commit 4ec8fb4097de969b534cdb35f3027c86a0b2abd1
parent f039ee11151b2367a5653218dabeb0950efe9eb5
Author: Christian Grothoff <christian@grothoff.org>
Date: Mon, 10 Apr 2023 12:14:49 +0200
bdf
Diffstat:
5 files changed, 1049 insertions(+), 0 deletions(-)
diff --git a/presentations/comprehensive/bdf.tex b/presentations/comprehensive/bdf.tex
@@ -0,0 +1,1049 @@
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+
+
+\title{GNU Taler}
+%\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]{taler-logo-2021-inkscape.pdf} \hfill}
+%\setbeamercovered{transparent=1}
+
+\author[E. Benoist, F. Dold, C. Grothoff, M. Walrafen]{{\bf E. Benoist, F. Dold, C. Grothoff, M. Walrafen}}
+\date{\today}
+\institute{Taler Systems SA \& BFH \& The GNU Project}
+
+
+\begin{document}
+
+\justifying
+
+\begin{frame}
+ \begin{center}
+ \LARGE {\bf GNU} \\
+ \vspace{0.3cm}
+% \includegraphics[width=0.66\textwidth]{logo-2017-fr.pdf}
+ \includegraphics[width=0.66\textwidth]{taler-logo-2021-inkscape.pdf}
+ \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*}{8cm}(4.7cm,6.7cm) % {block width} (coords)
+ {\hfill {{\bf Dr. Emmanuel Benoist} \\
+ \hfill {\bf Dr. Florian Dold} \\
+ \hfill {\bf Dr. Christian Grothoff} \\
+ \hfill {\bf Marie Walrafen} \\ }
+ \hfill \{benoist,dold,grothoff,walrafen\}@taler.net }
+\end{textblock*}
+
+\end{frame}
+
+\begin{frame}{Agenda}
+\tableofcontents
+\end{frame}
+
+\section{Introduction}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ {\bf Part I: Introduction}
+ \end{center}
+ \vfill
+\end{frame}
+
+
+\section{What is Taler?}
+\begin{frame}{What is Taler?}
+ \framesubtitle{\url{https://taler.net/en/features.html}} \noindent
+Taler is
+ \vfill
+ \begin{itemize}
+ \item a Free/Libre software \emph{payment system} infrastructure project
+ \item ... with a surrounding software ecosystem
+ \item ... and a company (Taler Systems S.A.) and community that wants to deploy it
+ as widely as possible.
+ \end{itemize}
+ \vfill
+\noindent
+ However, Taler is
+ \begin{itemize}
+ \item \emph{not} a currency
+ \item \emph{not} a 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
+ \item combinable with a DLT back-end if requested
+ \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} (but {\em available} under a commercial license).}
+ \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} in associated services.}
+\end{enumerate}
+\end{frame}
+
+
+\begin{frame}
+\frametitle{Taler Overview}
+\begin{center}
+\begin{tikzpicture}
+ \tikzstyle{def} = [node distance= 5em 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};
+ \node (merchant) [def, draw, below right=of origin] {Merchant};
+ \node (auditor) [def, draw, above right=of origin]{Auditor};
+% \node (regulator) [def, draw, above=of auditor]{CSSF};
+
+ \tikzstyle{C} = [color=black, line width=1pt]
+
+ \draw [<-, C] (customer) -- (exchange) node [midway, above, sloped] (TextNode) {withdraw coins};
+ \draw [<-, C] (exchange) -- (merchant) node [midway, above, sloped] (TextNode) {deposit coins};
+ \draw [<-, C] (merchant) -- (customer) node [midway, above, sloped] (TextNode) {spend coins};
+ \draw [<-, C] (exchange) -- (auditor) node [midway, above, sloped] (TextNode) {verify};
+% \draw [<-, C] (regulator) -- (auditor) node [midway, above, sloped] (TextNode) {report};
+
+\end{tikzpicture}
+\end{center}
+\end{frame}
+
+
+\begin{frame}{Architecture of Taler}
+\begin{center}
+ \includegraphics[width=1\textwidth]{operations.png}
+\end{center}
+\end{frame}
+
+
+\begin{frame}{Consumer Impact of Taler}
+\begin{itemize}
+\item {\bf Convenient:} pay with one click instantly --– in Euro,
+Dollar, Swiss Franc or Bitcoin
+\item {\bf Friction-free security:} Payments do not require sign-up,
+login or multi-factor authentication
+\item {\bf Privacy-preserving:} payment requires/shares no personal information
+\item {\bf Bank account:} not required
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{Merchant Impact of Taler}
+\begin{itemize}
+\item {\bf Instant clearance:} one-click transactions and instant clearance at par
+\item {\bf Easy \& compliant:} GDPR \& PCI-DSS compliance-free and without any effort
+\item {\bf Major profit increase:} efficient protocol $+$ no fraud $=$ extremely low costs
+\item {\bf 1-click checkout:} without Amazon and without false
+positives in fraud detection
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{Taler: Unique Regulatory Features for Central Banks}
+ \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}{Usability of Taler}
+ \vfill
+ \begin{center}
+ \url{https://demo.taler.net/}
+ \end{center}
+ \begin{enumerate}
+ \item Install browser extension.
+ \item Visit the {\tt bank.demo.taler.net} to withdraw coins.
+ \item Visit the {\tt shop.demo.taler.net} to spend coins.
+ \end{enumerate}
+ \vfill
+\end{frame}
+
+
+\section{Component Zoo}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ {\bf Part II: Component Zoo}
+ \end{center}
+ \vfill
+\end{frame}
+
+
+\begin{frame}{The Taler Software Ecosystem: Overview}
+ \framesubtitle{\url{https://taler.net/en/docs.html}}
+ Taler is based on modular components that work together to provide a
+ complete payment system:
+ \vfill
+ \begin{itemize}
+ \item {\bf Exchange:} Service provider for digital cash
+ \begin{itemize}
+ \item Core exchange software (cryptography, database)
+ \item Air-gapped key management, real-time {\bf auditing}
+ \item {\bf LibEuFin}: Modular integration with banking systems
+ \end{itemize}
+ \item {\bf Merchant:} Integration service for existing businesses
+ \begin{itemize}
+ \item Core merchant backend software (cryptography, database)
+ \item {\bf Back-office interface} for staff
+ \item {\bf Frontend integration} (E-commerce, Point-of-sale)
+ \end{itemize}
+ \item {\bf Wallet:} Consumer-controlled applications for e-cash
+ \begin{itemize}
+ \item Multi-platform wallet software (for browsers \& mobile phones)
+ \item Wallet backup storage providers ({\bf sync})
+ \item {\bf Anastasis}: Recovery of lost wallets based on secret splitting
+ \end{itemize}
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Taler Exchange}
+ The {\bf Exchange} is the core logic of the payment system.
+
+ \begin{itemize}
+ \item One exchange at minimum must be operated per currency
+ \item Offers a REST API for merchants and customers
+ \item Uses several helper processes for configuration and to
+ interact with RTGS and cryptography
+ \item KYC support via OAuth 2.0, KycAID or Persona APIs
+ \item Implemented in C on top of GNU libmicrohttpd
+ \end{itemize}
+ Scalability: 28'500 transactions/second measured % in BS-thesis
+ in 2022 using two servers on Grid5000. Likely several times
+ higher today (but we did not re-measure recently).
+\end{frame}
+
+
+\begin{frame}{Taler Merchant}
+ The {\bf Merchant} is the software run by merchants to accept\\
+ GNU Taler payments.
+
+ \begin{minipage}{6cm}
+ \begin{itemize}
+ \item REST API for integration with e-commerce
+ \item SPA provides Web interface for administration
+ \item Features include:
+ \begin{itemize}
+ \item Multi-tenant support
+ \item Refunds
+ \item Tipping (Website pays visitor)
+ \item Webhooks
+ \item Inventory management (optional)
+ \end{itemize}
+ \item Implemented in C on top of GNU libmicrohttpd
+ \end{itemize}
+ \end{minipage}
+ \begin{minipage}{5cm}
+ \includegraphics[width=5cm]{screenshots/merchant-spa-settings}
+ \end{minipage}
+\end{frame}
+
+
+\begin{frame}{Taler Wallet}
+ The {\bf Wallet} is the software run by consumers to store
+ their digital cash and authorize transactions.
+
+ \begin{minipage}{8cm}
+ \begin{itemize}
+ \item {\bf wallet-core} is the logic shared by all interfaces
+ \item Applications exist for Android, F-Droid,
+ WebExtension (Chrome, Chromium, Firefox, etc.), iOS ({\bf WiP})
+ \item Features include:
+ \begin{itemize}
+ \item Multi-currency support
+ \item Wallet-to-wallet payments (NFC or QR code)
+ \item CRDT-like data model
+ \end{itemize}
+ \item {\bf wallet-core} implemented in TypeScript
+ \end{itemize}
+ Can be integrated into other Apps if desired.
+ \end{minipage}
+ \begin{minipage}{3cm}
+ \includegraphics[width=3cm]{screenshots/Screenshot_20230225-103520.png}
+ \end{minipage}
+\end{frame}
+
+
+\begin{frame}{Taler Auditor}
+ The {\bf Auditor} is the software run by an independent auditor
+ to validate the operation of an Exchange.
+
+ \begin{itemize}
+ \item REST API for additional report inputs by merchants (optional)
+ \item Secure database replication logic
+ \item Implemented in C on top of GNU libmicrohttpd
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Pretix Taler payment plugin}
+\begin{center}
+\includegraphics[width=0.5\textwidth]{screenshots/pretix.png}
+\end{center}
+
+ Pretix is a ticket sales system.
+
+ \begin{itemize}
+ \item Pretix payment plugin enables payments via GNU Taler
+ \item Developed by Pretix.eu for \EUR{3,000} on behalf of Taler Systems SA
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{WooCommerce Taler payment plugin}
+\begin{minipage}{6cm}
+ \begin{itemize}
+ \item WooCommerce is an e-commerce plugin for WordPress.
+ \item WooCommerce payment plugin enables payments via GNU Taler
+ \item Features include:
+ \begin{itemize}
+ \item Trivial configuration
+ \item Support for refunds
+ \item Full internationalization
+ \end{itemize}
+ \item WooCommerce and its plugins are implemented in PHP
+ \end{itemize}
+\end{minipage}
+\begin{minipage}{5cm}
+ \includegraphics[width=4cm]{screenshots/woocommerce-cart.png}
+ \includegraphics[width=4cm]{screenshots/woocommerce-settings.png}
+ \end{minipage}
+\end{frame}
+
+
+\begin{frame}{Point-of-Sale App for Android}
+
+\begin{minipage}{7cm}
+ \begin{itemize}
+ \item Allows merchant to generate orders against Taler backend
+ and display QR code to enable customer to pay in person
+ \item Patterned after ViewTouch restaurant UI
+ \item Features include:
+ \begin{itemize}
+ \item Internet-based configuration
+ \item Products sorted by categories
+ \item Easy undo of every operation
+ \item Manages multiple concurrent orders
+ \end{itemize}
+ \item The Point-of-Sale App is implemented in Kotlin
+ \end{itemize}
+\end{minipage}
+\begin{minipage}{4cm}
+ \includegraphics[width=4cm]{screenshots/Screenshot_20230224-194112.jpg}
+ \includegraphics[width=4cm]{screenshots/Screenshot_20230224-194119.jpg}
+ \includegraphics[width=4cm]{screenshots/Screenshot_20230224-195348.jpg}
+\end{minipage}
+\end{frame}
+
+
+\begin{frame}[c]{The Taler Snack Machine\footnote{by M. Boss and D. Hofer}}
+ \framesubtitle{Integration of a MDB/ICP to Taler gateway.\\Implementation of a NFC or QR-Code to Taler wallet interface.}
+ \vfill
+ \begin{figure}
+ \centering
+ \includegraphics[width=1.0\textwidth]{design}
+ \end{figure}
+\end{frame}
+
+\begin{frame}[c]{User story: Dr. Thomas Moser (SNB)}
+ \begin{figure}
+ \includegraphics[width=0.45\textwidth]{moser1.jpeg}
+ \includegraphics[width=0.45\textwidth]{moser2.jpeg}
+ \includegraphics[width=0.45\textwidth]{moser3.jpeg}
+ \includegraphics[width=0.45\textwidth]{moser4.jpeg}
+ \end{figure}
+\end{frame}
+
+
+\begin{frame}{LibEuFin}
+ LibEuFin is a standalone project that provides adapters to bank account
+ access APIs.
+
+ \begin{itemize}
+ \item LibEuFin provides both a generic access layer and an
+ implementation of the Wire Gateway for the exchange
+ \item Supports EBICS 2.5
+ \item other APIs such as FinTS or PSD2-style XS2A APIs can be added
+ without requiring changes to the Exchange
+ \item tested with German bank GLS business account and real Euros
+ \end{itemize}
+ \vfill
+ \begin{itemize}
+ \item \texttt{libeufin-nexus} is the main service
+ \item Almost all configuration (except DB credentials)
+ is stored in the database and managed via a RESTful HTTP API
+ \item \texttt{libeufin-sandbox} implements a toy EBICS host for protocol
+ testing
+ \item \texttt{libeufin-cli} is client for the HTTP API (only implements a subset
+ of available functionality)
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Cashier App for Android}
+\begin{minipage}{4cm}
+ \begin{itemize}
+ \item Enables BFH staff to convert cash to e-cash
+ \item Staff has special bank accounts with limited funds
+ \item Students can pay staff in cash to receive e-cash
+ \item The Cashier App is implemented in Kotlin
+ \end{itemize}
+ \end{minipage}
+ \begin{minipage}{3cm}
+ \includegraphics[width=3cm]{screenshots/Screenshot_20230225-103315.png}
+ \end{minipage}
+ \begin{minipage}{3cm}
+ \includegraphics[width=3cm]{screenshots/Screenshot_20230225-103325.png}
+ \end{minipage}
+\end{frame}
+
+
+\begin{frame}{Depolymerization}
+ Depolymerization is a bridge between GNU Taler and blockchains,
+ making Taler a layer 2 system for crypto-currencies (like Lightning).
+
+ \begin{itemize}
+ \item Currently implemented for Bitcoin and Ethereum
+ crypto-currencies, with the DLTs as the ``RTGS''
+ \item Provides same API to Exchange as LibEuFin
+% \item Transaction rate and speed limited by the underlying blockchain
+ \item Implemented in Rust
+ \end{itemize}
+ \begin{center}
+ \url{https://bitcoin.ice.bfh.ch/}
+ \end{center}
+\end{frame}
+
+
+\begin{frame}{TalDir (WiP)}
+ TalDir is an extension to the existing
+ peer-to-peer payment functionality.
+
+ \begin{itemize}
+ \item Registry to associate wallets with network addresses
+ \item Extensible to different types of network services:
+ \begin{itemize}
+ \item E-mail
+ \item SMS
+ \item Twitter
+ \item ...
+ \end{itemize}
+ \item Send payments or invoices to wallets associated with network address
+ \item Will {\bf not} require sending wallet to use same network service
+ \end{itemize}
+\end{frame}
+
+
+\section{Basic Cryptography}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ {\bf Part III: Basic Cryptography}
+ \end{center}
+ \vfill
+\end{frame}
+
+
+\begin{frame}{How does it work?}
+We use a few well established and tested 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}{Withdrawing coins on the Web}
+ \begin{center}
+ \includegraphics[height=0.9\textheight]{figs/taler-withdraw.pdf}
+ \end{center}
+\end{frame}
+
+
+\begin{frame}{Payment processing with Taler}
+ \begin{center}
+ \includegraphics[height=0.9\textheight]{figs/taler-pay.pdf}
+ \end{center}
+\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}
+
+
+\section{Illustration of Programmable Money: Age Restrictions}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ \vfill
+ {\bf Part IV:}
+ \vfill
+ {\bf Illustration of Programmable Money}
+ \vfill
+ {\bf Zero-knowledge Age Restrictions}
+ \vfill
+ \end{center}
+ \vfill
+\end{frame}
+
+
+\begin{frame}{Age restriction in e-commerce}
+
+ \begin{description}
+ \item[Problem:]~\\[1em]
+ Verification of minimum age requirements in e-commerce.\\[2em]
+
+ \item[Common solutions:]
+
+\begin{tabular}{l<{\onslide<2->}c<{\onslide<3->}cr<{\onslide}}
+ & \blue{Privacy} & \tikzmark{topau} \blue{Ext. authority}& \\[\medskipamount]
+ 1. ID Verification & bad & required & \\[\medskipamount]
+ 2. Restricted Accounts & bad & required & \\[\medskipamount]
+ 3. Attribute-based & good & required &\tikzmark{bottomau} \\[\medskipamount]
+\end{tabular}
+ \end{description}
+
+\uncover<4->{
+ \begin{tikzpicture}[overlay,remember picture]
+ \draw[orange,thick,rounded corners]
+ ($(pic cs:topau) +(0,0.5)$) rectangle ($(pic cs:bottomau) -(0.3, 0.2)$);
+ \end{tikzpicture}
+ \begin{center}
+ \bf Principle of subsidiarity is violated
+ \end{center}
+}
+\end{frame}
+
+
+\begin{frame}{Age restriction design for GNU Taler}
+Design and implementation of an age restriction scheme\\
+with the following goals:
+
+\begin{enumerate}
+\item It ties age restriction to the \textbf{ability to pay} (not to ID's)
+\item maintains \textbf{anonymity of buyers}
+\item maintains \textbf{unlinkability of transactions}
+\item aligns with \textbf{principle of subsidiarity}
+\item is \textbf{practical and efficient}
+\end{enumerate}
+
+\end{frame}
+
+
+\begin{frame}{Age restriction}
+ \framesubtitle{Assumptions and scenario}
+
+ \begin{columns}
+ \column{7.5cm}
+ \begin{itemize}
+ \item<1-> Assumption: Checking accounts are under control of eligible adults/guardians.
+ \item<2-> \textit{Guardians} \textbf{commit} to an maximum age
+ \item<3-> \textit{Minors} \textbf{attest} their adequate age
+ \item<4-> \textit{Merchants} \textbf{verify} the attestations
+ \item<5-> Minors \textbf{derive} age commitments from existing ones
+ \item<6-> \textit{Exchanges} \textbf{compare} the derived age commitments
+ \end{itemize}
+ \column{5cm}
+ \uncover<7->
+ {
+ \begin{center}
+ \fontsize{7pt}{7pt}\selectfont
+ \begin{tikzpicture}[scale=.5]
+ \node[circle,minimum size=15pt,fill=black!15] at ( 60:4) (Exchange) {$\Exchange$};
+ \node[circle,minimum size=15pt,fill=black!15] at ( 0:0) (Client) {$\Child$};
+ \node[circle,minimum size=15pt,fill=black!15] at ( 0:4) (Merchant) {$\Merchant$};
+ \node[circle,minimum size=15pt,fill=blue!15] at (140:3) (Guardian) {$\Guardian$};
+
+ \draw[->] (Guardian) to [out=50,in=130, loop] node[above]
+ {$\Commit$} (Guardian);
+ \draw[->,blue] (Client) to [out=-125,in=-190, loop] node[below,left]
+ {\blue{$\Attest$}} (Client);
+ \draw[->,blue] (Merchant) to [out=50,in=130, loop] node[above]
+ {\blue{$\Verify$}} (Merchant);
+ \draw[->,orange] (Client) to [out=-35,in=-100, loop] node[below]
+ {\orange{$\Derive$}} (Client);
+ \draw[->,orange] (Exchange) to [out=50,in=130, loop] node[above]
+ {\orange{$\Compare$}} (Exchange);
+
+ \draw[orange,|->] (Client) to node[sloped,above,align=left]
+ {\orange{\scriptsize }} (Exchange);
+ \draw[blue,|->] (Client) to node[sloped, above]
+ {\blue{\scriptsize }} (Merchant);
+ \draw[,|->] (Guardian) to node[above,sloped,align=left]
+ {{\scriptsize }} (Client);
+ \end{tikzpicture}
+ \end{center}
+ }
+ \end{columns}
+ \vfill
+% \uncover<7->{Note: Scheme is independent of payment service protocol.}
+\end{frame}
+
+
+\section{Offline Payments}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ {\bf Part V: Offline Payments}
+ \end{center}
+ \vfill
+\end{frame}
+
+
+\begin{frame}{Fully Offline Payments {\bf (WiP)}}
+\framesubtitle{\url{https://docs.taler.net/design-documents/030-offline-payments.html}}
+Many central banks today demand offline capabilities for digital payment solutions.
+\vfill
+\noindent
+Three possible approaches:
+\begin{enumerate}
+ \item Trust-based offline payments (has counterparty and/or privacy risks)
+ \item Full HSM Taler wallet (has hardware costs)
+ \item Light-weight HSM balance register
+\end{enumerate}
+\vfill
+\end{frame}
+
+
+\begin{frame}{Partially Offline Payments with GNU Taler}
+
+\begin{center}
+\resizebox{8cm}{7cm}{
+\begin{sequencediagram}
+ \newinst{pos}{\shortstack{PoS \\
+ \\ \begin{tikzpicture}
+ \node [fill=gray!20,draw=black,thick ,align=center] {PoS key \\ PoS ID};
+ \end{tikzpicture}
+ }}
+ \newinst[2]{customer}{\shortstack{Customer \\
+ \\ \begin{tikzpicture}
+ \node [fill=gray!20,draw=black,thick ,align=center] {Digital \\ Wallet};
+ \end{tikzpicture}
+ }}
+ \newinst[2]{backend}{\shortstack{Merchant Backend \\
+ \\ \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 PoS key} \\ {\tiny PoS ID}}};
+ \end{tikzpicture}
+ }}
+ \postlevel
+ \mess[0]{pos}{PoS ID}{customer}
+ \begin{sdblock}{optional}{}
+ \begin{callself}{customer}{Amount}{}
+ \end{callself}
+ \end{sdblock}
+ \prelevel
+ \prelevel
+ \prelevel
+ \prelevel
+ \prelevel
+ \begin{sdblock}{optional}{}
+ \begin{callself}{pos}{Amount}{}
+ \end{callself}
+ \end{sdblock}
+ \postlevel
+ \mess[0]{customer}{PoS ID, [Amount]?}{backend}
+ \mess[0]{backend}{Contract}{customer}
+ \postlevel
+ \mess[0]{customer}{Payment}{backend}
+ \begin{callself}{pos}{OTP(PoS key)}{}
+ \end{callself}
+ \prelevel
+ \prelevel
+ \begin{callself}{backend}{OTP(PoS key)}{}
+ \end{callself}
+ \mess[0]{backend}{OTP code}{customer}
+ \postlevel
+ \mess[0]{customer}{OTP code}{pos}
+\end{sequencediagram}
+}
+\end{center}
+\end{frame}
+
+
+\section{Conclusion}
+
+\begin{frame}
+ \vfill
+ \begin{center}
+ {\bf Part VI: Conclusion}
+ \end{center}
+ \vfill
+\end{frame}
+
+\begin{frame}{Feature comparison}
+ \begin{center} \small
+ \begin{tabular}{l||c|c|c|c|c}
+ & Cash & Bitcoin & Zerocoin & Creditcard & GNU Taler \\ \hline \hline
+ Online &$-$$-$$-$ & ++ & ++ & + & +++ \\ \hline
+ Offline & +++ & $-$$-$ & $-$$-$ & + & ++ \\ \hline
+ Trans. cost & + & $-$$-$$-$ & $-$$-$$-$ & $-$ & ++ \\ \hline
+ Speed & + & $-$$-$$-$ & $-$$-$$-$ & o & ++ \\ \hline
+ Taxation & $-$ & $-$$-$ & $-$$-$$-$ & +++ & +++ \\ \hline
+ Payer-anon & ++ & o & ++ & $-$$-$$-$ & +++ \\ \hline
+ Payee-anon & ++ & o & ++ & $-$$-$$-$ & $-$$-$$-$ \\ \hline
+ Security & $-$ & o & o & $-$$-$ & ++ \\ \hline
+ Conversion & +++ & $-$$-$$-$ & $-$$-$$-$ & +++ & +++ \\ \hline
+ Libre & $-$ & +++ & +++ & $-$ $-$ $-$ & +++ \\
+ \end{tabular}
+ \end{center}
+\end{frame}
+
+
+\begin{frame}{Rights}
+ \begin{itemize}
+ \item GNUnet e.V. shared copyrights of their AGPLv3+ licensed code with Taler Systems SA
+ \item Taler Systems SA holds copyrights to entire GNU Taler code base (AGPLv3+, GPLv3+,
+ dual-licensing exclusive domain of Taler Systems SA)
+ \item Taler Systems SA applied for patent on offline payment solution
+ \item Taler Systems SA holds trademark on ``Taler''.
+ \item FSF holds trademark on ``GNU'', we are authorized to use ``GNU Taler''.
+ \item Taler Systems SA owns {\tt taler.net} and {\tt taler-systems.com}.
+ \end{itemize}
+\end{frame}
+
+
+\begin{frame}{Summary of Taler Solution}
+
+\begin{enumerate}
+\item {\bf Frictionless one click}, cash-like digital payments \&
+instant
+confirmation for all fiat- and crypto-currencies and for all users,
+unbanked, young and old.
+\item With {\bf income-transparency on the recipient side} is
+crime-preventing \& Taler coins are as secure as cash without
+counterfeits. No ID theft.
+\item {\bf Guaranteed privacy} for spender \& data minimization: payment
+requires/shares no personal information.
+\item {\bf No bank account needed}.
+\item Highly efficient in power, processing \& storage, extremely low
+cost \& {\bf highly scalable}.
+\item Economically viable (sub-cent) instant {\bf micro-transactions} for
+e-commerce, Internet of Things, machine2machine, $\ldots$
+\end{enumerate}
+\end{frame}
+
+
+\begin{frame}{Do you have any questions?}
+ \framesubtitle{\url{https://taler.net/en/bibliography.html}}
+ \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{Martin Summer and Hannes Hermanky.
+ {\em A digital euro and the future of cash}.
+ {\bf Monetary Policy \& The Economy Q1-Q2/22}.}
+ \item{Antoine d’Aligny, Emmanuel Benoist, Florian Dold, Christian Grothoff, Özgür Kesim and Martin Schanzenbach.
+ {\em Who comes after us? The correct mindset for designing a Central Bank Digital Currency}.
+ {\bf SUERF Policy Notes 279/2022}.}
+ \item{Florian Dold.
+ {\em GNU Taler}.
+ {\bf University of Rennes 1, PhD Thesis, 2019}.}
+ \item{Christian Grothoff and Alex Pentland.
+ {\em Digital cash and privacy: What are the alternatives to Libra?}.
+ {\bf MIT Media Lab, 2019}.}
+ \item{Jeffrey Burdges, Florian Dold, Christian Grothoff and Marcello Stanisci.
+ {\em Enabling Secure Web Payments with GNU Taler}.
+ {\bf SPACE 2016}.}
+ \item{Özgür Kesim, Christian Grothoff, Florian Dold and Martin Schanzenbach.
+ {\em Zero-Knowledge Age Restriction for GNU Taler}.
+ {\bf ESORICS, 2022}.}
+ \item{Gian Demarmels and Lucien Heuzeveldt.
+ {\em Adding Schnorr's Blind Signature in Taler}.
+ {\bf BFH, Bachelor's Thesis, 2022}.}
+ \item{Marco Boss.
+ {\em GNU Taler Scalability}.
+ {\bf BFH, Bachelor's Thesis, 2022}.}
+\end{enumerate}
+}
+\end{frame}
+
+\end{document}
+
+\begin{frame}{Active collaborations}
+{\tiny
+ \begin{description}
+ \item {\bf Association EFREI}: \\ Offline payments
+ \item {\bf Technische Universit\"at Eindhoven:} \\ Post-quantum cryptogrpahy
+ \item {\bf Berner Fachhochschule:} \\ Snack machine \& blockchain integration \& scalability
+ \item {\bf Freie Universit\"at Berlin:} \\ Programmability \& embedded systems
+ \item {\bf Fraunhofer Gesellschaft}: \\ Identity management \& SSI \& wallet-to-wallet communication
+ \item {\bf The GNU Project}: \\ Integration into FLOSS software
+ \item {\bf Fiscaltrust GmbH}: \\ Point-of-sale integration ({\bf
+new})
+ \item {\bf Bank of International Settlements}: \\ Participation in Point Zero Forum 2023 ({\bf new})
+ \end{description}
+ }
+\end{frame}
+
+
+\begin{frame}{Launch Timeline}
+ \begin{description}
+ \item[2022] Internal deployment at BFH
+ \item[Q1'2023] Deployment using Bitcoin at BFH (running, but not yet announced)
+ \item[Q2-3'2023] Deployment of local currency Netzbon in Basel
+ \item[Q3'2023] Public deployment of eCHF stablecoin in Switzerland, cleared by FINMA
+ \item[2024] German bank executes ``new product process'' for launch in Eurozone ({\bf planned})
+ \item[2025] MagNet bank begins process for launch in Hungary ({\bf planned})
+ \end{description}
+\end{frame}
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