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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) 
39)     <li><b>Pyobfsproxy</b> is a Python framework for implementing new
40)     transport protocols. It uses Twisted for its networking needs, and
41)     <a href="https://gitweb.torproject.org/pluggable-transports/pyptlib.git/blob/HEAD:/README.rst">pyptlib</a>
42)     for some pluggable transport-related features. It supports the
43)     <a href="https://gitweb.torproject.org/obfsproxy.git/blob/HEAD:/doc/obfs2/protocol-spec.txt">obfs2</a>
44)     and
45)     <a href="https://gitweb.torproject.org/pluggable-transports/pyobfsproxy.git/blob/HEAD:/doc/obfs3/obfs3-protocol-spec.txt">obfs3</a>
46)     pluggable transports. Maintained by George Kadianakis. <br>
47) 
48)     Status: <a href="https://blog.torproject.org/blog/combined-flash-proxy-pyobfsproxy-browser-bundles">Deployed</a>
49)     </li>
50) 

51)     <li><b>Obfsproxy</b> is a framework for implementing new transport
52)     protocols in C using libevent. See its
53)     <a href="<page projects/obfsproxy>">web page</a>,
54)     <a href="https://gitweb.torproject.org/obfsproxy.git">git repository</a>,
55)     <a href="https://gitweb.torproject.org/obfsproxy.git/blob/HEAD:/doc/obfs2/protocol-spec.txt">obfs2 protocol description</a>,
56)     and
57)     <a href="https://blog.torproject.org/blog/obfsproxy-next-step-censorship-arms-race">blog post</a>.

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

60)     </li>
61) 
62)     <li><b>Flashproxy</b> turns ordinary web browsers into bridges using
63)     websockets, and has a little python stub to hook Tor clients to the
64)     websocket connection. See its
65)     <a href="http://crypto.stanford.edu/flashproxy/">web page</a>,
66)     <a href="https://gitweb.torproject.org/flashproxy.git">git repository</a>,
67)     and
68)     <a href="http://crypto.stanford.edu/flashproxy/flashproxy.pdf">design paper</a>.

69)     Maintained by David Fifield.

70)     # <iframe src="//crypto.stanford.edu/flashproxy/embed.html" width="80" height="15" frameborder="0" scrolling="no"></iframe>

71)     <br>

72)     Status: <a href="https://blog.torproject.org/blog/combined-flash-proxy-pyobfsproxy-browser-bundles">Deployed</a>

73)     </li>
74) 
75)     <li><b>StegoTorus</b> is an Obfsproxy fork that extends it to a)
76)     split Tor streams across multiple connections to avoid packet size
77)     signatures, and b) embed the traffic flows in traces that look like
78)     html, javascript, or pdf. See its
79)     <a href="https://gitweb.torproject.org/stegotorus.git">git repository</a>.

80)     Maintained by Zack Weinberg. <br>
81)     Status: <em>Undeployed</em>

82)     </li>
83) 
84)     <li><b>SkypeMorph</b> transforms Tor traffic flows so they look like
85)     Skype Video. See its
86)     <a href="http://crysp.uwaterloo.ca/software/SkypeMorph-0.5.1.tar.gz">source code</a>
87)     and
88)     <a href="http://cacr.uwaterloo.ca/techreports/2012/cacr2012-08.pdf">design paper</a>.

89)     Maintained by Ian Goldberg. <br>
90)     Status: <em>Undeployed</em>

91)     </li>
92) 
93)     <li><b>Dust</b> aims to provide a packet-based (rather than
94)     connection-based) DPI-resistant protocol. See its
95)     <a href="https://github.com/blanu/Dust">git repository</a>.

96)     Maintained by Brandon Wiley. <br>
97)     Status: <em>Undeployed</em>

98)     </li>
99) 

100)     <li><b>Format-Transforming Encryption</b> transforms Tor traffic
101)     to arbitrary formats using their language descriptions. See

102)     the <a href="https://eprint.iacr.org/2012/494">research

103)     paper</a>. <br>
104)     Status: <em>Undeployed</em>

105)     </li>
106) 

107)     </ul>

108)     <hr>
109) 
110)     <p>
111)     Our goal is to have a wide variety of pluggable transport designs.
112)     Many are at the research phase now, so it's a perfect time to play
113)     with them or suggest new designs. Please let us know if you find or
114)     start other projects that could be useful for making Tor's traffic
115)     flows more DPI-resistant!
116)     </p>