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pre-talk slides
svn:r1115
This commit is contained in:
Roger Dingledine
+106
-29
@@ -60,26 +60,43 @@ Deployed: 20 nodes, hundreds (?) of users
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Many improvements on earlier design
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Free software -- available source code
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Free software -- modified BSD license
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Design is not covered by earlier onion routing
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patent
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Uses SOCKS to interface with client apps
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Talk Overview
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We have working code
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A bit about Onion Routing
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(14 kloc of C)
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Improvements we've made
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and a design document,
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and a byte-level specification,
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and a Debian package (in Unstable)
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Some related work
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Works on Linux, BSD, OSX, Cygwin, ...
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User-space, doesn't need kernel mods or root
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Some lessons learned
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Ask me questions
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%size 9
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http://freehaven.net/tor/
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%page
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%%
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%%Talk Overview
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%%
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%%A bit about Onion Routing
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%%
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%%Improvements we've made
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%%
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%%Some related work
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%%
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%%Ask me questions
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%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -95,7 +112,8 @@ Government applications
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research, law enforcement
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%size 6
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Business applications
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hide relationships and volumes of communication
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%size 5
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(hide relationships and volumes of communication)
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Who is visiting job sites?
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Which groups are talking to patent lawyers?
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Who are your suppliers and customers?
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@@ -106,6 +124,19 @@ Business applications
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Anonymity is a network effect
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Systems need traffic (many low-sensitivity users) to attract the high-sensitivity users
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Most users do not value anonymity much
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Weak security (fast system) can mean more users
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which can mean
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%cont, font "italic"
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stronger
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%cont, font "standard"
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anonymity
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High-sensitivity agents have incentive to run nodes
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so they can be certain first node in their path is good
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to attract traffic for their messages
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There can be an optimal level of free-riding
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -122,10 +153,12 @@ Fixed-size cells
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Tor's goal
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Tor's goals
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Conservative design (minimize new design work needed)
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Conservative design
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minimize new design work needed
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%size 6
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Support testing of future research
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Design for deployment; deploy for use
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@@ -133,13 +166,13 @@ Design for deployment; deploy for use
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Threat model
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Protect against curious Bob
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Threat model -- what we aim for
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Protect against somebody watching Alice
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Protect against a few curious nodes in the middle
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Protect against curious Bob
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Protect against `some' curious nodes in the middle
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -149,11 +182,13 @@ Differences / limitations
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We're TCP-only, not all IP (but we're user-space and very portable)
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Not as strong as high-latency systems (Mixmaster, Mixminion)
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Not peer-to-peer
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No protocol normalization
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%%Not unobservable
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Not unobservable (no steg, etc)
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -164,12 +199,8 @@ Perfect forward secrecy
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Telescoping circuit
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negotiates keys at each hop
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no more need for replay detection
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%%page
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%%
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%%Separation from "protocol cleaning"
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%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -183,6 +214,33 @@ Please show us they're worth the usability tradeoff
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%%
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%%Many TCP streams can share one circuit
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%%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Many TCP streams share a circuit
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Previous designs built a new circuit for each stream
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lots of public key ops per request
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plus anonymity dangers from making so many circuits
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Leaky-pipe circuit topology
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Alice can direct cells to any node in her circuit
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So we can support long-range padding,
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have multiple streams exiting at different places in the circuit
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etc
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%size 6
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Unclear whether this is dangerous or useful
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More research needed
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -193,11 +251,14 @@ Simple rate limiting
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Plus have to keep internal nodes from overflowing
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(Can't use global state or inter-node control)
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Directory servers
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To solve the `introduction' problem
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Approve new servers
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@@ -233,17 +294,32 @@ Even an external adversary could do this!
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Rendezvous points
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allow hidden services
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don't need (brittle) reply onions
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Access-controlled: Bob can control who he talks to
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Robust: Bob's service is available even when some Tor nodes go down
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Smear-resistant: Evil service can't frame a rendezvous router
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Application-transparent: Don't need to modify Bob's apache
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%size 6
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(Not implemented yet)
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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Related work
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How do we compare security?
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c/n vs c^2/n^2 vs 2
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Assume adversary owns c of n nodes
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can choose which
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%size 6
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What's the chance for a random Alice and Bob that he wins?
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freedom, peekabooty, jap
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Freedom, Tor: (c/n)^2
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Peekabooty, six-four, etc: c/n
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Jap (if no padding): 1 if c>1
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Anonymizer: 1 if c>0
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%page
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@@ -252,11 +328,12 @@ Future work
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Threshold directory agreement
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Restricted-route (non-clique) topology
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Scalability: Morphmix/p2p extensions?
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Restricted-route (non-clique topology)
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Morphmix/p2p extensions?
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Non-TCP transport
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Location-hidden servers via rendezvous points
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Implement rendezvous points
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Make it work better
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@@ -265,9 +342,9 @@ Make it work better
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We have working code
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Plus a design document,
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and a byte-level specification
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and a Debian package (in Unstable)
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%size 9
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http://freehaven.net/tor/
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