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[freehaven-cvs] three questions that need more attention, possibly c...
Update of /home/freehaven/cvsroot/doc/alpha-mixing
In directory moria:/home/arma/work/freehaven/doc/alpha-mixing
Modified Files:
alpha-mixing.tex
Log Message:
three questions that need more attention, possibly controversial.
Index: alpha-mixing.tex
===================================================================
RCS file: /home/freehaven/cvsroot/doc/alpha-mixing/alpha-mixing.tex,v
retrieving revision 1.39
retrieving revision 1.40
diff -u -d -r1.39 -r1.40
--- alpha-mixing.tex 8 Jul 2006 19:27:28 -0000 1.39
+++ alpha-mixing.tex 8 Jul 2006 19:39:51 -0000 1.40
@@ -205,6 +205,12 @@
steady-state (i.e., messages arrive with various alphas at a regular rate, and
the mix fires at regular intervals). In this case the threshold mix is
indistinguishable by a local observer from a timed mix.
+%% XXX Actually, we need another assumption if we want steady-state to
+%% still mean that we fire at regular intervals. It seems this assumption
+%% is that the alphas we receive are uniformly distributed? -RD
+
+%% XXX Is it the case that assuming some fixed distribution of incoming
+%% alphas, timed and threshold alpha mixes are still indistinguishable? -RD
We assume the adversary does not know the specific alpha of any
message entering the mix, e.g., that this is provided to the mix
@@ -244,7 +250,12 @@
If the adversary does know the strategy (although still not the actual
$\alpha$) for each incoming message, then the anonymity of $M$ is
unaffected by the strategy that other messages use for choosing $\alpha$
-in a steady-state network. However, if the strategies are not known,
+in a steady-state network.
+%% XXX I'm not sure I buy this. Compare the situation when other users
+%% use high-variance strategies or low-variance strategies. Doesn't Alice
+%% get different anonymity in these cases, even if the adversary does know
+%% the strategy of alpha distribution for each incoming message? -RD
+However, if the strategies are not known,
then choosing $\alpha$ from a broader range increases the anonymity
for other messages in the mix as well, although it is difficult to say
by how much. If the distribution of strategies across all
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