marketing

2023-bdf.tex (34654B)

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 \title{GNU Taler}
 %\subtitle{}
 
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 \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, 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}