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authorFlorian Dold <florian.dold@gmail.com>2017-11-10 03:05:04 +0100
committerFlorian Dold <florian.dold@gmail.com>2017-11-10 03:05:04 +0100
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-rw-r--r--games/games.tex16
1 files changed, 10 insertions, 6 deletions
diff --git a/games/games.tex b/games/games.tex
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--- a/games/games.tex
+++ b/games/games.tex
@@ -242,7 +242,7 @@ given in literature.
\section{Proofs}
\subsection{Anonymity}
-\paragraph{``Proof sketch''.} Proof by looking at withdraw/deposit/refresh transcripts. Do game hopping, replace
+\paragraph{``Proof sketch''.} Proof by looking at withdraw/deposit/refresh transcripts seen by the adversary. Do game hopping, replace
everything that's not random by something random (with computationally indistinguishable distribution) until everything that the adversary
could see in a game has the same probability, and he must win with probability $1/2$.
@@ -255,7 +255,8 @@ could see in a game has the same probability, and he must win with probability $
\end{itemize}
\subsection{Income Transparency}
-To win the game, the adversary must produce coins that are not in the wallet of any non-corrupted user.
+To win the game, the adversary must produce enough coins that are not in the wallet of any non-corrupted user, but withdraw little
+coins via corrupted users.
\begin{lemma}
The signatures on $C_1, \dots, C_\ell$ must have been obtained by using either \ora{Withdraw}, \ora{RefreshReveal} or \ora{Link}.
@@ -267,15 +268,18 @@ To win the game, the adversary must produce coins that are not in the wallet of
\begin{lemma}
To win the Income Transparency game, the adversary must call $\ora{RefreshReveal}$ at least $(\kappa V_r - V_w) > 0$ times
- in a way that causes the linking step to fail.
+ in a way that causes the linking step to fail. (This implies unforgeability.)
+\end{lemma}
+
+\begin{lemma}
+ The probability to use \ora{RefreshCommit} and \ora{RefreshReveal} in a way that causes \algo{Link} to return $\bot$ at most $1/\kappa$.
\end{lemma}
\begin{theorem}
- The adversary wins the Income Transparency game with with probability ...
+ The adversary wins the Income Transparency game with with probability at most $1 / \kappa$.
\end{theorem}
-Conclusion: Even the best adversary needs to waste $\kappa$ coins to obtain one untaxable coin.
-
+FIXME: We should also include what the expected ``untaxed'' money for the adversary is for each won game, vs. the money wasted.
\section{Standard Definitions}
\begin{definition}[One-more forgery]