Commit fb4d66f0 authored by Roger Dingledine's avatar Roger Dingledine
Browse files

pre-talk slides


svn:r1115
parent 67a27396
......@@ -60,26 +60,43 @@ Deployed: 20 nodes, hundreds (?) of users
Many improvements on earlier design
Free software -- available source code
Free software -- modified BSD license
Design is not covered by earlier onion routing
patent
Uses SOCKS to interface with client apps
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Talk Overview
A bit about Onion Routing
We have working code
Improvements we've made
(14 kloc of C)
Some related work
and a design document,
and a byte-level specification,
and a Debian package (in Unstable)
Some lessons learned
Works on Linux, BSD, OSX, Cygwin, ...
User-space, doesn't need kernel mods or root
Ask me questions
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http://freehaven.net/tor/
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%%Talk Overview
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%%A bit about Onion Routing
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%%Improvements we've made
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%%Some related work
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%%Ask me questions
%%
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......@@ -95,7 +112,8 @@ Government applications
research, law enforcement
%size 6
Business applications
hide relationships and volumes of communication
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(hide relationships and volumes of communication)
Who is visiting job sites?
Which groups are talking to patent lawyers?
Who are your suppliers and customers?
......@@ -106,6 +124,19 @@ Business applications
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
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......@@ -122,10 +153,12 @@ Fixed-size cells
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Tor's goal
Tor's goals
Conservative design (minimize new design work needed)
Conservative design
minimize new design work needed
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Support testing of future research
Design for deployment; deploy for use
......@@ -133,13 +166,13 @@ Design for deployment; deploy for use
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Threat model
Protect against curious Bob
Threat model -- what we aim for
Protect against somebody watching Alice
Protect against a few curious nodes in the middle
Protect against curious Bob
Protect against `some' curious nodes in the middle
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......@@ -149,11 +182,13 @@ 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
Not unobservable (no steg, etc)
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......@@ -164,12 +199,8 @@ Perfect forward secrecy
Telescoping circuit
negotiates keys at each hop
no more need for replay detection
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%%Separation from "protocol cleaning"
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......@@ -183,6 +214,33 @@ Please show us they're worth the usability tradeoff
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%%Many TCP streams can share one circuit
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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
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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
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Unclear whether this is dangerous or useful
More research needed
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......@@ -193,11 +251,14 @@ Simple rate limiting
Plus have to keep internal nodes from overflowing
(Can't use global state or inter-node control)
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Directory servers
To solve the `introduction' problem
Approve new servers
......@@ -233,17 +294,32 @@ Even an external adversary could do this!
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
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(Not implemented yet)
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Related work
How do we compare security?
c/n vs c^2/n^2 vs 2
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, peekabooty, jap
Freedom, Tor: (c/n)^2
Peekabooty, six-four, etc: c/n
Jap (if no padding): 1 if c>1
Anonymizer: 1 if c>0
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......@@ -252,11 +328,12 @@ Future work
Threshold directory agreement
Restricted-route (non-clique) topology
Scalability: Morphmix/p2p extensions?
Restricted-route (non-clique topology)
Morphmix/p2p extensions?
Non-TCP transport
Location-hidden servers via rendezvous points
Implement rendezvous points
Make it work better
......@@ -265,9 +342,9 @@ Make it work better
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/
......
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