
\documentclass[landscape]{slides}

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\newcommand\slidetitle[1]{\begin{center} \huge #1 \end{center}}

\begin{slide}
\begin{center}
\Huge
Reputation and Anonymity\\
\vspace{1in}
Roger Dingledine\\
\vspace{.5in}
The Free Haven Project\\
\end{center}
\end{slide}

\begin{slide}
\slidetitle{Why reputation is critical for anonymity systems}
\large
\begin{tightlist}
\item Traditional accountability (eg contract) doesn't work
\item Since we don't know full network state, \\transactions tend to
be unreliable
\item With many nodes, each node won't interact with everybody often.
Free riding?
\item Shared reputation can maybe help reliability?
\end{tightlist}
\end{slide}

\begin{slide}
\slidetitle{Why reputation is problematic for anonymity systems}
\Large
\begin{tightlist}
\item Attacker or freeloader can cheaply throw away bad-reputation nyms
\item Hard to detect/verify a node's behavior while maintaining anonymity
\item Reputation information can be exploited to subvert anonymity
\end{tightlist}
\end{slide}

\begin{slide}
\slidetitle{Example: Free Haven}
\large
\begin{tightlist}
\item Decentralized anonymous publishing system
\item Publishers decide lifetime of their file\\
Tit for tat: I'll store your file if you'll store mine.
\item Hard: need reputation system to determine who will cheat
\item Harder: how do you verify a claim?
\end{tightlist}
\end{slide}

\begin{slide}
\slidetitle{Reputation can be exploited}
\large
\begin{tightlist}
\item A node can't measure all nodes. If he measures only
some, he gives away who he might use.
\item But central reputation server can give different info to different
people
\item Adversary has incentive to get good reputation --- and discredit
other nodes --- to see traffic
\item Tension between giving users accurate timely \\information, and
preventing adversary from \\manipulating user behavior
\end{tightlist}
\end{slide}

\begin{slide}
\slidetitle{More open topics}
\large
\begin{tightlist}
\item Are dynamic p2p systems that don't allow claim verifiability
doomed? Altruism, yhprum?
\item Can we model reputation as currency? May allow easier
decentralization.
%\item Incentives: If anonymity for all requires each user doing similar
%things, how do we deal with users who don't want as much anonymity?
\item Do we have to abandon statistical rigor in the face of this
uncertainty?
\end{tightlist}
\end{slide}

\end{document}

