092e1ed5259c45d363ef2110654fc4aa12f24163
Andrew Lewman first cut of the new, shiny...

Andrew Lewman authored 14 years ago

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5) #include "head.wmi" TITLE="Tor: Volunteer" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">
Andrew Lewman change all of the breadcrum...

Andrew Lewman authored 14 years ago

8)     <a href="<page index>">Home &raquo; </a>
Andrew Lewman first cut of the new, shiny...

Andrew Lewman authored 14 years ago

9)     <a href="<page getinvolved/getinvolved>">Get Involved</a>
10)     <a href="<page getinvolved/volunteer>">Volunteer</a>
11)   </div>
12)   <div id="maincol"> 
13)     <!-- PUT CONTENT AFTER THIS TAG -->
14)     <h1>A few things everyone can do now:</h1>
15)     <ol>
16)     <li>Please consider <a href="<page docs/tor-doc-relay>">running
17)     a relay</a> to help the Tor network grow.</li>
18)     <li>Tell your friends! Get them to run relays. Get them to run hidden
19)     services. Get them to tell their friends.</li>
20)     <li>If you like Tor's goals, please <a href="<page donate/donate>">take a moment
21)     to donate to support further Tor development</a>. We're also looking
22)     for more sponsors &mdash; if you know any companies, NGOs, agencies,
23)     or other organizations that want anonymity / privacy / communications
24)     security, let them know about us.</li>
25)     <li>We're looking for more <a href="<page about/torusers>">good examples of Tor
26)     users and Tor use cases</a>. If you use Tor for a scenario or purpose not
27)     yet described on that page, and you're comfortable sharing it with us,
28)     we'd love to hear from you.</li>
29)     </ol>
30)     
31)     <p>Tor has <a href="<page getinvolved/open-positions>">two open positions</a>.
32)     Please <a href="<page about/contact>">contact us</a> if you are qualified!</p>
33)     
34)     <a id="Documentation"></a>
35)     <h2><a class="anchor" href="#Documentation">Documentation</a></h2>
36)     <ol>
37)     <li>Help translate the web page and documentation into other
38)     languages. See the <a href="<page getinvolved/translation>">translation
39)     guidelines</a> if you want to help out. We especially need Arabic or
40)     Farsi translations, for the many Tor users in censored areas.</li>
41)     <li>Evaluate and document
42)     <a href="https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/TorifyHOWTO">our
43)     list of programs</a> that can be configured to use Tor.</li>
44)     <li>We have a huge list of <a
45)     href="https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/SupportPrograms">potentially useful
46)     programs that interface to Tor</a>. Which ones are useful in which
47)     situations? Please help us test them out and document your results.</li>
48)     </ol>
49)     
50)     <a id="Advocacy"></a>
51)     <h2><a class="anchor" href="#Advocacy">Advocacy</a></h2>
52)     <ol>
53)     <li>Create a <a href="https://trac.torproject.org/projects/tor/wiki/CommunityLogos">community logo</a> under a Creative Commons license that all can use and modify</li>
54)     <li>Create a presentation that can be used for various user group meetings around the world</li>
55)     <li>Create a video about the positive uses of Tor, what Tor is, or how
56)     to use it.  Some have already
57)     started on <a href="http://media.torproject.org/video/">Tor's Media
58)     server</a>, <a
59)     href="http://www.howcast.com/videos/90601-How-To-Circumvent-an-Internet-Proxy">Howcast</a>,
60)     and <a href="http://www.youtube.com/thetorproject">Youtube</a>.</li> 
61)     <li>Create a poster, or a set of posters, around a theme,
62)     such as "Tor for Freedom!"</li>
63)     </ol>
64)     
65)     <a id="Coding"></a>
66)     <a id="Summer"></a>
67)     <a id="Projects"></a>
68)     <h2><a class="anchor" href="#Projects">Good Coding Projects</a></h2>
69)     
70)     <p>
71)     You may find some of these projects to be good <a href="<page
72)     about/gsoc>">Google Summer of Code 2010</a> ideas. We have labelled each idea
73)     with how useful it would be to the overall Tor project (priority), how
74)     much work we expect it would be (effort level), how much clue you should
75)     start with (skill level), and which of our <a href="<page
76)     about/people>#Core">core developers</a> would be good mentors.
77)     If one or more of these ideas looks promising to you, please <a
78)     href="<page about/contact>">contact us</a> to discuss your plans rather than
79)     sending blind applications. You may also want to propose your own project
80)     idea &mdash; which often results in the best applications.
81)     </p>
82)     
83)     <ol>
84)     
85)     <li>
86)     <b>Tor Browser Bundle for Mac OS X</b>
87)     <br />
88)     Priority: <i>High</i>
89)     <br />
90)     Effort Level: <i>High</i>
91)     <br />
92)     Skill Level: <i>Medium</i>
93)     <br />
94)     Likely Mentors: <i>Steven, Erinn, Jacob, Andrew</i>
95)     <br />
96)     The Tor Browser Bundle incorporates Tor, Firefox, Polipo, and the Vidalia
97)     user interface (and optionally the <a href="http://pidgin.im/">Pidgin</a>
98)     Instant Messaging client). Components are pre-configured to operate in a
99)     secure way, and it has very few dependencies on the installed operating
100)     system. It has therefore become one of the most easy to use, and popular,
101)     ways to use Tor on Windows.
102)     <br />
103)     However, there is currently no released package for Mac OS X, so this project
104)     would be to implement Tor Browser Bundle for OS X. This will involve
105)     modifications to Vidalia (C++), possibly Firefox (C) then creating and testing
106)     the launcher on a range of operating system versions and configurations to
107)     verify portability.  Some work on this was completed as part of the Google
108)     Summer of Code 2009. Another part of this project is to identify all of the
109)     traces left behind by using a Tor Browser Bundle on Mac OS X or Linux.
110)     Developing ways to stop, counter, or remove these traces is a final step.
111)     <br />
112)     Students should be familiar with application development on one or
113)     preferably both of Linux and Mac OS X, and be comfortable with C/C++
114)     and shell scripting.
115)     <br />
116)     Part of this project could be usability testing of Tor Browser Bundle,
117)     ideally amongst our target demographic.  That would help a lot in knowing
118)     what needs to be done in terms of bug fixes or new features. We get this
119)     informally at the moment, but a more structured process would be better.
120)     <br />
121)     A beta version of the Tor Browser Bundle has been released for GNU/Linux, but
122)     work is still required for the Tor IM Browser bundle. Work is currently being
123)     done on the Mac OS X version as well. If you would like to help extend or do
124)     security auditing for either (or both) of these, please contact Erinn.
125)     </li>
126)     
127)     <li>
128)     <b>Help track the overall Tor Network status</b>
129)     <br />
130)     Priority: <i>Medium to High</i>
131)     <br />
132)     Effort Level: <i>Medium</i>
133)     <br />
134)     Skill Level: <i>Medium</i>
135)     <br />
136)     Likely Mentors: <i>Karsten, Roger</i>
137)     <br />
138)     It would be great to set up an automated system for tracking network
139)     health over time, graphing it, etc. Part of this project would involve
140)     inventing better metrics for assessing network health and growth. Is the
141)     average uptime of the network increasing? How many relays are qualifying
142)     for Guard status this month compared to last month? What's the turnover
143)     in terms of new relays showing up and relays shutting off? Periodically
144)     people collect brief snapshots, but where it gets really interesting is
145)     when we start tracking data points over time.
146)     <br />
147)     Data could be collected from the Tor Network Scanners in <a
148)     href="https://svn.torproject.org/svn/torflow/trunk/README">TorFlow</a>, from
149)     the server descriptors that each relay publishes, and from other
150)     sources. Results over time could be integrated into one of the <a
151)     href="https://torstatus.blutmagie.de/">Tor Status</a> web pages, or be
152)     kept separate. Speaking of the Tor Status pages, take a look at Roger's
153)     <a href="http://archives.seul.org/or/talk/Jan-2008/msg00300.html">Tor
154)     Status wish list</a>.
155)     </li>
156)     
157)     <li>
158)     <b>Rewrite TorDNSEL, this time with a spec!</b>
159)     <br />
160)     Priority: <i>High</i>
161)     <br />
162)     Effort Level: <i>Medium</i>
163)     <br />
164)     Skill Level: <i>Medium</i>
165)     <br />
166)     Likely Mentors: <i>Mike, Roger, Sebastian, Damian</i>
167)     <br />
168)     The <a href="<page projects/tordnsel>">Tor DNS Exit List</a> is an
169)     unmaintained Haskell
170)     program that serves three purposes. First, it provides an rbl-style DNS
171)     interface for people to look up whether a given IP address is (or has
172)     recently been) a Tor exit relay. Second, it actively builds circuits over
173)     the Tor network and connects back to itself, to learn the actual exit
174)     IP address of each relay &mdash; some Tor relays exit from a different
175)     address than they advertise in their descriptor. Third, it exports a <a
176)     href="http://exitlist.torproject.org/exitAddresses">set of conclusions</a>
177)     so that <a href="https://check.torproject.org/">check.torproject.org</a>
178)     can guess for you whether your browser is configured to point to Tor.
179)     <br />
180)     This project would make use of <a
181)     href="https://svn.torproject.org/svn/torflow/trunk/README">TorFlow</a>,
182)     a set of Python scripts to interact with Tor,
183)     to figure out how our Tor Exit Checker should actually work, and then
184)     build it &mdash; probably in Python since Torflow is in Python. The main
185)     goal is to reduce false positives as much as possible, by making sure
186)     that it learns about new relays as soon as possible, making sure that
187)     the testing phase concludes quickly, and making sure the answers get
188)     passed to the Check script quickly. As a bonus, we should standardize
189)     (specify) the format of the exitAddresses file, and rewrite the <a
190)     href="https://svn.torproject.org/svn/check/trunk/cgi-bin/TorBulkExitList.py">Tor
191)     Bulk Exit List</a> script to use that file rather than its current <a
192)     href="https://bugs.torproject.org/flyspray/index.php?do=details&id=1019">horrible
193)     DNS hacks</a>. As an extra bonus, we should work with Freenode, OFTC,
194)     and/or other IRC networks to make sure that the scripts we offer are
195)     actually the scripts they want, in terms of accurately identifying which
196)     of their users are coming from the Tor network.
197)     <br />
198)     You can fetch the <a href="git://git.torproject.org/git/tordnsel">latest
199)     tordnsel</a> via git.
200)     </li>
201)     
202)     <li>
203)     <b>Improving Tor's ability to resist censorship</b>
204)     <br />
205)     Priority: <i>Medium to High</i>
206)     <br />
207)     Effort Level: <i>Medium to High</i>
208)     <br />
209)     Skill Level: <i>High</i>
210)     <br />
211)     Likely Mentors: <i>Roger, Nick, Steven</i>
212)     <br />
213)     The Tor 0.2.1.x series makes <a
214)     href="<svnprojects>design-paper/blocking.html">significant
215)     improvements</a> in resisting national and organizational censorship.
216)     But Tor still needs better mechanisms for some parts of its
217)     anti-censorship design.
218)     <br />
219)     One huge category of work is adding features to our <a
220)     href="http://gitweb.torproject.org//bridgedb.git?a=tree">bridgedb</a>
221)     service (Python). Tor aims to give out <a href="<page docs/bridges>">bridge
222)     relay addresses</a> to users that can't reach the Tor network
223)     directly, but there's an arms race between algorithms for distributing
224)     addresses and algorithms for gathering and blocking them. See <a
225)     href="https://blog.torproject.org/blog/bridge-distribution-strategies">our
226)     blog post on the topic</a> as an overview, and then look at <a
227)     href="http://archives.seul.org/or/dev/Dec-2009/msg00000.html">Roger's
228)     or-dev post</a> from December for more recent thoughts &mdash; lots of
229)     design work remains.
230)     <br />
231)     If you want to get more into the guts of Tor itself (C), a more minor problem
232)     we should address is that current Tors can only listen on a single
233)     address/port combination at a time. There's
234)     <a href="<gitblob>doc/spec/proposals/118-multiple-orports.txt">a
235)     proposal to address this limitation</a> and allow clients to connect
236)     to any given Tor on multiple addresses and ports, but it needs more
237)     work.
238)     <br />
239)     This project could involve a lot of research and design. One of the big
240)     challenges will be identifying and crafting approaches that can still
241)     resist an adversary even after the adversary knows the design, and
242)     then trading off censorship resistance with usability and robustness.
243)     </li>
244)     
245)     <!--<li>
246)     <b>Tuneup Tor!</b>
247)     <br />
248)     Priority: <i>Medium to High</i>
249)     <br />
250)     Effort Level: <i>Medium to High</i>
251)     <br />
252)     Skill Level: <i>High</i>
253)     <br />
254)     Likely Mentors: <i>Nick, Roger, Mike, Karsten</i>
255)     <br />
256)     Right now, Tor relays measure and report their own bandwidth, and Tor
257)     clients choose which relays to use in part based on that bandwidth.
258)     This approach is vulnerable to
259)     <a href="http://freehaven.net/anonbib/#bauer:wpes2007">attacks where
260)     relays lie about their bandwidth</a>;
261)     to address this, Tor currently caps the maximum bandwidth
262)     it's willing to believe any relay provides.  This is a limited fix, and
263)     a waste of bandwidth capacity to boot.  Instead,
264)     Tor should possibly measure bandwidth in a more distributed way, perhaps
265)     as described in the
266)     <a href="http://freehaven.net/anonbib/author.html#snader08">"A Tune-up for
267)     Tor"</a> paper
268)     by Snader and Borisov. One could use current testing code to
269)     double-check this paper's findings and verify the extent to which they
270)     dovetail with Tor as deployed in the wild, and determine good ways to
271)     incorporate them into their suggestions Tor network without adding too
272)     much communications overhead between relays and directory
273)     authorities.
274)     </li>-->
275)     
276)     <li>
277)     <b>Improving Polipo on Windows</b>
278)     <br />
279)     Priority: <i>Medium to High</i>
280)     <br />
281)     Effort Level: <i>Medium</i>
282)     <br />
283)     Skill Level: <i>Medium</i>
284)     <br />
285)     Likely Mentors: <i>Chris</i>
286)     <br />
287)     Help port <a
288)     href="http://www.pps.jussieu.fr/~jch/software/polipo/">Polipo</a> to
289)     Windows. Example topics to tackle include:
290)     <ol><li> the ability to asynchronously query name servers, find the
291)     system nameservers, and manage netbios and dns queries.</li>
292)     <li> manage events and buffers natively (i.e. in Unix-like OSes,
293)     Polipo defaults to 25% of ram, in Windows it's whatever the config
294)     specifies).</li>
295)     <li> some sort of GUI config and reporting tool, bonus if it has a
296)     systray icon with right clickable menu options. Double bonus if it's
297)     cross-platform compatible.</li>
298)     <li> allow the software to use the Windows Registry and handle proper
299)     Windows directory locations, such as "C:\Program Files\Polipo"</li>
300)     </ol>
301)     </li>
302)     
303)     <li>
304)     <b>Tor Controller Status Event Interface for Vidalia</b>
305)     <br />
306)     Priority: <i>Medium</i>
307)     <br />
308)     Effort Level: <i>Medium</i>
309)     <br />
310)     Skill Level: <i>Low to Medium</i>
311)     <br />
312)     Likely Mentors: <i>Matt</i>
313)     <br />
314)     There are a number of status changes inside Tor of which the user may need
315)     to be informed. For example, if the user is trying to set up his Tor as a
316)     relay and Tor decides that its ports are not reachable from outside
317)     the user's network, we should alert the user. Currently, all the user
318)     gets is a couple log messages in Vidalia's 'message log' window, which they
319)     likely never see since they don't receive a notification that something
320)     has gone wrong. Even if the user does actually look at the message log,
321)     most of the messages make little sense to the novice user.
322)     <br />
323)     Tor has the ability to inform Vidalia of many such status changes, and
324)     we recently implemented support for a couple of these events. Still,
325)     there are many more status events the user should be informed of and we
326)     need a better UI for actually displaying them to the user.
327)     <br />
328)     The goal of this project then is to design and implement a UI for
329)     displaying Tor status events to the user. For example, we might put a
330)     little badge on Vidalia's tray icon that alerts the user to new status
331)     events they should look at. Double-clicking the icon could bring up a
332)     dialog that summarizes recent status events in simple terms and maybe
333)     suggests a remedy for any negative events if they can be corrected by
334)     the user. Of course, this is just an example and one is free to
335)     suggest another approach.
336)     <br />
337)     A person undertaking this project should have good UI design and layout
338)     and some C++ development experience. Previous experience with Qt and
339)     Qt's Designer will be very helpful, but are not required. Some
340)     English writing ability will also be useful, since this project will
341)     likely involve writing small amounts of help documentation that should
342)     be understandable by non-technical users. Bonus points for some graphic
343)     design/Photoshop fu, since we might want/need some shiny new icons too.
344)     </li>
345)     
346)     <li>
347)     <b>Improve our unit testing process</b>
348)     <br />
349)     Priority: <i>Medium</i>
350)     <br />
351)     Effort Level: <i>Medium</i>
352)     <br />
353)     Skill Level: <i>Medium</i>
354)     <br />
355)     Likely Mentors: <i>Nick, Erinn</i>
356)     <br />
357)     Tor needs to be far more tested. This is a multi-part effort. To start
358)     with, our unit test coverage should rise substantially, especially in
359)     the areas outside the utility functions. This will require significant
360)     refactoring of some parts of Tor, in order to dissociate as much logic
361)     as possible from globals.
362)     <br />
363)     Additionally, we need to automate our performance testing. We've got
364)     buildbot to automate our regular integration and compile testing already
365)     (though we need somebody to set it up on Windows),
366)     but we need to get our network simulation tests (as built in <a
367)     href="https://svn.torproject.org/svn/torflow/trunk/README">TorFlow</a>)
368)     updated for more recent versions of Tor, and designed to launch a test
369)     network either on a single machine, or across several, so we can test
370)     changes in performance on machines in different roles automatically.
371)     </li>
372)     
373)     <li>
374)     <b>Help with independent Tor client implementations</b>
375)     <br />
376)     Priority: <i>Medium</i>
377)     <br />
378)     Effort Level: <i>High</i>
379)     <br />
380)     Skill Level: <i>Medium to High</i>
381)     <br />
382)     Likely Mentors: <i>Bruce, Nathan</i>
383)     <br />
384)     Others are currently working on Tor clients for Java, Android, and Maemo
385)     environments.  The first step is to get a handle on the current state of
386)     the project in which you are interested in helping; <a
387)     href="http://github.com/brl/JTor">Tor for Java</a>,
388)     <a href="https://svn.torproject.org/svn/projects/android/trunk/">Android/Orbot</a>
389)     , or <a href="<page docs/N900>">Tor for Maemo</a>. Check out the
390)     repository and familiarize yourself
391)     with the source code.  Further, support for requesting or even providing
392)     Tor hidden services would be neat, but not required.
393)     <br />
394)     A prospective developer should be able to understand and write new Java
395)     code, including a Java cryptography API. Being able to read C code would be helpful,
396)     too. One should be willing to read the existing documentation,
397)     implement code based on it, and refine the documentation
398)     when things are underdocumented. This project is mostly about coding and
399)     to a small degree about design.
400)     </li>
401)     <li>
402)     <b>More on Orbot &amp; Android OS-specific development</b>
403)     <br/>
404)     <br />
405)     Priority: <i>Medium</i>
406)     <br />
407)     Effort Level: <i>High</i>
408)     <br />
409)     Skill Level: <i>Medium to High</i>
410)     <br />
411)     Likely Mentors: <i>Nathan</i>
412)     <br />
413)     
414)     <b>Android Java UI work:</b> Improved home screen to show better statistics about data transferred (up/down), number of circuits connected, quality of connection and so on. The "Tether Wifi" Android application is a good model to follow in how it shows a realtime count of bytes transferred as well as notifications when wifi client connect. In addition, better display/handling of Tor system/error messages would also be very helpful. Finally, the addition of a wizard or tutorial walkthrough for novice users to explain to them exactly what or what is not anonymized or protected would greatly improve the likelihood they will use Orbot correctly.
415)     <br/><br/>
416)     
417)     <b>Android Java OS/Core app work:</b> Better system-wide indicator either via the notification bar, "Toast" pop-up dialogs or some other indicator that an application's traffic is indeed moving through Orbot/Tor. For instance, right now you need to first go to a torcheck web service to ensure your browser is routing via Tor. Orbot should be able to notify you that circuits are being opened, used, etc. The aforementioned data transfer tracker might provide this type of awareness as well.
418)     
419)     <br/><br/>
420)     <b>Android Java Library/Community Outreach work:</b> We need to package a simple library for use with third-party application to easily enable them to support "Torification" on non-root devices (aka w/o transparent proxying). This library should include a wrapper for the Apache HTTPClient library, a utility class for detecting the state of Orbot connectivity, and other relevant/useful things an Android app might need to anonymize itself. This work would include the creation of the library, documentation, and sample code. Outreach or effort to implement the library within other open-source apps would follow.
421)     
422)     <br/><br/>
423)     <b>Android OS/C/Linux work:</b> The port of Tor to Android is basically a straight cross-compile to Linux ARM. There has been no work done in looking the optimization of Tor within a mobile hardware environment, on the ARM processor or other Android hardware, or on mobile networks. It should be noted, that even without optimization, Tor is handling the mobile network environment very well, automatically detecting change in IP addresses, reconnecting circuits, etc across switching from 2G to 3G to Wifi, and so forth. 
424)     </li>
425)     
426)     <!--<li>
427)     <b>New Torbutton Features</b>
428)     <br />
429)     Priority: <i>Medium</i>
430)     <br />
431)     Effort Level: <i>High</i>
432)     <br />
433)     Skill Level: <i>High</i>
434)     <br />
435)     Likely Mentors: <i>Mike</i>
436)     <br/>
437)     There are several <a
438)     href="https://bugs.torproject.org/flyspray/index.php?tasks=all&amp;project=5&amp;type=2">good
439)     feature requests</a> on the Torbutton Flyspray section. In particular, <a
440)     href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=523">Integrating
441)     'New Identity' with Vidalia</a>,
442)     <a href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=940">ways of
443)     managing multiple cookie jars/identities</a>, <a
444)     href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=637">preserving
445)     specific cookies</a> when cookies are cleared,
446)     <a
447)     href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=524">better
448)     referrer spoofing</a>, <a
449)     href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=564">correct
450)     Tor status reporting</a>, and <a
451)     href="https://bugs.torproject.org/flyspray/index.php?do=details&amp;id=462">"tor://"
452)     and "tors://" urls</a> are all interesting
453)     features that could be added.
454)     <br />
455)     This work would be independent coding in Javascript and the fun world of <a
456)     href="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">XUL</a>,
457)     with not too much involvement in the Tor internals.
458)     </li>-->
459)     
460)     <!-- <li>
461)     <b>New Thandy Features</b>
462)     <br />
463)     Priority: <i>Medium</i>
464)     <br />
465)     Effort Level: <i>Medium</i>
466)     <br />
467)     Skill Level: <i>Medium to High</i>
468)     <br />
469)     Likely Mentors: <i>Martin</i>
470)     <br />
471)     Additional capabilities are needed for assisted updates of all the Tor
472)     related software for Windows and other operating systems. Some of the
473)     features to consider include:
474)     <ol>
475)     <li> Integration of the <a
476)     href="http://chandlerproject.org/Projects/MeTooCrypto">MeTooCrypto
477)     Python library</a>
478)     for authenticated HTTPS downloads.</li>
479)     <li> Adding a level of indirection
480)     between the timestamp signatures and the package files included in an
481)     update. See the "Thandy attacks / suggestions" thread on or-dev.</li>
482)     <li> Support locale specific installation and configuration of assisted
483)     updates based on preference, host, or user account language settings.
484)     Familiarity with Windows codepages, unicode, and other character sets
485)     is helpful in addition to general win32 and posix API experience and
486)     Python proficiency.</li>
487)     </ol>
488)     </li> -->
489)     
490)     <li>
491)     <b>Simulator for slow Internet connections</b>
492)     <br />
493)     Priority: <i>Medium</i>
494)     <br />
495)     Effort Level: <i>Medium</i>
496)     <br />
497)     Skill Level: <i>Medium</i>
498)     <br />
499)     Likely Mentors: <i>Steven</i>
500)     <br />
501)     Many users of Tor have poor-quality Internet connections, giving low
502)     bandwidth, high latency, and high packet loss/re-ordering. User
503)     experience is that Tor reacts badly to these conditions, but it is
504)     difficult to improve the situation without being able to repeat the
505)     problems in the lab.
506)     <br />
507)     This project would be to build a simulation environment which
508)     replicates the poor connectivity so that the effect on Tor performance
509)     can be measured. Other components would be a testing utility to
510)     establish what are the properties of connections available, and to
511)     measure the effect of performance-improving modifications to Tor.
512)     <br />
513)     The tools used would be up to the student, but dummynet (for FreeBSD)
514)     and nistnet (for Linux) are two potential components on which this
515)     project could be built. Students should be experienced with network
516)     programming/debugging and TCP/IP, and preferably familiar with C and a
517)     scripting language.
518)     </li>
519)     
520)     <li>
521)     <b>An Improved and More Usable Network Map in Vidalia</b>
522)     <br />
523)     Priority: <i>Low to Medium</i>
524)     <br />
525)     Effort Level: <i>Medium</i>
526)     <br />
527)     Skill Level: <i>Medium</i>
528)     <br />
529)     Likely Mentors: <i>Matt</i>
530)     <br />
531)     One of Vidalia's existing features is a network map that shows the user
532)     the approximate geographic location of relays in the Tor network and
533)     plots the paths the user's traffic takes as it is tunneled through the
534)     Tor network. The map is currently not very interactive and has rather
535)     poor graphics. Instead, we implemented KDE's Marble widget such
536)     that it gives us a better quality map and enables improved interactivity,
537)     such as allowing the user to click on individual relays or circuits to
538)     display additional information. We want to add the ability
539)     for users to click on a particular relay or a country containing one or
540)     more Tor exit relays and say, "I want my connections to exit
541)     from here."
542)     <br />
543)     This project will first involve getting familiar with Vidalia
544)     and the Marble widget's API. One will then integrate the widget
545)     into Vidalia and customize Marble to be better suited for our application,
546)     such as making circuits clickable, storing cached map data in Vidalia's
547)     own data directory, and customizing some of the widget's dialogs.
548)     <br />
549)     A person undertaking this project should have good C++ development
550)     experience. Previous experience with Qt and CMake is helpful, but not
551)     required.
552)     </li>
553)     
554)     <li>
555)     <b>Torbutton equivalent for Thunderbird</b>
556)     <br />
557)     Priority: <i>Medium</i>
558)     <br />
559)     Effort Level: <i>High</i>
560)     <br />
561)     Skill Level: <i>High</i>
562)     <br />
563)     Likely Mentors: <i>Mike</i>
564)     <br />
565)     We're hearing from an increasing number of users that they want to use
566)     Thunderbird with Tor. However, there are plenty of application-level
567)     concerns, for example, by default Thunderbird will put your hostname in
568)     the outgoing mail that it sends. At some point we should start a new
569)     push to build a Thunderbird extension similar to Torbutton.
570)     </li>
571)     
572)     <!--<li>
573)     <b>Intermediate Level Network Device Driver</b>
574)     <br />
575)     Priority: <i>Low</i>
576)     <br />
577)     Effort Level: <i>High</i>
578)     <br />
579)     Skill Level: <i>High</i>
580)     <br />
581)     Likely Mentors: <i>Martin</i>
582)     <br />
583)     The WinPCAP device driver used by Tor VM for bridged networking does
584)     not support a number of wireless and non-Ethernet network adapters.
585)     Implementation of a intermediate level network device driver for win32
586)     and 64bit would provide a way to intercept and route traffic over such
587)     networks. This project will require knowledge of and experience with
588)     Windows kernel device driver development and testing. Familiarity with
589)     Winsock and Qemu would also be helpful.
590)     </li>-->
591)     
592)     <li>
593)     <b>Improve Tor Weather</b>
594)     <br />
595)     Priority: <i>Medium</i>
596)     <br />
597)     Effort Level: <i>Medium</i>
598)     <br />
599)     Skill Level: <i>Medium</i>
600)     <br />
601)     Likely Mentors: <i>Christian, Roger, Damian</i>
602)     <br />
603)     <a href="https://weather.torproject.org/">Tor weather</a> is a tool
604)     that allows signing up to receive notifications via email when the
605)     tracked Tor relay is down. Currently, it isn't really useful for
606)     people who use the hibernation feature of Tor, or for those who
607)     have to shut down their relay regularly. During the project, Tor
608)     weather could be extended to allow more flexible configurations.
609)     Other enhancements are also possible: Weather could send out warnings
610)     when your relay runs an out-of-date version of Tor, or when its
611)     observed bandwith drops below a certain value. It might also be a
612)     nice tool that allows for checking whether your relay has earned
613)     you a <a href="<page getinvolved/tshirt>">T-Shirt</a>, or sending reminders to
614)     directory authorities that
615)     their keys are about to expire. Be creative, and consider how the
616)     above project to track overall network status can help you get your job
617)     done more quickly! See also its
618)     <a href="https://svn.torproject.org/svn/weather/trunk/README">README</a>
619)     and <a href="https://svn.torproject.org/svn/weather/trunk/TODO">TODO</a>.
620)     </li>
621)     
622)     <li>
623)     <b>Improvements for Tor+Vidalia interaction on Linux/Unix platforms</b>
624)     <br />
625)     Priority: <i>Medium</i>
626)     <br />
627)     Effort Level: <i>Medium</i>
628)     <br />
629)     Skill Level: <i>Medium</i>
630)     <br />
631)     Likely Mentors: <i>Erinn, Peter</i>
632)     <br />
633)     Vidalia currently doesn't play nicely with Tor on Linux and Unix platforms.
634)     Currently, on Debian and Ubuntu, there is a configuration mechanism which
635)     allows Vidalia to override Tor's ability to start on boot (by sourcing
636)     <code>/etc/default/tor.vidalia</code> which sets <code>RUN_DAEMON=no</code> at the user's
637)     request), but full implementation of <a href="<gitblob>doc/spec/control-spec.txt">ControlPort</a> 
638)     communication is still required.
639)     <br />
640)     A better solution on Linux and Unix platforms would be to use Tor's
641)     ControlSocket, which allows Vidalia to talk to Tor via a Unix domain socket,
642)     and could possibly be enabled by default in Tor's distribution packages.
643)     Vidalia can then authenticate to Tor using filesystem-based (cookie)
644)     authentication if the user running Vidalia is also in the distribution-specific
645)     tor group.
646)     <br />
647)     This project will first involve adding support for Tor's ControlSocket to
648)     Vidalia. The student will then develop and test this support on various
649)     distributions to make sure it behaves in a predictable and consistent manner on
650)     all of them.
651)     <br />
652)     The next challenge would be to find an intuitive and usable way for Vidalia to be
653)     able to change Tor's configuration (torrc) even though it is located in
654)     <code>/etc/tor/torrc</code> and thus immutable. In Debian and Ubuntu we handle
655)     this with the aforementioned <code>/etc/default/tor.vidalia</code> but this
656)     functionality could (or should) be less distribution-specific. 
657)     <br />
658)     The best idea we've come up with so far is to feed Tor a new configuration via
659)     the ControlSocket when Vidalia starts, but that's bad because if the user is not
660)     using the latest Debian/Ubuntu packages, they may not have disabled Tor's
661)     ability to run on boot and will end up with a configuration that is different
662)     from what they want. The second best idea we've come up with is for Vidalia to
663)     write out a temporary torrc file and ask the user to manually move it to
664)     <code>/etc/tor/torrc</code>, but that's bad because users shouldn't have to
665)     mess with files directly.
666)     <br />
667)     A person undertaking this project should have prior knowledge of various Linux
668)     distributions and their packaging mechanisms as well as some C++ development
669)     experience. Previous experience with Qt is helpful, but not required.
670)     </li>
671)     
672)     <!--<li>
673)     <b>Tor/Polipo/Vidalia Auto-Update Framework</b>
674)     <br />
675)     We're in need of a good authenticated-update framework.
676)     Vidalia already has the ability to notice when the user is running an
677)     outdated or unrecommended version of Tor, using signed statements inside
678)     the Tor directory information. Currently, Vidalia simply pops
679)     up a little message box that lets the user know they should manually
680)     upgrade. The goal of this project would be to extend Vidalia with the
681)     ability to also fetch and install the updated Tor software for the
682)     user. We should do the fetches via Tor when possible, but also fall back
683)     to direct fetches in a smart way. Time permitting, we would also like
684)     to be able to update other
685)     applications included in the bundled installers, such as Polipo and
686)     Vidalia itself.
687)     <br />
688)     To complete this project, the student will first need to first investigate
689)     the existing auto-update frameworks (e.g., Sparkle on OS X) to evaluate
690)     their strengths, weaknesses, security properties, and ability to be
691)     integrated into Vidalia. If none are found to be suitable, the student
692)     will design their own auto-update framework, document the design, and
693)     then discuss the design with other developers to assess any security
694)     issues. The student will then implement their framework (or integrate
695)     an existing one) and test it.
696)     <br />
697)     A person undertaking this project should have good C++ development
698)     experience. Previous experience with Qt is helpful, but not required. One
699)     should also have a good understanding of common security
700)     practices, such as package signature verification. Good writing ability
701)     is also important for this project, since a vital step of the project
702)     will be producing a design document to review and discuss
703)     with others prior to implementation.
704)     </li>-->
705)     
706)     <li>
707)     <b>Improving the Tor QA process: Continuous Integration for builds</b>
708)     <br />
709)     Priority: <i>Medium</i>
710)     <br />
711)     Effort Level: <i>Medium</i>
712)     <br />
713)     Skill Level: <i>Medium</i>
714)     <br />
715)     Likely Mentors: <i>Erinn</i>
716)     <br />
717)     It would be useful to have automated build processes for Windows and
718)     probably other platforms. The purpose of having a continuous integration
719)     build environment is to ensure that Windows isn't left behind for any of
720)     the software projects used in the Tor project or its accompanying.<br />
721)     Buildbot may be a good choice for this as it appears to support all of
722)     the platforms Tor does. See the
723)     <a href="http://en.wikipedia.org/wiki/BuildBot">wikipedia entry for
724)     buildbot</a>.<br />
725)     There may be better options and the person undertaking this task should
726)     evaluate other options. Any person working on this automatic build
727)     process should have experience or be willing to learn how to build all
728)     of the respective Tor related code bases from scratch. Furthermore, the
729)     person should have some experience building software in Windows
730)     environments as this is the target audience we want to ensure we do not
731)     leave behind. It would require close work with the Tor source code but
732)     probably only in the form of building, not authoring.<br />
733)     Additionally, we need to automate our performance testing for all platforms.
734)     We've got buildbot (except on Windows &mdash; as noted above) to automate
735)     our regular integration and compile testing already,
736)     but we need to get our network simulation tests (as built in torflow)
737)     updated for more recent versions of Tor, and designed to launch a test
738)     network either on a single machine, or across several, so we can test
739)     changes in performance on machines in different roles automatically.
740)     </li>
741)     
742)     <!--<li>
743)     <b>Usability testing of Tor</b>
744)     <br />
745)     Priority: <i>Medium</i>
746)     <br />
747)     Effort Level: <i>Medium</i>
748)     <br />
749)     Skill Level: <i>Low to Medium</i>
750)     <br />
751)     Likely Mentors: <i>Andrew</i>
752)     <br />
753)     Especially the browser bundle, ideally amongst our target demographic.
754)     That would help a lot in knowing what needs to be done in terms of bug
755)     fixes or new features. We get this informally at the moment, but a more
756)     structured process would be better.
757)     </li>-->
758)     
759)     <li>
760)     <b>An authenticating IRC proxy</b>
761)     <br />
762)     Priority: <i>Low</i>
763)     <br />
764)     Effort Level: <i>Medium to High</i>
765)     <br />
766)     Skill Level: <i>Medium to High</i>
767)     <br />
768)     Likely Mentors: <i>Sebastian, Weasel, Roger</i>
769)     <br />
770)     The world needs an authenticating irc proxy. As we're periodically
771)     reminded from the Penny Arcade web comic, "Internet user + anonymity =
772)     jerk". With respect to websites we're actually doing ok, since websites
773)     can make their users log in and use other application-level authentication
774)     approaches. But IRC servers are much worse off, because most IRC server
775)     code is poorly written: hard to maintain, and harder to modify. Many
776)     IRC networks now block connections from Tor, and we're basically down to
777)     two holdouts (OFTC and Freenode). This state of affairs means that a lot
778)     of people around the world are thinking "I told you so" about anonymity
779)     online, when in fact the problem is simply lack of technology to make the
780)     problem manageable. We need some way to let the IRC networks distinguish
781)     which users have developed a reputation as not being jerks, so they can
782)     treat the two groups separately. There are some really cool research
783)     designs like <a href="http://www.cs.dartmouth.edu/~nymble/">Nymble</a>,
784)     which aim to let websites blacklist users without needing to learn who
785)     they are.  But Nymble is designed around web interactions. We need to
786)     build the glue around the IRC protocol that would let us plug in a project
787)     like Nymble (or a simpler one to start, as a proof-of-concept). One way
788)     to do that would be to build an IRC proxy that knows how to hear from
789)     IRC clients, knows how to talk to IRC servers, and has an additional
790)     layer that requires the users to authenticate.  Some work on this has
791)     begun by other volunteers, see their progress at <a
792)     href="http://github.com/anonirc/orc">http://github.com/anonirc/orc</a>.
793)     </li>
794)     
795)     <li>
796)     <b>Make torsocks/dsocks work on OS X</b>
797)     <br />
798)     Priority: <i>Medium</i>
799)     <br />
800)     Effort Level: <i>Medium</i>
801)     <br />
802)     Skill Level: <i>Medium</i>
803)     <br />
804)     Likely Mentors: <i>?</i>
805)     <br />
806)     <a href="http://code.google.com/p/torsocks/">Torsocks</a> and <a
807)     href="http://code.google.com/p/dsocks/">dsocks</a> are wrappers that will
808)     run applications, intercept their outgoing network connections, and push
809)     those connections through Tor. The goal is to handle applications that
810)     don't support proxies (or don't supporting them well). To get it right,
811)     they need to intercept many system calls. The syscalls you need to
812)     intercept on Linux differ dramatically from those on BSD. So Torsocks
813)     works fine on Linux, dsocks works ok on BSD (though it may be less
814)     maintained and thus might miss more syscalls), and nothing works well
815)     on both. First, we should patch dsocks to use Tor's <i>mapaddress</i>
816)     commands from the controller interface, so we don't waste a whole
817)     round-trip inside Tor doing the resolve before connecting. Second,
818)     we should make our <i>torify</i> script detect which of torsocks or
819)     dsocks is installed, and call them appropriately. This probably means
820)     unifying their interfaces, and might involve sharing code between them
821)     or discarding one entirely.
822)     </li>
823)     
824)     <li>
825)     <b>Bring up new ideas!</b>
826)     <br />
827)     Don't like any of these? Look at the <a
828)     href="<gitblob>doc/roadmaps/2008-12-19-roadmap-full.pdf">Tor development
829)     roadmap</a> for more ideas, or just try out Tor, Vidalia, and Torbutton,
830)     and find out what you think needs fixing.
831)     Some of the <a href="<gittree>doc/spec/proposals">current proposals</a>
832)     might also be short on developers.
833)     </li>
834)     
835)     </ol>
836)     
837)     <a id="OtherCoding"></a>
838)     <h2><a class="anchor" href="#OtherCoding">Other Coding and Design related ideas</a></h2>
839)     <ol>
840)     <li>Tor relays don't work well on Windows XP. On
841)     Windows, Tor uses the standard <tt>select()</tt> system
842)     call, which uses space in the non-page pool. This means
843)     that a medium sized Tor relay will empty the non-page pool, <a
844)     href="https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/WindowsBufferProblems">causing
845)     havoc and system crashes</a>. We should probably be using overlapped IO
846)     instead. One solution would be to teach <a
847)     href="http://www.monkey.org/~provos/libevent/">libevent</a> how to use
848)     overlapped IO rather than select() on Windows, and then adapt Tor to
849)     the new libevent interface. Christian King made a
850)     <a href="https://svn.torproject.org/svn/libevent-urz/trunk/">good
851)     start</a> on this in the summer of 2007.</li>
852)     
853)     <li>We need to actually start building our <a href="<page
854)     docs/documentation>#DesignDoc">blocking-resistance design</a>. This involves
855)     fleshing out the design, modifying many different pieces of Tor, adapting
856)     <a href="<page projects/vidalia>">Vidalia</a> so it supports the
857)     new features, and planning for deployment.</li>
858)     
859)     <li>We need a flexible simulator framework for studying end-to-end
860)     traffic confirmation attacks. Many researchers have whipped up ad hoc
861)     simulators to support their intuition either that the attacks work
862)     really well or that some defense works great. Can we build a simulator
863)     that's clearly documented and open enough that everybody knows it's
864)     giving a reasonable answer? This will spur a lot of new research.
865)     See the entry <a href="#Research">below</a> on confirmation attacks for
866)     details on the research side of this task &mdash; who knows, when it's
867)     done maybe you can help write a paper or three also.</li>
868)     
869)     <li>Tor 0.1.1.x and later include support for hardware crypto accelerators
870)     via OpenSSL. It has been lightly tested and is possibly very buggy.  We're looking for more rigorous testing, performance analysis, and optimally, code fixes to openssl and Tor if needed.</li>
871)     
872)     <li>Perform a security analysis of Tor with <a
873)     href="http://en.wikipedia.org/wiki/Fuzz_testing">"fuzz"</a>. Determine
874)     if there are good fuzzing libraries out there for what we want. Win fame by
875)     getting credit when we put out a new release because of you!</li>
876)     
877)     <li>Tor uses TCP for transport and TLS for link
878)     encryption. This is nice and simple, but it means all cells
879)     on a link are delayed when a single packet gets dropped, and
880)     it means we can only reasonably support TCP streams. We have a <a
881)     href="https://trac.torproject.org/projects/tor/wiki/TheOnionRouter/TorFAQ#YoushouldtransportallIPpacketsnotjustTCPpackets.">list
882)     of reasons why we haven't shifted to UDP transport</a>, but it would
883)     be great to see that list get shorter. We also have a proposed <a
884)     href="<gitblob>doc/spec/proposals/100-tor-spec-udp.txt">specification
885)     for Tor and
886)     UDP</a> &mdash; please let us know what's wrong with it.</li>
887)     
888)     <li>We're not that far from having IPv6 support for destination addresses
889)     (at exit nodes). If you care strongly about IPv6, that's probably the
890)     first place to start.</li>
891)     
892)     <li>We need a way to generate the website diagrams (for example, the "How
893)     Tor Works" pictures on the <a href="<page about/overview>">overview page</a>
894)     from source, so we can translate them as UTF-8 text rather than edit
895)     them by hand with Gimp. We might want to
896)     integrate this as an wml file so translations are easy and images are
897)     generated in multiple languages whenever we build the website.</li>
898)     
899)     <li>How can we make the various LiveCD/USB systems easier
900)     to maintain, improve, and document?  One example is <a
901)     href="https://amnesia.boum.org/">The (Amnesic) Incognito Live
902)     System</a>.
903)     </li>
904)     
905)     <li>
906)     Another anti-censorship project is to try to make Tor
907)     more scanning-resistant.  Right now, an adversary can identify <a
908)     href="<gitblob>doc/spec/proposals/125-bridges.txt">Tor bridges</a>
909)     just by trying to connect to them, following the Tor protocol,
910)     and seeing if they respond.  To solve this, bridges could <a
911)     href="<svnprojects>design-paper/blocking.html#tth_sEc9.3">act like
912)     webservers</a> (HTTP or HTTPS) when contacted by port-scanning tools,
913)     and not act like bridges until the user provides a bridge-specific key.
914)     To start, check out Shane Pope's <a
915)     href="http://dl.dropbox.com/u/37735/index.html">thesis and prototype</a>.
916)     </li>
917)     
918)     </ol>
919)     
920)     <a id="Research"></a>
921)     <h2><a class="anchor" href="#Research">Research</a></h2>
922)     <ol>
923)     <li>The "end-to-end traffic confirmation attack":
924)     by watching traffic at Alice and at Bob, we can <a
925)     href="http://freehaven.net/anonbib/#danezis:pet2004">compare
926)     traffic signatures and become convinced that we're watching the same
927)     stream</a>. So far Tor accepts this as a fact of life and assumes this
928)     attack is trivial in all cases. First of all, is that actually true? How
929)     much traffic of what sort of distribution is needed before the adversary
930)     is confident he has won? Are there scenarios (e.g. not transmitting much)
931)     that slow down the attack? Do some traffic padding or traffic shaping
932)     schemes work better than others?</li>
933)     <li>A related question is: Does running a relay/bridge provide additional
934)     protection against these timing attacks? Can an external adversary that can't
935)     see inside TLS links still recognize individual streams reliably?
936)     Does the amount of traffic carried degrade this ability any? What if the
937)     client-relay deliberately delayed upstream relayed traffic to create a queue
938)     that could be used to mimic timings of client downstream traffic to make it
939)     look like it was also relayed? This same queue could also be used for masking
940)     timings in client upstream traffic with the techniques from <a
941)     href="http://www.freehaven.net/anonbib/#ShWa-Timing06">adaptive padding</a>,
942)     but without the need for additional traffic. Would such an interleaving of
943)     client upstream traffic obscure timings for external adversaries? Would the
944)     strategies need to be adjusted for asymmetric links? For example, on
945)     asymmetric links, is it actually possible to differentiate client traffic from
946)     natural bursts due to their asymmetric capacity? Or is it easier than
947)     symmetric links for some other reason?</li>
948)     <li>Repeat Murdoch and Danezis's <a
949)     href="http://www.cl.cam.ac.uk/~sjm217/projects/anon/#torta">attack from
950)     Oakland 05</a> on the current Tor network. See if you can learn why it
951)     works well on some nodes and not well on others. (My theory is that the
952)     fast nodes with spare capacity resist the attack better.) If that's true,
953)     then experiment with the RelayBandwidthRate and RelayBandwidthBurst
954)     options to run a relay that is used as a client while relaying the
955)     attacker's traffic: as we crank down the RelayBandwidthRate, does the
956)     attack get harder? What's the right ratio of RelayBandwidthRate to
957)     actually capacity? Or is it a ratio at all? While we're at it, does a
958)     much larger set of candidate relays increase the false positive rate
959)     or other complexity for the attack? (The Tor network is now almost two
960)     orders of magnitude larger than it was when they wrote their paper.) Be
961)     sure to read <a href="http://freehaven.net/anonbib/#clog-the-queue">Don't
962)     Clog the Queue</a> too.</li>
963)     <li>The "routing zones attack": most of the literature thinks of
964)     the network path between Alice and her entry node (and between the
965)     exit node and Bob) as a single link on some graph. In practice,
966)     though, the path traverses many autonomous systems (ASes), and <a
967)     href="http://freehaven.net/anonbib/#feamster:wpes2004">it's not uncommon
968)     that the same AS appears on both the entry path and the exit path</a>.
969)     Unfortunately, to accurately predict whether a given Alice, entry,
970)     exit, Bob quad will be dangerous, we need to download an entire Internet
971)     routing zone and perform expensive operations on it. Are there practical
972)     approximations, such as avoiding IP addresses in the same /8 network?</li>
973)     <li>Other research questions regarding geographic diversity consider
974)     the tradeoff between choosing an efficient circuit and choosing a random
975)     circuit. Look at Stephen Rollyson's <a
976)     href="http://swiki.cc.gatech.edu:8080/ugResearch/uploads/7/ImprovingTor.pdf">position
977)     paper</a> on how to discard particularly slow choices without hurting
978)     anonymity "too much". This line of reasoning needs more work and more
979)     thinking, but it looks very promising.</li>
980)     <li>Tor doesn't work very well when relays have asymmetric bandwidth
981)     (e.g. cable or DSL). Because Tor has separate TCP connections between
982)     each hop, if the incoming bytes are arriving just fine and the outgoing
983)     bytes are all getting dropped on the floor, the TCP push-back mechanisms
984)     don't really transmit this information back to the incoming streams.
985)     Perhaps Tor should detect when it's dropping a lot of outgoing packets,
986)     and rate-limit incoming streams to regulate this itself? I can imagine
987)     a build-up and drop-off scheme where we pick a conservative rate-limit,
988)     slowly increase it until we get lost packets, back off, repeat. We
989)     need somebody who's good with networks to simulate this and help design
990)     solutions; and/or we need to understand the extent of the performance
991)     degradation, and use this as motivation to reconsider UDP transport.</li>
992)     <li>A related topic is congestion control. Is our
993)     current design sufficient once we have heavy use? Maybe
994)     we should experiment with variable-sized windows rather
995)     than fixed-size windows? That seemed to go well in an <a
996)     href="http://www.psc.edu/networking/projects/hpn-ssh/theory.php">ssh
997)     throughput experiment</a>. We'll need to measure and tweak, and maybe
998)     overhaul if the results are good.</li>
999)     <li>Our censorship-resistance goals include preventing
1000)     an attacker who's looking at Tor traffic on the wire from <a
1001)     href="<svnprojects>design-paper/blocking.html#sec:network-fingerprint">distinguishing
1002)     it from normal SSL traffic</a>. Obviously we can't achieve perfect
1003)     steganography and still remain usable, but for a first step we'd like to
1004)     block any attacks that can win by observing only a few packets. One of
1005)     the remaining attacks we haven't examined much is that Tor cells are 512
1006)     bytes, so the traffic on the wire may well be a multiple of 512 bytes.
1007)     How much does the batching and overhead in TLS records blur this on the
1008)     wire? Do different buffer flushing strategies in Tor affect this? Could
1009)     a bit of padding help a lot, or is this an attack we must accept?</li>
1010)     <li>Tor circuits are built one hop at a time, so in theory we have the
1011)     ability to make some streams exit from the second hop, some from the
1012)     third, and so on. This seems nice because it breaks up the set of exiting
1013)     streams that a given relay can see. But if we want each stream to be safe,
1014)     the "shortest" path should be at least 3 hops long by our current logic, so
1015)     the rest will be even longer. We need to examine this performance / security
1016)     tradeoff.</li>
1017)     <li>It's not that hard to DoS Tor relays or directory authorities. Are client
1018)     puzzles the right answer? What other practical approaches are there? Bonus
1019)     if they're backward-compatible with the current Tor protocol.</li>
1020)     <li>Programs like <a
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Andrew Lewman authored 14 years ago

1021)     href="<page torbutton/index>">Torbutton</a> aim to hide