
725) extension, make sure you don't have any other proxy add-on such as
726) Foxy Proxy enabled, as it will bypass Torbutton's proxy settings
727) for your browser. Note that using Foxy Proxy is NOT a sufficient
728) substitute for Torbutton. There are many known attacks against
729) a browser setup that does not include Torbutton. Read more in the
730) <a href="<page torbutton/faq>">Torbutton FAQ</a> and

731) the <a href="https://www.torproject.org/torbutton/design/>">Torbutton design</a>

732) specification.
733) </p>
734) 
735) <p>
736) Check your <a href="<wiki>TorFAQ#HowdoIsetuploggingorseeTorslogs">Tor
737) logs</a>. Do they give you any hints about what's going wrong?
738) </p>
739) 
740) <p>
741) Check your system clock. If it's more than a few hours off, Tor will
742) refuse to build circuits. For XP users, synchronize your clock under
743) the clock -&gt; Internet time tab. In addition, correct the day and date
744) under the 'Date &amp; Time' Tab.
745) </p>
746) 
747) <p>
748) Is your Internet connection <a
749) href="<wiki>TorFAQ#Myfirewallonlyallowsafewoutgoingports.">firewalled</a>,
750) or do you normally need to use a <a
751) href="<wiki>TorFAQ#MyInternetconnectionrequiresanHTTPorSOCKSproxy.">proxy</a>?
752) Are you running programs like Norton Internet Security that block certain
753) connections, even though you don't realize they do?
754) </p>
755) 
756) <p>
757) If you installed Polipo yourself (not from a bundle), did you edit the
758) config file as described? Did you restart Polipo after this change?
759) </p>
760) 
761) <p>
762) For Red Hat Linux and related systems, do you have SELinux enabled? If
763) so, it might be preventing Polipo from talking to Tor. We also run across
764) BSD users periodically who have local firewall rules that prevent some
765) connections to localhost.
766) </p>
767) 
768) <p>
769) When it's working, Tor should report that it "has successfully opened
770) a circuit.  Looks like client functionality is working."
771) </p>
772) 
773) <hr />
774) 

775) <a id="VidaliaPassword"></a>
776) <h3><a class="anchor" href="#VidaliaPassword">Tor/Vidalia prompts for

777) a password at start.</a></h3>

778) 
779) <p>

780) Vidalia interacts with the Tor software via Tor's "control port". The
781) control port lets Vidalia receive status updates from Tor, request a new
782) identity, configure Tor's settings, etc. Each time Vidalia starts Tor,
783) Vidalia sets a random password for Tor's control port to prevent other
784) applications from also connecting to the control port and potentially
785) compromising your anonymity.
786) </p>
787) 
788) <p>
789) Usually this process of generating and setting a random control password

790) happens in the background. There are three common situations, though,

791) where Vidalia may prompt you for a password:

792) </p>
793) 

794) <ol>

795) <li>You're already running Vidalia and Tor. For example, this situation
796) can happen if you installed the Vidalia bundle and now you're trying to
797) run the Tor Browser Bundle. In that case, you'll need to close the old
798) Vidalia and Tor before you can run this one.
799) </li>

800) <li>Vidalia crashed, but left Tor running with the last known random
801) password. After you restart Vidalia, it generates a new random password,
802) but Vidalia can't talk to Tor, because the random passwords are different.
803) <br />
804) If the dialog that prompts you for a control password has a Reset button,
805) you can click the button and Vidalia will restart Tor with a new random
806) control password.
807) <br />
808) If you do not see a Reset button, or if Vidalia is unable to restart
809) Tor for you, you can still fix the problem manually. Simply go into your
810) process or task manager, and terminate the Tor process. Then use Vidalia
811) to restart Tor and all will work again.
812) </li>

813) <li>You had previously set Tor to run as a Windows NT service. When Tor
814) is set to

815) run as a service, it starts up when the system boots. If you configured
816) Tor to start as a service through Vidalia, a random password was set
817) and saved in Tor. When you reboot, Tor starts up and uses the random
818) password it saved. You login and start up Vidalia. Vidalia attempts to
819) talk to the already running Tor. Vidalia generates a random password,
820) but it is different than the saved password in the Tor service.
821) <br />
822) You need to reconfigure Tor to not be a service. See the FAQ entry on

823) <a href="<wiki>TorFAQ#HowdoIrunmyTorrelayasanNTservice">running Tor as a Windows NT service</a>

824) for more information on how to remove the Tor service.
825) </li>

826) </ol>

827) 
828) <hr />
829) 

830) <a id="ChooseEntryExit"></a>
831) <h3><a class="anchor" href="#ChooseEntryExit">Can I control which nodes (or country) are used for entry/exit?</a></h3>
832) 
833) <p>
834) Yes. You can set preferred entry and exit nodes as well as 
835) inform Tor which nodes you do not want to use. 
836) The following options can be added to your config file "torrc" 
837) or specified on the command line:
838) </p>
839) <dl>
840)   <dt><tt>EntryNodes $fingerprint,$fingerprint,...</tt></dt>
841)     <dd>A list of preferred nodes to use for the first hop in the circuit, if possible.
842)     </dd>
843)   <dt><tt>ExitNodes $fingerprint,$fingerprint,...</tt></dt>
844)     <dd>A list of preferred nodes to use for the last hop in the circuit, if possible. 
845)     </dd>
846)   <dt><tt>ExcludeNodes $fingerprint,$fingerprint,...</tt></dt>
847)     <dd>A list of nodes to never use when building a circuit. 
848)     </dd>
849)   <dt><tt>ExcludeExitNodes $fingerprint,$fingerprint,...</tt></dt>
850)     <dd>A list of nodes to never use when picking an exit. 
851)         Nodes listed in <tt>ExcludeNodes</tt> are automatically in this list. 
852)     </dd>
853) </dl>
854) <p>
855) <em>We recommend you do not use these</em> 

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

857) You get the best security that Tor can provide when you leave the route selection to Tor; 
858) overriding the entry / exit nodes can mess up your anonymity in ways we don't understand.
859) </p>
860) <p>
861) The <tt>EntryNodes</tt> and <tt>ExitNodes</tt> config options are treated as a request, 
862) meaning if the nodes are down or seem slow, Tor will still avoid them. 
863) You can make the option mandatory by setting 
864) <tt>StrictExitNodes 1</tt> or <tt>StrictEntryNodes 1</tt> 

865) — but if you do, your Tor connections will stop working 

866) if all of the nodes you have specified become unreachable. 

867) See the <a href="<page documentation>#NeatLinks">Tor status pages</a>

868) for some nodes you might pick.
869) </p>
870) <p>
871) Instead of <tt>$fingerprint</tt> you can also specify 
872) a 2 letter ISO3166 country code in curly braces 
873) (for example {de}), 
874) or an ip address pattern (for example 255.254.0.0/8), 
875) or a node nickname. 
876) Make sure there are no spaces between the commas and the list items. 
877) </p>
878) <p>
879) If you want to access a service directly through Tor's SOCKS interface 
880) (eg. using ssh via connect.c), another option is to 
881) set up an internal mapping in your configuration file using <tt>MapAddress</tt>. 
882) See the manual page for details.
883) </p>
884) 
885) <hr />
886) 

887) <a id="RelayFlexible"></a>
888) <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
889) need to be?</a></h3>
890) 
891) <p>
892) We aim to make setting up a Tor relay easy and convenient:
893) </p>
894) 
895) <ul>
896) <li>Tor has built-in support for <a

897) href="<wiki>TorFAQ#LimitBandwidth">

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

901) href="<wiki>TorFAQ#Hibernation">hibernation

902) feature</a>.
903) </li>

904) <li>Each Tor relay has an <a href="#ExitPolicies">exit policy</a> that
905) specifies what sort of outbound connections are allowed or refused from
906) that relay. If you are uncomfortable allowing people to exit from your
907) relay, you can set it up to only allow connections to other Tor relays.

908) </li>
909) <li>It's fine if the relay goes offline sometimes. The directories
910) notice this quickly and stop advertising the relay. Just try to make
911) sure it's not too often, since connections using the relay when it
912) disconnects will break.
913) </li>
914) <li>We can handle relays with dynamic IPs just fine &mdash; simply
915) leave the Address config option blank, and Tor will try to guess.
916) </li>
917) <li>If your relay is behind a NAT and it doesn't know its public
918) IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port

919) forwarding. Forwarding TCP connections is system dependent but 

920) <a href="<wiki>TorFAQ#ServerForFirewalledClients">this FAQ entry</a>

921) offers some examples on how to do this.

922) </li>
923) <li>Your relay will passively estimate and advertise its recent
924) bandwidth capacity, so high-bandwidth relays will attract more users than
925) low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
926) </li>
927) </ul>
928) 
929) <hr />
930) 

931) <a id="RunARelayBut"></a>

932) <a id="ExitPolicies"></a>
933) <h3><a class="anchor" href="#ExitPolicies">I'd run a relay, but I don't

934) want to deal with abuse issues.</a></h3>
935) 
936) <p>
937) Great. That's exactly why we implemented exit policies.
938) </p>
939) 
940) <p>

941) Each Tor relay has an exit policy that specifies what sort of
942) outbound connections are allowed or refused from that relay. The exit

943) policies are propagated to Tor clients via the directory, so clients

944) will automatically avoid picking exit relays that would refuse to
945) exit to their intended destination. This way each relay can decide
946) the services, hosts, and networks he wants to allow connections to,

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

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

951) for running an exit node with minimal harassment</a>.
952) </p>
953) 
954) <p>

955) The default exit policy allows access to many popular services (e.g. web browsing), but 

956) <a href="<wiki>TorFAQ#DefaultPorts">restricts</a>

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

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

961) <a href="<wiki>TorFAQ#torrc">torrc</a>

962) file. If you want to avoid most if not all abuse potential, set it to

963) "reject *:*" (or un-check all the boxes in Vidalia). This setting means
964) that your relay will be used for relaying traffic inside the Tor network,
965) but not for connections to external websites or other services.

966) </p>
967) 
968) <p>

969) If you do allow any exit connections, make sure name resolution works
970) (that is, your computer can resolve Internet addresses correctly).

971) If there are any resources that your computer can't reach (for example,
972) you are behind a restrictive firewall or content filter), please
973) explicitly reject them in your exit policy — otherwise Tor users
974) will be impacted too.

975) </p>
976) 
977) <hr />
978) 

979) <a id="RelayOrBridge"></a>
980) <h3><a class="anchor" href="#RelayOrBridge">Should I be a normal relay
981) or bridge relay?</a></h3>
982) 
983) <p><a href="<page bridges>">Bridge relays</a> (or "bridges" for short)

984) are <a href="<page docs/tor-doc-relay>">Tor relays</a> that aren't listed
985) in the main Tor directory. That means

986) that even an ISP or government trying to filter connections to the Tor
987) network probably won't be able to block all the bridges.
988) </p>
989) 
990) <p>Being a normal relay vs being a bridge relay is almost the same
991) configuration: it's just a matter of whether your relay is listed
992) publically or not.
993) </p>
994) 

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

996) connections to the Tor network. So getting a lot of bridges running
997) right now is mostly a backup measure, a) in case the Tor network does
998) get blocked somewhere, and b) for people who want an extra layer of
999) security because they're worried somebody will recognize that it's a

1000) public Tor relay IP address they're contacting.

1001) </p>
1002) 
1003) <p>So should you run a normal relay or bridge relay? If you have
1004) lots of bandwidth, you should definitely run a normal relay &mdash;

1005) bridge relays see very little use these days. If you're willing to 
1006) <a href="#ExitPolicies">be an exit</a>, you should definitely run a normal

1007) relay, since we need more exits. If you can't be an exit and only have
1008) a little bit of bandwidth, then flip a coin. Thanks for volunteering!
1009) </p>
1010) 
1011) <hr />
1012) 

1013) <a id="RelayMemory"></a>
1014) <h3><a class="anchor" href="#RelayMemory">Why is my Tor relay using so
1015) much memory?</a></h3>
1016) 

1017) <p>If your Tor relay is using more memory than you'd like, here are some
1018) tips for reducing its footprint:
1019) </p>
1020) 
1021) <ol>
1022) <li>If you're on Linux, you may be encountering memory fragmentation
1023) bugs in glibc's malloc implementation. That is, when Tor releases memory
1024) back to the system, the pieces of memory are fragmented so they're hard
1025) to reuse. The Tor tarball ships with OpenBSD's malloc implementation,
1026) which doesn't have as many fragmentation bugs (but the tradeoff is higher
1027) CPU load). You can tell Tor to use this malloc implementation instead:
1028) <tt>./configure --enable-openbsd-malloc</tt></li>
1029) 
1030) <li>If you're running a fast relay, meaning you have many TLS connections
1031) open, you are probably losing a lot of memory to OpenSSL's internal

1032) buffers (38KB+ per socket). We've patched OpenSSL to <a
1033) href="http://archives.seul.org/or/dev/Jun-2008/msg00001.html">release
1034) unused buffer memory more aggressively</a>. If you update to OpenSSL
1035) 1.0.0-beta5, Tor's build process will automatically recognize and use
1036) this feature.</li>

1037) 
1038) <li>If you're running on Solaris, OpenBSD, NetBSD, or
1039) old FreeBSD, Tor is probably forking separate processes
1040) rather than using threads. Consider switching to a <a

1041) href="<wiki>TorFAQ#RelayOS">better

1042) operating system</a>.</li>
1043) 
1044) <li>If you still can't handle the memory load, consider reducing the
1045) amount of bandwidth your relay advertises. Advertising less bandwidth
1046) means you will attract fewer users, so your relay shouldn't grow
1047) as large. See the <tt>MaxAdvertisedBandwidth</tt> option in the man
1048) page.</li>
1049) 
1050) </ol>
1051) 
1052) <p>
1053) All of this said, fast Tor relays do use a lot of ram. It is not unusual
1054) for a fast exit relay to use 500-1000 MB of memory.

1055) </p>
1056) 
1057) <hr />
1058) 

1059) <a id="WhyNotNamed"></a>
1060) <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not named?</a></h3>
1061) 
1062) <p>
1063) We currently use these metrics to determine if your relay should be named:<br />
1064) </p>
1065) <ul>
1066) <li>The name is not currently mapped to a different key. Existing mappings
1067) are removed after 6 months of inactivity from a relay.</li>
1068) <li>The relay must have been around for at least two weeks.</li>
1069) <li>No other router may have wanted the same name in the past month.</li>
1070) </ul>
1071) 
1072) <hr />
1073) 

1074) <a id="KeyManagement"></a>

1075) <h3><a class="anchor" href="#KeyManagement">Tell me about all the keys
1076) Tor uses.</a></h3>

1077) 
1078) <p>

1079) Tor uses a variety of different keys, with three goals in mind: 1)

1080) encryption to ensure privacy of data within the Tor network, 2)
1081) authentication so clients know they're
1082) talking to the relays they meant to talk to, and 3) signatures to make
1083) sure all clients know the same set of relays.

1084) </p>
1085) 
1086) <p>
1087) <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
1088) so observers can't look inside to see which circuit a given cell is
1089) intended for. Further, the Tor client establishes an ephemeral encryption
1090) key with each relay in the circuit, so only the exit relay can read
1091) the cells. Both sides discard the circuit key when the circuit ends,
1092) so logging traffic and then breaking into the relay to discover the key
1093) won't work.
1094) </p>
1095) 
1096) <p>
1097) <b>Authentication</b>:
1098) Every Tor relay has a public decryption key called the "onion key".
1099) When the Tor client establishes circuits, at each step it <a

1100) href="<svnprojects>design-paper/tor-design.html#subsec:circuits">demands

1101) that the Tor relay prove knowledge of its onion key</a>. That way

1102) the first node in the path can't just spoof the rest of the path.

1103) Each relay rotates its onion key once a week.

1104) </p>
1105) 
1106) <p>

1107) <b>Coordination</b>:

1108) How do clients know what the relays are, and how do they know that they

1109) have the right keys for them? Each relay has a long-term public signing
1110) key called the "identity key". Each directory authority additionally has a

1111) "directory signing key". The directory authorities <a

1112) href="<gitblob>doc/spec/dir-spec.txt">provide a signed list</a>

1113) of all the known relays, and in that list are a set of certificates from
1114) each relay (self-signed by their identity key) specifying their keys,
1115) locations, exit policies, and so on. So unless the adversary can control
1116) a threshold of the directory authorities, he can't trick the Tor client
1117) into using other Tor relays.

1118) </p>
1119) 
1120) <p>

1121) How do clients know what the directory authorities are? The Tor software
1122) comes with a built-in list of location and public key for each directory
1123) authority. So the only way to trick users into using a fake Tor network

1124) is to give them a specially modified version of the software.
1125) </p>

1126) 

1127) <p>
1128) How do users know they've got the right software? When we distribute
1129) the source code or a package, we digitally sign it with <a

1130) href="http://www.gnupg.org/">GNU Privacy Guard</a>. See the <a

1131) href="<page verifying-signatures>">instructions

1132) on how to check Tor's signatures</a>.
1133) </p>

1134) 

1135) <p>

1136) In order to be certain that it's really signed by us, you need to have
1137) met us in person and gotten a copy of our GPG key fingerprint, or you
1138) need to know somebody who has. If you're concerned about an attack on
1139) this level, we recommend you get involved with the security community
1140) and start meeting people.

1141) </p>

1142) 

1143) <hr />
1144) 

1145) <a id="EverybodyARelay"></a>
1146) <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
1147) user be a relay.</a></h3>
1148) 
1149) <p>
1150) Requiring every Tor user to be a relay would help with scaling the

1151) network to handle all our users, and <a href="<wiki>TorFAQ#RelayAnonymity">running a Tor

1152) relay may help your anonymity</a>. However, many Tor users cannot be good
1153) relays &mdash; for example, some Tor clients operate from behind restrictive
1154) firewalls, connect via modem, or otherwise aren't in a position where they
1155) can relay traffic. Providing service to these clients is a critical

1156) part of providing effective anonymity for everyone, since many Tor users
1157) are subject to these or similar constraints and including these clients
1158) increases the size of the anonymity set.
1159) </p>
1160) 
1161) <p>
1162) That said, we do want to encourage Tor users to run relays, so what we
1163) really want to do is simplify the process of setting up and maintaining

1164) a relay. We've made a lot of progress with easy configuration in the past
1165) few years: Vidalia has an easy relay configuration interface, and supports
1166) uPnP too. Tor is good at automatically detecting whether it's reachable and
1167) how much bandwidth it can offer.

1168) </p>
1169) 
1170) <p>
1171) There are five steps we need to address before we can do this though:
1172) </p>
1173) 
1174) <p>

1175) First, we need to make Tor stable as a relay on all common
1176) operating systems. The main remaining platform is Windows,
1177) and we plan to finally address that in 2009. See Section 4.1 of <a
1178) href="https://www.torproject.org/press/2008-12-19-roadmap-press-release">our
1179) development roadmap</a>.

1180) </p>
1181) 
1182) <p>

1183) Second, we still need to get better at automatically estimating
1184) the right amount of bandwidth to allow. See item #7 on the
1185) <a href="<page volunteer>#Research">research section of the
1186) volunteer page</a>: "Tor doesn't work very well when relays
1187) have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a

1188) href="<wiki>TorFAQ#TransportIPnotTCP">switching

1189) to UDP transport</a> is the simplest answer here &mdash; which alas is
1190) not a very simple answer at all.

1191) </p>
1192) 
1193) <p>

1194) Third, we need to work on scalability, both of the network (how to
1195) stop requiring that all Tor relays be able to connect to all Tor
1196) relays) and of the directory (how to stop requiring that all Tor
1197) users know about all Tor relays). Changes like this can have large
1198) impact on potential and actual anonymity. See Section 5 of the <a

1199) href="<svnprojects>design-paper/challenges.pdf">Challenges</a> paper

1200) for details. Again, UDP transport would help here.

1201) </p>
1202) 
1203) <p>

1204) Fourth, we need to better understand the risks from
1205) letting the attacker send traffic through your relay while
1206) you're also initiating your own anonymized traffic. <a
1207) href="http://freehaven.net/anonbib/#back01">Three</a> <a
1208) href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
1209) <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
1210) describe ways to identify the relays in a circuit by running traffic
1211) through candidate relays and looking for dips in the traffic while the
1212) circuit is active. These clogging attacks are not that scary in the Tor
1213) context so long as relays are never clients too. But if we're trying to
1214) encourage more clients to turn on relay functionality too (whether as
1215) <a href="<page bridges>">bridge relays</a> or as normal relays), then
1216) we need to understand this threat better and learn how to mitigate it.

1217) </p>
1218) 
1219) <p>
1220) Fifth, we might need some sort of incentive scheme to encourage people
1221) to relay traffic for others, and/or to become exit nodes. Here are our

1222) <a href="<blog>two-incentive-designs-tor">current

1223) thoughts on Tor incentives</a>.

1224) </p>
1225) 
1226) <p>
1227) Please help on all of these!
1228) </p>
1229) 
1230) <hr />
1231) 

1232) <a id="Criminals"></a>
1233) <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
1234) things?</a></h3>
1235) 
1236) <p>

1237) For the answer to this question and others, please see our <a

1238) href="<page faq-abuse>">Tor Abuse FAQ</a>.

1239) </p>
1240) 
1241) <hr />
1242) 
1243) <a id="RespondISP"></a>
1244) <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
1245) exit relay?</a></h3>
1246) 
1247) <p>
1248) A collection of templates for successfully responding to ISPs is <a

1249) href="<wiki>TorAbuseTemplates">collected

1250) here</a>.
1251) </p>
1252) 

1253) <hr />

1254) 

1255)   </div><!-- #main -->

1256) 
1257) #include <foot.wmi>