commit c2c7321210d9cb07832d77eceffc5ac7eb304530
parent 8165240714b7fcb1b939f12cc7317a2e35a89b85
Author: Christian Grothoff <christian@grothoff.org>
Date: Wed, 19 Oct 2022 11:40:08 +0200
irgc pres
Diffstat:
7 files changed, 458 insertions(+), 0 deletions(-)
diff --git a/presentations/2021-cb/irgc.tex b/presentations/2021-cb/irgc.tex
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+\pdfminorversion=3
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+
+\usetikzlibrary{shapes,arrows}
+\usetikzlibrary{positioning}
+\usetikzlibrary{calc}
+
+\title{GNU Taler as a Retail CBDC}
+%\subtitle{}
+
+\setbeamertemplate{navigation symbols}{\includegraphics[width=1cm]{inria.pdf} \includegraphics[width=2.3cm]{bfh.png} \includegraphics[width=1.6cm]{fub.pdf} \includegraphics[width=0.4cm]{ashoka.png} \includegraphics[width=0.4cm]{gnu.png} \includegraphics[width=1cm]{logo-2021.pdf} \hfill}
+%\setbeamercovered{transparent=1}
+
+\author[C. Grothoff]{{\bf C. Grothoff}}
+\date{25.10.2022}
+\institute{Bern University of Applied Sciences}
+
+
+\begin{document}
+
+\justifying
+
+\begin{frame}
+ \begin{center}
+ \LARGE {\bf GNU}
+
+ \vfill
+% \includegraphics[width=0.66\textwidth]{logo-2017-fr.pdf}
+ \includegraphics[width=0.66\textwidth]{logo-2021.pdf}
+
+ as a Retail CBDC
+ \vfill
+ \end{center}
+\begin{textblock*}{6cm}(.5cm,7.7cm) % {block width} (coords)
+ {\Large {\bf \href{https://taler.net/}{taler.net}} \\
+ \href{https://twitter.com/taler}{taler@twitter} \\
+ \href{https://taler-systems.com/}{taler-systems.com}}
+\end{textblock*}
+
+% Substitute based on who is giving the talk!
+ \begin{textblock*}{6cm}(6.7cm,7.7cm) % {block width} (coords)
+ {%\hfill {\Large {\bf Florian Dold \&} \\
+ \hfill {\bf Christian Grothoff} \\
+ \hfill grothoff@taler.net }
+\end{textblock*}
+
+\end{frame}
+
+\section{Introduction}
+
+\begin{frame}{Payment Systems: Accounts vs. Tokens}
+Two types of payment systems:
+\begin{enumerate}
+\item {\bf account-based system}: transfer occurs by charging the payer’s account and crediting
+the payee’s account (e.g., bank deposits)
+\item {\bf token-based (value-based) system}: transfer occurs by transferring the value itself, or a
+token that represents the monetary asset (e.g., banknotes)
+\end{enumerate}
+Key Difference is the information carried by the information asset:
+\begin{itemize}
+\item account (assets): associated with a transaction history
+\item token (assets): carry information about value and entity that issued the token
+\end{itemize}
+Bitcoin, and Distributed Ledger Technologies (DLTs) in general, are account-based systems!
+Novelty is that the ledger is distributed (decentralized).
+\end{frame}
+
+
+\section{What is Taler?}
+\begin{frame}{What is Taler?}
+\noindent
+Taler is an electronic instant payment system based on tokens.
+ \begin{itemize}
+ \item Uses electronic coins stored in {\bf wallets} on customer's device
+ \item Like {\bf cash}
+ \item Pay in {\bf existing currencies} (i.e. CHF, EUR, USD)
+ \end{itemize}
+ \vfill
+ \pause
+ \noindent
+ However, Taler is
+ \begin{itemize}
+ \item \emph{not} a currency
+ \item \emph{not} suitable for long-term store of value
+ \item \emph{not} a network or instance of a system
+ \item \emph{not} decentralized
+ \item \emph{not} based on proof-of-work or proof-of-stake
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Design Principles}
+ \framesubtitle{https://taler.net/en/principles.html}
+GNU Taler must ...
+\begin{enumerate}
+ \item {... be implemented as {\bf free software}.}
+ \item {... protect the {\bf privacy of buyers}.}
+ \item {... must enable the state to {\bf tax income} and crack down on
+ illegal business activities.}
+ \item {... prevent payment fraud.}
+ \item {... only {\bf disclose the minimal amount of information
+ necessary}.}
+ \item {... be usable.}
+ \item {... be efficient.}
+ \item {... avoid single points of failure.}
+ \item {... foster {\bf competition}.}
+\end{enumerate}
+\end{frame}
+
+
+\begin{frame}{The Big Picture}
+\begin{center}
+\includegraphics[width=0.8\textwidth]{bp.png}
+\end{center}
+\end{frame}
+
+
+\begin{frame}{Taler: Unique Regulatory Features for CBs}
+ \framesubtitle{\url{https://www.snb.ch/en/mmr/papers/id/working_paper_2021_03}}
+ \begin{itemize}
+ \item Central bank issues digital coins equivalent to issuing cash \\
+ $\Rightarrow$ monetary policy remains under CB control
+ \item Architecture with consumer accounts at commercial banks \\
+ $\Rightarrow$ no competition for commercial banking (S\&L) \\
+ $\Rightarrow$ CB does not have to manage KYC, customer support
+ \item Withdrawal limits and denomination expiration \\
+ $\Rightarrow$ protects against bank runs and hoarding
+ \item Income transparency and possibility to set fees \\
+ $\Rightarrow$ additional insights into economy and new policy options
+ \item Revocation protocols and loss limitations \\
+ $\Rightarrow$ exit strategy and handles catastrophic security incidents
+ \item Privacy by cryptographic design not organizational compliance \\
+ $\Rightarrow$ CB cannot be forced to facilitate mass-surveillance
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Feature Summary (some are still WiP)}
+ \begin{itemize}
+ \item Wallets for Firefox, Chrome, Android, CLI, iOS
+ \item Merchant integrations for MDB, WooCommerce, Joomla!, Pretix, PoS App
+ \item Payment via NFC, QR code or integrated in browser
+ \item Peer-to-peer payments (with KYC for receiver), invoicing
+ \item External KYC providers with configurable KYC trigger rules
+ \item Age-restricted payments, accessible design
+ \item Escrow functionality (``smart contracts''), i.e. auctions
+ \item Privacy-preserving backup and recovery of wallet state
+ \item RTGS integrations with libeufin over EBICS or Depolymerization over Bitcoin/Ethereum
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}
+\frametitle{Do you have any questions?}
+\vfill
+References:
+{\tiny
+ \begin{enumerate}
+ \item{David Chaum, Christian Grothoff and Thomas Moser.
+ {\em How to issue a central bank digital currency}.
+ {\bf SNB Working Papers, 2021}.}
+ \item{Christian Grothoff, Bart Polot and Carlo von Loesch.
+ {\em The Internet is broken: Idealistic Ideas for Building a GNU Network}.
+ {\bf W3C/IAB Workshop on Strengthening the Internet Against Pervasive Monitoring (STRINT)}, 2014.}
+ \item{Jeffrey Burdges, Florian Dold, Christian Grothoff and Marcello Stanisci.
+ {\em Enabling Secure Web Payments with GNU Taler}.
+ {\bf SPACE 2016}.}
+ \item{Florian Dold, Sree Harsha Totakura, Benedikt M\"uller, Jeffrey Burdges and Christian Grothoff.
+ {\em Taler: Taxable Anonymous Libre Electronic Reserves}.
+ Available upon request. 2016.}
+ \item{Eli Ben-Sasson, Alessandro Chiesa, Christina Garman, Matthew Green, Ian Miers, Eran Tromer and Madars Virza.
+ {\em Zerocash: Decentralized Anonymous Payments from Bitcoin}.
+ {\bf IEEE Symposium on Security \& Privacy, 2016}.}
+ \item{David Chaum, Amos Fiat and Moni Naor.
+ {\em Untraceable electronic cash}.
+ {\bf Proceedings on Advances in Cryptology, 1990}.}
+ \item{Phillip Rogaway.
+ {\em The Moral Character of Cryptographic Work}.
+ {\bf Asiacrypt}, 2015.} \label{bib:rogaway}
+\end{enumerate}
+}
+\end{frame}
+
+
+\begin{frame}{How does it work?}
+ \framesubtitle{\url{https://taler.net/papers/thesis-dold-phd-2019.pdf}}
+ We use a few ancient constructions:
+ \begin{itemize}
+ \item Cryptographic hash function (1989)
+ \item Blind signature (1983)
+ \item Schnorr signature (1989)
+ \item Diffie-Hellman key exchange (1976)
+ \item Cut-and-choose zero-knowledge proof (1985)
+ \end{itemize}
+But of course we use modern instantiations.
+\end{frame}
+
+
+\begin{frame}{Definition: Taxability}
+ We say Taler is taxable because:
+ \begin{itemize}
+ \item Merchant's income is visible from deposits.
+ \item Hash of contract is part of deposit data.
+ \item State can trace income and enforce taxation.
+ \end{itemize}\pause
+ Limitations:
+ \begin{itemize}
+ \item withdraw loophole
+ \item {\em sharing} coins among family and friends
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Giving change}
+ It would be inefficient to pay EUR 100 with 1 cent coins!
+ \begin{itemize}
+ \item Denomination key represents value of a coin.
+ \item Exchange may offer various denominations for coins.
+ \item Wallet may not have exact change!
+ \item Usability requires ability to pay given sufficient total funds.
+ \end{itemize}\pause
+ Key goals:
+ \begin{itemize}
+ \item maintain unlinkability
+ \item maintain taxability of transactions
+ \end{itemize}\pause
+ Method:
+ \begin{itemize}
+ \item Contract can specify to only pay {\em partial value} of a coin.
+ \item Exchange allows wallet to obtain {\em unlinkable change}
+ for remaining coin value.
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Refresh protocol summary}
+ \begin{itemize}
+ \item Customer asks exchange to convert old coin to new coin
+ \item Protocol ensures new coins can be recovered from old coin
+ \item[$\Rightarrow$] New coins are owned by the same entity!
+ \end{itemize}
+ Thus, the refresh protocol allows:
+ \begin{itemize}
+ \item To give unlinkable change.
+ \item To give refunds to an anonymous customer.
+ \item To expire old keys and migrate coins to new ones.
+ \item To handle protocol aborts.
+ \end{itemize}
+% \noindent
+% \begin{center}
+% \bf
+% Transactions via refresh are equivalent to {\em sharing} a wallet.
+%\end{center}
+\end{frame}
+
+
+\begin{frame}{Scalability}
+On paper, the design scales linearly with computing resources:
+\begin{itemize}
+\item Front-end logic at the central bank only needs to perform a few signature operations, a
+single CPU core can typically do a few thousands per second.
+\item Front-end servers need to talk to a database to prevent double-spending. A single database server can handle tens of thousands of such operations per second.
+\item All operations are easily split across multiple database servers by simply assigning
+each database server a range of values.
+\item The frontends need to talk to the backends using an interconnect. The size of an
+individual transaction is typically about 1–10 kilobytes. Modern interconnects
+can support millions of such transactions per second.
+\item To securely store 1-10 kilobytes per transaction, using AWS pricing, the cost of the
+system (storage, bandwidth, computation) at scale would be 0.0001 USD per transaction.
+\end{itemize}
+\end{frame}
+
+
+\begin{frame} \frametitle{Performance} \framesubtitle{Other Payment Systems}
+ \centering
+ \begin{minipage}{0.32\textwidth}
+ \centering
+ \visible<1->{Bitcoin}\\\vspace{1em}
+ {4 TPS}\\
+ {
+ \vspace{2em}
+ \includegraphics[width=0.2\linewidth]{performance.pdf}\hspace{1em}
+ \includegraphics[width=0.2\linewidth]{mining.pdf}
+ }
+ \end{minipage}
+ \begin{minipage}{0.32\textwidth}
+ \centering
+ {PayPal\\\vspace{1em}193 TPS}\\
+ {
+ \vspace{2em}
+ \includegraphics[width=0.2\linewidth]{privacy.pdf}
+ }
+ \end{minipage}
+ \begin{minipage}{0.32\textwidth}
+ \centering
+ {Visa\\\vspace{1em}1'667 TPS}\\
+ {
+ \vspace{2em}
+ \includegraphics[width=0.2\textwidth]{privacy.pdf}
+ }
+ \end{minipage}
+ \let\thefootnote\relax\footnote{
+ \tiny
+ [06.22]\hspace{3em}
+ - \href{https://www.researchgate.net/publication/330585021_Analysis_of_the_Possibilities_for_Improvement_of_BlockChain_Technology}{Researchgate}
+ }
+\end{frame}
+
+\begin{frame} \frametitle{Performance} \framesubtitle{CBDC Projects}
+ \centering
+ \begin{minipage}{0.28\textwidth}
+ \centering
+ {e-Krona (Sweden)\\\vspace{1em}100 TPS}\\
+ {
+ \vspace{2em}
+ \includegraphics[width=0.2\linewidth]{performance.pdf}\hspace{1em}
+ \includegraphics[width=0.2\linewidth]{privacy.pdf}
+ }
+ \end{minipage}
+ \begin{minipage}{0.28\textwidth}
+ \centering
+ {e-CNY (China)\\\vspace{1em}10'000 TPS}\\
+ {
+ \vspace{2em}
+ \includegraphics[width=0.2\linewidth]{privacy.pdf}
+ }
+ \end{minipage}
+ \begin{minipage}{0.38\textwidth}
+ \centering
+ \visible<2->{GNU Taler (Grid5000)\\\vspace{1em}28'500 TPS}\\
+ {
+ \vspace{2em}
+ \visible<2->{\includegraphics[width=0.4\linewidth]{logo-2021.pdf}}
+ }
+ \end{minipage}
+ \let\thefootnote\relax\footnote{
+ \tiny
+ [06.22]\hspace{3em}
+ \hspace{3em}- \href{https://www.atlanticcouncil.org/blogs/econographics/a-report-card-on-chinas-central-bank-digital-currency-the-e-cny/}{Atlatic Council}
+ \hspace{3em}- \href{https://www.riksbank.se/globalassets/media/rapporter/e-krona/2022/e-krona-pilot-phase-2.pdf}{Riksbank}
+ }
+\end{frame}
+
+
+\section{Competitor comparison}
+\begin{frame}{Competitor comparison}
+ \begin{center} \small
+ \begin{tabular}{l||c|c|c|c|c}
+ & Cash & DLT & HW-Token & CB-Account & GNU Taler \\ \hline \hline
+ Online &$-$$-$$-$ & + & $-$ & ++ & +++ \\ \hline
+ Offline & +++ & $-$$-$$-$ & $+$ & $-$$-$ & $-$$-$ \\ \hline
+ Cost & $-$ & $-$$-$$-$ & $-$ & + & ++ \\ \hline
+ Speed & + & $-$$-$$-$ & $+$ & o & ++ \\ \hline
+ Taxation & $-$ & +++ & $-$$-$ & +++ & +++ \\ \hline
+ Payer-anon & ++ & $-$$-$ & ??? & $-$$-$ & +++ \\ \hline
+ Payee-anon & ++ & $-$$-$ & ??? & $-$$-$ & $-$$-$$-$ \\ \hline
+ Security & $-$ & ??? & $-$$-$ & o & ++ \\ \hline
+ Migration & +++ & $-$$-$$-$ & $-$$-$$-$& o & + \\ \hline
+ Libre & $-$ & ??? & $-$$-$$-$& N/A & +++ \\
+ \end{tabular}
+ \end{center}
+\end{frame}
+
+
+
+\end{document}
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