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add reserve state machine

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Christian Grothoff 2020-07-12 19:19:13 +02:00
parent fdee6830e6
commit 4cfcf842fe
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3 changed files with 30 additions and 2 deletions
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18
doc/system/taler/design.tex
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@ -125,8 +125,8 @@ payment.
% FIXME: who needs to be trusted for anonymity? % FIXME: who needs to be trusted for anonymity?
\subsection{Reserves} \subsection{Reserves}
A \emph{reserve} refers to a customer's non-anonymous funds at an exchange, A \emph{reserve} refers to a customer's non-anonymous funds at an exchange,
identified by a reserve public key. Suppose a customer wants to convert money identified by a reserve public key. Suppose a customer wants to convert money
into anonymized digital coins. To do that, the customer first creates a into anonymized digital coins. To do that, the customer first creates a
@ -149,7 +149,20 @@ customers that lost their reserve private key to eventually recover their
funds. If a wire transfer to the exchange does not include a valid reserve public key, funds. If a wire transfer to the exchange does not include a valid reserve public key,
the exchange transfers the money back to the sender. the exchange transfers the money back to the sender.
% FIXME: this really needs a diagram Figure~\ref{fig:reserve:state} illustrates the state machine for a reserve.
Long-terms states are shown in boxes, while actions are in circles. The
final state is in a double-circle.
A reserve is first {\em filled} by a wire transfer. The amount in it is reduced
by withdraw operations. If the balance reaches zero, the reserve is
{\em drained}. If a reserve is not drained after a certain amount of time,
it is automatically closed. A reserve can also be filled via a recoup
action in case that the denomination of an unspent coin that was
withdrawn from the reserve is revoked.
\begin{figure}
\includegraphics{reserve.pdf}
\caption{State machine of a reserve.}
\label{fig:reserve:states}
\end{figure}
Instead of requiring the customer to manually generate reserve key pairs and Instead of requiring the customer to manually generate reserve key pairs and
copy them onto a wire transfer form, banks can offer tight integration with the copy them onto a wire transfer form, banks can offer tight integration with the
@ -187,6 +200,7 @@ for acceptance as an IETF Internet Standard.
% FIXME: withdrawal strategy, coin selection % FIXME: withdrawal strategy, coin selection
\subsection{Coins and Denominations} \subsection{Coins and Denominations}
Unlike plain Chaumian e-cash, where a coin just contains a serial number, a Unlike plain Chaumian e-cash, where a coin just contains a serial number, a
\emph{coin} in Taler is a public/private key pair where the private key is only \emph{coin} in Taler is a public/private key pair where the private key is only
known to the owner of the coin. known to the owner of the coin.

14
doc/system/taler/reserve.dot Normal file
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@ -0,0 +1,14 @@
digraph Reserve {
filled [color=blue, label="filled reserve", shape="box"];
drained [color=blue, label="drained reserve", shape="doublecircle"];
transfer->filled;
recoup->filled;
filled->withdraw;
withdraw->drained;
withdraw->filled;
filled->close;
close->drained;
drained->recoup;
}

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doc/system/taler/reserve.pdf Normal file
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