exchange/doc/flows/int-pull.tex
2023-07-02 16:09:09 +02:00

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\section{Pull payment (aka invoicing)} \label{sec:pull}
\begin{figure}[h!]
\begin{sequencediagram}
\newinst{payer}{\shortstack{Payer \\
\\ \begin{tikzpicture}
\node [fill=gray!20,draw=black,thick,align=center] {Pre-funded \\ Wallet};
\end{tikzpicture}
}}
\newinst[2]{exchange}{\shortstack{Taler (exchange) \\
\\ \begin{tikzpicture}[shape aspect=.5]
\tikzset{every node/.style={cylinder,shape border rotate=90, draw,fill=gray!25}}
\node at (1.5,0) {\shortstack{{{\tiny Database}}}};
\end{tikzpicture}
}}
\newinst[2]{payee}{\shortstack{Payee \\
\\ \begin{tikzpicture}
\node [fill=gray!20,draw=black,thick,align=center] { Unique \\ Wallet ID};
\end{tikzpicture}
}}
\postlevel
\begin{callself}{payee}{Review pull payment fees}{}
\end{callself}
\mess[0]{payee}{{Create invoice (Wallet ID)}}{exchange}
\mess[0]{exchange}{{Invoice ready}}{payee}
\mess[0]{payee}{{Send invoice (e.g. via QR code)}}{payer}
\begin{callself}{payer}{Review invoice}{}
\end{callself}
\mess[0]{payer}{{Make payment (Coins)}}{exchange}
\begin{sdblock}{Domestic wallet?}{}
\begin{callself}{exchange}{Figure~\ref{fig:proc:domestic}}{}
\end{callself}
\end{sdblock}
\begin{sdblock}{KYC/AML required?}{}
\begin{callself}{exchange}{Figures~\ref{fig:proc:kyc}, \ref{fig:proc:aml}}{}
\end{callself}
\end{sdblock}
\mess[0]{exchange}{{Distribute digital cash}}{payee}
\end{sequencediagram}
\caption{Interactions between wallets and Taler exchange
in a pull payment. KYC/AML checks are described in
Section~\ref{sec:kyc:pull}.}
\label{fig:int:pull}
\end{figure}
We do {\bf not} permit the payer to regain control over their funds, once the
payment was made they are locked {\em until} the payee passes the KYC/AML
checks. We only do the AML/KYC process once the funds are locked at the
exchange. This ensures we know the actual transacted amounts (which may be
lower than the total amounts requested) and prevents risk-free probing
attacks.