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5) #include "head.wmi" TITLE="Tor Project: Pluggable Transports" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">
8)     <a href="<page index>">Home &raquo; </a>
9)     <a href="<page docs/documentation>">Documentation &raquo; </a>
10)     <a href="<page docs/pluggable-transports>">Pluggable Transports</a>
11)   </div>
12)   <div id="maincol">
13)     <h2>Tor: Pluggable Transports</h2>
14)     <hr>
15) 
16)     <p>
17)     An increasing number of censoring countries are using Deep Packet
18)     Inspection (DPI) to classify Internet traffic flows by protocol.
19)     While Tor uses <a href="<page docs/bridges>">bridge relays</a> to
20)     get around a censor that blocks by IP address, the censor can use
21)     DPI to recognize and filter Tor traffic flows even when they connect
22)     to unexpected IP addresses.
23)     </p>
24) 
25)     <p>
26)     Pluggable transports transform the Tor traffic flow between the client
27)     and the bridge. This way, censors who monitor traffic between the
28)     client and the bridge will see innocent-looking transformed traffic
29)     instead of the actual Tor traffic.
30)     External programs can talk to Tor clients and Tor bridges using the <a
31) href="https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/180-pluggable-transport.txt">pluggable
32) transport API</a>, to make it easier to build interoperable programs.
33)     </p>
34) 
35)     <hr>
36) 
37)     <ul>
38)     <li><b>Obfsproxy</b> is a framework for implementing new transport
39)     protocols in C using libevent. See its
40)     <a href="<page projects/obfsproxy>">web page</a>,
41)     <a href="https://gitweb.torproject.org/obfsproxy.git">git repository</a>,
42)     <a href="https://gitweb.torproject.org/obfsproxy.git/blob/HEAD:/doc/obfs2/protocol-spec.txt">obfs2 protocol description</a>,
43)     and
44)     <a href="https://blog.torproject.org/blog/obfsproxy-next-step-censorship-arms-race">blog post</a>.

45)     Maintained by George Kadianakis. <br>
46)     Status: <a href="../projects/obfsproxy.html.en#download">Deployed</a> <a href="https://bridges.torproject.org/?transport=obfs2">(Bridges)</a>

47)     </li>
48) 
49)     <li><b>Flashproxy</b> turns ordinary web browsers into bridges using
50)     websockets, and has a little python stub to hook Tor clients to the
51)     websocket connection. See its
52)     <a href="http://crypto.stanford.edu/flashproxy/">web page</a>,
53)     <a href="https://gitweb.torproject.org/flashproxy.git">git repository</a>,
54)     and
55)     <a href="http://crypto.stanford.edu/flashproxy/flashproxy.pdf">design paper</a>.

56)     Maintained by David Fifield.
57)     <iframe src="//crypto.stanford.edu/flashproxy/embed.html" width="80"
58)     height="15" frameborder="0" scrolling="no"></iframe>
59)     <br>

60)     Status: <em>Implemented and tested, but there are no bundles yet;
61)     <a href="https://crypto.stanford.edu/flashproxy/#how-to">need
62)     manual setup.</a></em>

63)     </li>
64) 
65)     <li><b>StegoTorus</b> is an Obfsproxy fork that extends it to a)
66)     split Tor streams across multiple connections to avoid packet size
67)     signatures, and b) embed the traffic flows in traces that look like
68)     html, javascript, or pdf. See its
69)     <a href="https://gitweb.torproject.org/stegotorus.git">git repository</a>.

70)     Maintained by Zack Weinberg. <br>
71)     Status: <em>Undeployed</em>

72)     </li>
73) 
74)     <li><b>SkypeMorph</b> transforms Tor traffic flows so they look like
75)     Skype Video. See its
76)     <a href="http://crysp.uwaterloo.ca/software/SkypeMorph-0.5.1.tar.gz">source code</a>
77)     and
78)     <a href="http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf">design paper</a>.

79)     Maintained by Ian Goldberg. <br>
80)     Status: <em>Undeployed</em>

81)     </li>
82) 
83)     <li><b>Dust</b> aims to provide a packet-based (rather than
84)     connection-based) DPI-resistant protocol. See its
85)     <a href="https://github.com/blanu/Dust">git repository</a>.

86)     Maintained by Brandon Wiley. <br>
87)     Status: <em>Undeployed</em>

88)     </li>
89) 

90)     <li><b>Format-Transforming Encryption</b> transforms Tor traffic
91)     to arbitrary formats using their language descriptions. See
92)     the <a href="http://eprint.iacr.org/2012/494">research

93)     paper</a>. <br>
94)     Status: <em>Undeployed</em>

95)     </li>
96) 

97)     </ul>

98)     <hr>
99) 
100)     <p>
101)     Our goal is to have a wide variety of pluggable transport designs.
102)     Many are at the research phase now, so it's a perfect time to play
103)     with them or suggest new designs. Please let us know if you find or
104)     start other projects that could be useful for making Tor's traffic
105)     flows more DPI-resistant!
106)     </p>