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add ownership transfer corollary

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Christian Grothoff 2017-05-16 11:24:50 +02:00
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doc/paper/taler.tex
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@ -1422,10 +1422,10 @@ exchange.
\begin{theorem}
Let $C$ denote a coin controlled by users Alice and Bob.
Suppose Bob creates a coin $C'$ from $C$ using the refresh protocol.
Suppose Bob creates a coin $C'$ from $C$ following the refresh protocol.
Assuming the exchange and Bob operated the refresh protocol correctly,
and that they continue to operate the linking protocol
\S\ref{subsec:linking} correctly,
and that the exchange continues to operate the linking protocol
(\S\ref{subsec:linking}) correctly,
then Alice can gain control of $C'$ using the linking protocol.
\end{theorem}
@ -1442,7 +1442,10 @@ for the residual value on $C'$ and runs the linking protocol to
determine if it was refreshed too.
\end{proof}
At a result, there is no way for a user to loose control over a coin,
\begin{corollary}
Abusing the refresh protocol to transfer ownership has an
expected loss of $1 - \frac{1}{\kappa}$ of the transaction value.
\end{corollary}
\section{Privacy arguments}