[freehaven-cvs] Add numbers for statistical disclosure section

[nickm@seul.org (Nick Mathewson)]

Update of /home/freehaven/cvsroot/doc/pynchon-gate
In directory moria.mit.edu:/tmp/cvs-serv28882

Modified Files:
	pynchon.tex 
Log Message:
Add numbers for statistical disclosure section

Index: pynchon.tex
===================================================================
RCS file: /home/freehaven/cvsroot/doc/pynchon-gate/pynchon.tex,v
retrieving revision 1.34
retrieving revision 1.35
diff -u -d -r1.34 -r1.35
--- pynchon.tex	17 Sep 2004 18:22:29 -0000	1.34
+++ pynchon.tex	17 Sep 2004 19:08:41 -0000	1.35
@@ -372,7 +372,23 @@
 identical reply blocks with path length $\ell$ through mixes in a steady
 state that delay each message each round with probability $P_D$.
 
-% XXXX Describe results
+We ran the simulated attack with different values for $P_M$, $P_D$, and
+$\ell$, against a nym server with $N=2^{16}$ active pseudonymous users.
+(This is probably an overestimate of the number of users on typical nymserver
+today~\cite{nym-alias-net}.)   We performed 100 trials for each set of
+paramaters.  In the worst case (for the nym holder), when
+$P_M=0.5, \ell=1, P_D=0.1$, the lack of
+mix-net delay variance allowed the simulated
+attacker to guess the user's identity correctly after the user received an
+average of only 37 messages.  In the best simulated case ($P_M=0.5,
+P_D=0.9,\ell=4$), the user was able to receive an average of only 1775
+messages before the attacker guessed correctly.  For an active user, this is
+well within a month's expected traffic.
+
+Although there are various proposals to use dummy traffic to resist
+statistical disclosure attacks, these difficult to implement perfectly in
+practise (due to outages and so forth) and even slight imperfections render
+users vulnerable to attack~\cite{e2e-traffic}.
 
 \section{The Pynchon Gate Design}
 \label{sec:design}

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