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5) #include "head.wmi" TITLE="Tor FAQ"
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10) 

11) # Translators: you probably don't want to translate this file yet,
12) # since I'm hoping it will keep changing for a while. Thanks! -RD
13) 

14) <h2>Tor FAQ</h2>
15) <hr />

16) 

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

18) <ul>

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

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

21) <li><a href="#CompatibleApplications">What programs can I use with
22) Tor?</a></li>
23) <li><a href="#WhyCalledTor">Why is it called Tor?</a></li>
24) <li><a href="#Backdoor">Is there a backdoor in Tor?</a></li>
25) <li><a href="#DistributingTor">Can I distribute Tor on my magazine's
26) CD?</a></li>
27) <li><a href="#SupportMail">How can I get an answer to my
28) Tor support mail?</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) </ul>
33) 

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

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

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

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

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

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

43) </ul>

44) 
45) <p>Running Tor:</p>
46) 
47) <p>Running a Tor client:</p>
48) 
49) <p>Running a Tor relay:</p>

50) <ul>

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

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

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

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

55) </ul>

56) 
57) <p>Running a Tor hidden service:</p>
58) 

59) <p>Anonymity and Security:</p>
60) <ul>

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

62) </ul>
63) 

64) <p>Alternate designs that we don't do (yet):</p>
65) <ul>
66) <li><a href="#EverybodyARelay">You should make every Tor user be a
67) relay.</a></li>
68) </ul>
69) 

70) <p>Abuse</p>
71) <ul>
72) <li><a href="#Criminals">Doesn't Tor enable criminals to do bad things?</a></li>
73) <li><a href="#RespondISP">How do I respond to my ISP about my exit
74) relay?</a></li>
75) </ul>
76) 

77) <p>For other questions not yet on this version of the FAQ, see the <a
78) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ">wiki
79) FAQ</a> for now.</p>
80) 

81) <hr />
82) 
83) <a id="General"></a>
84) 

85) <a id="WhatIsTor"></a>
86) <h3><a class="anchor" href="#WhatIsTor">What is Tor?</a></h3>
87) 
88) <p>
89) The name "Tor" can refer to several different components.
90) </p>
91) 
92) <p>
93) The Tor software is a program you can run on your computer that helps keep
94) you safe on the Internet. Tor protects you by bouncing your communications
95) around a distributed network of relays run by volunteers all around
96) the world: it prevents somebody watching your Internet connection from
97) learning what sites you visit, and it prevents the sites you visit
98) from learning your physical location. This set of volunteer relays is
99) called the Tor network. You can read more about how Tor works on the <a
100) href="<page overview>">overview page</a>.
101) </p>
102) 
103) <p>
104) The Tor Project is a non-profit (charity) organization that maintains

105) and develops the Tor software.

106) </p>
107) 

108) <hr />
109) 

110) <a id="Torisdifferent"></a>
111) <h3><a class="anchor" href="#Torisdifferent">How is Tor different from other proxies?</a></h3>
112) <p>
113) 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.
114) </p>
115) <p>
116) 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.
117) </p>
118) <p>
119) 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>
120) <p>

121) <dl>

122) <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>
123) <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 ecommerce 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>

124) </dl>

125) </p>
126) 

127) <hr />
128) 

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

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

132) 
133) <p>
134) There are two pieces to "Torifying" a program: connection-level anonymity
135) and application-level anonymity. Connection-level anonymity focuses on

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

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

145) </p>
146) 
147) <p>

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

154) </p>
155) 
156) <p>

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

161) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorifyHOWTO">Torifying

162) specific applications</a>. There's also a <a
163) href="https://wiki.torproject.org/noreply/TheOnionRouter/SupportPrograms">list
164) of applications that help you direct your traffic through Tor</a>.
165) Please add to these lists and help us keep them accurate!

166) </p>
167) 

168) <hr />
169) 

170) <a id="WhyCalledTor"></a>
171) <h3><a class="anchor" href="#WhyCalledTor">Why is it called Tor?</a></h3>
172) 
173) <p>

174) Because Tor is the onion routing network. When we were starting the
175) new next-generation design and implementation of onion routing in
176) 2001-2002, we would tell people we were working on onion routing,
177) and they would say "Neat. Which one?" Even if onion routing has
178) become a standard household term, Tor was born out of the actual <a
179) href="http://www.onion-router.net/">onion routing project</a> run by
180) the Naval Research Lab.

181) </p>
182) 
183) <p>

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

185) </p>
186) 
187) <p>

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

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

193) </p>
194) 

195) <hr />
196) 

197) <a id="Backdoor"></a>
198) <h3><a class="anchor" href="#Backdoor">Is there a backdoor in Tor?</a></h3>
199) 
200) <p>

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

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

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

204) ask us, we will fight them, and (the lawyers say) probably win.
205) </p>
206) 
207) <p>
208) We think that putting a backdoor in Tor would be tremendously
209) irresponsible to our users, and a bad precedent for security software

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

212) trust our software ever again — for excellent reason!
213) </p>
214) 
215) <p>
216) But that said, there are still plenty of subtle attacks

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

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

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

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

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

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

225) </p>
226) 
227) <p>
228) Also, there might be accidental bugs in Tor that could affect your

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

231) </p>
232) 

233) <hr />
234) 

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

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

238) 
239) <p>
240) Yes.
241) </p>
242) 
243) <p>

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

245) means we give you the rights to redistribute the Tor software, either
246) modified or unmodified, either for a fee or gratis. You don't have to
247) ask us for specific permission.
248) </p>
249) 
250) <p>
251) However, if you want to redistribute the Tor software you must follow our

252) <a href="<svnsandbox>LICENSE">LICENSE</a>.

253) Essentially this means that you need to include our LICENSE file along
254) with whatever part of the Tor software you're distributing.
255) </p>
256) 
257) <p>
258) Most people who ask us this question don't want to distribute just the
259) Tor software, though. They want to distribute the Tor bundles, which
260) typically include <a href="http://www.privoxy.org/">Privoxy</a>

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

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

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

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

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

269) href="http://sourceforge.net/project/showfiles.php?group_id=11118">Privoxy
270) download page</a>.
271) </p>
272) 
273) <p>

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

275) who makes it, and what properties it provides (and doesn't provide). See
276) our <a href="<page trademark-faq>">trademark FAQ</a> for details.
277) </p>
278) 
279) <p>
280) Lastly, you should realize that we release new versions of the
281) Tor software frequently, and sometimes we make backward incompatible
282) changes. So if you distribute a particular version of the Tor software, it
283) may not be supported &mdash; or even work &mdash; six months later. This
284) is a fact of life for all security software under heavy development.
285) </p>
286) 

287) <hr />
288) 

289) <a id="SupportMail"></a>
290) <h3><a class="anchor" href="#SupportMail">How can I get an answer to my
291) Tor support mail?</a></h3>
292) 
293) <p>
294) Many people send the Tor developers mail privately, or send mail to

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

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

297) they can't configure Privoxy correctly, or so on. Sometimes our
298) volunteers can answer these mails, but typically they need to spend
299) most of their time on development tasks that will benefit more people.
300) This is especially true if your question is already covered in the <a
301) href="<page documentation>">documentation</a> or on this FAQ. We don't
302) hate you; we're just busy.
303) </p>
304) 
305) <p>
306) So if we don't answer your mail, first check the <a href="<page
307) documentation>">documentation</a> page, along with this FAQ,
308) to make sure your question isn't already answered.  Then read <a
309) href="http://www.catb.org/~esr/faqs/smart-questions.html">"How to ask
310) questions the smart way"</a>. If this doesn't help you, note that we
311) have <a href="<page documentation>#Support">an IRC channel</a> where you
312) can ask your questions (but if they are still open-ended, ill-formed,
313) or not about Tor, you likely won't get much help there either). Lastly,
314) people on the <a href="<page documentation>#MailingLists">or-talk
315) mailing list</a> may be able to provide some hints for you, if
316) others have experienced your problems too. Be sure to look over <a
317) href="http://archives.seul.org/or/talk/">the archives</a> first.
318) </p>
319) 
320) <p>
321) Another strategy is to <a href="<page docs/tor-doc-relay>">run a Tor
322) relay for a while</a>, and/or <a href="<page donate>">donate money</a>
323) <a href="<page volunteer>">or time</a> to the effort. We're more likely
324) to pay attention to people who have demonstrated interest and commitment
325) to giving back to the Tor community.
326) </p>
327) 
328) <p>

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

330) mailing list and answer questions from others.
331) </p>
332) 

333) <hr />
334) 

335) <a id="WhySlow"></a>
336) <h3><a class="anchor" href="#WhySlow">Why is Tor so slow?</a></h3>
337) 
338) <p>
339) There are many reasons why the Tor network is currently slow.
340) </p>
341) 
342) <p>
343) Before we answer, though, you should realize that Tor is never going to
344) be blazing fast. Your traffic is bouncing through volunteers' computers
345) in various parts of the world, and some bottlenecks and network latency
346) will always be present. You shouldn't expect to see university-style
347) bandwidth through Tor.
348) </p>
349) 
350) <p>
351) But that doesn't mean that it can't be improved. The current Tor network
352) is quite small compared to the number of people trying to use it, and
353) many of these users don't understand or care that Tor can't currently
354) handle file-sharing traffic load.
355) </p>
356) 
357) <p>
358) What can you do to help?
359) </p>
360) 
361) <ul>
362) 
363) <li>
364) <a href="<page docs/tor-doc-relay>">Configure your Tor to relay traffic
365) for others</a>. Help make the Tor network large enough that we can handle
366) all the users who want privacy and security on the Internet.
367) </li>
368) 
369) <li>
370) <a href="<page gui/index>">Help us make Tor more usable</a>. We
371) especially need people to help make it easier to configure your Tor
372) as a relay. Also, we need help with clear simple documentation to
373) walk people through setting it up.
374) </li>
375) 
376) <li>
377) There are some bottlenecks in the current Tor network. Help us design
378) experiments to track down and demonstrate where the problems are, and
379) then we can focus better on fixing them.
380) </li>
381) 
382) <li>
383) There are some steps that individuals
384) can take to improve their Tor performance. <a
385) href="https://wiki.torproject.org/noreply/TheOnionRouter/FireFoxTorPerf">You
386) can configure your Firefox to handle Tor better</a>, <a
387) href="http://www.pps.jussieu.fr/~jch/software/polipo/tor.html">you can use
388) Polipo with Tor</a>, or you can try <a href="<page download>">upgrading
389) to the latest version of Tor</a>.  If this works well, please help by
390) documenting what you did, and letting us know about it.
391) </li>
392) 
393) <li>
394) Tor needs some architectural changes too. One important change is to

395) start providing <a

396) href="#EverybodyARelay">better

397) service to people who relay traffic</a>. We're working on this, and
398) we'll finish faster if we get to spend more time on it.

399) </li>
400) 
401) <li>
402) Help do other things so we can do the hard stuff. Please take a moment
403) to figure out what your skills and interests are, and then <a href="<page
404) volunteer>">look at our volunteer page</a>.
405) </li>
406) 
407) <li>
408) Help find sponsors for Tor. Do you work at a company or government agency
409) that uses Tor or has a use for Internet privacy, e.g. to browse the
410) competition's websites discreetly, or to connect back to the home servers
411) when on the road without revealing affiliations? If your organization has
412) an interest in keeping the Tor network working, please contact them about
413) supporting Tor. Without sponsors, Tor is going to become even slower.
414) </li>
415) 
416) <li>
417) If you can't help out with any of the above, you can still help out
418) individually by <a href="<page donate>">donating a bit of money to the
419) cause</a>. It adds up!
420) </li>
421) 
422) </ul>
423) 

424) <hr />
425) 

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

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

428) more funding?</a></h3>
429) 
430) <p>
431) We have about 1500 relays right now, pushing over 150 MB/s average
432) traffic. We have several hundred thousand active users. But the Tor
433) network is not yet self-sustaining.
434) </p>
435) 
436) <p>
437) There are six main development/maintenance pushes that need attention:
438) </p>
439) 
440) <ul>
441) 
442) <li>
443) Scalability: We need to keep scaling and decentralizing the Tor
444) architecture so it can handle thousands of relays and millions of
445) users. The upcoming stable release is a major improvement, but there's
446) lots more to be done next in terms of keeping Tor fast and stable.
447) </li>
448) 
449) <li>
450) User support: With this many users, a lot of people are asking questions
451) all the time, offering to help out with things, and so on. We need good
452) clean docs, and we need to spend some effort coordinating volunteers.
453) </li>
454) 
455) <li>
456) Relay support: the Tor network is run by volunteers, but they still need
457) attention with prompt bug fixes, explanations when things go wrong,
458) reminders to upgrade, and so on. The network itself is a commons, and
459) somebody needs to spend some energy making sure the relay operators stay
460) happy. We also need to work on <a href="#RelayOS">stability</a> on some
461) platforms &mdash; e.g., Tor relays have problems on Win XP currently.
462) </li>
463) 
464) <li>
465) Usability: Beyond documentation, we also need to work on usability of the
466) software itself. This includes installers, clean GUIs, easy configuration
467) to interface with other applications, and generally automating all of
468) the difficult and confusing steps inside Tor. We've got a start on this
469) with the <a href="<page gui/index>">GUI Contest</a>, but much more work
470) remains &mdash; usability for privacy software has never been easy.
471) </li>
472) 
473) <li>
474) Incentives: We need to work on ways to encourage people to configure
475) their Tors as relays and exit nodes rather than just clients.
476) <a href="#EverybodyARelay">We need to make it easy to become a relay,
477) and we need to give people incentives to do it.</a>
478) </li>
479) 
480) <li>
481) Research: The anonymous communications field is full
482) of surprises and gotchas. In our copious free time, we
483) also help run top anonymity and privacy conferences like <a
484) href="http://petsymposium.org/">PETS</a>. We've identified a set of
485) critical <a href="<page volunteer>#Research">Tor research questions</a>
486) that will help us figure out how to make Tor secure against the variety of
487) attacks out there. Of course, there are more research questions waiting
488) behind these.
489) </li>
490) 
491) </ul>
492) 
493) <p>
494) We're continuing to move forward on all of these, but at this rate
495) <a href="#WhySlow">the Tor network is growing faster than the developers
496) can keep up</a>.
497) Now would be an excellent time to add a few more developers to the effort
498) so we can continue to grow the network.
499) </p>
500) 
501) <p>
502) We are also excited about tackling related problems, such as
503) censorship-resistance.
504) </p>
505) 
506) <p>
507) We are proud to have <a href="<page sponsors>">sponsorship and support</a>
508) from the Omidyar Network, the International Broadcasting Bureau, Bell
509) Security Solutions, the Electronic Frontier Foundation, several government
510) agencies and research groups, and hundreds of private contributors.
511) </p>
512) 
513) <p>
514) However, this support is not enough to keep Tor abreast of changes in the
515) Internet privacy landscape. Please <a href="<page donate>">donate</a>
516) to the project, or <a href="<page contact>">contact</a> our executive
517) director for information on making grants or major donations.
518) </p>
519) 
520) <hr />
521) 

522) <a id="HowUninstallTor"></a>
523) <h3><a class="anchor" href="#HowUninstallTor">How do I uninstall Tor?</a></h3>
524) 
525) <p>
526) This depends entirely on how you installed it and which operating system you
527) have. If you installed a package, then hopefully your package has a way to

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

529) completely remove Tor, Vidalia, Torbutton for Firefox, and Privoxy on any
530) version of Windows is as follows:
531) </p>
532) 
533) <ol>
534) <li>In your taskbar, right click on Privoxy (the blue icon with a white "P")
535) and choose exit.</li>
536) <li>In your taskbar, right click on Vidalia (the green onion or the black head)
537) and choose exit.</li>
538) <li>Right click on the taskbar to bring up TaskManager. Look for tor.exe in the
539) Process List. If it's running, right click and choose End Process.</li>
540) <li>Click the Start button, go to Programs, go to Vidalia, choose Uninstall.
541) This will remove the Vidalia bundle, which includes Tor and Privoxy.</li>
542) <li>Start Firefox. Go to the Tools menu, choose Add-ons. Select Torbutton.
543) Click the Uninstall button.</li>

544) </ol>

545) 
546) <p>

547) If you do not follow these steps (for example by trying to uninstall
548) Vidalia, Tor, and Privoxy while they are still running), you will need to
549) reboot and manually remove the directory "Program Files\Vidalia Bundle".

550) </p>
551) 
552) <p>
553) For Mac OS X, follow the <a

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

555) </p>
556) 
557) <p>
558) If you installed by source, I'm afraid there is no easy uninstall method. But
559) on the bright side, by default it only installs into /usr/local/ and it should
560) be pretty easy to notice things there.
561) </p>
562) 
563) <hr />
564) 

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

568) 
569) <p>
570) These are PGP signatures, so you can verify that the file you've downloaded is
571) exactly the one that we intended you to get.
572) </p>
573) 
574) <p>
575) Please read the <a

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

577) </p>
578) 
579) <hr />
580) 
581) <a id="CompileTorWindows"></a>
582) <h3><a class="anchor" href="#CompileTorWindows">How do I compile Tor under
583) Windows?</a></h3>
584) 
585) <p>
586) Try following the steps at <a

587) href="<svnsandbox>doc/tor-win32-mingw-creation.txt"><svnsandbox>doc/tor-win32-mingw-creation.txt</a>.

588) </p>
589) 

590) <p>
591) (Note that you don't need to compile Tor yourself in order to use
592) it. Most people just use the packages available on the <a href="<page
593) download>">download page</a>.)
594) </p>
595) 

596) <hr />
597) 

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

601) 
602) <p>
603) Sometimes, overzealous Windows virus and spyware detectors trigger on some
604) parts of the Tor Windows binary. Our best guess is that these are false

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

606) guessing game anyway. You should contact your vendor and explain that you have
607) a program that seems to be triggering false positives. Or pick a better vendor.
608) </p>
609) 
610) <p>

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

614) </p>
615) 
616) <hr />
617) 
618) <a id="LiveCD"></a>
619) <h3><a class="anchor" href="#LiveCD">Is there a LiveCD or other bundle that
620) includes Tor?</a></h3>
621) 
622) <p>
623) There isn't any official LiveCD at this point. We're still trying to find good
624) solutions and trying to understand the security and anonymity implications of
625) the various options. In the mean time, feel free to check out the list below
626) and use your best judgement:
627) </p>
628) 
629) <p>

630) LiveCDs:

631) </p>
632) 
633) <ol>
634) <li><a href="http://incognito.anonymityanywhere.com/">Incognito LiveCD/USB</a>
635) is a CD you can boot that has several Internet applications (Firefox, IRC,
636) Mail, etc) pre-configured to use Tor. For most computers everything is
637) automatically configured and you're ready to go. You can even copy the CD to a
638) USB drive. Includes TorK.</li>

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

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

647) </ol>
648) 
649) <p>
650) Windows bundles:
651) </p>
652) 
653) <ol>

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

655) for Windows comes with a pre-configured web browser and is self contained
656) so you can run it from a USB stick.</li>
657) <li><a href="http://www.janusvm.com/tor_vm/">Tor VM</a> is a successor
658) to JanusVM. It needs testing from you!</li>
659) <li><a href="http://janusvm.com/">JanusVM</a> is a Linux kernel and software
660) running in VMWare that sits between your Windows computer and the Internet,
661) making sure that your Internet traffic is scrubbed and anonymized.</li>
662) <li><a href="http://www.xerobank.com/xB_browser.html">xB Browser</a>,
663) previously known as Torpark, is a Firefox+Tor package for Win32 that can
664) installed on a USB key. It needs a host Win32 operating system.</li>

665) </ol>
666) 
667) <p>
668) Not currently maintained as far as we know:
669) </p>
670) 
671) <ol>

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

675) <li>ELE is a Linux LiveCD which is focused on privacy related
676) software. It includes Tor and you can download it at
677) <a
678) href="http://www.northernsecurity.net/download/ele/">http://www.northernsecurity.net/download/ele/</a>.</li>
679) <li>Virtual Privacy Machine is a Linux LiveCD that includes Firefox, Privoxy,
680) Tor, some IRC and IM applications, and a set of ipchains rules aimed to prevent
681) non-Tor traffic from accidentally leaving your computer. More information at
682) <a

683) href="https://wiki.torproject.org/noreply/VirtualPrivacyMachine">https://wiki.torproject.org/noreply/VirtualPrivacyMachine</a>.</li>

684) <li>Anonym.OS is a LiveCD similar to the above but is based on OpenBSD rather
685) than Linux for maximum security. It was designed to be anonymous and secure
686) from the ground up, and thus has some features and limitations not found in
687) other LiveCDs (Tor related or otherwise). You can obtain more information and
688) download Anonym.OS from <a
689) href="http://theory.kaos.to/projects.html">Kaos.Theory</a>.</li>
690) <li>Phantomix is a LiveCD for anonymous surfing and chatting based on the most
691) recent KNOPPIX release. It comes preconfigured with tor and privoxy. You can
692) get it from the <a href="http://phantomix.ytternhagen.de/">Phantomix
693) Website</a>.</li>
694) </ol>
695) 

696) <p>
697) Please contact us if you know any others.
698) </p>
699) 

700) <hr />
701) 

702) <a id="RelayFlexible"></a>
703) <h3><a class="anchor" href="#RelayFlexible">How stable does my relay
704) need to be?</a></h3>
705) 
706) <p>
707) We aim to make setting up a Tor relay easy and convenient:
708) </p>
709) 
710) <ul>
711) <li>Tor has built-in support for <a
712) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#LimitBandwidth">
713) rate
714) limiting</a>. Further, if you have a fast link
715) but want to limit the number of bytes per day
716) (or week or month) that you donate, check out the <a
717) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#Hibernation">hib
718) ernation
719) feature</a>.
720) </li>
721) <li>Each Tor relay has an <a

722) href="#ExitPolicies">exit

723) policy</a> that specifies what sort of outbound connections are allowed
724) or refused from that relay. If you are uncomfortable allowing people
725) to exit from your relay, you can set it up to only allow connections
726) to other Tor relays.
727) </li>
728) <li>It's fine if the relay goes offline sometimes. The directories
729) notice this quickly and stop advertising the relay. Just try to make
730) sure it's not too often, since connections using the relay when it
731) disconnects will break.
732) </li>
733) <li>We can handle relays with dynamic IPs just fine &mdash; simply
734) leave the Address config option blank, and Tor will try to guess.
735) </li>
736) <li>If your relay is behind a NAT and it doesn't know its public
737) IP (e.g. it has an IP of 192.168.x.y), you'll need to set up port
738) forwarding. Forwarding TCP connections is system dependent but <a
739) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#ServerForFirewal
740) ledClients">this
741) FAQ entry</a> offers some examples on how to do this.
742) </li>
743) <li>Your relay will passively estimate and advertise its recent
744) bandwidth capacity, so high-bandwidth relays will attract more users than
745) low-bandwidth ones. Therefore having low-bandwidth relays is useful too.
746) </li>
747) </ul>
748) 
749) <hr />
750) 

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

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

754) want to deal with abuse issues.</a></h3>
755) 
756) <p>
757) Great. That's exactly why we implemented exit policies.
758) </p>
759) 
760) <p>

761) Each Tor relay has an exit policy that specifies what sort of
762) outbound connections are allowed or refused from that relay. The exit
763) policies are propagated to the client via the directory, so clients
764) will automatically avoid picking exit relays that would refuse to
765) exit to their intended destination. This way each relay can decide
766) the services, hosts, and networks he wants to allow connections to,
767) based on abuse potential and his own situation. Read the FAQ entry on
768) <a href="<page faq-abuse>#TypicalAbuses">issues you might encounter
769) if you use the default exit policy</a>, and then read Mike Perry's <a
770) href="https://blog.torproject.org/blog/tips-running-exit-node-minimal-harassment">tips
771) for running an exit node with minimal harassment</a>.
772) </p>
773) 
774) <p>
775) The default exit policy allows access to
776) many popular services (e.g. web browsing), but <a
777) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#DefaultPorts">restricts</a>
778) some due to abuse potential (e.g. mail) and some since
779) the Tor network can't handle the load (e.g. default
780) file-sharing ports). You can change your exit policy
781) using Vidalia's "Sharing" tab, or by manually editing your <a
782) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#torrc">torrc</a>
783) file. If you want to avoid most if not all abuse potential, set it to
784) "reject *:*". This setting means that your relay will be used for
785) relaying traffic inside the Tor network, but not for connections to
786) external websites or other services.
787) </p>
788) 
789) <p>

790) Make sure name resolution works (that is, your computer can resolve
791) Internet addresses correctly).

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

796) </p>
797) 
798) <hr />
799) 

800) <a id="WhyNotNamed"></a>
801) <h3><a class="anchor" href="#WhyNotNamed">Why is my Tor relay not named?</a></h3>
802) 
803) <p>
804) We currently use these metrics to determine if your relay should be named:<br />
805) </p>
806) <ul>
807) <li>The name is not currently mapped to a different key. Existing mappings
808) are removed after 6 months of inactivity from a relay.</li>
809) <li>The relay must have been around for at least two weeks.</li>
810) <li>No other router may have wanted the same name in the past month.</li>
811) </ul>
812) 
813) <hr />
814) 

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

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

818) 
819) <p>

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

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

825) </p>
826) 
827) <p>
828) <b>Encryption</b>: first, all connections in Tor use TLS link encryption,
829) so observers can't look inside to see which circuit a given cell is
830) intended for. Further, the Tor client establishes an ephemeral encryption
831) key with each relay in the circuit, so only the exit relay can read
832) the cells. Both sides discard the circuit key when the circuit ends,
833) so logging traffic and then breaking into the relay to discover the key
834) won't work.
835) </p>
836) 
837) <p>
838) <b>Authentication</b>:
839) Every Tor relay has a public decryption key called the "onion key".
840) When the Tor client establishes circuits, at each step it <a
841) href="<svnsandbox>doc/design-paper/tor-design.html#subsec:circuits">demands
842) that the Tor relay prove knowledge of its onion key</a>. That way

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

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

845) </p>
846) 
847) <p>

848) <b>Coordination</b>:

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

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

852) "directory signing key". The directory authorities <a
853) href="<svnsandbox>doc/spec/dir-spec.txt">provide a signed list</a>

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

859) </p>
860) 
861) <p>

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

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

867) 

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

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

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

873) on how to check Tor's signatures</a>.
874) </p>

875) 

876) <p>

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

882) </p>

883) 

884) <hr />
885) 

886) <a id="EverybodyARelay"></a>
887) <h3><a class="anchor" href="#EverybodyARelay">You should make every Tor
888) user be a relay.</a></h3>
889) 
890) <p>
891) Requiring every Tor user to be a relay would help with scaling the

892) network to handle all our users, and <a href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#RelayAnonymity">running a Tor

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

897) part of providing effective anonymity for everyone, since many Tor users
898) are subject to these or similar constraints and including these clients
899) increases the size of the anonymity set.
900) </p>
901) 
902) <p>
903) That said, we do want to encourage Tor users to run relays, so what we
904) really want to do is simplify the process of setting up and maintaining

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

909) </p>
910) 
911) <p>
912) There are five steps we need to address before we can do this though:
913) </p>
914) 
915) <p>

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

921) </p>
922) 
923) <p>

924) Second, we still need to get better at automatically estimating
925) the right amount of bandwidth to allow. See item #7 on the
926) <a href="<page volunteer>#Research">research section of the
927) volunteer page</a>: "Tor doesn't work very well when relays
928) have asymmetric bandwidth (e.g. cable or DSL)". It might be that <a
929) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#TransportIPnotTCP">switching
930) to UDP transport</a> is the simplest answer here &mdash; which alas is
931) not a very simple answer at all.

932) </p>
933) 
934) <p>

935) Third, we need to work on scalability, both of the network (how to
936) stop requiring that all Tor relays be able to connect to all Tor
937) relays) and of the directory (how to stop requiring that all Tor
938) users know about all Tor relays). Changes like this can have large
939) impact on potential and actual anonymity. See Section 5 of the <a
940) href="<svnsandbox>doc/design-paper/challenges.pdf">Challenges</a> paper
941) for details. Again, UDP transport would help here.

942) </p>
943) 
944) <p>

945) Fourth, we need to better understand the risks from
946) letting the attacker send traffic through your relay while
947) you're also initiating your own anonymized traffic. <a
948) href="http://freehaven.net/anonbib/#back01">Three</a> <a
949) href="http://freehaven.net/anonbib/#clog-the-queue">different</a>
950) <a href="http://freehaven.net/anonbib/#torta05">research</a> papers
951) describe ways to identify the relays in a circuit by running traffic
952) through candidate relays and looking for dips in the traffic while the
953) circuit is active. These clogging attacks are not that scary in the Tor
954) context so long as relays are never clients too. But if we're trying to
955) encourage more clients to turn on relay functionality too (whether as
956) <a href="<page bridges>">bridge relays</a> or as normal relays), then
957) we need to understand this threat better and learn how to mitigate it.

958) </p>
959) 
960) <p>
961) Fifth, we might need some sort of incentive scheme to encourage people
962) to relay traffic for others, and/or to become exit nodes. Here are our

963) <a href="https://blog.torproject.org/blog/two-incentive-designs-tor">current
964) thoughts on Tor incentives</a>.

965) </p>
966) 
967) <p>
968) Please help on all of these!
969) </p>
970) 
971) <hr />
972) 

973) <a id="Criminals"></a>
974) <h3><a class="anchor" href="#Criminals">Doesn't Tor enable criminals to do bad
975) things?</a></h3>
976) 
977) <p>
978) For the answer to this question and others, please see our new <a

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

980) </p>
981) 
982) <hr />
983) 
984) <a id="RespondISP"></a>
985) <h3><a class="anchor" href="#RespondISP">How do I respond to my ISP about my
986) exit relay?</a></h3>
987) 
988) <p>
989) A collection of templates for successfully responding to ISPs is <a
990) href="https://wiki.torproject.org/noreply/TheOnionRouter/TorAbuseTemplates">collected
991) here</a>.
992) </p>
993) 

994) <hr />

995) 

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

997) 
998) #include <foot.wmi>