mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-24 04:13:28 +01:00
Merge commit 'sebastian/oldstuff'
Conflicts: ChangeLog
This commit is contained in:
Roger Dingledine
commit
de0330b092
41
AUTHORS
41
AUTHORS
@ -1,41 +0,0 @@
|
||||
This file lists the authors for Tor,
|
||||
a free software project to provide anonymity on the Internet.
|
||||
|
||||
For more information about Tor, see https://www.torproject.org/.
|
||||
|
||||
If you got this file as a part of a larger bundle,
|
||||
there are probably other authors that you should be aware of.
|
||||
|
||||
Main authors:
|
||||
-------------
|
||||
|
||||
Roger Dingledine <arma@freehaven.net> overhauled all of the code, did
|
||||
a bunch of new design work, etc.
|
||||
|
||||
Nick Mathewson <nickm@freehaven.net> wrote lots of stuff too, in
|
||||
particular the router and descriptor parsing, and the crypto and tls
|
||||
wrappers.
|
||||
|
||||
Matej Pfajfar <badbytes@freehaven.net> wrote the first version of the code
|
||||
(called OR) in 2001-2002.
|
||||
|
||||
Contributors:
|
||||
-------------
|
||||
|
||||
John Bashinski <jbash@velvet.com> contributed the initial rpm spec file.
|
||||
|
||||
Christian Grothoff <grothoff@cs.purdue.edu> contributed better daemonizing
|
||||
behavior.
|
||||
|
||||
Steven Hazel <sah@thalassocracy.org> made 'make install' do the right
|
||||
thing.
|
||||
|
||||
Jason Holt <jason@lunkwill.org> contributed patches to the instructions
|
||||
and the man page.
|
||||
|
||||
Peter Palfrader <peter@palfrader.org> maintains everything that's
|
||||
debian-specific, and has written other useful features.
|
||||
|
||||
Aaron Turner <aturner@netscreen.com> contributed the first version of
|
||||
the tor.sh initscripts shell script.
|
||||
|
||||
@ -28,6 +28,10 @@ Changes in version 0.2.2.9-alpha - 2010-??-??
|
||||
- Remove the --enable-iphone option. According to reports from
|
||||
Marco Bonetti, Tor builds fine without any special tweaking on
|
||||
recent iPhone SDK versions.
|
||||
- Removed some unnecessary files from the source distribution. The
|
||||
AUTHORS file had its content merged into the people page on the
|
||||
website. The roadmaps and design doc can now be found in the
|
||||
projects directory in svn.
|
||||
|
||||
o Removed features:
|
||||
- Stop shipping parts of the website and the design paper in the
|
||||
|
||||
@ -1,73 +0,0 @@
|
||||
#!/bin/sh
|
||||
# A script to turn Tor SOCKS4a in Privoxy on or off.
|
||||
|
||||
CONFFILE=/etc/privoxy/config # privoxy config file.
|
||||
TOR_REG="forward.*localhost:9050" # Regular expression to find Tor in privoxy
|
||||
PRIVOXY="/etc/init.d/privoxy restart" # command to reload privoxy config file.
|
||||
SED="/bin/sed" # sed command, of course.
|
||||
GREP="/bin/grep" # grep command.
|
||||
|
||||
usage () {
|
||||
echo "\
|
||||
privoxy-tor-toggle: Change Privoxy's configuration to use/not use Tor.
|
||||
Usage:
|
||||
privoxy.tor <-- Switch Tor on or off.
|
||||
privoxy.tor [on|off] <-- Set Tor on or off.
|
||||
privoxy.tor status <-- Display Tor's current status.
|
||||
privoxy.tor [-h|--help|-?] <-- Print usage.
|
||||
"
|
||||
}
|
||||
|
||||
# Find out the current status of tor. Set $tor_status
|
||||
get_status () {
|
||||
gret=`$GREP -l -e "^$TOR_REG" $CONFFILE`
|
||||
if [ x$gret = x ] ; then
|
||||
tor_status=off;
|
||||
else
|
||||
tor_status=on;
|
||||
fi
|
||||
return
|
||||
}
|
||||
|
||||
# Turn tor on/off according to $1
|
||||
set_tor () {
|
||||
tor_gate=$1
|
||||
get_status
|
||||
if [ $tor_status = $tor_gate ] ; then
|
||||
echo "Tor is already $1."
|
||||
return
|
||||
elif [ $tor_gate = flip ] ; then
|
||||
if [ $tor_status = on ] ; then
|
||||
tor_gate=off
|
||||
elif [ $tor_status = off ] ; then
|
||||
tor_gate=on
|
||||
fi
|
||||
fi
|
||||
echo "Turning Tor $tor_gate..."
|
||||
if [ $tor_gate = on ] ; then
|
||||
reg=s/^#\($TOR_REG\)/\\1/
|
||||
$SED -i.bak -r "$reg" $CONFFILE
|
||||
else
|
||||
reg=s/^\($TOR_REG\)/#\\1/
|
||||
$SED -i.bak -r "$reg" $CONFFILE
|
||||
fi
|
||||
$PRIVOXY
|
||||
return 0;
|
||||
}
|
||||
|
||||
if [ x$1 = x ] ; then
|
||||
set_tor flip
|
||||
elif [ $1 = on ] ; then
|
||||
set_tor on
|
||||
elif [ $1 = off ] ; then
|
||||
set_tor off
|
||||
elif [ $1 = status ] ; then
|
||||
get_status
|
||||
echo "Tor is $tor_status"
|
||||
elif [ $1 = --help ] || [ $1 = -h ] || [ $1 = "-?" ] ; then
|
||||
usage
|
||||
exit 0
|
||||
else
|
||||
echo "Unrecognized option: \"$1\""
|
||||
fi
|
||||
|
||||
@ -1,52 +0,0 @@
|
||||
Subject:
|
||||
Re: Anonymous/Nonymous Communication Coexisting?
|
||||
From:
|
||||
Kristian Köhntopp <kris@xn--khntopp-90a.de>
|
||||
Date:
|
||||
Fri, 10 Jun 2005 08:56:19 +0200
|
||||
To:
|
||||
or-talk@freehaven.net
|
||||
|
||||
On Wednesday 08 June 2005 04:20, yancm@sdf.lonestar.org wrote:
|
||||
|
||||
>> Is it possible to have a single application, such as a web
|
||||
>> browser or a p2p client behave normally with normal url's but
|
||||
>> use tor if the url is an xyz.onion address? Or is it
|
||||
>> everything or nothing?
|
||||
|
||||
|
||||
This is basically a question of using your proxy or not. You can
|
||||
control the behaviour of your browser in great detail writing a
|
||||
proxy.pac program in Javascript and setting that program as the
|
||||
proxy autoconfiguration URL in your browser.
|
||||
|
||||
An example:
|
||||
|
||||
kris@jordan01:~> cat /srv/www/htdocs/proxy.pac
|
||||
|
||||
function FindProxyForURL(url, host)
|
||||
{
|
||||
var proxy_yes = "PROXY jordan01.int.cinetic.de:3128";
|
||||
var proxy_no = "DIRECT";
|
||||
|
||||
// Redirect all accesses to mlan hosts to the mlan proxy
|
||||
if (dnsDomainIs(host, ".mlan.cinetic.de")) {
|
||||
return proxy_yes;
|
||||
}
|
||||
|
||||
// Everything else is direct
|
||||
return proxy_no;
|
||||
}
|
||||
|
||||
So here the program checks if the destination is a mlan-Host, and
|
||||
if so, uses the appropriate proxy on jordan for the access,
|
||||
while all other accesses are direct.
|
||||
|
||||
You could do a similar thing with .onion accesses with a trivial
|
||||
modification.
|
||||
|
||||
Docs:
|
||||
http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html
|
||||
|
||||
Kristian
|
||||
|
||||
@ -1,41 +0,0 @@
|
||||
<?xml version="1.0" encoding="utf-8"?>
|
||||
<metalink version="3.0" generator="Metalink Editor version 1.1.0" xmlns="http://www.metalinker.org/">
|
||||
<publisher>
|
||||
<name>The Tor Project</name>
|
||||
<url>https://www.torproject.org</url>
|
||||
</publisher>
|
||||
<license>
|
||||
<name>BSD</name>
|
||||
<url>http://opensource.org/licenses/bsd-license.php</url>
|
||||
</license>
|
||||
<identity>Tor</identity>
|
||||
<version>@VERSION@</version>
|
||||
<copyright>2007 The Tor Project, Inc.</copyright>
|
||||
<description>Anonymity Online</description>
|
||||
<files>
|
||||
<file name="tor-@VERSION@.tar.gz">
|
||||
<size>1251636</size>
|
||||
<language>en</language>
|
||||
<os>Source</os>
|
||||
<verification>
|
||||
<hash type="md5">ef8fc7f45d167875c337063d437c9832</hash>
|
||||
<hash type="sha1">01092fb75c407b5c1d7f33db069cf7641973d94d</hash>
|
||||
<hash type="sha256">fc0fb0c2891ae09854a69512c6b4988964f2eaf62ce80ed6644cb21f87f6056a</hash>
|
||||
<pieces type="sha1" length="262144">
|
||||
<hash piece="0">c778dd01e05734d57f769082545f9802386e42bb</hash>
|
||||
<hash piece="1">39b172ed8b9290884c7bd129db633a79e28d5ae9</hash>
|
||||
<hash piece="2">28d708e7489a1e9951e757443672535aedfa3abe</hash>
|
||||
<hash piece="3">a7623e07081819a37300de0511bbdda0bdc960bd</hash>
|
||||
<hash piece="4">f246021e55affe320a1f86eac5b049dd0caad828</hash>
|
||||
</pieces>
|
||||
</verification>
|
||||
<resources>
|
||||
<url type="http" location="at">http://tor.cypherpunks.at/dist/</url>
|
||||
<url type="http" location="ca">http://tor.depthstrike.com/dist/</url>
|
||||
<url type="http" location="ca">http://tor.hermetix.org/dist/</url>
|
||||
<url type="http" location="ch">http://tor.boinc.ch/dist/</url>
|
||||
<url type="http" location="cn">http://tor.anonymity.cn/dist/</url>
|
||||
</resources>
|
||||
</file>
|
||||
</files>
|
||||
</metalink>
|
||||
@ -1,357 +0,0 @@
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%deffont "standard" xfont "comic sans ms-medium-r"
|
||||
%%deffont "thick" xfont "arial black-medium-r"
|
||||
%%deffont "typewriter" xfont "courier new-bold-r"
|
||||
%%deffont "type2writer" xfont "arial narrow-bold-r"
|
||||
%%deffont "standard" tfont "standard.ttf", tmfont "kochi-mincho.ttf"
|
||||
%%deffont "thick" tfont "thick.ttf", tmfont "goth.ttf"
|
||||
%%deffont "typewriter" tfont "typewriter.ttf", tmfont "goth.ttf"
|
||||
%deffont "standard" xfont "helvetica-medium-r", tfont "arial.ttf", tmfont "times.ttf"
|
||||
%deffont "thick" xfont "helvetica-bold-r", tfont "arialbd.ttf", tmfont "hoso6.ttf"
|
||||
%deffont "italic" xfont "helvetica-italic-r", tfont "ariali.ttf", tmfont "hoso6.ttf"
|
||||
%deffont "typewriter" xfont "courier-medium-r", tfont "typewriter.ttf", tmfont "hoso6.ttf"
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%
|
||||
%% Default settings per each line numbers.
|
||||
%%
|
||||
%default 1 leftfill, size 8, fore "black", back "white", font "thick", hgap 1
|
||||
%default 2 size 8, vgap 10, prefix " ", ccolor "black"
|
||||
%default 3 size 6, bar "gray70", vgap 0
|
||||
%default 4 size 6, fore "black", vgap 0, prefix " ", font "standard"
|
||||
%%
|
||||
%%default 1 area 90 90, leftfill, size 9, fore "yellow", back "blue", font "thick"
|
||||
%%default 2 size 9, vgap 10, prefix " "
|
||||
%%default 3 size 7, bar "gray70", vgap 10
|
||||
%%default 4 size 7, vgap 30, prefix " ", font "standard"
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%
|
||||
%% Default settings that are applied to TAB-indented lines.
|
||||
%%
|
||||
%tab 1 size 5, vgap 40, prefix " ", icon arc "red" 50
|
||||
%tab 2 size 4, vgap 35, prefix " ", icon delta3 "blue" 40
|
||||
%tab 3 size 3, vgap 35, prefix " ", icon dia "DarkViolet" 40
|
||||
%%
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
%nodefault
|
||||
%center, size 9, font "thick", back "white", fore "black"
|
||||
|
||||
Tor:
|
||||
%size 8
|
||||
Next-generation Onion Routing
|
||||
|
||||
|
||||
%size 7
|
||||
Roger Dingledine
|
||||
Nick Mathewson
|
||||
Paul Syverson
|
||||
|
||||
The Free Haven Project
|
||||
%font "typewriter", fore "blue"
|
||||
http://freehaven.net/
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Low-latency anonymity system
|
||||
|
||||
%leftfill
|
||||
Deployed: 20 nodes, hundreds (?) of users
|
||||
|
||||
Many improvements on earlier design
|
||||
|
||||
Free software -- modified BSD license
|
||||
|
||||
Design is not covered by earlier onion routing
|
||||
patent
|
||||
|
||||
Uses SOCKS to interface with client apps
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
We have working code
|
||||
|
||||
(14 kloc of C)
|
||||
|
||||
and a design document,
|
||||
and a byte-level specification,
|
||||
and a Debian package (in Unstable)
|
||||
|
||||
Works on Linux, BSD, OSX, Cygwin, ...
|
||||
User-space, doesn't need kernel mods or root
|
||||
|
||||
%size 9
|
||||
http://freehaven.net/tor/
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%page
|
||||
%%
|
||||
%%Talk Overview
|
||||
%%
|
||||
%%A bit about Onion Routing
|
||||
%%
|
||||
%%Improvements we've made
|
||||
%%
|
||||
%%Some related work
|
||||
%%
|
||||
%%Ask me questions
|
||||
%%
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Anonymity: Who needs it?
|
||||
|
||||
Private citizens
|
||||
advocacy, counseling, whistleblowing, reporting, ...
|
||||
%size 6
|
||||
Higher-level protocols
|
||||
voting, e-cash, auctions
|
||||
%size 6
|
||||
Government applications
|
||||
research, law enforcement
|
||||
%size 6
|
||||
Business applications
|
||||
%size 5
|
||||
(hide relationships and volumes of communication)
|
||||
Who is visiting job sites?
|
||||
Which groups are talking to patent lawyers?
|
||||
Who are your suppliers and customers?
|
||||
Is the CEO talking to a buyout partner?
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Anonymity is a network effect
|
||||
|
||||
Systems need traffic (many low-sensitivity users) to attract the high-sensitivity users
|
||||
Most users do not value anonymity much
|
||||
Weak security (fast system) can mean more users
|
||||
which can mean
|
||||
%cont, font "italic"
|
||||
stronger
|
||||
%cont, font "standard"
|
||||
anonymity
|
||||
High-sensitivity agents have incentive to run nodes
|
||||
so they can be certain first node in their path is good
|
||||
to attract traffic for their messages
|
||||
There can be an optimal level of free-riding
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Onion Routing is...
|
||||
|
||||
An overlay network
|
||||
|
||||
Users build virtual circuits through the network
|
||||
|
||||
One layer of encryption at each hop
|
||||
|
||||
Fixed-size cells
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Tor's goals
|
||||
|
||||
Conservative design
|
||||
minimize new design work needed
|
||||
|
||||
%size 6
|
||||
Support testing of future research
|
||||
|
||||
Design for deployment; deploy for use
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Threat model -- what we aim for
|
||||
|
||||
Protect against somebody watching Alice
|
||||
|
||||
Protect against curious Bob
|
||||
|
||||
Protect against `some' curious nodes in the middle
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Differences / limitations
|
||||
|
||||
|
||||
We're TCP-only, not all IP (but we're user-space and very portable)
|
||||
|
||||
Not as strong as high-latency systems (Mixmaster, Mixminion)
|
||||
|
||||
Not peer-to-peer
|
||||
|
||||
No protocol normalization
|
||||
|
||||
Not unobservable (no steg, etc)
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Perfect forward secrecy
|
||||
|
||||
|
||||
Telescoping circuit
|
||||
|
||||
negotiates keys at each hop
|
||||
no more need for replay detection
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
No mixing, padding, traffic shaping (yet)
|
||||
|
||||
|
||||
Please show us they're worth the usability tradeoff
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%page
|
||||
%%
|
||||
%%Many TCP streams can share one circuit
|
||||
%%
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Many TCP streams share a circuit
|
||||
|
||||
Previous designs built a new circuit for each stream
|
||||
|
||||
lots of public key ops per request
|
||||
plus anonymity dangers from making so many circuits
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Leaky-pipe circuit topology
|
||||
|
||||
Alice can direct cells to any node in her circuit
|
||||
|
||||
So we can support long-range padding,
|
||||
have multiple streams exiting at different places in the circuit
|
||||
etc
|
||||
|
||||
%size 6
|
||||
Unclear whether this is dangerous or useful
|
||||
|
||||
More research needed
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Congestion control
|
||||
|
||||
|
||||
Simple rate limiting
|
||||
|
||||
Plus have to keep internal nodes from overflowing
|
||||
|
||||
(Can't use global state or inter-node control)
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Directory servers
|
||||
|
||||
To solve the `introduction' problem
|
||||
|
||||
Approve new servers
|
||||
|
||||
Tell clients who's up right now
|
||||
|
||||
plus their keys, location, etc
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Variable exit policies
|
||||
|
||||
|
||||
Each server allows different outgoing connections
|
||||
|
||||
E.g. no servers allow outgoing mail currently
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
End-to-end integrity checking
|
||||
|
||||
|
||||
In previous onion routing, an insider could change
|
||||
the text being transmitted:
|
||||
|
||||
"dir" => "rm *"
|
||||
|
||||
Even an external adversary could do this!
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Rendezvous points
|
||||
|
||||
allow hidden services
|
||||
|
||||
don't need (brittle) reply onions
|
||||
|
||||
Access-controlled: Bob can control who he talks to
|
||||
Robust: Bob's service is available even when some Tor nodes go down
|
||||
Smear-resistant: Evil service can't frame a rendezvous router
|
||||
Application-transparent: Don't need to modify Bob's apache
|
||||
|
||||
%size 6
|
||||
(Not implemented yet)
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
How do we compare security?
|
||||
|
||||
Assume adversary owns c of n nodes
|
||||
can choose which
|
||||
%size 6
|
||||
What's the chance for a random Alice and Bob that he wins?
|
||||
|
||||
Freedom, Tor: (c/n)^2
|
||||
Peekabooty, six-four, etc: c/n
|
||||
Jap (if no padding): 1 if c>1
|
||||
Anonymizer: 1 if c>0
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Future work
|
||||
|
||||
Threshold directory agreement
|
||||
|
||||
Scalability: Morphmix/p2p extensions?
|
||||
Restricted-route (non-clique topology)
|
||||
|
||||
Non-TCP transport
|
||||
|
||||
Implement rendezvous points
|
||||
|
||||
Make it work better
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
We have working code
|
||||
|
||||
Plus a design document,
|
||||
and a byte-level specification
|
||||
and a Debian package (in Unstable)
|
||||
|
||||
%size 9
|
||||
http://freehaven.net/tor/
|
||||
|
||||
%size 6
|
||||
Privacy Enhancing Technologies workshop
|
||||
|
||||
%size 9
|
||||
http://petworkshop.org/
|
||||
|
||||
@ -1,21 +0,0 @@
|
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cell-struct.eps: cell-struct.fig
|
||||
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|
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interaction.eps: interaction.fig
|
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|
||||
cell-struct.pdf: cell-struct.fig
|
||||
fig2dev -L pdf $< $@
|
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interaction.pdf: interaction.fig
|
||||
fig2dev -L pdf $< $@
|
||||
|
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tor-design.ps: cell-struct.eps interaction.eps tor-design.bib tor-design.tex usenix.sty latex8.bst
|
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latex tor-design.tex
|
||||
bibtex tor-design
|
||||
latex tor-design.tex
|
||||
latex tor-design.tex
|
||||
dvips -o $@ tor-design.dvi
|
||||
|
||||
tor-design.pdf: cell-struct.pdf interaction.pdf tor-design.bib tor-design.tex usenix.sty latex8.bst
|
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|
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|
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||||
bind def
|
||||
/shd {dup dup currentrgbcolor 4 -2 roll mul 4 -2 roll mul
|
||||
4 -2 roll mul srgb} bind def
|
||||
/reencdict 12 dict def /ReEncode { reencdict begin
|
||||
/newcodesandnames exch def /newfontname exch def /basefontname exch def
|
||||
/basefontdict basefontname findfont def /newfont basefontdict maxlength dict def
|
||||
basefontdict { exch dup /FID ne { dup /Encoding eq
|
||||
{ exch dup length array copy newfont 3 1 roll put }
|
||||
{ exch newfont 3 1 roll put } ifelse } { pop pop } ifelse } forall
|
||||
newfont /FontName newfontname put newcodesandnames aload pop
|
||||
128 1 255 { newfont /Encoding get exch /.notdef put } for
|
||||
newcodesandnames length 2 idiv { newfont /Encoding get 3 1 roll put } repeat
|
||||
newfontname newfont definefont pop end } def
|
||||
/isovec [
|
||||
8#055 /minus 8#200 /grave 8#201 /acute 8#202 /circumflex 8#203 /tilde
|
||||
8#204 /macron 8#205 /breve 8#206 /dotaccent 8#207 /dieresis
|
||||
8#210 /ring 8#211 /cedilla 8#212 /hungarumlaut 8#213 /ogonek 8#214 /caron
|
||||
8#220 /dotlessi 8#230 /oe 8#231 /OE
|
||||
8#240 /space 8#241 /exclamdown 8#242 /cent 8#243 /sterling
|
||||
8#244 /currency 8#245 /yen 8#246 /brokenbar 8#247 /section 8#250 /dieresis
|
||||
8#251 /copyright 8#252 /ordfeminine 8#253 /guillemotleft 8#254 /logicalnot
|
||||
8#255 /hyphen 8#256 /registered 8#257 /macron 8#260 /degree 8#261 /plusminus
|
||||
8#262 /twosuperior 8#263 /threesuperior 8#264 /acute 8#265 /mu 8#266 /paragraph
|
||||
8#267 /periodcentered 8#270 /cedilla 8#271 /onesuperior 8#272 /ordmasculine
|
||||
8#273 /guillemotright 8#274 /onequarter 8#275 /onehalf
|
||||
8#276 /threequarters 8#277 /questiondown 8#300 /Agrave 8#301 /Aacute
|
||||
8#302 /Acircumflex 8#303 /Atilde 8#304 /Adieresis 8#305 /Aring
|
||||
8#306 /AE 8#307 /Ccedilla 8#310 /Egrave 8#311 /Eacute
|
||||
8#312 /Ecircumflex 8#313 /Edieresis 8#314 /Igrave 8#315 /Iacute
|
||||
8#316 /Icircumflex 8#317 /Idieresis 8#320 /Eth 8#321 /Ntilde 8#322 /Ograve
|
||||
8#323 /Oacute 8#324 /Ocircumflex 8#325 /Otilde 8#326 /Odieresis 8#327 /multiply
|
||||
8#330 /Oslash 8#331 /Ugrave 8#332 /Uacute 8#333 /Ucircumflex
|
||||
8#334 /Udieresis 8#335 /Yacute 8#336 /Thorn 8#337 /germandbls 8#340 /agrave
|
||||
8#341 /aacute 8#342 /acircumflex 8#343 /atilde 8#344 /adieresis 8#345 /aring
|
||||
8#346 /ae 8#347 /ccedilla 8#350 /egrave 8#351 /eacute
|
||||
8#352 /ecircumflex 8#353 /edieresis 8#354 /igrave 8#355 /iacute
|
||||
8#356 /icircumflex 8#357 /idieresis 8#360 /eth 8#361 /ntilde 8#362 /ograve
|
||||
8#363 /oacute 8#364 /ocircumflex 8#365 /otilde 8#366 /odieresis 8#367 /divide
|
||||
8#370 /oslash 8#371 /ugrave 8#372 /uacute 8#373 /ucircumflex
|
||||
8#374 /udieresis 8#375 /yacute 8#376 /thorn 8#377 /ydieresis] def
|
||||
/Times-Bold /Times-Bold-iso isovec ReEncode
|
||||
/Times-Roman /Times-Roman-iso isovec ReEncode
|
||||
/$F2psBegin {$F2psDict begin /$F2psEnteredState save def} def
|
||||
/$F2psEnd {$F2psEnteredState restore end} def
|
||||
|
||||
$F2psBegin
|
||||
10 setmiterlimit
|
||||
0.06000 0.06000 sc
|
||||
%
|
||||
% Fig objects follow
|
||||
%
|
||||
% Polyline
|
||||
15.000 slw
|
||||
n 6000 300 m
|
||||
6000 3975 l gs col0 s gr
|
||||
% Polyline
|
||||
7.500 slw
|
||||
gs clippath
|
||||
3615 555 m 3615 495 l 3464 495 l 3584 525 l 3464 555 l cp
|
||||
eoclip
|
||||
n 1200 525 m
|
||||
3600 525 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3464 555 m 3584 525 l 3464 495 l 3464 555 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 795 m 1185 855 l 1336 855 l 1216 825 l 1336 795 l cp
|
||||
eoclip
|
||||
n 3600 825 m
|
||||
1200 825 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 795 m 1216 825 l 1336 855 l 1336 795 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
15.000 slw
|
||||
n 1200 300 m
|
||||
1200 3975 l gs col0 s gr
|
||||
% Polyline
|
||||
7.500 slw
|
||||
gs clippath
|
||||
3615 1155 m 3615 1095 l 3464 1095 l 3584 1125 l 3464 1155 l cp
|
||||
eoclip
|
||||
n 1200 1125 m
|
||||
3600 1125 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3464 1155 m 3584 1125 l 3464 1095 l 3464 1155 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
15.000 slw
|
||||
n 3600 300 m
|
||||
3600 3975 l gs col0 s gr
|
||||
% Polyline
|
||||
7.500 slw
|
||||
gs clippath
|
||||
6015 1230 m 6015 1170 l 5864 1170 l 5984 1200 l 5864 1230 l cp
|
||||
eoclip
|
||||
n 3600 1200 m
|
||||
6000 1200 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 5864 1230 m 5984 1200 l 5864 1170 l 5864 1230 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3585 1470 m 3585 1530 l 3736 1530 l 3616 1500 l 3736 1470 l cp
|
||||
eoclip
|
||||
n 6000 1500 m
|
||||
3600 1500 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3736 1470 m 3616 1500 l 3736 1530 l 3736 1470 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 1545 m 1185 1605 l 1336 1605 l 1216 1575 l 1336 1545 l cp
|
||||
eoclip
|
||||
n 3600 1575 m
|
||||
1200 1575 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 1545 m 1216 1575 l 1336 1605 l 1336 1545 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
[15 45] 45 sd
|
||||
n 1050 1800 m
|
||||
8325 1800 l gs col0 s gr [] 0 sd
|
||||
% Polyline
|
||||
gs clippath
|
||||
3615 2130 m 3615 2070 l 3464 2070 l 3584 2100 l 3464 2130 l cp
|
||||
eoclip
|
||||
n 1200 2100 m
|
||||
3600 2100 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3464 2130 m 3584 2100 l 3464 2070 l 3464 2130 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
6015 2205 m 6015 2145 l 5864 2145 l 5984 2175 l 5864 2205 l cp
|
||||
eoclip
|
||||
n 3600 2175 m
|
||||
6000 2175 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 5864 2205 m 5984 2175 l 5864 2145 l 5864 2205 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
[60] 0 sd
|
||||
gs clippath
|
||||
8190 2430 m 8190 2370 l 8039 2370 l 8159 2400 l 8039 2430 l cp
|
||||
5985 2370 m 5985 2430 l 6136 2430 l 6016 2400 l 6136 2370 l cp
|
||||
eoclip
|
||||
n 6000 2400 m
|
||||
8175 2400 l gs col0 s gr gr
|
||||
[] 0 sd
|
||||
% arrowhead
|
||||
n 6136 2370 m 6016 2400 l 6136 2430 l 6136 2370 l cp gs 0.00 setgray ef gr col0 s
|
||||
% arrowhead
|
||||
n 8039 2430 m 8159 2400 l 8039 2370 l 8039 2430 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3585 2520 m 3585 2580 l 3736 2580 l 3616 2550 l 3736 2520 l cp
|
||||
eoclip
|
||||
n 6000 2550 m
|
||||
3600 2550 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3736 2520 m 3616 2550 l 3736 2580 l 3736 2520 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 2595 m 1185 2655 l 1336 2655 l 1216 2625 l 1336 2595 l cp
|
||||
eoclip
|
||||
n 3600 2625 m
|
||||
1200 2625 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 2595 m 1216 2625 l 1336 2655 l 1336 2595 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3615 3030 m 3615 2970 l 3464 2970 l 3584 3000 l 3464 3030 l cp
|
||||
eoclip
|
||||
n 1200 3000 m
|
||||
3600 3000 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3464 3030 m 3584 3000 l 3464 2970 l 3464 3030 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
6015 3105 m 6015 3045 l 5864 3045 l 5984 3075 l 5864 3105 l cp
|
||||
eoclip
|
||||
n 3600 3075 m
|
||||
6000 3075 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 5864 3105 m 5984 3075 l 5864 3045 l 5864 3105 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
8190 3180 m 8190 3120 l 8039 3120 l 8159 3150 l 8039 3180 l cp
|
||||
eoclip
|
||||
n 6000 3150 m
|
||||
8175 3150 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 8039 3180 m 8159 3150 l 8039 3120 l 8039 3180 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
5985 3420 m 5985 3480 l 6136 3480 l 6016 3450 l 6136 3420 l cp
|
||||
eoclip
|
||||
n 8175 3450 m
|
||||
6000 3450 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 6136 3420 m 6016 3450 l 6136 3480 l 6136 3420 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
5985 3495 m 5985 3555 l 6136 3555 l 6016 3525 l 6136 3495 l cp
|
||||
eoclip
|
||||
n 8175 3525 m
|
||||
6000 3525 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 6136 3495 m 6016 3525 l 6136 3555 l 6136 3495 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
5985 3570 m 5985 3630 l 6136 3630 l 6016 3600 l 6136 3570 l cp
|
||||
eoclip
|
||||
n 8175 3600 m
|
||||
6000 3600 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 6136 3570 m 6016 3600 l 6136 3630 l 6136 3570 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3585 3495 m 3585 3555 l 3736 3555 l 3616 3525 l 3736 3495 l cp
|
||||
eoclip
|
||||
n 6000 3525 m
|
||||
3600 3525 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3736 3495 m 3616 3525 l 3736 3555 l 3736 3495 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3585 3645 m 3585 3705 l 3736 3705 l 3616 3675 l 3736 3645 l cp
|
||||
eoclip
|
||||
n 6000 3675 m
|
||||
3600 3675 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3736 3645 m 3616 3675 l 3736 3705 l 3736 3645 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
3585 3570 m 3585 3630 l 3736 3630 l 3616 3600 l 3736 3570 l cp
|
||||
eoclip
|
||||
n 6000 3600 m
|
||||
3600 3600 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 3736 3570 m 3616 3600 l 3736 3630 l 3736 3570 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 3645 m 1185 3705 l 1336 3705 l 1216 3675 l 1336 3645 l cp
|
||||
eoclip
|
||||
n 3600 3675 m
|
||||
1200 3675 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 3645 m 1216 3675 l 1336 3705 l 1336 3645 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 3720 m 1185 3780 l 1336 3780 l 1216 3750 l 1336 3720 l cp
|
||||
eoclip
|
||||
n 3600 3750 m
|
||||
1200 3750 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 3720 m 1216 3750 l 1336 3780 l 1336 3720 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
gs clippath
|
||||
1185 3795 m 1185 3855 l 1336 3855 l 1216 3825 l 1336 3795 l cp
|
||||
eoclip
|
||||
n 3600 3825 m
|
||||
1200 3825 l gs col0 s gr gr
|
||||
|
||||
% arrowhead
|
||||
n 1336 3795 m 1216 3825 l 1336 3855 l 1336 3795 l cp gs 0.00 setgray ef gr col0 s
|
||||
% Polyline
|
||||
15.000 slw
|
||||
n 8175 300 m
|
||||
8175 3975 l gs col0 s gr
|
||||
% Polyline
|
||||
7.500 slw
|
||||
n 6300 825 m 7950 825 l 7950 1725 l 6300 1725 l
|
||||
cp gs col7 1.00 shd ef gr gs col0 s gr
|
||||
/Times-Bold-iso ff 180.00 scf sf
|
||||
3375 225 m
|
||||
gs 1 -1 sc (OR 1) col0 sh gr
|
||||
/Times-Bold-iso ff 180.00 scf sf
|
||||
1050 225 m
|
||||
gs 1 -1 sc (Alice) col0 sh gr
|
||||
/Times-Bold-iso ff 180.00 scf sf
|
||||
5775 225 m
|
||||
gs 1 -1 sc (OR 2) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
6075 3075 m
|
||||
gs 1 -1 sc ("HTTP GET...") col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
4800 3975 m
|
||||
gs 1 -1 sc (. . .) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 3975 m
|
||||
gs 1 -1 sc (. . .) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
2400 3975 m
|
||||
gs 1 -1 sc (. . .) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 2325 m
|
||||
gs 1 -1 sc (\(TCP handshake\)) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Bold-iso ff 180.00 scf sf
|
||||
7875 225 m
|
||||
gs 1 -1 sc (website) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 1425 m
|
||||
gs 1 -1 sc ({X}--AES encryption) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 1200 m
|
||||
gs 1 -1 sc (E\(x\)--RSA encryption) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 975 m
|
||||
gs 1 -1 sc (Legend:) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
2400 225 m
|
||||
gs 1 -1 sc (\(link is TLS-encrypted\)) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
1275 1050 m
|
||||
gs 1 -1 sc (Relay c1{Extend, OR2, E\(g^x2\)}) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
1275 2025 m
|
||||
gs 1 -1 sc (Relay c1{{Begin <website>:80}}) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3525 1500 m
|
||||
gs 1 -1 sc (Relay c1{Extended, g^y2, H\(K2\)}) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3675 2100 m
|
||||
gs 1 -1 sc (Relay c2{Begin <website>:80}) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3525 2550 m
|
||||
gs 1 -1 sc (Relay c1{{Connected}}) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
5925 2475 m
|
||||
gs 1 -1 sc (Relay c2{Connected}) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
1275 2925 m
|
||||
gs 1 -1 sc (Relay c1{{Data, "HTTP GET..."}}) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3675 3000 m
|
||||
gs 1 -1 sc (Relay c2{Data, "HTTP GET..."}) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
4800 225 m
|
||||
gs 1 -1 sc (\(link is TLS-encryped\)) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7050 225 m
|
||||
gs 1 -1 sc (\(unencrypted\)) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
7125 1650 m
|
||||
gs 1 -1 sc (cN--a circID) dup sw pop 2 div neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3525 3600 m
|
||||
gs 1 -1 sc (Relay c1{{Data, \(response\)}}) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
8100 3375 m
|
||||
gs 1 -1 sc (\(response\)) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
5925 3450 m
|
||||
gs 1 -1 sc (Relay c2{Data, \(response\)}) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
5925 1425 m
|
||||
gs 1 -1 sc (Created c2, g^y2, H\(K2\)) dup sw pop neg 0 rm col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3675 1125 m
|
||||
gs 1 -1 sc (Create c2, E\(g^x2\)) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
1275 450 m
|
||||
gs 1 -1 sc (Create c1, E\(g^x1\)) col0 sh gr
|
||||
/Times-Roman-iso ff 150.00 scf sf
|
||||
3525 750 m
|
||||
gs 1 -1 sc (Created c1, g^y1, H\(K1\)) dup sw pop neg 0 rm col0 sh gr
|
||||
$F2psEnd
|
||||
rs
|
||||
@ -1,122 +0,0 @@
|
||||
#FIG 3.2
|
||||
Landscape
|
||||
Center
|
||||
Inches
|
||||
Letter
|
||||
100.00
|
||||
Single
|
||||
-2
|
||||
1200 2
|
||||
2 1 0 2 0 7 50 0 -1 0.000 0 0 -1 0 0 2
|
||||
6000 300 6000 3975
|
||||
2 1 0 1 0 7 50 0 -1 0.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
1200 525 3600 525
|
||||
2 1 0 1 0 7 50 0 -1 0.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 825 1200 825
|
||||
2 1 0 2 0 7 50 0 -1 0.000 0 0 -1 0 0 2
|
||||
1200 300 1200 3975
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
1200 1125 3600 1125
|
||||
2 1 0 2 0 7 50 0 -1 0.000 0 0 -1 0 0 2
|
||||
3600 300 3600 3975
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 1200 6000 1200
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 1500 3600 1500
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 1575 1200 1575
|
||||
2 1 2 1 0 7 50 0 -1 3.000 0 0 -1 0 0 2
|
||||
1050 1800 8325 1800
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
1200 2100 3600 2100
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 2175 6000 2175
|
||||
2 1 1 1 0 7 50 0 -1 4.000 0 0 -1 1 1 2
|
||||
1 1 1.00 60.00 120.00
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 2400 8175 2400
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 2550 3600 2550
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 2625 1200 2625
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
1200 3000 3600 3000
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 3075 6000 3075
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 3150 8175 3150
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
8175 3450 6000 3450
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
8175 3525 6000 3525
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
8175 3600 6000 3600
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 3525 3600 3525
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 3675 3600 3675
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
6000 3600 3600 3600
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 3675 1200 3675
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 3750 1200 3750
|
||||
2 1 0 1 0 7 50 0 -1 3.000 0 0 -1 1 0 2
|
||||
1 1 1.00 60.00 120.00
|
||||
3600 3825 1200 3825
|
||||
2 1 0 2 0 7 50 0 -1 0.000 0 0 -1 0 0 2
|
||||
8175 300 8175 3975
|
||||
2 2 0 1 0 7 50 0 20 3.000 0 0 -1 0 0 5
|
||||
6300 825 7950 825 7950 1725 6300 1725 6300 825
|
||||
4 0 0 50 0 2 12 0.0000 4 135 450 3375 225 OR 1\001
|
||||
4 0 0 50 0 2 12 0.0000 4 135 420 1050 225 Alice\001
|
||||
4 0 0 50 0 2 12 0.0000 4 135 450 5775 225 OR 2\001
|
||||
4 0 0 50 0 0 10 0.0000 4 105 960 6075 3075 "HTTP GET..."\001
|
||||
4 1 0 50 0 0 10 0.0000 4 15 135 4800 3975 . . .\001
|
||||
4 1 0 50 0 0 10 0.0000 4 15 135 7125 3975 . . .\001
|
||||
4 1 0 50 0 0 10 0.0000 4 15 135 2400 3975 . . .\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 1050 7125 2325 (TCP handshake)\001
|
||||
4 0 0 50 0 2 12 0.0000 4 135 630 7875 225 website\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 1335 7125 1425 {X}--AES encryption\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 1410 7125 1200 E(x)--RSA encryption\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 480 7125 975 Legend:\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 1455 2400 225 (link is TLS-encrypted)\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 2085 1275 1050 Relay c1{Extend, OR2, E(g^x2)}\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 1965 1275 2025 Relay c1{{Begin <website>:80}}\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 2190 3525 1500 Relay c1{Extended, g^y2, H(K2)}\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 1845 3675 2100 Relay c2{Begin <website>:80}\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1410 3525 2550 Relay c1{{Connected}}\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1290 5925 2475 Relay c2{Connected}\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 2085 1275 2925 Relay c1{{Data, "HTTP GET..."}}\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 1965 3675 3000 Relay c2{Data, "HTTP GET..."}\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 1365 4800 225 (link is TLS-encryped)\001
|
||||
4 1 0 50 0 0 10 0.0000 4 135 870 7050 225 (unencrypted)\001
|
||||
4 1 0 50 0 0 10 0.0000 4 105 780 7125 1650 cN--a circID\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1860 3525 3600 Relay c1{{Data, (response)}}\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 645 8100 3375 (response)\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1650 5925 3450 Relay c2{Data, (response)}\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1545 5925 1425 Created c2, g^y2, H(K2)\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 1170 3675 1125 Create c2, E(g^x2)\001
|
||||
4 0 0 50 0 0 10 0.0000 4 135 1170 1275 450 Create c1, E(g^x1)\001
|
||||
4 2 0 50 0 0 10 0.0000 4 135 1545 3525 750 Created c1, g^y1, H(K1)\001
|
||||
Binary file not shown.
Binary file not shown.
|
Before Width: | Height: | Size: 29 KiB |
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
@ -1,353 +0,0 @@
|
||||
\documentclass{llncs}
|
||||
|
||||
\usepackage{url}
|
||||
\usepackage{amsmath}
|
||||
\usepackage{epsfig}
|
||||
|
||||
\setlength{\textwidth}{5.9in}
|
||||
\setlength{\textheight}{8.4in}
|
||||
\setlength{\topmargin}{.5cm}
|
||||
\setlength{\oddsidemargin}{1cm}
|
||||
\setlength{\evensidemargin}{1cm}
|
||||
|
||||
\newenvironment{tightlist}{\begin{list}{$\bullet$}{
|
||||
\setlength{\itemsep}{0mm}
|
||||
\setlength{\parsep}{0mm}
|
||||
% \setlength{\labelsep}{0mm}
|
||||
% \setlength{\labelwidth}{0mm}
|
||||
% \setlength{\topsep}{0mm}
|
||||
}}{\end{list}}
|
||||
|
||||
|
||||
\newcommand{\workingnote}[1]{} % The version that hides the note.
|
||||
%\newcommand{\workingnote}[1]{(**#1)} % The version that makes the note visible.
|
||||
|
||||
|
||||
\begin{document}
|
||||
|
||||
\title{Design challenges and social factors in deploying low-latency anonymity}
|
||||
% Could still use a better title -PFS
|
||||
|
||||
\author{Roger Dingledine\inst{1} \and
|
||||
Nick Mathewson\inst{1} \and
|
||||
Paul Syverson\inst{2}}
|
||||
\institute{The Tor Project \email{<\{arma,nickm\}@torproject.org>} \and
|
||||
Naval Research Laboratory \email{<syverson@itd.nrl.navy.mil>}}
|
||||
|
||||
\maketitle
|
||||
\pagestyle{plain}
|
||||
|
||||
\begin{abstract}
|
||||
There are many unexpected or unexpectedly difficult obstacles to
|
||||
deploying anonymous communications. We describe Tor (\emph{the}
|
||||
onion routing), how to use it, our design philosophy, and some of
|
||||
the challenges that we have faced and continue to face in building,
|
||||
deploying, and sustaining a scalable, distributed, low-latency
|
||||
anonymity network.
|
||||
\end{abstract}
|
||||
|
||||
\section{Introduction}
|
||||
This article describes Tor, a widely-used low-latency general-purpose
|
||||
anonymous communication system, and discusses some unexpected
|
||||
challenges arising from our experiences deploying Tor. We will tell
|
||||
you how to use it, who uses it, how it works, why we designed it the
|
||||
way we did, and why this makes it usable and stable.
|
||||
|
||||
Tor is an overlay network for anonymizing TCP streams over the
|
||||
Internet~\cite{tor-design}. Tor works on the real-world Internet,
|
||||
requires no special privileges or kernel modifications, requires
|
||||
little synchronization or coordination between nodes, and provides a
|
||||
reasonable trade-off between anonymity, usability, and efficiency.
|
||||
|
||||
Since deployment in October 2003 the public Tor network has grown to
|
||||
about a thousand volunteer-operated nodes worldwide and over 110
|
||||
megabytes average traffic per second from hundreds of thousands of
|
||||
concurrent users.
|
||||
|
||||
\section{Tor Design and Design Philosophy: Distributed Trust and Usability}
|
||||
|
||||
Tor enables users to connect to Internet sites without revealing their
|
||||
logical or physical locations to those sites or to observers. It
|
||||
enables hosts to be publicly accessible yet have similar protection
|
||||
against location through its \emph{location-hidden services}.
|
||||
|
||||
To connect to a remote server via Tor the client software first learns
|
||||
a %signed
|
||||
list of Tor nodes from several central \emph{directory servers} via a
|
||||
voting protocol (to avoid dependence on or complete trust in any one
|
||||
of these servers). It then incrementally creates a private pathway or
|
||||
\emph{circuit} across the network. This circuit consists of
|
||||
encrypted connections through authenticated Tor nodes
|
||||
whose public keys were obtained from the directory servers. The client
|
||||
software negotiates a separate set of encryption keys for each hop along the
|
||||
circuit. The nodes in the circuit are chosen at random by the client
|
||||
subject to a preference for higher performing nodes to allocate
|
||||
resources effectively and with a client-chosen preferred set of first
|
||||
nodes called \emph{entry guards} to complicate profiling attacks by
|
||||
internal adversaries~\cite{hs-attack}.
|
||||
The circuit is extended one node at a time, tunneling extensions
|
||||
through already established portions of the circuit, and each node
|
||||
along the way knows only the immediately previous and following nodes
|
||||
in the circuit, so no individual Tor node knows the complete path that
|
||||
each fixed-sized data packet (or \emph{cell}) will take. Thus,
|
||||
neither an eavesdropper nor a compromised node can see both the
|
||||
connection's source and destination. Later requests use a new
|
||||
circuit to complicate long-term linkability between different actions
|
||||
by a single user.
|
||||
|
||||
Tor attempts to anonymize the transport layer, not the application
|
||||
layer. Thus, applications such as SSH can provide
|
||||
authenticated communication that is hidden by Tor from outside observers.
|
||||
When anonymity from communication partners is desired,
|
||||
application-level protocols that transmit identifying
|
||||
information need additional scrubbing proxies, such as
|
||||
Privoxy~\cite{privoxy} for HTTP\@. Furthermore, Tor does not relay
|
||||
arbitrary IP packets; it only anonymizes TCP streams and DNS requests.
|
||||
|
||||
Tor, the third generation of deployed onion-routing
|
||||
designs~\cite{or-ih96,or-jsac98,tor-design}, was researched, developed,
|
||||
and deployed by the Naval Research Laboratory and the Free Haven
|
||||
Project under ONR and DARPA funding for secure government
|
||||
communications. In 2005, continuing work by Free Haven was funded by
|
||||
the Electronic Frontier Foundation for maintaining civil liberties of
|
||||
ordinary citizens online. In 2006, The Tor Project incorporated as a
|
||||
non-profit and has received continued funding from the Omidyar Network,
|
||||
the U.S. International Broadcasting Bureau, and other groups to combat
|
||||
blocking and censorship on the Internet. This diversity of funding fits
|
||||
Tor's overall philosophy: a wide variety of interests helps maintain
|
||||
both the stability and the security of the network.
|
||||
|
||||
Usability is also a central goal. Downloading and installing Tor is
|
||||
easy. Simply go to\\
|
||||
http://www.torproject.org/ and download. Tor comes with install
|
||||
wizards and a GUI for major operating systems: GNU/Linux, OS X, and
|
||||
Windows. It also runs on various flavors of BSD and UNIX\@. Basic
|
||||
instructions, documentation, FAQs, etc.\ are available in many
|
||||
languages. The Tor GUI Vidalia makes server configuration easy, e.g.,
|
||||
choosing how much bandwidth to allocate to Tor, exit policy choices,
|
||||
etc. And, the GUI Torbutton allows Firefox users a one-click toggle of
|
||||
whether browsing goes through Tor or not. Tor is easily configured by
|
||||
a site administrator to run at either individual desktops or just at a
|
||||
site firewall or combinations of these.
|
||||
|
||||
The ideal Tor network would be practical, useful and anonymous. When
|
||||
trade-offs arise between these properties, Tor's research strategy has
|
||||
been to remain useful enough to attract many users, and practical
|
||||
enough to support them. Only subject to these constraints do we try
|
||||
to maximize anonymity. Tor thus differs from other deployed systems
|
||||
for traffic analysis resistance in its security and flexibility. Mix
|
||||
networks such as
|
||||
% Mixmaster~\cite{mixmaster-spec} or its successor
|
||||
Mixminion~\cite{minion-design} gain the highest degrees of practical
|
||||
anonymity at the expense of introducing highly variable delays, making
|
||||
them unsuitable for applications such as web browsing. Commercial
|
||||
single-hop proxies~\cite{anonymizer} can provide good performance, but
|
||||
a single-point compromise can expose all users' traffic, and a
|
||||
single-point eavesdropper can perform traffic analysis on the entire
|
||||
network. Also, their proprietary implementations place any
|
||||
infrastructure that depends on these single-hop solutions at the mercy
|
||||
of their providers' financial health as well as network security.
|
||||
There are numerous other designs for distributed anonymous low-latency
|
||||
communication~\cite{crowds-tissec,web-mix,freedom21-security,i2p,tarzan:ccs02,morphmix:fc04}.
|
||||
Some have been deployed or even commercialized; some exist only on
|
||||
paper. Though each has something unique to offer, we feel Tor has
|
||||
advantages over each of them that make it a superior choice for most
|
||||
users and applications. For example, unlike purely P2P designs we
|
||||
neither limit ordinary users to content and services available only
|
||||
within our network nor require them to take on responsibility for
|
||||
connections outside the network, unless they separately choose to run
|
||||
server nodes. Nonetheless because we support low-latency interactive
|
||||
communications, end-to-end \emph{traffic correlation}
|
||||
attacks~\cite{danezis:pet2004,defensive-dropping,SS03,hs-attack,bauer:tr2007}
|
||||
allow an attacker who can observe both ends of a communication to
|
||||
correlate packet timing and volume, quickly linking the initiator to
|
||||
her destination.
|
||||
|
||||
|
||||
Our defense lies in having a diverse enough set of nodes to prevent
|
||||
most real-world adversaries from being in the right places to attack
|
||||
users, by distributing each transaction over several nodes in the
|
||||
network. This ``distributed trust'' approach means the Tor network
|
||||
can be safely operated and used by a wide variety of mutually
|
||||
distrustful users, providing sustainability and security.
|
||||
|
||||
The Tor network has a broad range of users, making it difficult for
|
||||
eavesdroppers to track them or profile interests. These include
|
||||
ordinary citizens concerned about their privacy, corporations who
|
||||
don't want to reveal information to their competitors, and law
|
||||
enforcement and government intelligence agencies who need to do
|
||||
operations on the Internet without being noticed. Naturally,
|
||||
organizations will not want to depend on others for their security.
|
||||
If most participating providers are reliable, Tor tolerates some
|
||||
hostile infiltration of the network.
|
||||
|
||||
This distribution of trust is central to the Tor philosophy and
|
||||
pervades Tor at all levels: Onion routing has been open source since
|
||||
the mid-nineties (mistrusting users can inspect the code themselves);
|
||||
Tor is free software (anyone could take up the development of Tor from
|
||||
the current team); anyone can use Tor without license or charge (which
|
||||
encourages a broad user base with diverse interests); Tor is designed to be
|
||||
usable (also promotes a large, diverse user base) and configurable (so
|
||||
users can easily set up and run server nodes); the Tor
|
||||
infrastructure is run by volunteers (it is not dependent on the
|
||||
economic viability or business strategy of any company) who are
|
||||
scattered around the globe (not completely under the jurisdiction of
|
||||
any single country); ongoing development and deployment has been
|
||||
funded by diverse sources (development does not fully depend on
|
||||
funding from any one source or even funding for any one primary
|
||||
purpose or sources in any one jurisdiction). All of these contribute
|
||||
to Tor's resilience and sustainability.
|
||||
|
||||
|
||||
\section{Social challenges}
|
||||
|
||||
Many of the issues the Tor project needs to address extend beyond
|
||||
system design and technology development. In particular, the Tor
|
||||
project's \emph{image} with respect to its users and the rest of the
|
||||
Internet impacts the security it can provide. With this image issue
|
||||
in mind, this section discusses the Tor user base and Tor's
|
||||
interaction with other services on the Internet.
|
||||
|
||||
\subsection{Communicating security}
|
||||
|
||||
Usability for anonymity systems contributes to their security, because
|
||||
usability affects the possible anonymity set~\cite{econymics,back01}.
|
||||
Conversely, an unusable system attracts few users and thus can't
|
||||
provide much anonymity.
|
||||
|
||||
This phenomenon has a second-order effect: knowing this, users should
|
||||
choose which anonymity system to use based in part on how usable and
|
||||
secure \emph{others} will find it, in order to get the protection of a
|
||||
larger anonymity set. Thus we might supplement the adage ``usability
|
||||
is a security parameter''~\cite{back01} with a new one: ``perceived
|
||||
usability is a security parameter.''~\cite{usability-network-effect}.
|
||||
|
||||
|
||||
|
||||
\subsection{Reputability and perceived social value}
|
||||
Another factor impacting the network's security is its reputability,
|
||||
the perception of its social value based on its current user base. If
|
||||
Alice is the only user who has ever downloaded the software, it might
|
||||
be socially accepted, but she's not getting much anonymity. Add a
|
||||
thousand activists, and she's anonymous, but everyone thinks she's an
|
||||
activist too. Add a thousand diverse citizens (cancer survivors,
|
||||
people concerned about identity theft, law enforcement agents, and so
|
||||
on) and now she's harder to profile.
|
||||
|
||||
Furthermore, the network's reputability affects its operator base:
|
||||
more people are willing to run a service if they believe it will be
|
||||
used by human rights workers than if they believe it will be used
|
||||
exclusively for disreputable ends. This effect becomes stronger if
|
||||
node operators themselves think they will be associated with their
|
||||
users' ends.
|
||||
|
||||
So the more cancer survivors on Tor, the better for the human rights
|
||||
activists. The more malicious hackers, the worse for the normal
|
||||
users. Thus, reputability is an anonymity issue for two
|
||||
reasons. First, it impacts the sustainability of the network: a
|
||||
network that's always about to be shut down has difficulty attracting
|
||||
and keeping adequate nodes. Second, a disreputable network is more
|
||||
vulnerable to legal and political attacks, since it will attract fewer
|
||||
supporters.
|
||||
|
||||
Reputability becomes even more tricky in the case of privacy networks,
|
||||
since the good uses of the network (such as publishing by journalists
|
||||
in dangerous countries, protecting road warriors from profiling and
|
||||
potential physical harm, tracking of criminals by law enforcement,
|
||||
protecting corporate research interests, etc.) are typically kept private,
|
||||
whereas network abuses or other problems tend to be more widely
|
||||
publicized.
|
||||
|
||||
|
||||
\subsection{Abuse}
|
||||
\label{subsec:tor-and-blacklists}
|
||||
|
||||
For someone willing to be antisocial or even break the law, Tor is
|
||||
usually a poor choice to hide bad behavior. For example, Tor nodes are
|
||||
publicly identified, unlike the million-node botnets that are now
|
||||
common on the Internet. Nonetheless, we always expected that,
|
||||
alongside legitimate users, Tor would also attract troublemakers who
|
||||
exploit Tor to abuse services on the Internet with vandalism, rude
|
||||
mail, and so on. \emph{Exit policies} have allowed individual nodes
|
||||
to block access to specific IP/port ranges. This approach aims to
|
||||
make operators more willing to run Tor by allowing them to prevent
|
||||
their nodes from being used for abusing particular services. For
|
||||
example, by default Tor nodes block SMTP (port 25), to avoid the issue
|
||||
of spam.
|
||||
|
||||
Exit policies are useful but insufficient: if not all nodes block a
|
||||
given service, that service may try to block Tor instead. While being
|
||||
blockable is important to being good netizens, we would like to
|
||||
encourage services to allow anonymous access. Services should not need
|
||||
to decide between blocking legitimate anonymous use and allowing
|
||||
unlimited abuse. Nonetheless, blocking IP addresses is a
|
||||
course-grained solution~\cite{netauth}: entire apartment buildings,
|
||||
campuses, and even countries sometimes share a single IP address.
|
||||
Also, whether intended or not, such blocking supports repression of
|
||||
free speech. In many locations where Internet access of various kinds
|
||||
is censored or even punished by imprisonment, Tor is a path both to
|
||||
the outside world and to others inside. Blocking posts from Tor makes
|
||||
the job of censoring authorities easier. This is a loss for both Tor
|
||||
and services that block, such as Wikipedia: we don't want to compete
|
||||
for (or divvy up) the NAT-protected entities of the world. This is
|
||||
also unfortunate because there are relatively simple technical
|
||||
solutions~\cite{nym}. Various schemes for escrowing anonymous posts
|
||||
until they are reviewed by editors would both prevent abuse and remove
|
||||
incentives for attempts to abuse. Further, pseudonymous reputation
|
||||
tracking of posters through Tor would allow those who establish
|
||||
adequate reputation to post without escrow~\cite{nym,nymble}.
|
||||
|
||||
We stress that as far as we can tell, most Tor uses are not
|
||||
abusive. Most services have not complained, and others are actively
|
||||
working to find ways besides banning to cope with the abuse. For
|
||||
example, the Freenode IRC network had a problem with a coordinated
|
||||
group of abusers joining channels and subtly taking over the
|
||||
conversation; but when they labelled all users coming from Tor IP
|
||||
addresses as ``anonymous users,'' removing the ability of the abusers
|
||||
to blend in, the abusers stopped using Tor. This is an illustration of
|
||||
how simple
|
||||
technical mechanisms can remove the ability to abuse anonymously
|
||||
without undermining the ability to communicate anonymously and can
|
||||
thus remove the incentive to attempt abusing in this way.
|
||||
|
||||
|
||||
|
||||
\section{The Future}
|
||||
\label{sec:conclusion}
|
||||
|
||||
Tor is the largest and most diverse low-latency anonymity network
|
||||
available, but we are still in the early stages. Several major
|
||||
questions remain.
|
||||
|
||||
First, will our volunteer-based approach to sustainability continue to
|
||||
work as well in the long term as it has the first several years?
|
||||
Besides node operation, Tor research, deployment, maintainance, and
|
||||
development is increasingly done by volunteers: package maintenance
|
||||
for various OSes, document translation, GUI design and implementation,
|
||||
live CDs, specification of new design changes, etc.\
|
||||
%
|
||||
Second, Tor is only one of many components that preserve privacy
|
||||
online. For applications where it is desirable to keep identifying
|
||||
information out of application traffic, someone must build more and
|
||||
better protocol-aware proxies that are usable by ordinary people.
|
||||
%
|
||||
Third, we need to maintain a reputation for social good, and learn how to
|
||||
coexist with the variety of Internet services and their established
|
||||
authentication mechanisms. We can't just keep escalating the blacklist
|
||||
standoff forever.
|
||||
%
|
||||
Fourth, the current Tor architecture hardly scales even to handle
|
||||
current user demand. We must deploy designs and incentives to further
|
||||
encourage clients to relay traffic too, without thereby trading away
|
||||
too much anonymity or other properties.
|
||||
|
||||
These are difficult and open questions. Yet choosing not to solve them
|
||||
means leaving most users to a less secure network or no anonymizing
|
||||
network at all.\\
|
||||
|
||||
\noindent{\bf Acknowledgment:} Thanks to Matt Edman for many
|
||||
helpful comments on a draft of this article.
|
||||
\bibliographystyle{plain} \bibliography{tor-design}
|
||||
|
||||
\end{document}
|
||||
|
||||
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|
||||
% usenix-2e.sty - to be used with latex2e (the new one) for USENIX.
|
||||
% To use this style file, do this:
|
||||
%
|
||||
% \documentclass[twocolumn]{article}
|
||||
% \usepackage{usenix-2e}
|
||||
% and put {\rm ....} around the author names.
|
||||
%
|
||||
% The following definitions are modifications of standard article.sty
|
||||
% definitions, arranged to do a better job of matching the USENIX
|
||||
% guidelines.
|
||||
% It will automatically select two-column mode and the Times-Roman
|
||||
% font.
|
||||
|
||||
%
|
||||
% USENIX papers are two-column.
|
||||
% Times-Roman font is nice if you can get it (requires NFSS,
|
||||
% which is in latex2e.
|
||||
|
||||
\if@twocolumn\else\input twocolumn.sty\fi
|
||||
\usepackage{times}
|
||||
|
||||
%
|
||||
% USENIX wants margins of: 7/8" side, 1" bottom, and 3/4" top.
|
||||
% 0.25" gutter between columns.
|
||||
% Gives active areas of 6.75" x 9.25"
|
||||
%
|
||||
\setlength{\textheight}{9.0in}
|
||||
\setlength{\columnsep}{0.25in}
|
||||
%%\setlength{\textwidth}{6.75in}
|
||||
\setlength{\textwidth}{7.00in}
|
||||
%\setlength{\footheight}{0.0in}
|
||||
\setlength{\topmargin}{-0.25in}
|
||||
\setlength{\headheight}{0.0in}
|
||||
\setlength{\headsep}{0.0in}
|
||||
\setlength{\evensidemargin}{-0.125in}
|
||||
\setlength{\oddsidemargin}{-0.125in}
|
||||
|
||||
%
|
||||
% Usenix wants no page numbers for submitted papers, so that they can
|
||||
% number them themselves.
|
||||
%
|
||||
\pagestyle{empty}
|
||||
|
||||
%
|
||||
% Usenix titles are in 14-point bold type, with no date, and with no
|
||||
% change in the empty page headers. The whol author section is 12 point
|
||||
% italic--- you must use {\rm } around the actual author names to get
|
||||
% them in roman.
|
||||
%
|
||||
\def\maketitle{\par
|
||||
\begingroup
|
||||
\renewcommand\thefootnote{\fnsymbol{footnote}}%
|
||||
\def\@makefnmark{\hbox to\z@{$\m@th^{\@thefnmark}$\hss}}%
|
||||
\long\def\@makefntext##1{\parindent 1em\noindent
|
||||
\hbox to1.8em{\hss$\m@th^{\@thefnmark}$}##1}%
|
||||
\if@twocolumn
|
||||
\twocolumn[\@maketitle]%
|
||||
\else \newpage
|
||||
\global\@topnum\z@
|
||||
\@maketitle \fi\@thanks
|
||||
\endgroup
|
||||
\setcounter{footnote}{0}%
|
||||
\let\maketitle\relax
|
||||
\let\@maketitle\relax
|
||||
\gdef\@thanks{}\gdef\@author{}\gdef\@title{}\let\thanks\relax}
|
||||
|
||||
\def\@maketitle{\newpage
|
||||
\vbox to 2.5in{
|
||||
\vspace*{\fill}
|
||||
\vskip 2em
|
||||
\begin{center}%
|
||||
{\Large\bf \@title \par}%
|
||||
\vskip 0.375in minus 0.300in
|
||||
{\large\it
|
||||
\lineskip .5em
|
||||
\begin{tabular}[t]{c}\@author
|
||||
\end{tabular}\par}%
|
||||
\end{center}%
|
||||
\par
|
||||
\vspace*{\fill}
|
||||
% \vskip 1.5em
|
||||
}
|
||||
}
|
||||
|
||||
%
|
||||
% The abstract is preceded by a 12-pt bold centered heading
|
||||
\def\abstract{\begin{center}%
|
||||
{\large\bf \abstractname\vspace{-.5em}\vspace{\z@}}%
|
||||
\end{center}}
|
||||
\def\endabstract{}
|
||||
|
||||
%
|
||||
% Main section titles are 12-pt bold. Others can be same or smaller.
|
||||
%
|
||||
\def\section{\@startsection {section}{1}{\z@}{-3.5ex plus-1ex minus
|
||||
-.2ex}{2.3ex plus.2ex}{\reset@font\large\bf}}
|
||||
@ -1,7 +0,0 @@
|
||||
% Created by Anil Somayaji
|
||||
|
||||
\ProvidesClass{usenixsubmit}
|
||||
\LoadClass[11pt,letterpaper]{article}
|
||||
\usepackage{times}
|
||||
\usepackage[margin=1in]{geometry}
|
||||
|
||||
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@ -1,690 +0,0 @@
|
||||
\documentclass{article}
|
||||
|
||||
\usepackage{url}
|
||||
|
||||
\newenvironment{tightlist}{\begin{list}{$\bullet$}{
|
||||
\setlength{\itemsep}{0mm}
|
||||
\setlength{\parsep}{0mm}
|
||||
% \setlength{\labelsep}{0mm}
|
||||
% \setlength{\labelwidth}{0mm}
|
||||
% \setlength{\topsep}{0mm}
|
||||
}}{\end{list}}
|
||||
\newcommand{\tmp}[1]{{\bf #1} [......] \\}
|
||||
\newcommand{\plan}[1]{ {\bf (#1)}}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\title{Tor Development Roadmap: Wishlist for Nov 2006--Dec 2007}
|
||||
\author{Roger Dingledine \and Nick Mathewson \and Shava Nerad}
|
||||
|
||||
\maketitle
|
||||
\pagestyle{plain}
|
||||
|
||||
% TO DO:
|
||||
% add cites
|
||||
% add time estimates
|
||||
|
||||
|
||||
\section{Introduction}
|
||||
%Hi, Roger! Hi, Shava. This paragraph should get deleted soon. Right now,
|
||||
%this document goes into about as much detail as I'd like to go into for a
|
||||
%technical audience, since that's the audience I know best. It doesn't have
|
||||
%time estimates everywhere. It isn't well prioritized, and it doesn't
|
||||
%distinguish well between things that need lots of research and things that
|
||||
%don't. The breakdowns don't all make sense. There are lots of things where
|
||||
%I don't make it clear how they fit into larger goals, and lots of larger
|
||||
%goals that don't break down into little things. It isn't all stuff we can do
|
||||
%for sure, and it isn't even all stuff we can do for sure in 2007. The
|
||||
%tmp\{\} macro indicates stuff I haven't said enough about. That said, here
|
||||
%plangoes...
|
||||
|
||||
Tor (the software) and Tor (the overall software/network/support/document
|
||||
suite) are now experiencing all the crises of success. Over the next year,
|
||||
we're probably going to grow more in terms of users, developers, and funding
|
||||
than before. This gives us the opportunity to perform long-neglected
|
||||
maintenance tasks.
|
||||
|
||||
\section{Code and design infrastructure}
|
||||
|
||||
\subsection{Protocol revision}
|
||||
To maintain backward compatibility, we've postponed major protocol
|
||||
changes and redesigns for a long time. Because of this, there are a number
|
||||
of sensible revisions we've been putting off until we could deploy several of
|
||||
them at once. To do each of these, we first need to discuss design
|
||||
alternatives with other cryptographers and outside collaborators to
|
||||
make sure that our choices are secure.
|
||||
|
||||
First of all, our protocol needs better {\bf versioning support} so that we
|
||||
can make backward-incompatible changes to our core protocol. There are
|
||||
difficult anonymity issues here, since many naive designs would make it easy
|
||||
to tell clients apart (and then track them) based on their supported versions.
|
||||
|
||||
With protocol versioning support would come the ability to {\bf future-proof
|
||||
our ciphersuites}. For example, not only our OR protocol, but also our
|
||||
directory protocol, is pretty firmly tied to the SHA-1 hash function, which
|
||||
though not yet known to be insecure for our purposes, has begun to show
|
||||
its age. We should
|
||||
remove assumptions throughout our design based on the assumption that public
|
||||
keys, secret keys, or digests will remain any particular size indefinitely.
|
||||
|
||||
Our OR {\bf authentication protocol}, though provably
|
||||
secure\cite{tap:pet2006}, relies more on particular aspects of RSA and our
|
||||
implementation thereof than we had initially believed. To future-proof
|
||||
against changes, we should replace it with a less delicate approach.
|
||||
|
||||
\plan{For all the above: 2 person-months to specify, spread over several
|
||||
months with time for interaction with external participants. One
|
||||
person-month to implement. Start specifying in early 2007.}
|
||||
|
||||
We might design a {\bf stream migration} feature so that streams tunneled
|
||||
over Tor could be more resilient to dropped connections and changed IPs.
|
||||
\plan{Not in 2007.}
|
||||
|
||||
A new protocol could support {\bf multiple cell sizes}. Right now, all data
|
||||
passes through the Tor network divided into 512-byte cells. This is
|
||||
efficient for high-bandwidth protocols, but inefficient for protocols
|
||||
like SSH or AIM that send information in small chunks. Of course, we need to
|
||||
investigate the extent to which multiple sizes could make it easier for an
|
||||
adversary to fingerprint a traffic pattern. \plan{Not in 2007.}
|
||||
|
||||
As a part of our design, we should investigate possible {\bf cipher modes}
|
||||
other than counter mode. For example, a mode with built-in integrity
|
||||
checking, error propagation, and random access could simplify our protocol
|
||||
significantly. Sadly, many of these are patented and unavailable for us.
|
||||
\plan{Not in 2007.}
|
||||
|
||||
\subsection{Scalability}
|
||||
|
||||
\subsubsection{Improved directory efficiency}
|
||||
Right now, clients download a statement of the {\bf network status} made by
|
||||
each directory authority. We could reduce network bandwidth significantly by
|
||||
having the authorities jointly sign a statement reflecting their vote on the
|
||||
current network status. This would save clients up to 160K per hour, and
|
||||
make their view of the network more uniform. Of course, we'd need to make
|
||||
sure the voting process was secure and resilient to failures in the
|
||||
network.\plan{Must do; specify in 2006. 2 weeks to specify, 3-4 weeks to
|
||||
implement.}
|
||||
|
||||
We should {\bf shorten router descriptors}, since the current format includes
|
||||
a great deal of information that's only of interest to the directory
|
||||
authorities, and not of interest to clients. We can do this by having each
|
||||
router upload a short-form and a long-form signed descriptor, and having
|
||||
clients download only the short form. Even a naive version of this would
|
||||
save about 40\% of the bandwidth currently spent by clients downloading
|
||||
descriptors.\plan{Must do; specify in 2006. 3-4 weeks.}
|
||||
|
||||
We should {\bf have routers upload their descriptors even less often}, so
|
||||
that clients do not need to download replacements every 18 hours whether any
|
||||
information has changed or not. (As of Tor 0.1.2.3-alpha, clients tolerate
|
||||
routers that don't upload often, but routers still upload at least every 18
|
||||
hours to support older clients.) \plan{Must do, but not until 0.1.1.x is
|
||||
deprecated in mid 2007. 1 week.}
|
||||
|
||||
\subsubsection{Non-clique topology}
|
||||
Our current network design achieves a certain amount of its anonymity by
|
||||
making clients act like each other through the simple expedient of making
|
||||
sure that all clients know all servers, and that any server can talk to any
|
||||
other server. But as the number of servers increases to serve an
|
||||
ever-greater number of clients, these assumptions become impractical.
|
||||
|
||||
At worst, if these scalability issues become troubling before a solution is
|
||||
found, we can design and build a solution to {\bf split the network into
|
||||
multiple slices} until a better solution comes along. This is not ideal,
|
||||
since rather than looking like all other users from a point of view of path
|
||||
selection, users would ``only'' look like 200,000--300,000 other
|
||||
users.\plan{Not unless needed.}
|
||||
|
||||
We are in the process of designing {\bf improved schemes for network
|
||||
scalability}. Some approaches focus on limiting what an adversary can know
|
||||
about what a user knows; others focus on reducing the extent to which an
|
||||
adversary can exploit this knowledge. These are currently in their infancy,
|
||||
and will probably not be needed in 2007, but they must be designed in 2007 if
|
||||
they are to be deployed in 2008.\plan{Design in 2007; unknown difficulty.
|
||||
Write a paper.}
|
||||
|
||||
\subsubsection{Relay incentives}
|
||||
To support more users on the network, we need to get more servers. So far,
|
||||
we've relied on volunteerism to attract server operators, and so far it's
|
||||
served us well. But in the long run, we need to {\bf design incentives for
|
||||
users to run servers} and relay traffic for others. Most obviously, we
|
||||
could try to build the network so that servers offered improved service for
|
||||
other servers, but we would need to do so without weakening anonymity and
|
||||
making it obvious which connections originate from users running servers. We
|
||||
have some preliminary designs~\cite{incentives-txt,tor-challenges},
|
||||
but need to perform
|
||||
some more research to make sure they would be safe and effective.\plan{Write
|
||||
a draft paper; 2 person-months.}
|
||||
|
||||
\subsection{Portability}
|
||||
Our {\bf Windows implementation}, though much improved, continues to lag
|
||||
behind Unix and Mac OS X, especially when running as a server. We hope to
|
||||
merge promising patches from Mike Chiussi to address this point, and bring
|
||||
Windows performance on par with other platforms.\plan{Do in 2007; 1.5 months
|
||||
to integrate not counting Mike's work.}
|
||||
|
||||
We should have {\bf better support for portable devices}, including modes of
|
||||
operation that require less RAM, and that write to disk less frequently (to
|
||||
avoid wearing out flash RAM).\plan{Optional; 2 weeks.}
|
||||
|
||||
We should {\bf stop using socketpair on Windows}; instead, we can use
|
||||
in-memory structures to communicate between cpuworkers and the main thread,
|
||||
and between connections.\plan{Optional; 1 week.}
|
||||
|
||||
\subsection{Performance: resource usage}
|
||||
We've been working on {\bf using less RAM}, especially on servers. This has
|
||||
paid off a lot for directory caches in the 0.1.2, which in some cases are
|
||||
using 90\% less memory than they used to require. But we can do better,
|
||||
especially in the area around our buffer management algorithms, by using an
|
||||
approach more like the BSD and Linux kernels use instead of our current ring
|
||||
buffer approach. (For OR connections, we can just use queues of cell-sized
|
||||
chunks produced with a specialized allocator.) This could potentially save
|
||||
around 25 to 50\% of the memory currently allocated for network buffers, and
|
||||
make Tor a more attractive proposition for restricted-memory environments
|
||||
like old computers, mobile devices, and the like.\plan{Do in 2007; 2-3 weeks
|
||||
plus one week measurement.}
|
||||
|
||||
We should improve our {\bf bandwidth limiting}. The current system has been
|
||||
crucial in making users willing to run servers: nobody is willing to run a
|
||||
server if it might use an unbounded amount of bandwidth, especially if they
|
||||
are charged for their usage. We can make our system better by letting users
|
||||
configure bandwidth limits independently for their own traffic and traffic
|
||||
relayed for others; and by adding write limits for users running directory
|
||||
servers.\plan{Do in 2006; 2-3 weeks.}
|
||||
|
||||
On many hosts, sockets are still in short supply, and will be until we can
|
||||
migrate our protocol to UDP. We can {\bf use fewer sockets} by making our
|
||||
self-to-self connections happen internally to the code rather than involving
|
||||
the operating system's socket implementation.\plan{Optional; 1 week.}
|
||||
|
||||
\subsection{Performance: network usage}
|
||||
We know too little about how well our current path
|
||||
selection algorithms actually spread traffic around the network in practice.
|
||||
We should {\bf research the efficacy of our traffic allocation} and either
|
||||
assure ourselves that it is close enough to optimal as to need no improvement
|
||||
(unlikely) or {\bf identify ways to improve network usage}, and get more
|
||||
users' traffic delivered faster. Performing this research will require
|
||||
careful thought about anonymity implications.
|
||||
|
||||
We should also {\bf examine the efficacy of our congestion control
|
||||
algorithm}, and see whether we can improve client performance in the
|
||||
presence of a congested network through dynamic `sendme' window sizes or
|
||||
other means. This will have anonymity implications too if we aren't careful.
|
||||
|
||||
\plan{For both of the above: research, design and write
|
||||
a measurement tool in 2007: 1 month. See if we can interest a graduate
|
||||
student.}
|
||||
|
||||
We should work on making Tor's cell-based protocol perform better on
|
||||
networks with low bandwidth
|
||||
and high packet loss.\plan{Do in 2007 if we're funded to do it; 4-6 weeks.}
|
||||
|
||||
\subsection{Performance scenario: one Tor client, many users}
|
||||
We should {\bf improve Tor's performance when a single Tor handles many
|
||||
clients}. Many organizations want to manage a single Tor client on their
|
||||
firewall for many users, rather than having each user install a separate
|
||||
Tor client. We haven't optimized for this scenario, and it is likely that
|
||||
there are some code paths in the current implementation that become
|
||||
inefficient when a single Tor is servicing hundreds or thousands of client
|
||||
connections. (Additionally, it is likely that such clients have interesting
|
||||
anonymity requirements the we should investigate.) We should profile Tor
|
||||
under appropriate loads, identify bottlenecks, and fix them.\plan{Do in 2007
|
||||
if we're funded to do it; 4-8 weeks.}
|
||||
|
||||
\subsection{Tor servers on asymmetric bandwidth}
|
||||
|
||||
Tor should work better on servers that have asymmetric connections like cable
|
||||
or DSL. Because Tor has separate TCP connections between each
|
||||
hop, if the incoming bytes are arriving just fine and the outgoing bytes are
|
||||
all getting dropped on the floor, the TCP push-back mechanisms don't really
|
||||
transmit this information back to the incoming streams.\plan{Do in 2007 since
|
||||
related to bandwidth limiting. 3-4 weeks.}
|
||||
|
||||
\subsection{Running Tor as both client and server}
|
||||
|
||||
Many performance tradeoffs and balances that might need more attention.
|
||||
We first need to track and fix whatever bottlenecks emerge; but we also
|
||||
need to invent good algorithms for prioritizing the client's traffic
|
||||
without starving the server's traffic too much.\plan{No idea; try
|
||||
profiling and improving things in 2007.}
|
||||
|
||||
\subsection{Protocol redesign for UDP}
|
||||
Tor has relayed only TCP traffic since its first versions, and has used
|
||||
TLS-over-TCP to do so. This approach has proved reliable and flexible, but
|
||||
in the long term we will need to allow UDP traffic on the network, and switch
|
||||
some or all of the network to using a UDP transport. {\bf Supporting UDP
|
||||
traffic} will make Tor more suitable for protocols that require UDP, such
|
||||
as many VOIP protocols. {\bf Using a UDP transport} could greatly reduce
|
||||
resource limitations on servers, and make the network far less interruptible
|
||||
by lossy connections. Either of these protocol changes would require a great
|
||||
deal of design work, however. We hope to be able to enlist the aid of a few
|
||||
talented graduate students to assist with the initial design and
|
||||
specification, but the actual implementation will require significant testing
|
||||
of different reliable transport approaches.\plan{Maybe do a design in 2007 if
|
||||
we find an interested academic. Ian or Ben L might be good partners here.}
|
||||
|
||||
\section{Blocking resistance}
|
||||
|
||||
\subsection{Design for blocking resistance}
|
||||
We have written a design document explaining our general approach to blocking
|
||||
resistance. We should workshop it with other experts in the field to get
|
||||
their ideas about how we can improve Tor's efficacy as an anti-censorship
|
||||
tool.
|
||||
|
||||
\subsection{Implementation: client-side and bridges-side}
|
||||
|
||||
Our anticensorship design calls for some nodes to act as ``bridges''
|
||||
that are outside a national firewall, and others inside the firewall to
|
||||
act as pure clients. This part of the design is quite clear-cut; we're
|
||||
probably ready to begin implementing it. To {\bf implement bridges}, we
|
||||
need to have servers publish themselves as limited-availability relays
|
||||
to a special bridge authority if they judge they'd make good servers.
|
||||
We will also need to help provide documentation for port forwarding,
|
||||
and an easy configuration tool for running as a bridge.
|
||||
|
||||
To {\bf implement clients}, we need to provide a flexible interface to
|
||||
learn about bridges and to act on knowledge of bridges. We also need
|
||||
to teach them how to know to use bridges as their first hop, and how to
|
||||
fetch directory information from both classes of directory authority.
|
||||
|
||||
Clients also need to {\bf use the encrypted directory variant} added in Tor
|
||||
0.1.2.3-alpha. This will let them retrieve directory information over Tor
|
||||
once they've got their initial bridges. We may want to get the rest of the
|
||||
Tor user base to begin using this encrypted directory variant too, to
|
||||
provide cover.
|
||||
|
||||
Bridges will want to be able to {\bf listen on multiple addresses and ports}
|
||||
if they can, to give the adversary more ports to block.
|
||||
|
||||
\subsection{Research: anonymity implications from becoming a bridge}
|
||||
|
||||
\subsection{Implementation: bridge authority}
|
||||
|
||||
The design here is also reasonably clear-cut: we need to run some
|
||||
directory authorities with a slightly modified protocol that doesn't leak
|
||||
the entire list of bridges. Thus users can learn up-to-date information
|
||||
for bridges they already know about, but they can't learn about arbitrary
|
||||
new bridges.
|
||||
|
||||
\subsection{Normalizing the Tor protocol on the wire}
|
||||
Additionally, we should {\bf resist content-based filters}. Though an
|
||||
adversary can't see what users are saying, some aspects of our protocol are
|
||||
easy to fingerprint {\em as} Tor. We should correct this where possible.
|
||||
|
||||
Look like Firefox; or look like nothing?
|
||||
Future research: investigate timing similarities with other protocols.
|
||||
|
||||
\subsection{Access control for bridges}
|
||||
Design/impl: password-protecting bridges, in light of above.
|
||||
And/or more general access control.
|
||||
|
||||
\subsection{Research: scanning-resistance}
|
||||
|
||||
\subsection{Research/Design/Impl: how users discover bridges}
|
||||
Our design anticipates an arms race between discovery methods and censors.
|
||||
We need to begin the infrastructure on our side quickly, preferably in a
|
||||
flexible language like Python, so we can adapt quickly to censorship.
|
||||
|
||||
phase one: personal bridges
|
||||
phase two: families of personal bridges
|
||||
phase three: more structured social network
|
||||
phase four: bag of tricks
|
||||
Research: phase five...
|
||||
|
||||
Integration with Psiphon, etc?
|
||||
|
||||
\subsection{Document best practices for users}
|
||||
Document best practices for various activities common among
|
||||
blocked users (e.g. WordPress use).
|
||||
|
||||
\subsection{Research: how to know if a bridge has been blocked?}
|
||||
|
||||
\subsection{GeoIP maintenance, and "private" user statistics}
|
||||
How to know if the whole idea is working?
|
||||
|
||||
\subsection{Research: hiding whether the user is reading or publishing?}
|
||||
|
||||
\subsection{Research: how many bridges do you need to know to maintain
|
||||
reachability?}
|
||||
|
||||
\subsection{Resisting censorship of the Tor website, docs, and mirrors}
|
||||
|
||||
We should take some effort to consider {\bf initial distribution of Tor and
|
||||
related information} in countries where the Tor website and mirrors are
|
||||
censored. (Right now, most countries that block access to Tor block only the
|
||||
main website and leave mirrors and the network itself untouched.) Falling
|
||||
back on word-of-mouth is always a good last resort, but we should also take
|
||||
steps to make sure it's relatively easy for users to get ahold of a copy.
|
||||
|
||||
\section{Security}
|
||||
|
||||
\subsection{Security research projects}
|
||||
|
||||
We should investigate approaches with some promise to help Tor resist
|
||||
end-to-end traffic correlation attacks. It's an open research question
|
||||
whether (and to what extent) {\bf mixed-latency} networks, {\bf low-volume
|
||||
long-distance padding}, or other approaches can resist these attacks, which
|
||||
are currently some of the most effective against careful Tor users. We
|
||||
should research these questions and perform simulations to identify
|
||||
opportunities for strengthening our design without dropping performance to
|
||||
unacceptable levels. %Cite something
|
||||
\plan{Start doing this in 2007; write a paper. 8-16 weeks.}
|
||||
|
||||
We've got some preliminary results suggesting that {\bf a topology-aware
|
||||
routing algorithm}~\cite{feamster:wpes2004} could reduce Tor users'
|
||||
vulnerability against local or ISP-level adversaries, by ensuring that they
|
||||
are never in a position to watch both ends of a connection. We need to
|
||||
examine the effects of this approach in more detail and consider side-effects
|
||||
on anonymity against other kinds of adversaries. If the approach still looks
|
||||
promising, we should investigate ways for clients to implement it (or an
|
||||
approximation of it) without having to download routing tables for the whole
|
||||
Internet. \plan{Not in 2007 unless a graduate student wants to do it.}
|
||||
|
||||
%\tmp{defenses against end-to-end correlation} We don't expect any to work
|
||||
%right now, but it would be useful to learn that one did. Alternatively,
|
||||
%proving that one didn't would free up researchers in the field to go work on
|
||||
%other things.
|
||||
%
|
||||
% See above; I think I got this.
|
||||
|
||||
We should research the efficacy of {\bf website fingerprinting} attacks,
|
||||
wherein an adversary tries to match the distinctive traffic and timing
|
||||
pattern of the resources constituting a given website to the traffic pattern
|
||||
of a user's client. These attacks work great in simulations, but in
|
||||
practice we hear they don't work nearly as well. We should get some actual
|
||||
numbers to investigate the issue, and figure out what's going on. If we
|
||||
resist these attacks, or can improve our design to resist them, we should.
|
||||
% add cites
|
||||
\plan{Possibly part of end-to-end correlation paper. Otherwise, not in 2007
|
||||
unless a graduate student is interested.}
|
||||
|
||||
\subsection{Implementation security}
|
||||
Right now, each Tor node stores its keys unencrypted. We should {\bf encrypt
|
||||
more Tor keys} so that Tor authorities can require a startup password. We
|
||||
should look into adding intermediary medium-term ``signing keys'' between
|
||||
identity keys and onion keys, so that a password could be required to replace
|
||||
a signing key, but not to start Tor. This would improve Tor's long-term
|
||||
security, especially in its directory authority infrastructure.\plan{Design this
|
||||
as a part of the revised ``v2.1'' directory protocol; implement it in
|
||||
2007. 3-4 weeks.}
|
||||
|
||||
We should also {\bf mark RAM that holds key material as non-swappable} so
|
||||
that there is no risk of recovering key material from a hard disk
|
||||
compromise. This would require submitting patches upstream to OpenSSL, where
|
||||
support for marking memory as sensitive is currently in a very preliminary
|
||||
state.\plan{Nice to do, but not in immediate Tor scope.}
|
||||
|
||||
There are numerous tools for identifying trouble spots in code (such as
|
||||
Coverity or even VS2005's code analysis tool) and we should convince somebody
|
||||
to run some of them against the Tor codebase. Ideally, we could figure out a
|
||||
way to get our code checked periodically rather than just once.\plan{Almost
|
||||
no time once we talk somebody into it.}
|
||||
|
||||
We should try {\bf protocol fuzzing} to identify errors in our
|
||||
implementation.\plan{Not in 2007 unless we find a grad student or
|
||||
undergraduate who wants to try.}
|
||||
|
||||
Our guard nodes help prevent an attacker from being able to become a chosen
|
||||
client's entry point by having each client choose a few favorite entry points
|
||||
as ``guards'' and stick to them. We should implement a {\bf directory
|
||||
guards} feature to keep adversaries from enumerating Tor users by acting as
|
||||
a directory cache.\plan{Do in 2007; 2 weeks.}
|
||||
|
||||
\subsection{Detect corrupt exits and other servers}
|
||||
With the success of our network, we've attracted servers in many locations,
|
||||
operated by many kinds of people. Unfortunately, some of these locations
|
||||
have compromised or defective networks, and some of these people are
|
||||
untrustworthy or incompetent. Our current design relies on authority
|
||||
administrators to identify bad nodes and mark them as nonfunctioning. We
|
||||
should {\bf automate the process of identifying malfunctioning nodes} as
|
||||
follows:
|
||||
|
||||
We should create a generic {\bf feedback mechanism for add-on tools} like
|
||||
Mike Perry's ``Snakes on a Tor'' to report failing nodes to authorities.
|
||||
\plan{Do in 2006; 1-2 weeks.}
|
||||
|
||||
We should write tools to {\bf detect more kinds of innocent node failure},
|
||||
such as nodes whose network providers intercept SSL, nodes whose network
|
||||
providers censor popular websites, and so on. We should also try to detect
|
||||
{\bf routers that snoop traffic}; we could do this by launching connections
|
||||
to throwaway accounts, and seeing which accounts get used.\plan{Do in 2007;
|
||||
ask Mike Perry if he's interested. 4-6 weeks.}
|
||||
|
||||
We should add {\bf an efficient way for authorities to mark a set of servers
|
||||
as probably collaborating} though not necessarily otherwise dishonest.
|
||||
This happens when an administrator starts multiple routers, but doesn't mark
|
||||
them as belonging to the same family.\plan{Do during v2.1 directory protocol
|
||||
redesign; 1-2 weeks to implement.}
|
||||
|
||||
To avoid attacks where an adversary claims good performance in order to
|
||||
attract traffic, we should {\bf have authorities measure node performance}
|
||||
(including stability and bandwidth) themselves, and not simply believe what
|
||||
they're told. Measuring stability can be done by tracking MTBF. Measuring
|
||||
bandwidth can be tricky, since it's hard to distinguish between a server with
|
||||
low capacity, and a high-capacity server with most of its capacity in
|
||||
use.\plan{Do ``Stable'' in 2007; 2-3 weeks. ``Fast'' will be harder; do it
|
||||
if we can interest a grad student.}
|
||||
|
||||
{\bf Operating a directory authority should be easier.} We rely on authority
|
||||
operators to keep the network running well, but right now their job involves
|
||||
too much busywork and administrative overhead. A better interface for them
|
||||
to use could free their time to work on exception cases rather than on
|
||||
adding named nodes to the network.\plan{Do in 2007; 4-5 weeks.}
|
||||
|
||||
\subsection{Protocol security}
|
||||
|
||||
In addition to other protocol changes discussed above,
|
||||
% And should we move some of them down here? -NM
|
||||
we should add {\bf hooks for denial-of-service resistance}; we have some
|
||||
preliminary designs, but we shouldn't postpone them until we really need them.
|
||||
If somebody tries a DDoS attack against the Tor network, we won't want to
|
||||
wait for all the servers and clients to upgrade to a new
|
||||
version.\plan{Research project; do this in 2007 if funded.}
|
||||
|
||||
\section{Development infrastructure}
|
||||
|
||||
\subsection{Build farm}
|
||||
We've begun to deploy a cross-platform distributed build farm of hosts
|
||||
that build and test the Tor source every time it changes in our development
|
||||
repository.
|
||||
|
||||
We need to {\bf get more participants}, so that we can test a larger variety
|
||||
of platforms. (Previously, we've only found out when our code had broken on
|
||||
obscure platforms when somebody got around to building it.)
|
||||
|
||||
We need also to {\bf add our dependencies} to the build farm, so that we can
|
||||
ensure that libraries we need (especially libevent) do not stop working on
|
||||
any important platform between one release and the next.
|
||||
|
||||
\plan{This is ongoing as more buildbots arrive.}
|
||||
|
||||
\subsection{Improved testing harness}
|
||||
Currently, our {\bf unit tests} cover only about 20\% of the code base. This
|
||||
is uncomfortably low; we should write more and switch to a more flexible
|
||||
testing framework.\plan{Ongoing basis, time permitting.}
|
||||
|
||||
We should also write flexible {\bf automated single-host deployment tests} so
|
||||
we can more easily verify that the current codebase works with the
|
||||
network.\plan{Worthwhile in 2007; would save lots of time. 2-4 weeks.}
|
||||
|
||||
We should build automated {\bf stress testing} frameworks so we can see which
|
||||
realistic loads cause Tor to perform badly, and regularly profile Tor against
|
||||
these loads. This would give us {\it in vitro} performance values to
|
||||
supplement our deployment experience.\plan{Worthwhile in 2007; 2-6 weeks.}
|
||||
|
||||
We should improve our memory profiling code.\plan{...}
|
||||
|
||||
|
||||
\subsection{Centralized build system}
|
||||
We currently rely on a separate packager to maintain the packaging system and
|
||||
to build Tor on each platform for which we distribute binaries. Separate
|
||||
package maintainers is sensible, but separate package builders has meant
|
||||
long turnaround times between source releases and package releases. We
|
||||
should create the necessary infrastructure for us to produce binaries for all
|
||||
major packages within an hour or so of source release.\plan{We should
|
||||
brainstorm this at least in 2007.}
|
||||
|
||||
\subsection{Improved metrics}
|
||||
We need a way to {\bf measure the network's health, capacity, and degree of
|
||||
utilization}. Our current means for doing this are ad hoc and not
|
||||
completely accurate
|
||||
|
||||
We need better ways to {\bf tell which countries are users are coming from,
|
||||
and how many there are}. A good perspective of the network helps us
|
||||
allocate resources and identify trouble spots, but our current approaches
|
||||
will work less and less well as we make it harder for adversaries to
|
||||
enumerate users. We'll probably want to shift to a smarter, statistical
|
||||
approach rather than our current ``count and extrapolate'' method.
|
||||
|
||||
\plan{All of this in 2007 if funded; 4-8 weeks}
|
||||
|
||||
% \tmp{We'd like to know how much of the network is getting used.}
|
||||
% I think this is covered above -NM
|
||||
|
||||
\subsection{Controller library}
|
||||
We've done lots of design and development on our controller interface, which
|
||||
allows UI applications and other tools to interact with Tor. We could
|
||||
encourage the development of more such tools by releasing a {\bf
|
||||
general-purpose controller library}, ideally with API support for several
|
||||
popular programming languages.\plan{2006 or 2007; 1-2 weeks.}
|
||||
|
||||
\section{User experience}
|
||||
|
||||
\subsection{Get blocked less, get blocked less broadly}
|
||||
Right now, some services block connections from the Tor network because
|
||||
they don't have a better
|
||||
way to keep vandals from abusing them than blocking IP addresses associated
|
||||
with vandalism. Our approach so far has been to educate them about better
|
||||
solutions that currently exist, but we should also {\bf create better
|
||||
solutions for limiting vandalism by anonymous users} like credential and
|
||||
blind-signature based implementations, and encourage their use. Other
|
||||
promising starting points including writing a patch and explanation for
|
||||
Wikipedia, and helping Freenode to document, maintain, and expand its
|
||||
current Tor-friendly position.\plan{Do a writeup here in 2007; 1-2 weeks.}
|
||||
|
||||
Those who do block Tor users also block overbroadly, sometimes blacklisting
|
||||
operators of Tor servers that do not permit exit to their services. We could
|
||||
obviate innocent reasons for doing so by designing a {\bf narrowly-targeted Tor
|
||||
RBL service} so that those who wanted to overblock Tor could no longer
|
||||
plead incompetence.\plan{Possibly in 2007 if we decide it's a good idea; 3
|
||||
weeks.}
|
||||
|
||||
\subsection{All-in-one bundle}
|
||||
We need a well-tested, well-documented bundle of Tor and supporting
|
||||
applications configured to use it correctly. We have an initial
|
||||
implementation well under way, but it will need additional work in
|
||||
identifying requisite Firefox extensions, identifying security threats,
|
||||
improving user experience, and so on. This will need significantly more work
|
||||
before it's ready for a general public release.
|
||||
|
||||
\subsection{LiveCD Tor}
|
||||
We need a nice bootable livecd containing a minimal OS and a few applications
|
||||
configured to use it correctly. The Anonym.OS project demonstrated that this
|
||||
is quite feasible, but their project is not currently maintained.
|
||||
|
||||
\subsection{A Tor client in a VM}
|
||||
\tmp{a.k.a JanusVM} which is quite related to the firewall-level deployment
|
||||
section below. JanusVM is a Linux kernel running in VMWare. It gets an IP
|
||||
address from the network, and serves as a DHCP server for its host Windows
|
||||
machine. It intercepts all outgoing traffic and redirects it into Privoxy,
|
||||
Tor, etc. This Linux-in-Windows approach may help us with scalability in
|
||||
the short term, and it may also be a good long-term solution rather than
|
||||
accepting all security risks in Windows.
|
||||
|
||||
%\subsection{Interface improvements}
|
||||
%\tmp{Allow controllers to manipulate server status.}
|
||||
% (Why is this in the User Experience section?) -RD
|
||||
% I think it's better left to a generic ``make controller iface better'' item.
|
||||
|
||||
\subsection{Firewall-level deployment}
|
||||
Another useful deployment mode for some users is using {\bf Tor in a firewall
|
||||
configuration}, and directing all their traffic through Tor. This can be a
|
||||
little tricky to set up currently, but it's an effective way to make sure no
|
||||
traffic leaves the host un-anonymized. To achieve this, we need to {\bf
|
||||
improve and port our new TransPort} feature which allows Tor to be used
|
||||
without SOCKS support; to {\bf add an anonymizing DNS proxy} feature to Tor;
|
||||
and to {\bf construct a recommended set of firewall configurations} to redirect
|
||||
traffic to Tor.
|
||||
|
||||
This is an area where {\bf deployment via a livecd}, or an installation
|
||||
targeted at specialized home routing hardware, could be useful.
|
||||
|
||||
\subsection{Assess software and configurations for anonymity risks}
|
||||
Right now, users and packagers are more or less on their own when selecting
|
||||
Firefox extensions. We should {\bf assemble a recommended list of browser
|
||||
extensions} through experiment, and include this in the application bundles
|
||||
we distribute.
|
||||
|
||||
We should also describe {\bf best practices for using Tor with each class of
|
||||
application}. For example, Ethan Zuckerman has written a detailed
|
||||
tutorial on how to use Tor, Firefox, GMail, and Wordpress to blog with
|
||||
improved safety. There are many other cases on the Internet where anonymity
|
||||
would be helpful, and there are a lot of ways to screw up using Tor.
|
||||
|
||||
The Foxtor and Torbutton extensions serve similar purposes; we should pick a
|
||||
favorite, and merge in the useful features of the other.
|
||||
|
||||
%\tmp{clean up our own bundled software:
|
||||
%E.g. Merge the good features of Foxtor into Torbutton}
|
||||
%
|
||||
% What else did you have in mind? -NM
|
||||
|
||||
\subsection{Localization}
|
||||
Right now, most of our user-facing code is internationalized. We need to
|
||||
internationalize the last few hold-outs (like the Tor expert installer), and get
|
||||
more translations for the parts that are already internationalized.
|
||||
|
||||
Also, we should look into a {\bf unified translator's solution}. Currently,
|
||||
since different tools have been internationalized using the
|
||||
framework-appropriate method, different tools require translators to localize
|
||||
them via different interfaces. Inasmuch as possible, we should make
|
||||
translators only need to use a single tool to translate the whole Tor suite.
|
||||
|
||||
\section{Support}
|
||||
|
||||
It would be nice to set up some {\bf user support infrastructure} and
|
||||
{\bf contributor support infrastructure}, especially focusing on server
|
||||
operators and on coordinating volunteers.
|
||||
|
||||
This includes intuitive and easy ticket systems for bug reports and
|
||||
feature suggestions (not just mailing lists with a half dozen people
|
||||
and no clear roles for who answers what), but it also includes a more
|
||||
personalized and efficient framework for interaction so we keep the
|
||||
attention and interest of the contributors, and so we make them feel
|
||||
helpful and wanted.
|
||||
|
||||
\section{Documentation}
|
||||
|
||||
\subsection{Unified documentation scheme}
|
||||
|
||||
We need to {\bf inventory our documentation.} Our documentation so far has
|
||||
been mostly produced on an {\it ad hoc} basis, in response to particular
|
||||
needs and requests. We should figure out what documentation we have, which of
|
||||
it (if any) should get priority, and whether we can't put it all into a
|
||||
single format.
|
||||
|
||||
We could {\bf unify the docs} into a single book-like thing. This will also
|
||||
help us identify what sections of the ``book'' are missing.
|
||||
|
||||
\subsection{Missing technical documentation}
|
||||
|
||||
We should {\bf revise our design paper} to reflect the new decisions and
|
||||
research we've made since it was published in 2004. This will help other
|
||||
researchers evaluate and suggest improvements to Tor's current design.
|
||||
|
||||
Other projects sometimes implement the client side of our protocol. We
|
||||
encourage this, but we should write {\bf a document about how to avoid
|
||||
excessive resource use}, so we don't need to worry that they will do so
|
||||
without regard to the effect of their choices on server resources.
|
||||
|
||||
\subsection{Missing user documentation}
|
||||
|
||||
Our documentation falls into two broad categories: some is `discoursive' and
|
||||
explains in detail why users should take certain actions, and other
|
||||
documentation is `comprehensive' and describes all of Tor's features. Right
|
||||
now, we have no document that is both deep, readable, and thorough. We
|
||||
should correct this by identifying missing spots in our design.
|
||||
|
||||
\bibliographystyle{plain} \bibliography{tor-design}
|
||||
|
||||
\end{document}
|
||||
|
||||
Binary file not shown.
@ -1,895 +0,0 @@
|
||||
\documentclass{article}
|
||||
|
||||
\usepackage{url}
|
||||
\usepackage{fullpage}
|
||||
|
||||
\newenvironment{tightlist}{\begin{list}{$\bullet$}{
|
||||
\setlength{\itemsep}{0mm}
|
||||
\setlength{\parsep}{0mm}
|
||||
% \setlength{\labelsep}{0mm}
|
||||
% \setlength{\labelwidth}{0mm}
|
||||
% \setlength{\topsep}{0mm}
|
||||
}}{\end{list}}
|
||||
\newcommand{\tmp}[1]{{\bf #1} [......] \\}
|
||||
\newcommand{\plan}[1]{ {\bf (#1)}}
|
||||
|
||||
\begin{document}
|
||||
|
||||
\title{Tor Development Roadmap: Wishlist for 2008 and beyond}
|
||||
\author{Roger Dingledine \and Nick Mathewson}
|
||||
\date{}
|
||||
|
||||
\maketitle
|
||||
\pagestyle{plain}
|
||||
|
||||
\section{Introduction}
|
||||
|
||||
Tor (the software) and Tor (the overall software/network/support/document
|
||||
suite) are now experiencing all the crises of success. Over the next
|
||||
years, we're probably going to grow even more in terms of users, developers,
|
||||
and funding than before. This document attempts to lay out all the
|
||||
well-understood next steps that Tor needs to take. We should periodically
|
||||
reorganize it to reflect current and intended priorities.
|
||||
|
||||
\section{Everybody can be a relay}
|
||||
|
||||
We've made a lot of progress towards letting an ordinary Tor client also
|
||||
serve as a Tor relay. But these issues remain.
|
||||
|
||||
\subsection{UPNP}
|
||||
|
||||
We should teach Vidalia how to speak UPNP to automatically open and
|
||||
forward ports on common (e.g. Linksys) routers. There are some promising
|
||||
Qt-based UPNP libs out there, and in any case there are others (e.g. in
|
||||
Perl) that we can base it on.
|
||||
|
||||
\subsection{``ORPort auto'' to look for a reachable port}
|
||||
|
||||
Vidalia defaults to port 443 on Windows and port 8080 elsewhere. But if
|
||||
that port is already in use, or the ISP filters incoming connections
|
||||
on that port (some cablemodem providers filter 443 inbound), the user
|
||||
needs to learn how to notice this, and then pick a new one and type it
|
||||
into Vidalia.
|
||||
|
||||
We should add a new option ``auto'' that cycles through a set of preferred
|
||||
ports, testing bindability and reachability for each of them, and only
|
||||
complains to the user once it's given up on the common choices.
|
||||
|
||||
\subsection{Incentives design}
|
||||
|
||||
Roger has been working with researchers at Rice University to simulate
|
||||
and analyze a new design where the directory authorities assign gold
|
||||
stars to well-behaving relays, and then all the relays give priority
|
||||
to traffic from gold-starred relays. The great feature of the design is
|
||||
that not only does it provide the (explicit) incentive to run a relay,
|
||||
but it also aims to grow the overall capacity of the network, so even
|
||||
non-relays will benefit.
|
||||
|
||||
It needs more analysis, and perhaps more design work, before we try
|
||||
deploying it.
|
||||
|
||||
\subsection{Windows libevent}
|
||||
|
||||
Tor relays still don't work well or reliably on Windows XP or Windows
|
||||
Vista, because we don't use the Windows-native ``overlapped IO''
|
||||
approach. Christian King made a good start at teaching libevent about
|
||||
overlapped IO during Google Summer of Code 2007, and next steps are
|
||||
to a) finish that, b) teach Tor to do openssl calls on buffers rather
|
||||
than directly to the network, and c) teach Tor to use the new libevent
|
||||
buffers approach.
|
||||
|
||||
\subsection{Network scaling}
|
||||
|
||||
If we attract many more relays, we will need to handle the growing pains
|
||||
in terms of getting all the directory information to all the users.
|
||||
|
||||
The first piece of this issue is a practical question: since the
|
||||
directory size scales linearly with more relays, at some point it
|
||||
will no longer be practical for every client to learn about every
|
||||
relay. We can try to reduce the amount of information each client needs
|
||||
to fetch (e.g. based on fetching less information preemptively as in
|
||||
Section~\ref{subsec:fewer-descriptor-fetches} below), but eventually
|
||||
clients will need to learn about only a subset of the network, and we
|
||||
will need to design good ways to divide up the network information.
|
||||
|
||||
The second piece is an anonymity question that arises from this
|
||||
partitioning: if Tor's security comes from having all the clients
|
||||
behaving in similar ways, yet we are now giving different clients
|
||||
different directory information, how can we minimize the new anonymity
|
||||
attacks we introduce?
|
||||
|
||||
\subsection{Using fewer sockets}
|
||||
|
||||
Since in the current network every Tor relay can reach every other Tor
|
||||
relay, and we have many times more users than relays, pretty much every
|
||||
possible link in the network is in use. That is, the current network
|
||||
is a clique in practice.
|
||||
|
||||
And since each of these connections requires a TCP socket, it's going
|
||||
to be hard for the network to grow much larger: many systems come with
|
||||
a default of 1024 file descriptors allowed per process, and raising
|
||||
that ulimit is hard for end users. Worse, many low-end gateway/firewall
|
||||
routers can't handle this many connections in their routing table.
|
||||
|
||||
One approach is a restricted-route topology~\cite{danezis:pet2003}:
|
||||
predefine which relays can reach which other relays, and communicate
|
||||
these restrictions to the relays and the clients. We need to compute
|
||||
which links are acceptable in a way that's decentralized yet scalable,
|
||||
and in a way that achieves a small-worlds property; and we
|
||||
need an efficient (compact) way to characterize the topology information
|
||||
so all the users could keep up to date.
|
||||
|
||||
Another approach would be to switch to UDP-based transport between
|
||||
relays, so we don't need to keep the TCP sockets open at all. Needs more
|
||||
investigation too.
|
||||
|
||||
\subsection{Auto bandwidth detection and rate limiting, especially for
|
||||
asymmetric connections.}
|
||||
|
||||
|
||||
\subsection{Better algorithms for giving priority to local traffic}
|
||||
|
||||
Proposal 111 made a lot of progress at separating local traffic from
|
||||
relayed traffic, so Tor users can rate limit the relayed traffic at a
|
||||
stricter level. But since we want to pass both traffic classes over the
|
||||
same TCP connection, we can't keep them entirely separate. The current
|
||||
compromise is that we treat all bytes to/from a given connectin as
|
||||
local traffic if any of the bytes within the past N seconds were local
|
||||
bytes. But a) we could use some more intelligent heuristics, and b)
|
||||
this leaks information to an active attacker about when local traffic
|
||||
was sent/received.
|
||||
|
||||
\subsection{Tolerate absurdly wrong clocks, even for relays}
|
||||
|
||||
Many of our users are on Windows, running with a clock several days or
|
||||
even several years off from reality. Some of them are even intentionally
|
||||
in this state so they can run software that will only run in the past.
|
||||
|
||||
Before Tor 0.1.1.x, Tor clients would still function if their clock was
|
||||
wildly off --- they simply got a copy of the directory and believed it.
|
||||
Starting in Tor 0.1.1.x (and even moreso in Tor 0.2.0.x), the clients
|
||||
only use networkstatus documents that they believe to be recent, so
|
||||
clients with extremely wrong clocks no longer work. (This bug has been
|
||||
an unending source of vague and confusing bug reports.)
|
||||
|
||||
The first step is for clients to recognize when all the directory material
|
||||
they're fetching has roughly the same offset from their current time,
|
||||
and then automatically correct for it.
|
||||
|
||||
Once that's working well, clients who opt to become bridge relays should
|
||||
be able to use the same approach to serve accurate directory information
|
||||
to their bridge users.
|
||||
|
||||
\subsection{Risks from being a relay}
|
||||
|
||||
Three different research
|
||||
papers~\cite{back01,clog-the-queue,attack-tor-oak05} describe ways to
|
||||
identify the nodes in a circuit by running traffic through candidate nodes
|
||||
and looking for dips in the traffic while the circuit is active. These
|
||||
clogging attacks are not that scary in the Tor context so long as relays
|
||||
are never clients too. But if we're trying to encourage more clients to
|
||||
turn on relay functionality too (whether as bridge relays or as normal
|
||||
relays), then we need to understand this threat better and learn how to
|
||||
mitigate it.
|
||||
|
||||
One promising research direction is to investigate the RelayBandwidthRate
|
||||
feature that lets Tor rate limit relayed traffic differently from local
|
||||
traffic. Since the attacker's ``clogging'' traffic is not in the same
|
||||
bandwidth class as the traffic initiated by the user, it may be harder
|
||||
to detect interference. Or it may not be.
|
||||
|
||||
\subsection{First a bridge, then a public relay?}
|
||||
|
||||
Once enough of the items in this section are done, I want all clients
|
||||
to start out automatically detecting their reachability and opting
|
||||
to be bridge relays.
|
||||
|
||||
Then if they realize they have enough consistency and bandwidth, they
|
||||
should automatically upgrade to being non-exit relays.
|
||||
|
||||
What metrics should we use for deciding when we're fast enough
|
||||
and stable enough to switch? Given that the list of bridge relays needs
|
||||
to be kept secret, it doesn't make much sense to switch back.
|
||||
|
||||
\section{Tor on low resources / slow links}
|
||||
\subsection{Reducing directory fetches further}
|
||||
\label{subsec:fewer-descriptor-fetches}
|
||||
\subsection{AvoidDiskWrites}
|
||||
\subsection{Using less ram}
|
||||
\subsection{Better DoS resistance for tor servers / authorities}
|
||||
\section{Blocking resistance}
|
||||
\subsection{Better bridge-address-distribution strategies}
|
||||
\subsection{Get more volunteers running bridges}
|
||||
\subsection{Handle multiple bridge authorities}
|
||||
\subsection{Anonymity for bridge users: second layer of entry guards, etc?}
|
||||
\subsection{More TLS normalization}
|
||||
\subsection{Harder to block Tor software distribution}
|
||||
\subsection{Integration with Psiphon}
|
||||
\section{Packaging}
|
||||
\subsection{Switch Privoxy out for Polipo}
|
||||
- Make Vidalia able to launch more programs itself
|
||||
\subsection{Continue Torbutton improvements}
|
||||
especially better docs
|
||||
\subsection{Vidalia and stability (especially wrt ongoing Windows problems)}
|
||||
learn how to get useful crash reports (tracebacks) from Windows users
|
||||
\subsection{Polipo support on Windows}
|
||||
\subsection{Auto update for Tor, Vidalia, others}
|
||||
\subsection{Tor browser bundle for USB and standalone use}
|
||||
\subsection{LiveCD solution}
|
||||
\subsection{VM-based solution}
|
||||
\subsection{Tor-on-enclave-firewall configuration}
|
||||
\subsection{General tutorials on what common applications are Tor-friendly}
|
||||
\subsection{Controller libraries (torctl) plus documentation}
|
||||
\subsection{Localization and translation (Vidalia, Torbutton, web pages)}
|
||||
\section{Interacting better with Internet sites}
|
||||
\subsection{Make tordnsel (tor exitlist) better and more well-known}
|
||||
\subsection{Nymble}
|
||||
\subsection{Work with Wikipedia, Slashdot, Google(, IRC networks)}
|
||||
\subsection{IPv6 support for exit destinations}
|
||||
\section{Network health}
|
||||
\subsection{torflow / soat to detect bad relays}
|
||||
\subsection{make authorities more automated}
|
||||
\subsection{torstatus pages and better trend tracking}
|
||||
\subsection{better metrics for assessing network health / growth}
|
||||
- geoip usage-by-country reporting and aggregation
|
||||
(Once that's working, switch to Directory guards)
|
||||
\section{Performance research}
|
||||
\subsection{Load balance better}
|
||||
\subsection{Improve our congestion control algorithms}
|
||||
\subsection{Two-hops vs Three-hops}
|
||||
\subsection{Transport IP packets end-to-end}
|
||||
\section{Outreach and user education}
|
||||
\subsection{"Who uses Tor" use cases}
|
||||
\subsection{Law enforcement contacts}
|
||||
- "Was this IP address a Tor relay recently?" database
|
||||
\subsection{Commercial/enterprise outreach. Help them use Tor well and
|
||||
not fear it.}
|
||||
\subsection{NGO outreach and training.}
|
||||
- "How to be a safe blogger"
|
||||
\subsection{More activist coordinators, more people to answer user questions}
|
||||
\subsection{More people to hold hands of server operators}
|
||||
\subsection{Teaching the media about Tor}
|
||||
\subsection{The-dangers-of-plaintext awareness}
|
||||
\subsection{check.torproject.org and other "privacy checkers"}
|
||||
\subsection{Stronger legal FAQ for US}
|
||||
\subsection{Legal FAQs for other countries}
|
||||
\section{Anonymity research}
|
||||
\subsection{estimate relay bandwidth more securely}
|
||||
\subsection{website fingerprinting attacks}
|
||||
\subsection{safer e2e defenses}
|
||||
\subsection{Using Tor when you really need anonymity. Can you compose it
|
||||
with other steps, like more trusted guards or separate proxies?}
|
||||
\subsection{Topology-aware routing; routing-zones, steven's pet2007 paper.}
|
||||
\subsection{Exactly what do guard nodes provide?}
|
||||
|
||||
Entry guards seem to defend against all sorts of attacks. Can we work
|
||||
through all the benefits they provide? Papers like Nikita's CCS 2007
|
||||
paper make me think their value is not well-understood by the research
|
||||
community.
|
||||
|
||||
\section{Organizational growth and stability}
|
||||
\subsection{A contingency plan if Roger gets hit by a bus}
|
||||
- Get a new executive director
|
||||
\subsection{More diversity of funding}
|
||||
- Don't rely on any one funder as much
|
||||
- Don't rely on any sector or funder category as much
|
||||
\subsection{More Tor-funded people who are skilled at peripheral apps like
|
||||
Vidalia, Torbutton, Polipo, etc}
|
||||
\subsection{More coordinated media handling and strategy}
|
||||
\subsection{Clearer and more predictable trademark behavior}
|
||||
\subsection{More outside funding for internships, etc e.g. GSoC.}
|
||||
\section{Hidden services}
|
||||
\subsection{Scaling: how to handle many hidden services}
|
||||
\subsection{Performance: how to rendezvous with them quickly}
|
||||
\subsection{Authentication/authorization: how to tolerate DoS / load}
|
||||
\section{Tor as a general overlay network}
|
||||
\subsection{Choose paths / exit by country}
|
||||
\subsection{Easier to run your own private servers and have Tor use them
|
||||
anywhere in the path}
|
||||
\subsection{Easier to run an independent Tor network}
|
||||
\section{Code security/correctness}
|
||||
\subsection{veracode}
|
||||
\subsection{code audit}
|
||||
\subsection{more fuzzing tools}
|
||||
\subsection{build farm, better testing harness}
|
||||
\subsection{Long-overdue code refactoring and cleanup}
|
||||
\section{Protocol security}
|
||||
\subsection{safer circuit handshake}
|
||||
\subsection{protocol versioning for future compatibility}
|
||||
\subsection{cell sizes}
|
||||
\subsection{adapt to new key sizes, etc}
|
||||
|
||||
\bibliographystyle{plain} \bibliography{tor-design}
|
||||
|
||||
\end{document}
|
||||
|
||||
|
||||
|
||||
|
||||
\section{Code and design infrastructure}
|
||||
|
||||
\subsection{Protocol revision}
|
||||
To maintain backward compatibility, we've postponed major protocol
|
||||
changes and redesigns for a long time. Because of this, there are a number
|
||||
of sensible revisions we've been putting off until we could deploy several of
|
||||
them at once. To do each of these, we first need to discuss design
|
||||
alternatives with other cryptographers and outside collaborators to
|
||||
make sure that our choices are secure.
|
||||
|
||||
First of all, our protocol needs better {\bf versioning support} so that we
|
||||
can make backward-incompatible changes to our core protocol. There are
|
||||
difficult anonymity issues here, since many naive designs would make it easy
|
||||
to tell clients apart (and then track them) based on their supported versions.
|
||||
|
||||
With protocol versioning support would come the ability to {\bf future-proof
|
||||
our ciphersuites}. For example, not only our OR protocol, but also our
|
||||
directory protocol, is pretty firmly tied to the SHA-1 hash function, which
|
||||
though not yet known to be insecure for our purposes, has begun to show
|
||||
its age. We should
|
||||
remove assumptions throughout our design based on the assumption that public
|
||||
keys, secret keys, or digests will remain any particular size indefinitely.
|
||||
|
||||
Our OR {\bf authentication protocol}, though provably
|
||||
secure\cite{tap:pet2006}, relies more on particular aspects of RSA and our
|
||||
implementation thereof than we had initially believed. To future-proof
|
||||
against changes, we should replace it with a less delicate approach.
|
||||
|
||||
\plan{For all the above: 2 person-months to specify, spread over several
|
||||
months with time for interaction with external participants. One
|
||||
person-month to implement. Start specifying in early 2007.}
|
||||
|
||||
We might design a {\bf stream migration} feature so that streams tunneled
|
||||
over Tor could be more resilient to dropped connections and changed IPs.
|
||||
\plan{Not in 2007.}
|
||||
|
||||
A new protocol could support {\bf multiple cell sizes}. Right now, all data
|
||||
passes through the Tor network divided into 512-byte cells. This is
|
||||
efficient for high-bandwidth protocols, but inefficient for protocols
|
||||
like SSH or AIM that send information in small chunks. Of course, we need to
|
||||
investigate the extent to which multiple sizes could make it easier for an
|
||||
adversary to fingerprint a traffic pattern. \plan{Not in 2007.}
|
||||
|
||||
As a part of our design, we should investigate possible {\bf cipher modes}
|
||||
other than counter mode. For example, a mode with built-in integrity
|
||||
checking, error propagation, and random access could simplify our protocol
|
||||
significantly. Sadly, many of these are patented and unavailable for us.
|
||||
\plan{Not in 2007.}
|
||||
|
||||
\subsection{Scalability}
|
||||
|
||||
\subsubsection{Improved directory efficiency}
|
||||
|
||||
We should {\bf have routers upload their descriptors even less often}, so
|
||||
that clients do not need to download replacements every 18 hours whether any
|
||||
information has changed or not. (As of Tor 0.1.2.3-alpha, clients tolerate
|
||||
routers that don't upload often, but routers still upload at least every 18
|
||||
hours to support older clients.) \plan{Must do, but not until 0.1.1.x is
|
||||
deprecated in mid 2007. 1 week.}
|
||||
|
||||
\subsubsection{Non-clique topology}
|
||||
Our current network design achieves a certain amount of its anonymity by
|
||||
making clients act like each other through the simple expedient of making
|
||||
sure that all clients know all servers, and that any server can talk to any
|
||||
other server. But as the number of servers increases to serve an
|
||||
ever-greater number of clients, these assumptions become impractical.
|
||||
|
||||
At worst, if these scalability issues become troubling before a solution is
|
||||
found, we can design and build a solution to {\bf split the network into
|
||||
multiple slices} until a better solution comes along. This is not ideal,
|
||||
since rather than looking like all other users from a point of view of path
|
||||
selection, users would ``only'' look like 200,000--300,000 other
|
||||
users.\plan{Not unless needed.}
|
||||
|
||||
We are in the process of designing {\bf improved schemes for network
|
||||
scalability}. Some approaches focus on limiting what an adversary can know
|
||||
about what a user knows; others focus on reducing the extent to which an
|
||||
adversary can exploit this knowledge. These are currently in their infancy,
|
||||
and will probably not be needed in 2007, but they must be designed in 2007 if
|
||||
they are to be deployed in 2008.\plan{Design in 2007; unknown difficulty.
|
||||
Write a paper.}
|
||||
|
||||
\subsubsection{Relay incentives}
|
||||
To support more users on the network, we need to get more servers. So far,
|
||||
we've relied on volunteerism to attract server operators, and so far it's
|
||||
served us well. But in the long run, we need to {\bf design incentives for
|
||||
users to run servers} and relay traffic for others. Most obviously, we
|
||||
could try to build the network so that servers offered improved service for
|
||||
other servers, but we would need to do so without weakening anonymity and
|
||||
making it obvious which connections originate from users running servers. We
|
||||
have some preliminary designs~\cite{incentives-txt,tor-challenges},
|
||||
but need to perform
|
||||
some more research to make sure they would be safe and effective.\plan{Write
|
||||
a draft paper; 2 person-months.}
|
||||
(XXX we did that)
|
||||
|
||||
\subsection{Portability}
|
||||
Our {\bf Windows implementation}, though much improved, continues to lag
|
||||
behind Unix and Mac OS X, especially when running as a server. We hope to
|
||||
merge promising patches from Christian King to address this point, and bring
|
||||
Windows performance on par with other platforms.\plan{Do in 2007; 1.5 months
|
||||
to integrate not counting Mike's work.}
|
||||
|
||||
We should have {\bf better support for portable devices}, including modes of
|
||||
operation that require less RAM, and that write to disk less frequently (to
|
||||
avoid wearing out flash RAM).\plan{Optional; 2 weeks.}
|
||||
|
||||
\subsection{Performance: resource usage}
|
||||
We've been working on {\bf using less RAM}, especially on servers. This has
|
||||
paid off a lot for directory caches in the 0.1.2, which in some cases are
|
||||
using 90\% less memory than they used to require. But we can do better,
|
||||
especially in the area around our buffer management algorithms, by using an
|
||||
approach more like the BSD and Linux kernels use instead of our current ring
|
||||
buffer approach. (For OR connections, we can just use queues of cell-sized
|
||||
chunks produced with a specialized allocator.) This could potentially save
|
||||
around 25 to 50\% of the memory currently allocated for network buffers, and
|
||||
make Tor a more attractive proposition for restricted-memory environments
|
||||
like old computers, mobile devices, and the like.\plan{Do in 2007; 2-3 weeks
|
||||
plus one week measurement.} (XXX We did this, but we need to do something
|
||||
more/else.)
|
||||
|
||||
\subsection{Performance: network usage}
|
||||
We know too little about how well our current path
|
||||
selection algorithms actually spread traffic around the network in practice.
|
||||
We should {\bf research the efficacy of our traffic allocation} and either
|
||||
assure ourselves that it is close enough to optimal as to need no improvement
|
||||
(unlikely) or {\bf identify ways to improve network usage}, and get more
|
||||
users' traffic delivered faster. Performing this research will require
|
||||
careful thought about anonymity implications.
|
||||
|
||||
We should also {\bf examine the efficacy of our congestion control
|
||||
algorithm}, and see whether we can improve client performance in the
|
||||
presence of a congested network through dynamic `sendme' window sizes or
|
||||
other means. This will have anonymity implications too if we aren't careful.
|
||||
|
||||
\plan{For both of the above: research, design and write
|
||||
a measurement tool in 2007: 1 month. See if we can interest a graduate
|
||||
student.}
|
||||
|
||||
We should work on making Tor's cell-based protocol perform better on
|
||||
networks with low bandwidth
|
||||
and high packet loss.\plan{Do in 2007 if we're funded to do it; 4-6 weeks.}
|
||||
|
||||
\subsection{Performance scenario: one Tor client, many users}
|
||||
We should {\bf improve Tor's performance when a single Tor handles many
|
||||
clients}. Many organizations want to manage a single Tor client on their
|
||||
firewall for many users, rather than having each user install a separate
|
||||
Tor client. We haven't optimized for this scenario, and it is likely that
|
||||
there are some code paths in the current implementation that become
|
||||
inefficient when a single Tor is servicing hundreds or thousands of client
|
||||
connections. (Additionally, it is likely that such clients have interesting
|
||||
anonymity requirements the we should investigate.) We should profile Tor
|
||||
under appropriate loads, identify bottlenecks, and fix them.\plan{Do in 2007
|
||||
if we're funded to do it; 4-8 weeks.}
|
||||
|
||||
\subsection{Tor servers on asymmetric bandwidth}
|
||||
|
||||
Tor should work better on servers that have asymmetric connections like cable
|
||||
or DSL. Because Tor has separate TCP connections between each
|
||||
hop, if the incoming bytes are arriving just fine and the outgoing bytes are
|
||||
all getting dropped on the floor, the TCP push-back mechanisms don't really
|
||||
transmit this information back to the incoming streams.\plan{Do in 2007 since
|
||||
related to bandwidth limiting. 3-4 weeks.}
|
||||
|
||||
\subsection{Running Tor as both client and server}
|
||||
|
||||
Many performance tradeoffs and balances that might need more attention.
|
||||
We first need to track and fix whatever bottlenecks emerge; but we also
|
||||
need to invent good algorithms for prioritizing the client's traffic
|
||||
without starving the server's traffic too much.\plan{No idea; try
|
||||
profiling and improving things in 2007.}
|
||||
|
||||
\subsection{Protocol redesign for UDP}
|
||||
Tor has relayed only TCP traffic since its first versions, and has used
|
||||
TLS-over-TCP to do so. This approach has proved reliable and flexible, but
|
||||
in the long term we will need to allow UDP traffic on the network, and switch
|
||||
some or all of the network to using a UDP transport. {\bf Supporting UDP
|
||||
traffic} will make Tor more suitable for protocols that require UDP, such
|
||||
as many VOIP protocols. {\bf Using a UDP transport} could greatly reduce
|
||||
resource limitations on servers, and make the network far less interruptible
|
||||
by lossy connections. Either of these protocol changes would require a great
|
||||
deal of design work, however. We hope to be able to enlist the aid of a few
|
||||
talented graduate students to assist with the initial design and
|
||||
specification, but the actual implementation will require significant testing
|
||||
of different reliable transport approaches.\plan{Maybe do a design in 2007 if
|
||||
we find an interested academic. Ian or Ben L might be good partners here.}
|
||||
|
||||
\section{Blocking resistance}
|
||||
|
||||
\subsection{Design for blocking resistance}
|
||||
We have written a design document explaining our general approach to blocking
|
||||
resistance. We should workshop it with other experts in the field to get
|
||||
their ideas about how we can improve Tor's efficacy as an anti-censorship
|
||||
tool.
|
||||
|
||||
\subsection{Implementation: client-side and bridges-side}
|
||||
|
||||
Bridges will want to be able to {\bf listen on multiple addresses and ports}
|
||||
if they can, to give the adversary more ports to block.
|
||||
|
||||
\subsection{Research: anonymity implications from becoming a bridge}
|
||||
|
||||
see arma's bridge proposal; e.g. should bridge users use a second layer of
|
||||
entry guards?
|
||||
|
||||
\subsection{Implementation: bridge authority}
|
||||
|
||||
we run some
|
||||
directory authorities with a slightly modified protocol that doesn't leak
|
||||
the entire list of bridges. Thus users can learn up-to-date information
|
||||
for bridges they already know about, but they can't learn about arbitrary
|
||||
new bridges.
|
||||
|
||||
we need a design for distributing the bridge authority over more than one
|
||||
server
|
||||
|
||||
\subsection{Normalizing the Tor protocol on the wire}
|
||||
Additionally, we should {\bf resist content-based filters}. Though an
|
||||
adversary can't see what users are saying, some aspects of our protocol are
|
||||
easy to fingerprint {\em as} Tor. We should correct this where possible.
|
||||
|
||||
Look like Firefox; or look like nothing?
|
||||
Future research: investigate timing similarities with other protocols.
|
||||
|
||||
\subsection{Research: scanning-resistance}
|
||||
|
||||
\subsection{Research/Design/Impl: how users discover bridges}
|
||||
Our design anticipates an arms race between discovery methods and censors.
|
||||
We need to begin the infrastructure on our side quickly, preferably in a
|
||||
flexible language like Python, so we can adapt quickly to censorship.
|
||||
|
||||
phase one: personal bridges
|
||||
phase two: families of personal bridges
|
||||
phase three: more structured social network
|
||||
phase four: bag of tricks
|
||||
Research: phase five...
|
||||
|
||||
Integration with Psiphon, etc?
|
||||
|
||||
\subsection{Document best practices for users}
|
||||
Document best practices for various activities common among
|
||||
blocked users (e.g. WordPress use).
|
||||
|
||||
\subsection{Research: how to know if a bridge has been blocked?}
|
||||
|
||||
\subsection{GeoIP maintenance, and "private" user statistics}
|
||||
How to know if the whole idea is working?
|
||||
|
||||
\subsection{Research: hiding whether the user is reading or publishing?}
|
||||
|
||||
\subsection{Research: how many bridges do you need to know to maintain
|
||||
reachability?}
|
||||
|
||||
\subsection{Resisting censorship of the Tor website, docs, and mirrors}
|
||||
|
||||
We should take some effort to consider {\bf initial distribution of Tor and
|
||||
related information} in countries where the Tor website and mirrors are
|
||||
censored. (Right now, most countries that block access to Tor block only the
|
||||
main website and leave mirrors and the network itself untouched.) Falling
|
||||
back on word-of-mouth is always a good last resort, but we should also take
|
||||
steps to make sure it's relatively easy for users to get ahold of a copy.
|
||||
|
||||
\section{Security}
|
||||
|
||||
\subsection{Security research projects}
|
||||
|
||||
We should investigate approaches with some promise to help Tor resist
|
||||
end-to-end traffic correlation attacks. It's an open research question
|
||||
whether (and to what extent) {\bf mixed-latency} networks, {\bf low-volume
|
||||
long-distance padding}, or other approaches can resist these attacks, which
|
||||
are currently some of the most effective against careful Tor users. We
|
||||
should research these questions and perform simulations to identify
|
||||
opportunities for strengthening our design without dropping performance to
|
||||
unacceptable levels. %Cite something
|
||||
\plan{Start doing this in 2007; write a paper. 8-16 weeks.}
|
||||
|
||||
We've got some preliminary results suggesting that {\bf a topology-aware
|
||||
routing algorithm}~\cite{feamster:wpes2004} could reduce Tor users'
|
||||
vulnerability against local or ISP-level adversaries, by ensuring that they
|
||||
are never in a position to watch both ends of a connection. We need to
|
||||
examine the effects of this approach in more detail and consider side-effects
|
||||
on anonymity against other kinds of adversaries. If the approach still looks
|
||||
promising, we should investigate ways for clients to implement it (or an
|
||||
approximation of it) without having to download routing tables for the whole
|
||||
Internet. \plan{Not in 2007 unless a graduate student wants to do it.}
|
||||
|
||||
%\tmp{defenses against end-to-end correlation} We don't expect any to work
|
||||
%right now, but it would be useful to learn that one did. Alternatively,
|
||||
%proving that one didn't would free up researchers in the field to go work on
|
||||
%other things.
|
||||
%
|
||||
% See above; I think I got this.
|
||||
|
||||
We should research the efficacy of {\bf website fingerprinting} attacks,
|
||||
wherein an adversary tries to match the distinctive traffic and timing
|
||||
pattern of the resources constituting a given website to the traffic pattern
|
||||
of a user's client. These attacks work great in simulations, but in
|
||||
practice we hear they don't work nearly as well. We should get some actual
|
||||
numbers to investigate the issue, and figure out what's going on. If we
|
||||
resist these attacks, or can improve our design to resist them, we should.
|
||||
% add cites
|
||||
\plan{Possibly part of end-to-end correlation paper. Otherwise, not in 2007
|
||||
unless a graduate student is interested.}
|
||||
|
||||
\subsection{Implementation security}
|
||||
|
||||
We should also {\bf mark RAM that holds key material as non-swappable} so
|
||||
that there is no risk of recovering key material from a hard disk
|
||||
compromise. This would require submitting patches upstream to OpenSSL, where
|
||||
support for marking memory as sensitive is currently in a very preliminary
|
||||
state.\plan{Nice to do, but not in immediate Tor scope.}
|
||||
|
||||
There are numerous tools for identifying trouble spots in code (such as
|
||||
Coverity or even VS2005's code analysis tool) and we should convince somebody
|
||||
to run some of them against the Tor codebase. Ideally, we could figure out a
|
||||
way to get our code checked periodically rather than just once.\plan{Almost
|
||||
no time once we talk somebody into it.}
|
||||
|
||||
We should try {\bf protocol fuzzing} to identify errors in our
|
||||
implementation.\plan{Not in 2007 unless we find a grad student or
|
||||
undergraduate who wants to try.}
|
||||
|
||||
Our guard nodes help prevent an attacker from being able to become a chosen
|
||||
client's entry point by having each client choose a few favorite entry points
|
||||
as ``guards'' and stick to them. We should implement a {\bf directory
|
||||
guards} feature to keep adversaries from enumerating Tor users by acting as
|
||||
a directory cache.\plan{Do in 2007; 2 weeks.}
|
||||
|
||||
\subsection{Detect corrupt exits and other servers}
|
||||
With the success of our network, we've attracted servers in many locations,
|
||||
operated by many kinds of people. Unfortunately, some of these locations
|
||||
have compromised or defective networks, and some of these people are
|
||||
untrustworthy or incompetent. Our current design relies on authority
|
||||
administrators to identify bad nodes and mark them as nonfunctioning. We
|
||||
should {\bf automate the process of identifying malfunctioning nodes} as
|
||||
follows:
|
||||
|
||||
We should create a generic {\bf feedback mechanism for add-on tools} like
|
||||
Mike Perry's ``Snakes on a Tor'' to report failing nodes to authorities.
|
||||
\plan{Do in 2006; 1-2 weeks.}
|
||||
|
||||
We should write tools to {\bf detect more kinds of innocent node failure},
|
||||
such as nodes whose network providers intercept SSL, nodes whose network
|
||||
providers censor popular websites, and so on. We should also try to detect
|
||||
{\bf routers that snoop traffic}; we could do this by launching connections
|
||||
to throwaway accounts, and seeing which accounts get used.\plan{Do in 2007;
|
||||
ask Mike Perry if he's interested. 4-6 weeks.}
|
||||
|
||||
We should add {\bf an efficient way for authorities to mark a set of servers
|
||||
as probably collaborating} though not necessarily otherwise dishonest.
|
||||
This happens when an administrator starts multiple routers, but doesn't mark
|
||||
them as belonging to the same family.\plan{Do during v2.1 directory protocol
|
||||
redesign; 1-2 weeks to implement.}
|
||||
|
||||
To avoid attacks where an adversary claims good performance in order to
|
||||
attract traffic, we should {\bf have authorities measure node performance}
|
||||
(including stability and bandwidth) themselves, and not simply believe what
|
||||
they're told. We also measure stability by tracking MTBF. Measuring
|
||||
bandwidth will be tricky, since it's hard to distinguish between a server with
|
||||
low capacity, and a high-capacity server with most of its capacity in
|
||||
use. See also Nikita's NDSS 2008 paper.\plan{Do it if we can interest
|
||||
a grad student.}
|
||||
|
||||
{\bf Operating a directory authority should be easier.} We rely on authority
|
||||
operators to keep the network running well, but right now their job involves
|
||||
too much busywork and administrative overhead. A better interface for them
|
||||
to use could free their time to work on exception cases rather than on
|
||||
adding named nodes to the network.\plan{Do in 2007; 4-5 weeks.}
|
||||
|
||||
\subsection{Protocol security}
|
||||
|
||||
In addition to other protocol changes discussed above,
|
||||
% And should we move some of them down here? -NM
|
||||
we should add {\bf hooks for denial-of-service resistance}; we have some
|
||||
preliminary designs, but we shouldn't postpone them until we really need them.
|
||||
If somebody tries a DDoS attack against the Tor network, we won't want to
|
||||
wait for all the servers and clients to upgrade to a new
|
||||
version.\plan{Research project; do this in 2007 if funded.}
|
||||
|
||||
\section{Development infrastructure}
|
||||
|
||||
\subsection{Build farm}
|
||||
We've begun to deploy a cross-platform distributed build farm of hosts
|
||||
that build and test the Tor source every time it changes in our development
|
||||
repository.
|
||||
|
||||
We need to {\bf get more participants}, so that we can test a larger variety
|
||||
of platforms. (Previously, we've only found out when our code had broken on
|
||||
obscure platforms when somebody got around to building it.)
|
||||
|
||||
We need also to {\bf add our dependencies} to the build farm, so that we can
|
||||
ensure that libraries we need (especially libevent) do not stop working on
|
||||
any important platform between one release and the next.
|
||||
|
||||
\plan{This is ongoing as more buildbots arrive.}
|
||||
|
||||
\subsection{Improved testing harness}
|
||||
Currently, our {\bf unit tests} cover only about 20\% of the code base. This
|
||||
is uncomfortably low; we should write more and switch to a more flexible
|
||||
testing framework.\plan{Ongoing basis, time permitting.}
|
||||
|
||||
We should also write flexible {\bf automated single-host deployment tests} so
|
||||
we can more easily verify that the current codebase works with the
|
||||
network.\plan{Worthwhile in 2007; would save lots of time. 2-4 weeks.}
|
||||
|
||||
We should build automated {\bf stress testing} frameworks so we can see which
|
||||
realistic loads cause Tor to perform badly, and regularly profile Tor against
|
||||
these loads. This would give us {\it in vitro} performance values to
|
||||
supplement our deployment experience.\plan{Worthwhile in 2007; 2-6 weeks.}
|
||||
|
||||
We should improve our memory profiling code.\plan{...}
|
||||
|
||||
|
||||
\subsection{Centralized build system}
|
||||
We currently rely on a separate packager to maintain the packaging system and
|
||||
to build Tor on each platform for which we distribute binaries. Separate
|
||||
package maintainers is sensible, but separate package builders has meant
|
||||
long turnaround times between source releases and package releases. We
|
||||
should create the necessary infrastructure for us to produce binaries for all
|
||||
major packages within an hour or so of source release.\plan{We should
|
||||
brainstorm this at least in 2007.}
|
||||
|
||||
\subsection{Improved metrics}
|
||||
We need a way to {\bf measure the network's health, capacity, and degree of
|
||||
utilization}. Our current means for doing this are ad hoc and not
|
||||
completely accurate
|
||||
|
||||
We need better ways to {\bf tell which countries are users are coming from,
|
||||
and how many there are}. A good perspective of the network helps us
|
||||
allocate resources and identify trouble spots, but our current approaches
|
||||
will work less and less well as we make it harder for adversaries to
|
||||
enumerate users. We'll probably want to shift to a smarter, statistical
|
||||
approach rather than our current ``count and extrapolate'' method.
|
||||
|
||||
\plan{All of this in 2007 if funded; 4-8 weeks}
|
||||
|
||||
% \tmp{We'd like to know how much of the network is getting used.}
|
||||
% I think this is covered above -NM
|
||||
|
||||
\subsection{Controller library}
|
||||
We've done lots of design and development on our controller interface, which
|
||||
allows UI applications and other tools to interact with Tor. We could
|
||||
encourage the development of more such tools by releasing a {\bf
|
||||
general-purpose controller library}, ideally with API support for several
|
||||
popular programming languages.\plan{2006 or 2007; 1-2 weeks.}
|
||||
|
||||
\section{User experience}
|
||||
|
||||
\subsection{Get blocked less, get blocked less broadly}
|
||||
Right now, some services block connections from the Tor network because
|
||||
they don't have a better
|
||||
way to keep vandals from abusing them than blocking IP addresses associated
|
||||
with vandalism. Our approach so far has been to educate them about better
|
||||
solutions that currently exist, but we should also {\bf create better
|
||||
solutions for limiting vandalism by anonymous users} like credential and
|
||||
blind-signature based implementations, and encourage their use. Other
|
||||
promising starting points including writing a patch and explanation for
|
||||
Wikipedia, and helping Freenode to document, maintain, and expand its
|
||||
current Tor-friendly position.\plan{Do a writeup here in 2007; 1-2 weeks.}
|
||||
|
||||
Those who do block Tor users also block overbroadly, sometimes blacklisting
|
||||
operators of Tor servers that do not permit exit to their services. We could
|
||||
obviate innocent reasons for doing so by designing a {\bf narrowly-targeted Tor
|
||||
RBL service} so that those who wanted to overblock Tor could no longer
|
||||
plead incompetence.\plan{Possibly in 2007 if we decide it's a good idea; 3
|
||||
weeks.}
|
||||
|
||||
\subsection{All-in-one bundle}
|
||||
We need a well-tested, well-documented bundle of Tor and supporting
|
||||
applications configured to use it correctly. We have an initial
|
||||
implementation well under way, but it will need additional work in
|
||||
identifying requisite Firefox extensions, identifying security threats,
|
||||
improving user experience, and so on. This will need significantly more work
|
||||
before it's ready for a general public release.
|
||||
|
||||
\subsection{LiveCD Tor}
|
||||
We need a nice bootable livecd containing a minimal OS and a few applications
|
||||
configured to use it correctly. The Anonym.OS project demonstrated that this
|
||||
is quite feasible, but their project is not currently maintained.
|
||||
|
||||
\subsection{A Tor client in a VM}
|
||||
\tmp{a.k.a JanusVM} which is quite related to the firewall-level deployment
|
||||
section below. JanusVM is a Linux kernel running in VMWare. It gets an IP
|
||||
address from the network, and serves as a DHCP server for its host Windows
|
||||
machine. It intercepts all outgoing traffic and redirects it into Privoxy,
|
||||
Tor, etc. This Linux-in-Windows approach may help us with scalability in
|
||||
the short term, and it may also be a good long-term solution rather than
|
||||
accepting all security risks in Windows.
|
||||
|
||||
%\subsection{Interface improvements}
|
||||
%\tmp{Allow controllers to manipulate server status.}
|
||||
% (Why is this in the User Experience section?) -RD
|
||||
% I think it's better left to a generic ``make controller iface better'' item.
|
||||
|
||||
\subsection{Firewall-level deployment}
|
||||
Another useful deployment mode for some users is using {\bf Tor in a firewall
|
||||
configuration}, and directing all their traffic through Tor. This can be a
|
||||
little tricky to set up currently, but it's an effective way to make sure no
|
||||
traffic leaves the host un-anonymized. To achieve this, we need to {\bf
|
||||
improve and port our new TransPort} feature which allows Tor to be used
|
||||
without SOCKS support; to {\bf add an anonymizing DNS proxy} feature to Tor;
|
||||
and to {\bf construct a recommended set of firewall configurations} to redirect
|
||||
traffic to Tor.
|
||||
|
||||
This is an area where {\bf deployment via a livecd}, or an installation
|
||||
targeted at specialized home routing hardware, could be useful.
|
||||
|
||||
\subsection{Assess software and configurations for anonymity risks}
|
||||
Right now, users and packagers are more or less on their own when selecting
|
||||
Firefox extensions. We should {\bf assemble a recommended list of browser
|
||||
extensions} through experiment, and include this in the application bundles
|
||||
we distribute.
|
||||
|
||||
We should also describe {\bf best practices for using Tor with each class of
|
||||
application}. For example, Ethan Zuckerman has written a detailed
|
||||
tutorial on how to use Tor, Firefox, GMail, and Wordpress to blog with
|
||||
improved safety. There are many other cases on the Internet where anonymity
|
||||
would be helpful, and there are a lot of ways to screw up using Tor.
|
||||
|
||||
The Foxtor and Torbutton extensions serve similar purposes; we should pick a
|
||||
favorite, and merge in the useful features of the other.
|
||||
|
||||
%\tmp{clean up our own bundled software:
|
||||
%E.g. Merge the good features of Foxtor into Torbutton}
|
||||
%
|
||||
% What else did you have in mind? -NM
|
||||
|
||||
\subsection{Localization}
|
||||
Right now, most of our user-facing code is internationalized. We need to
|
||||
internationalize the last few hold-outs (like the Tor expert installer), and get
|
||||
more translations for the parts that are already internationalized.
|
||||
|
||||
Also, we should look into a {\bf unified translator's solution}. Currently,
|
||||
since different tools have been internationalized using the
|
||||
framework-appropriate method, different tools require translators to localize
|
||||
them via different interfaces. Inasmuch as possible, we should make
|
||||
translators only need to use a single tool to translate the whole Tor suite.
|
||||
|
||||
\section{Support}
|
||||
|
||||
It would be nice to set up some {\bf user support infrastructure} and
|
||||
{\bf contributor support infrastructure}, especially focusing on server
|
||||
operators and on coordinating volunteers.
|
||||
|
||||
This includes intuitive and easy ticket systems for bug reports and
|
||||
feature suggestions (not just mailing lists with a half dozen people
|
||||
and no clear roles for who answers what), but it also includes a more
|
||||
personalized and efficient framework for interaction so we keep the
|
||||
attention and interest of the contributors, and so we make them feel
|
||||
helpful and wanted.
|
||||
|
||||
\section{Documentation}
|
||||
|
||||
\subsection{Unified documentation scheme}
|
||||
|
||||
We need to {\bf inventory our documentation.} Our documentation so far has
|
||||
been mostly produced on an {\it ad hoc} basis, in response to particular
|
||||
needs and requests. We should figure out what documentation we have, which of
|
||||
it (if any) should get priority, and whether we can't put it all into a
|
||||
single format.
|
||||
|
||||
We could {\bf unify the docs} into a single book-like thing. This will also
|
||||
help us identify what sections of the ``book'' are missing.
|
||||
|
||||
\subsection{Missing technical documentation}
|
||||
|
||||
We should {\bf revise our design paper} to reflect the new decisions and
|
||||
research we've made since it was published in 2004. This will help other
|
||||
researchers evaluate and suggest improvements to Tor's current design.
|
||||
|
||||
Other projects sometimes implement the client side of our protocol. We
|
||||
encourage this, but we should write {\bf a document about how to avoid
|
||||
excessive resource use}, so we don't need to worry that they will do so
|
||||
without regard to the effect of their choices on server resources.
|
||||
|
||||
\subsection{Missing user documentation}
|
||||
|
||||
Our documentation falls into two broad categories: some is `discoursive' and
|
||||
explains in detail why users should take certain actions, and other
|
||||
documentation is `comprehensive' and describes all of Tor's features. Right
|
||||
now, we have no document that is both deep, readable, and thorough. We
|
||||
should correct this by identifying missing spots in our design.
|
||||
|
||||
\bibliographystyle{plain} \bibliography{tor-design}
|
||||
|
||||
\end{document}
|
||||
|
||||
@ -1,175 +0,0 @@
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%deffont "standard" xfont "comic sans ms-medium-r"
|
||||
%%deffont "thick" xfont "arial black-medium-r"
|
||||
%%deffont "typewriter" xfont "courier new-bold-r"
|
||||
%%deffont "type2writer" xfont "arial narrow-bold-r"
|
||||
%%deffont "standard" tfont "standard.ttf", tmfont "kochi-mincho.ttf"
|
||||
%%deffont "thick" tfont "thick.ttf", tmfont "goth.ttf"
|
||||
%%deffont "typewriter" tfont "typewriter.ttf", tmfont "goth.ttf"
|
||||
%deffont "standard" xfont "helvetica-medium-r", tfont "arial.ttf", tmfont "times.ttf"
|
||||
%deffont "thick" xfont "helvetica-bold-r", tfont "arialbd.ttf", tmfont "hoso6.ttf"
|
||||
%deffont "italic" xfont "helvetica-italic-r", tfont "ariali.ttf", tmfont "hoso6.ttf"
|
||||
%deffont "typewriter" xfont "courier-medium-r", tfont "typewriter.ttf", tmfont "hoso6.ttf"
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%
|
||||
%% Default settings per each line numbers.
|
||||
%%
|
||||
%default 1 leftfill, size 8, fore "black", back "white", font "thick", hgap 1
|
||||
%default 2 size 8, vgap 10, prefix " ", ccolor "black"
|
||||
%default 3 size 6, bar "gray70", vgap 0
|
||||
%default 4 size 6, fore "black", vgap 0, prefix " ", font "standard"
|
||||
%%
|
||||
%%default 1 area 90 90, leftfill, size 9, fore "yellow", back "blue", font "thick"
|
||||
%%default 2 size 9, vgap 10, prefix " "
|
||||
%%default 3 size 7, bar "gray70", vgap 10
|
||||
%%default 4 size 7, vgap 30, prefix " ", font "standard"
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%
|
||||
%% Default settings that are applied to TAB-indented lines.
|
||||
%%
|
||||
%tab 1 size 5, vgap 40, prefix " ", icon arc "red" 50
|
||||
%tab 2 size 4, vgap 35, prefix " ", icon delta3 "blue" 40
|
||||
%tab 3 size 3, vgap 35, prefix " ", icon dia "DarkViolet" 40
|
||||
%%
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
%nodefault
|
||||
%center, size 9, font "thick", back "white", fore "black"
|
||||
|
||||
|
||||
|
||||
Tor:
|
||||
%size 8
|
||||
Next-generation Onion Routing
|
||||
|
||||
|
||||
%size 7
|
||||
Roger Dingledine
|
||||
Nick Mathewson
|
||||
Paul Syverson
|
||||
|
||||
%%The Free Haven Project
|
||||
%%%font "typewriter", fore "blue"
|
||||
%%http://freehaven.net/
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Low-latency anonymity system
|
||||
|
||||
%leftfill
|
||||
Deployed: 19 nodes, hundreds of users (?)
|
||||
|
||||
Many improvements on earlier design
|
||||
|
||||
Free software -- available source code
|
||||
|
||||
Design is not covered by earlier onion routing
|
||||
patent
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Perfect forward secrecy
|
||||
|
||||
|
||||
Telescoping circuit
|
||||
|
||||
negotiates keys at each hop
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%page
|
||||
%%
|
||||
%%Separation from "protocol cleaning"
|
||||
%%
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
No mixing, padding, traffic shaping (yet)
|
||||
|
||||
|
||||
Please show us they're worth the usability tradeoff
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%%page
|
||||
%%
|
||||
%%Many TCP streams can share one circuit
|
||||
%%
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Congestion control
|
||||
|
||||
|
||||
Simple rate limiting
|
||||
|
||||
Plus have to keep internal nodes from overflowing
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Directory servers
|
||||
|
||||
|
||||
Approve new servers
|
||||
|
||||
Tell clients who's up right now
|
||||
|
||||
plus their keys, location, etc
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Variable exit policies
|
||||
|
||||
|
||||
Each server allows different outgoing connections
|
||||
|
||||
E.g. no servers allow outgoing mail currently
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
End-to-end integrity checking
|
||||
|
||||
|
||||
In previous onion routing, an insider could change
|
||||
the text being transmitted:
|
||||
|
||||
"dir" => "rm *"
|
||||
|
||||
Even an external adversary could do this!
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Rendezvous points
|
||||
|
||||
|
||||
allow hidden services
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
Differences / limitations
|
||||
|
||||
|
||||
We're TCP-only, not all IP (but we're user-space and very portable)
|
||||
|
||||
Not peer-to-peer
|
||||
|
||||
No protocol normalization
|
||||
|
||||
%%Not unobservable
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
%page
|
||||
|
||||
We have working code
|
||||
|
||||
|
||||
Plus a design document,
|
||||
and a byte-level specification
|
||||
|
||||
%size 9
|
||||
http://freehaven.net/tor/
|
||||
|
||||
Loading…
Reference in New Issue
Block a user