From 7b4b0f38ffd212587ac46ff035e1ac3573bd104a Mon Sep 17 00:00:00 2001 From: Christian Grothoff Date: Tue, 16 May 2017 13:34:17 +0200 Subject: [PATCH 1/2] english, linking --- doc/paper/taler.tex | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/doc/paper/taler.tex b/doc/paper/taler.tex index c32adc1b9..8b48ad82f 100644 --- a/doc/paper/taler.tex +++ b/doc/paper/taler.tex @@ -1492,29 +1492,35 @@ any PPT 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 ??? secure, and that - the independence of $c$, $t$, and the new coins key materials, then + the independence of $c_s$, $t$, and the new coins' key materials, then any PPT adversary with an advantage for linking Taler coins gives rise to an adversary with an advantage for recognizing SHA512 output. \end{proposition} % 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} \begin{proof} @@ -1541,7 +1547,13 @@ 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. From 7ce67006be0f4ca8e26e1e35d5751cbc4af40cb9 Mon Sep 17 00:00:00 2001 From: Florian Dold Date: Tue, 16 May 2017 13:39:12 +0200 Subject: [PATCH 2/2] use ACM sigconf format for 2017 --- doc/paper/taler.tex | 140 +++++++++++++++++++++++++++++++++----------- 1 file changed, 106 insertions(+), 34 deletions(-) diff --git a/doc/paper/taler.tex b/doc/paper/taler.tex index 8b48ad82f..9cff69e93 100644 --- a/doc/paper/taler.tex +++ b/doc/paper/taler.tex @@ -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} + + + 10010520.10010553.10010562 + Computer systems organization~Embedded systems + 500 + + + 10010520.10010575.10010755 + Computer systems organization~Redundancy + 300 + + + 10010520.10010553.10010554 + Computer systems organization~Robotics + 100 + + + 10003033.10003083.10003095 + Networks~Network reliability + 100 + + +\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} +\bibliographystyle{ACM-Reference-Format} +\bibliography{taler} + +\end{document} %\vfill %\begin{center} @@ -1875,3 +1946,4 @@ 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} +