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Anonymous Communications and Tor: History and Future Challenges

The history of anonymous communications on the Internet dates back to the early 80's but since then there have been dramatic changes in how anonymous communication systems have been built and how they have been used.

Steven Murdoch

on 26 June 2014

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Transcript of Anonymous Communications and Tor: History and Future Challenges

Who needs anonymity?
Military personnel
Law enforcement
Activists and whistle-blowers
Ordinary people
Anonymous Communications and Tor:
History and Future Challenges

penet.fi (1993–1996)
The Web
Web browsing is hard to secure
Censorship resistance
Simply stripped headers off emails sent via remailer
Allowed replies to be sent
Easy to use, but single point of compromise
Shut down following compromise by CoS
Mixmaster (1998–)
Layered encryption
Batching and re-ordering
Based on Chaum Mix (1981)
Type-1 (Cypherpunk)
Mix decrypts messages
Uses PGP
Mixminion (2002–)
Fixed many problems
Introduced replies
Number of users ≈ 0
Requires low latency
High variability
Low tolerance to padding
Equivalent systems
Open proxies ≈ penet.fi
VPN ≈ Type-0
MixMinion ≈ Tor
Open problems
Protocol obfuscation
Scanning resistance
Distribution mechanisms
Many users are unable to pay (tragedy of the commons)
Giving better performance to users who contribute could reduce anonymity
If money is changing hands, volunteers may give up
Encryption doesn't work
TLS, PGP, S/MIME only hide what is being said
Alice uploaded a gigabyte to CNN 6 hours before footage of human rights abuses were aired
Bob, who just joined our criminal organization sent an encrypted email to the FBI a week before our boss got arrested
Charlie keeps browsing our website of illegal material, maybe we should give him fake data?
Steven J. Murdoch
University of Cambridge Computer Laboratory
Full transcript