[freehaven-cvs] Fix another design section

[nickm@seul.org (Nick Mathewson)]

Update of /home/freehaven/cvsroot/doc/pynchon-gate
In directory moria.mit.edu:/tmp/cvs-serv9466

Modified Files:
	pynchon.tex 
Log Message:
Fix another design section

Index: pynchon.tex
===================================================================
RCS file: /home/freehaven/cvsroot/doc/pynchon-gate/pynchon.tex,v
retrieving revision 1.40
retrieving revision 1.41
diff -u -d -r1.40 -r1.41
--- pynchon.tex	17 Sep 2004 22:24:16 -0000	1.40
+++ pynchon.tex	17 Sep 2004 22:40:27 -0000	1.41
@@ -557,19 +557,31 @@
 $H(\SUBKEY(j,i) | \mbox{\tt "ID"})$, the user can tell which key to use for
 messages that are delivered out of order, or in different cycles.
 
-\subsection{The Distributor Nodes}
+\subsection{Distributors and clients}
+\label{subsec:client-design}
 Once the collator is done, it relays the signed meta-index, and the entire
 bucket pool, to a set of
 independently operated \emph{distributor nodes}. (This data should be
 transmitted using a bandwidth-sparing protocol such as
 BitTorrent~\cite{bittorrent}, so that the collator doesn't need to transmit
 the entire set of buckets to each distributor individually.)
-Client applications retrieve these buckets using the \emph{Pynchon Gate PIR
-  Protocol}.
 
-\subsection{The Pynchon Gate PIR Protocol}
-\label{subsec:client-design}
+At this point, clients can download their messages for the cycle.  First, a
+given client downloads the meta-index from a randomly chosen distributor, and
+verifies its signature.  The client then computes its $\UserID$ for the day,
+and uses the meta-index to tell which index bucket will contain an entry for
+that $\UserID$.
 
+The client then uses the \emph{Pynchon Gate PIR Protocol} (described below)
+to retrieve the correct index bucket, checks that the bucket's digest is as
+expected, and uses the index bucket to learn which message buckets will
+contain the client's messages.  The client downloads these buckets with PIR,
+and checks their digests.  If the client has received fewer buckets this
+cycle than her maximum, she performs extra PIR operations up to that maximum,
+to prevent an observer from learning how many messages she has received.
+
+\subsubsection{The Pynchon Gate PIR Protocol}
+\label{subsec:client-design}
 The \emph{Pynchon Gate Client} application resides on the nym owner's
 local computer, and periodically retrieves messages from the distributor
 nodes using the Pynchon Gate PIR Protocol.

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