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% bibliography)
% - Add some bibliographical references (for the motivation).
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%\documentclass{taler}	      % full lenth boiler plate
%\documentclass{taler-short} % for short deliverables with less boiler plate
\documentclass[letterpaper,twocolumn,10pt]{article}
\usepackage{usenix-2020-09}

\newif\ifanonymous
\anonymoustrue

\usepackage{xcolor}
\usepackage{amsmath}
\usepackage{amsthm}
\theoremstyle{definition}
\newtheorem{definition}{Definition}
%\definecolor{linkcolor}{rgb}{0.65,0,0}
%\definecolor{citecolor}{rgb}{0,0.4,0}
%\definecolor{urlcolor}{rgb}{0,0,0.65}
%\usepackage[colorlinks=true, linkcolor=linkcolor, urlcolor=urlcolor, citecolor=citecolor]{hyperref}

\usepackage{tikz}
\usepackage{listings}
\usepackage{graphicx}
\date{}
\title{Design of a privacy friendly tax deduction system for donations}

% \author{Emmanuel Benoist, Johannes Casaba, Bob Goudriaan,
% Christian Grothoff, Tanja Lange, Michiel Leenaars,
% Jonathan Levin, Lukas Matyja}

\author{\ }

% \author{
% {\rm Bob Goudriaan}\\
% NLnet Foundation
% \and
% {\rm Christian Grothoff}\\
% Bern University of Applied Sciences
% \and
% {\rm Tanja Lange}\\
% Technical University of Eindhoven
% \and
% {\rm Michiel Leenaars}\\
% NLnet Foundation
% \and
% {\rm Jonathan Levin}\\
% XXXXX
% } % end author

\begin{document}
\maketitle

\begin{abstract}
  Donations have complex requirements that also
  vary by country. Building on privacy-friendly digital cash protocols
  (which enable customers to pay anonymously using blind signatures)
  we created the {\em Donau} system to handle key use-cases for
  privacy-preserving donations.
  This paper explains how our Free Software implementation addresses the
  most common requirements, and also elaborates how others could be
  instantiated with significant changes or additions to the design.

  The Donau system achieves privacy for donors while providing
  them with a proof that they donated to some registered charity.
  The charity does not learn the identity of the donor and the tax
  authority does not learn which charities received donations from
  a particular donor. However, authorities do learn the total amount
  donated to a charity by all donors.

  Our design introduces a new entity, the {\em Donation Authority}
  which operates the {\em Donau} service. The {\em Donau} would typically
  be operated by or on behalf of the tax authority and ensures that
  only recognized charities can register and provide proofs to their
  donors. Also this entity does not learn who donated to which charity.

  Society would benefit from the Donau system as it simplifies
  filing taxes, contributes to fair taxation, and eliminates
  privacy-concerns from charitable giving.

\ifodd0
%\begin{abstract}
GNU Taler is a privacy-friendly payment protocol that offers full anonymity to
the customer, making their purchases anonymous and unlinkable not only to
third parties but even to merchants and banks involved. While this payment
mechanism obviously can be used to make donations, the anonymity guarantees
seem at odds with the desire of donors to receive tax benefits for their
charitable donations.

The main contribution of this paper is the technical design and implementation
of a system that achieves privacy for the donor while providing them with a
proof that they donated to a charity. The charity does not learn the identity
of the donor and the tax authority does not learn which charities received the
donations. Our design introduces a new  entity, the Donation Authority, which we
call Donau. This entity may be operated by the tax authority, and even then
they do not learn the identities of the charities and only get a summary
statement of all donations made by the tax payer in a certain timeframe.

The paper is based on our analysis of functional requirements for
privacy-preserving donations and of further desirable properties which
amount to requirements for some countries. We show how to realize some
of them within our design while showing how others could be
instantiated with significant changes or additions to the design.
\fi
\end{abstract}

%\reportkeywords{GNU Taler, Tax-deductible Donations. Donau, Donation Authority,
%Privacy-Preserving Payments}



\input{intro}
\input{requirements} % Michiel's part can go in this file
\input{technicaldesign}
\input{implementation2}
\input{discussion}
%\input{conclusion}


\ifodd0

\section*{Acknowledgments}

This work was funded by ANONYMIZED.
%in part by the European Commision through the
%Horizon Europe program under project number 101135475 (TALER). It also
%has received funding from the Swiss State Secretariat for Education,
%Research and Innovation (SERI).
%
We thank the tax authority of ANONYMIZED for an extensive and
constructive discussion on the subject.

\fi

\clearpage
\input{ethic}
\clearpage




\bibliographystyle{plainurl}
\bibliography{donau-paper,bibliography,tanja}

% Maybe for camera-ready?
\appendix
\input{appendix}

\input{app-impl}
%\input{implementation}

\end{document}
