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Merge branch 'master' of ssh://taler.net/exchange

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I need to refine the text for real after this sloppy merge
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Jeffrey Burdges 2017-05-16 14:03:41 +02:00
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doc/paper/taler.tex
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@ -20,25 +20,6 @@
% CG adds:
% We SHOULD do this for the FINAL paper, not for the anon submission.
\documentclass{llncs}
%\usepackage[margin=1in,a4paper]{geometry}
\usepackage[T1]{fontenc}
\usepackage{palatino}
\usepackage{xspace}
\usepackage{microtype}
\usepackage{amsmath,amssymb,eurosym}
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\usetikzlibrary{calc}
% \usepackage{enumitem}
\usepackage{caption}
%\usepackage{subcaption}
\usepackage{subfig}
% \usepackage{sidecap}
% \usepackage{wrapfig}
% Relate to:
% http://fc14.ifca.ai/papers/fc14_submission_124.pdf
@ -63,23 +44,70 @@
% - transaction = coin ownership transfer that should be taxed
% - sharing = coin copying that should not be taxed
\title{Refreshing Coins for Giving Change and Refunds \\ in Chaum-style Anonymous Payment Systems}
\begin{document}
\mainmatter
%\author{Florian Dold \and Sree Harsha Totakura \and Benedikt M\"uller \and Jeff Burdges \and Christian Grothoff}
%\institute{The GNUnet Project}
\maketitle
% FIXME: As a general comment, I think we're mixing the crypto stuff and the systems
% stuff too much. It might be more appropriate to have to systems stuff in a separate
% section, and the "pure" crypto stuff for the crypto people?
\documentclass[sigconf, authordraft]{acmart}
\usepackage{booktabs} % For formal tables
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}
\usetikzlibrary{positioning}
\usetikzlibrary{calc}
\usepackage{eurosym}
% Copyright
%\setcopyright{none}
%\setcopyright{acmcopyright}
%\setcopyright{acmlicensed}
\setcopyright{rightsretained}
%\setcopyright{usgov}
%\setcopyright{usgovmixed}
%\setcopyright{cagov}
%\setcopyright{cagovmixed}
% DOI
\acmDOI{10.475/123_4}
% ISBN
\acmISBN{123-4567-24-567/08/06}
%Conference
\acmConference[WOODSTOCK'97]{ACM Woodstock conference}{July 1997}{El
Paso, Texas USA}
\acmYear{1997}
\copyrightyear{2016}
\acmPrice{15.00}
\acmSubmissionID{123-A12-B3}
\begin{document}
\title{Refreshing Coins for Giving Change and Refunds \\ in Chaum-style Anonymous Payment Systems}
\subtitle{Authors' names blinded for review}
%\author{Ben Trovato}
%\authornote{Dr.~Trovato insisted his name be first.}
%\orcid{1234-5678-9012}
%\affiliation{%
% \institution{Institute for Clarity in Documentation}
% \streetaddress{P.O. Box 1212}
% \city{Dublin}
% \state{Ohio}
% \postcode{43017-6221}
%}
%\email{trovato@corporation.com}
% The default list of authors is too long for headers}
%\renewcommand{\shortauthors}{B. Trovato et al.}
\begin{abstract}
This paper introduces {\em Taler}, a Chaum-style digital payment system that
enables anonymous payments while ensuring that entities that receive
@ -106,6 +134,46 @@ and adequately balances the state's need for monetary control with the
citizen's needs for private economic activity.
\end{abstract}
%
% The code below should be generated by the tool at
% http://dl.acm.org/ccs.cfm
% Please copy and paste the code instead of the example below.
%
\begin{CCSXML}
<ccs2012>
<concept>
<concept_id>10010520.10010553.10010562</concept_id>
<concept_desc>Computer systems organization~Embedded systems</concept_desc>
<concept_significance>500</concept_significance>
</concept>
<concept>
<concept_id>10010520.10010575.10010755</concept_id>
<concept_desc>Computer systems organization~Redundancy</concept_desc>
<concept_significance>300</concept_significance>
</concept>
<concept>
<concept_id>10010520.10010553.10010554</concept_id>
<concept_desc>Computer systems organization~Robotics</concept_desc>
<concept_significance>100</concept_significance>
</concept>
<concept>
<concept_id>10003033.10003083.10003095</concept_id>
<concept_desc>Networks~Network reliability</concept_desc>
<concept_significance>100</concept_significance>
</concept>
</ccs2012>
\end{CCSXML}
\ccsdesc[500]{Computer systems organization~Embedded systems}
\ccsdesc[300]{Computer systems organization~Redundancy}
\ccsdesc{Computer systems organization~Robotics}
\ccsdesc[100]{Networks~Network reliability}
\keywords{ACM proceedings, \LaTeX, text tagging}
\maketitle
\section{Introduction}
The design of payment systems shapes economies and societies. Strong,
@ -151,7 +219,7 @@ provides fair exchange and exculpability via cryptographic proofs.
\begin{figure}[h]
\centering
\begin{tikzpicture}
\tikzstyle{def} = [node distance= 1em and 11em, inner sep=1em, outer sep=.3em];
\tikzstyle{def} = [node distance= 2em and 6.5em, inner sep=1em, outer sep=.3em];
\node (origin) at (0,0) {};
\node (exchange) [def,above=of origin,draw]{Exchange};
\node (customer) [def, draw, below left=of origin] {Customer};
@ -193,6 +261,7 @@ which owned the original coin.
%\vspace{-0.3cm}
\section{Related Work}
%\vspace{-0.3cm}
@ -1284,8 +1353,10 @@ We thank people (anonymized).
%Jacob Appelbaum for productive discussions and support.
\newpage
\bibliographystyle{alpha}
\bibliography{taler,rfc,ro}
\bibliographystyle{ACM-Reference-Format}
\bibliography{taler,ro} % rfc
\end{document} %TODO: What?!?
%\vfill
%\begin{center}
@ -1491,14 +1562,20 @@ any adversary with an advantage for linking Taler coins gives
rise to an adversary with an advantage for recognizing SHA512 output.
\end{corollary}
There was an earlier encryption-based version of the Taler protocol
in which refresh operated consisted of $\kappa$ normal coin withdrawals
encrypted using the secret $t^{(i)} C$ where $C = c G$ is the coin being
refreshed and $T^{(i)} = t^{(i)} G$ is the transfer key.
We will now consider the impact of the refresh operation. For the
sake of the argument, we will first consider an earlier
encryption-based version of the protocol in which refresh operated
consisted of $\kappa$ normal coin withdrawals where the commitment
consisted of the blinding factors and private keys of the fresh coins
encrypted using the secret $t^{(i)} C_s$ where $C_s = c_s G$ of the
dirty coin $C$ being refreshed and $T^{(i)} = t^{(i)} G$ is the
transfer key.\footnote{We abandoned that version as it required
slightly more storage space and the additional encryption
primitive.}
\begin{proposition}
Assuming the encryption used is semantically (IND-CPA) secure, and
that the independence of $c$, $t$, and the new coins key materials,
that the independence of $c_s$, $t$, and the new coins' key materials,
then any probabilistic polynomial time (PPT) adversary with an
advantage for linking Taler coins gives rise to an adversary with
an advantage for recognizing SHA512 output.
@ -1515,15 +1592,15 @@ this coin and report the exchange's fraudulent activity.
% TODO: Is independence here too strong?
We may now remove the encrpytion by appealing to the random oracle model
\cite{BR-RandomOracles}.
We may now remove the encrpytion by appealing to the random oracle
model~\cite{BR-RandomOracles}.
\begin{lemma}[\cite{??}]
Consider a protocol that commits to random data by encrypting it
using a secret derived from a Diffe-Hellman key exchange.
In the random oracle model, we may replace this encryption with
a hash function derives the random data by applying hash functions
to the same secret.
a hash function which derives the random data by applying hash
functions to the same secret.
\end{lemma}
% TODO: IND-CPA again? Anything else?
@ -1551,7 +1628,13 @@ Diffie-Hellman key exchange on Curve25519.
We do not distinguish between information known by the exchange and
information known by the merchant in the above. As a result, this
proves that out linking protocol \S\ref{subsec:linking} does not
degrade privacy.
degrade privacy. We note that the exchange could lie in the linking
protocol about the transfer public key to generate coins that it can
link (at a financial loss to the exchange that it would have to square
with its auditor). However, in the normal course of payments the link
protocol is never used. Furthermore, if a customer needs to recover
control over a coin using the linking protocol, they can use the
refresh protocol on the result to again obtain an unlinkable coin.
@ -1873,3 +1956,4 @@ provides a payment system with the following key properties:
The payment system handles both small and large payments in
an efficient and reliable manner.
\end{description}