Re: [freehaven-dev] mixnet thoughts

[Joseph Sokol-Margolis <seph@MIT.EDU>]

>> http://web.mit.edu/seph/anon/cordelia-deanon
>
> Error 403 - Forbidden. Even if I try from belegost. 

hum, guess it's acled more facist. eit. I'll just insert it here. yay
C-x i

How to perform a mutual deanonymization.

	Requires:  a semi-trusted third party
		   voluntary agents.

Naming scheme:
	principals:  The two people who whis to know each other
	agents: n random people, who are participating.
	third party/trusted agent: middle man.

For a deanonymization to take place, n agents must anonymously
volunteer to participate. Each agent, plus the two principals, should
zephyr to the third party a list of n+1 keywords.  

Protocol first: less work, easier for third party to break.

Note that each step should only occur when the third party/trusted
agent dictates for it to occur, to prevent asynchronous issues.

The third party responds with a single keyword to all participants.
In addition, the third party distributes the initial list of keywords
out to the participants, such that each participant receives exactly
one keyword generated by each other participant. At this point,
behavior does interesting things.

Each of the principals subscribes to each of the classes formed by the
concatenation of the thrid parties keyword and each of the keywords
they received from the other participants.  Each participant sends a zephyr
to each of the classes created by a similar concatenation of the third
party's keyword and the keywords they generated.  The contents of the
zephyr should be a new keyword. The zephyrs should be sent in rounds -
each participant sending one zephyr at a time (paced by the agent?),
and, if at any point the system appears to fail, any participant can
halt the system.


 The following
behavior should be observed:
a) each agent should successfully send exactly two zephyrs.
b) each principal should successfully send exactly one zephyr.
c) each principal should receive n+1 zephyrs (all agents +other principal)

Now each principal has n+1 keywords, plus their own.  These keywords
are not likely to be known to the third party, unless the third party
correctly guesed the identities of the two prinicpals already.  Each
principal should concatenate the keywords together, in ascending
alphabetical order, and attempt to send a zephyr to that class.  If
the zephyrs fail, then they should subscribe there and reveal
themselves.

Weaknesses:
	The third party and one agent in cahoots can determine the
	identities of the two principles.

	If multiple agents work with one principal, they can determine
	the other principals identity