commit eb2b3ac0ad4ebd011a9913de01d74e2ed503b85f
parent 90064998da3fc9e82acc7352a55429bc45a58d7e
Author: Christian Grothoff <grothoff@gnunet.org>
Date: Thu, 18 May 2023 23:31:28 +0200
lug
Diffstat:
1 file changed, 770 insertions(+), 0 deletions(-)
diff --git a/presentations/comprehensive/lug.tex b/presentations/comprehensive/lug.tex
@@ -0,0 +1,770 @@
+\pdfminorversion=3
+\documentclass[fleqn,xcolor={usenames,dvipsnames},handout
+]{beamer}
+\usepackage{amsmath}
+\usepackage{multimedia}
+\usepackage[utf8]{inputenc}
+\usepackage{framed,color,ragged2e}
+\usepackage[absolute,overlay]{textpos}
+\definecolor{shadecolor}{rgb}{0.8,0.8,0.8}
+\usetheme{boxes}
+\setbeamertemplate{navigation symbols}{}
+\usepackage{xcolor}
+\usepackage[normalem]{ulem}
+\usepackage{listings}
+\usepackage{adjustbox}
+\usepackage{array}
+\usepackage{bbding}
+\usepackage{relsize}
+\usepackage{graphicx}
+\usepackage{pgf-umlsd}
+\usepackage{tikz,eurosym,calc}
+\usetikzlibrary{tikzmark}
+\usetikzlibrary{shapes,arrows,arrows.meta}
+\usetikzlibrary{positioning,fit,patterns}
+\usetikzlibrary{calc}
+
+% CSS
+\lstdefinelanguage{CSS}{
+ basicstyle=\ttfamily\scriptsize,
+ keywords={color,background-image:,margin,padding,font,weight,display,position,top,left,right,bottom,list,style,border,size,white,space,min,width, transition:, transform:, transition-property, transition-duration, transition-timing-function},
+ sensitive=true,
+ morecomment=[l]{//},
+ morecomment=[s]{/*}{*/},
+ morestring=[b]',
+ morestring=[b]",
+ alsoletter={:},
+ alsodigit={-}
+}
+
+% JavaScript
+\lstdefinelanguage{JavaScript}{
+ basicstyle=\ttfamily\scriptsize,
+ morekeywords={typeof, new, true, false, catch, function, return, null, catch, switch, var, if, in, while, do, else, case, break},
+ morecomment=[s]{/*}{*/},
+ morecomment=[l]//,
+ morestring=[b]",
+ morestring=[b]'
+}
+
+\lstdefinelanguage{HTML5}{
+ basicstyle=\ttfamily\scriptsize,
+ language=html,
+ sensitive=true,
+ alsoletter={<>=-},
+ morecomment=[s]{<!-}{-->},
+ tag=[s],
+ otherkeywords={
+ % General
+ >,
+ % Standard tags
+ <!DOCTYPE,
+ </html, <html, <head, <title, </title, <style, </style, <link, </head, <meta, />,
+ % body
+ </body, <body,
+ % Divs
+ </div, <div, </div>,
+ % Paragraphs
+ </p, <p, </p>,
+ % scripts
+ </script, <script,
+ % More tags...
+ <canvas, /canvas>, <svg, <rect, <animateTransform, </rect>, </svg>, <video, <source, <iframe, </iframe>, </video>, <image, </image>
+ },
+ ndkeywords={
+ % General
+ =,
+ % HTML attributes
+ charset=, src=, id=, width=, height=, style=, type=, rel=, href=,
+ % SVG attributes
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+ % CSS properties
+ margin:, padding:, background-image:, border:, top:, left:, position:, width:, height:,
+ % CSS3 properties
+ transform:, -moz-transform:, -webkit-transform:,
+ animation:, -webkit-animation:,
+ transition:, transition-duration:, transition-property:, transition-timing-function:,
+ }
+}
+
+\lstdefinelanguage{JavaScript}{
+ basicstyle=\ttfamily\scriptsize,
+ keywords={typeof, new, true, false, catch, function, return, null, catch, switch, var, if, in, while, do, else, case, break, for},
+ keywordstyle=\color{blue}\bfseries,
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+ identifierstyle=\color{black},
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+ morecomment=[s]{/*}{*/},
+ commentstyle=\color{purple}\ttfamily,
+ stringstyle=\color{red}\ttfamily,
+ morestring=[b]',
+ morestring=[b]"
+}
+
+\def\checkmark{\tikz\fill[scale=0.4](0,.35) -- (.25,0) -- (1,.7) -- (.25,.15) -- cycle;}
+
+
+\setbeamersize{description width=1em}
+
+\definecolor{blue}{rgb}{0,0,0.7}
+\newcommand{\orange}[1]{{\color{orange}#1}}
+\newcommand{\blue}[1]{{\color{blue}#1}}
+\newcommand{\red}[1]{{\color{red}#1}}
+\newcommand{\Guardian}{\mathcal{G}}
+\newcommand{\Child}{\mathcal{C}}
+\newcommand{\Customer}{\mathcal{C}}
+\newcommand{\Merchant}{\mathcal{M}}
+\newcommand{\Exchange}{\mathcal{E}}
+
+\newcommand{\Commit}{\mathsf{Commit}}
+\newcommand{\Attest}{\mathsf{Attest}}
+\newcommand{\Verify}{\mathsf{Verify}}
+\newcommand{\Derive}{\mathsf{Derive}}
+\newcommand{\DeriveCompare}{\mathsf{DeriveCompare_\kappa}}
+\newcommand{\Compare}{\mathsf{Compare}}
+\newcommand{\AgeVer}{\mathsf{AgeVer}}
+
+\newcommand{\HashF}{\mathsf{H}}
+\newcommand{\Hash}{\mathsf{H}}
+\newcommand{\Block}{\mathbb{B}}
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+\newcommand{\Sign}{\mathsf{Sig}}
+\newcommand{\Ver}{\mathsf{Ver}}
+\newcommand{\Encoding}{\mathsf{Encoding}}
+\newcommand{\ECDSA}{\mathsf{ECDSA}}
+\newcommand{\Null}{\mathcal{O}}
+\newcommand{\EC}{\mathrm{ec}}
+\newcommand{\Curve}{\mathsf{Curve25519}}
+\newcommand{\SHA}{\mathsf{SHA256}}
+\newcommand{\SHAF}{\mathsf{SHA252}}
+\newcommand{\FDH}{\mathsf{FDH}}
+
+\newcommand{\negl}{\epsilon}
+
+\newcommand{\rand}{\mathsf{rand}}
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+\newcommand{\pruf}{\mathsf{P}}
+\newcommand{\Vcommitment}{\vec{\mathsf{Q}}}
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+\newcommand{\blinding}{\beta}
+
+\newcommand{\ZN}{\mathbb{Z}_N}
+\newcommand{\Z}{\mathbb{Z}}
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+\newcommand{\F}{\mathbb{F}}
+\newcommand{\seck}{\mathsf{s}}
+\newcommand{\pubk}{\mathsf{P}}
+\renewcommand{\H}{\mathbb{H}}
+\newcommand{\K}{\mathbb{K}}
+\newcommand{\Proofs}{\mathbb{P}}
+\newcommand{\Commitments}{\mathbb{O}}
+\newcommand{\Attests}{\mathbb{T}}
+\newcommand{\Blindings}{\mathbb{B}}
+\newcommand{\Nil}{\perp}
+
+\newcommand{\p}{\mathsf{p}}
+\newcommand{\com}{\mathsf{com}}
+\newcommand{\prf}{\mathsf{prf}}
+
+\newcommand{\Adv}{\mathcal{A}}
+\newcommand{\PPT}{\mathfrak{A}}
+\newcommand{\Probability}{\mathrm{Pr}}
+\newcommand{\Algorithm}{f}
+\renewcommand{\Game}[1]{G_\Adv^\mathsf{#1}}
+
+\DeclareMathOperator{\Image}{Im}
+\DeclareMathOperator{\Mod}{mod}
+
+\newcommand{\Encode}[1]{\overbracket[0.5pt][2pt]{\,#1\,}}
+\newcommand{\Decode}[1]{\underbracket[0.5pt][3pt]{\,#1\,}}
+\newcommand{\FDHg}[1]{[#1]_g\,}
+\newcommand{\logg}{{\breve{g}}}
+
+
+\newcommand{\drawfrom}{\xleftarrow{\$}}
+\newcommand\Exists{%
+ \mathop{\lower0.75ex\hbox{\ensuremath{%
+ \mathlarger{\mathlarger{\mathlarger{\mathlarger{\exists}}}}}}}%
+ \limits}
+
+\newcommand\Forall{%
+ \mathop{\lower0.75ex\hbox{\ensuremath{%
+ \mathlarger{\mathlarger{\mathlarger{\mathlarger{\forall}}}}}}}%
+ \limits}
+
+
+\title{GNU Taler}
+%\subtitle{}
+
+\setbeamertemplate{navigation symbols}{\includegraphics[width=1cm]{inria.pdf} \includegraphics[width=1cm]{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}
+
+% Page numbers
+\addtobeamertemplate{navigation symbols}{}{%
+ \usebeamerfont{footline}%
+ \usebeamercolor[fg]{footline}%
+ \hspace{1em}%
+ \insertframenumber
+}
+
+\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}{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}
+
+
+\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}
+
+
+\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}{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}
+
