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+\setbeamertemplate{navigation symbols}{} +\usepackage{xcolor} +\usepackage{tikz,eurosym} +\usepackage[normalem]{ulem} +\usepackage{listings} + +% 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 + , + % body + , + % Paragraphs + , + % scripts + , , , , , + }, + ndkeywords={ + % General + =, + % HTML attributes + charset=, src=, id=, width=, height=, style=, type=, rel=, href=, + % SVG attributes + fill=, attributeName=, begin=, dur=, from=, to=, poster=, controls=, x=, y=, repeatCount=, xlink:href=, + % 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, + ndkeywords={class, export, boolean, throw, implements, import, this}, + ndkeywordstyle=\color{darkgray}\bfseries, + identifierstyle=\color{black}, + sensitive=false, + comment=[l]{//}, + morecomment=[s]{/*}{*/}, + commentstyle=\color{purple}\ttfamily, + stringstyle=\color{red}\ttfamily, + morestring=[b]', + morestring=[b]" +} + +\usetikzlibrary{shapes,arrows} +\usetikzlibrary{positioning} +\usetikzlibrary{calc} + +\title{GNU Taler} +%\subtitle{} + +\setbeamertemplate{navigation symbols}{\includegraphics[width=1cm]{inria.pdf} \includegraphics[width=0.5cm]{gnu.png} \includegraphics[width=0.5cm]{gnunet-logo-dark-text.png} \includegraphics[width=0.5cm]{ashoka.png} \includegraphics[width=4cm]{bfh.png} \hfill} +%\setbeamercovered{transparent=1} + +\author[C. Grothoff]{J. Burdges, F. Dold, {\bf C. Grothoff}, M. Stanisci} +\date{\today} +\institute{The GNU Project} + + +\begin{document} + +\justifying + + +\begin{frame}[plain] + \includegraphics[width=1.2\textwidth]{hungry_dude} +\end{frame} + + +\begin{frame}{The Bank's Problem} + + 3D secure (``verified by visa'') is a nightmare: + + \begin{minipage}{5cm} + \begin{itemize} + \item Complicated process + \item Shifts liability to consumer + \item Significant latency + \item Can refuse valid requests + \item Legal vendors excluded + \item No privacy for buyers + \end{itemize} + \end{minipage} + \begin{minipage}{5cm} + \includegraphics[width=\textwidth]{illustrations/cc3ds.pdf} + \end{minipage} + \vfill + Online credit card payments will be replaced, but with what? +\end{frame} + + +\begin{frame}{The Bank's Problem} +\vfill + \begin{textblock*}{12cm}(0.5cm,1cm) % {block width} (coords) + \begin{itemize} + \item Global tech companies push oligopolies + \item Privacy and federated finance are at risk +% \item 30\% fees are conceivable + \item Economic sovereingity is in danger + \end{itemize} +\end{textblock*} +\begin{textblock*}{4cm}(3.5cm,5.2cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/amazon.png}} +\end{textblock*} +\begin{textblock*}{2cm}(7cm,3cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/alipay.jpeg}} +\end{textblock*} +\begin{textblock*}{2cm}(3cm,3.5cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/paypal.jpeg}} +\end{textblock*} +\begin{textblock*}{2cm}(9cm,5cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/applepay.jpeg}} +\end{textblock*} +\begin{textblock*}{2cm}(7.5cm,5.9cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/samsungpay.jpeg}} +\end{textblock*} +\begin{textblock*}{1cm}(9.5cm,6.3cm) % {block width} (coords) + {\includegraphics[width=\textwidth]{../investors/competitor-logos/android_pay.png}} +\end{textblock*} +\vfill +\end{frame} + + +\begin{frame}{Predicting the Future} + \begin{itemize} + \item Google, Apple or Facebook's Libra will be your bank and run your payment system + \item They target advertising based on your purchase history, location and + your ability to pay + \item They will provide more usable, faster and broadly available + payment solutions; our federated banking system will be history +% just like SMTP is now Gmail. + \item After dominating the payment sector, they will start to charge fees + befitting their oligopoly size + \item Competitors and vendors not aligning with their corporate ``values'' + will be excluded by terms of service and go bankrupt +% \item The imperium will have another major tool for its financial warfare + \end{itemize} +\end{frame} + + +\begin{frame} + \begin{center} + \LARGE {\bf GNU} + + \vfill +% \includegraphics[width=0.66\textwidth]{logo-2017-fr.pdf} + \includegraphics[width=0.66\textwidth]{taler-logo-2018.pdf} + \end{center} + \vfill + \begin{center} + {\huge {\bf Digital} cash, made \textbf{socially responsible}.} + \end{center} + \vfill +\begin{textblock*}{4cm}(.5cm,7.5cm) % {block width} (coords) + {\Large {\bf \url{taler.net}} \\ + twitter@taler \\ + mail@taler.net } +\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{What is Taler?} +\begin{frame}{What is Taler?} + \vfill + \begin{center} +Taler is an electronic instant payment system. + \end{center} + \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. EUR, USD, CHF) + \end{itemize} + \vfill +\end{frame} + + +\begin{frame}{Design goals for the GNU Taler Payment System} +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} +\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}; + + \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}; + +\end{tikzpicture} +\end{center} +\end{frame} + + +\begin{frame}{Taler in Operation} + \centering + \includegraphics[width=\textwidth]{operations.png} +\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} + + +\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}[t]{Software} + \begin{figure} + \centering + \includegraphics[width=.9\textwidth]{software_stack} + \end{figure} +\end{frame} + + +\begin{frame}[c]{How to use at WCEF: Install App on Android\footnote{\url{https://wallet.taler.net/}}} + \begin{figure} + \includegraphics[width=0.9\textwidth]{download_wallet.png} + \end{figure} +\end{frame} + +\begin{frame}{How to use at WCEF: Get e-cash} + \begin{figure} + \includegraphics[width=0.9\textwidth]{get_taler_coins.png} + \end{figure} +\end{frame} + +\begin{frame}{How to use at WCEF: Get snacks} + \begin{figure} + \includegraphics[width=0.9\textwidth]{get_snacks.png} + \end{figure} +\end{frame} + +\begin{frame}[c]{How to use afterwards: Shop online\footnote{Operational until 31.1.2020}} +\vfill + \begin{center} + \url{https://buywith.taler.net/} + \end{center} +\vfill +\end{frame} + + +\begin{frame}{Use Case: Journalism} + Today: + \begin{itemize} + \item Corporate structure % ($\Rightarrow$ filter) + \item Advertising primary revenue % ($\Rightarrow$ dependence) + \item Tracking readers critical for business success + \item Journalism and marketing hard to distinguish + \end{itemize}\vfill\pause + With GNU Taler: + \begin{itemize} + \item One-click micropayments per article + \item Hosting requires no expertise % (no PCI DSS) + \item Reader-funded reporting separated from marketing + \item Readers can remain anonymous + \end{itemize} +\end{frame} + + +\begin{frame}{Use Case: Anti-Spam} + Today, p$\equiv$p provides authenticated encryption for e-mail: + \begin{itemize} + \item Free software + \item Easy to use opportunistic encryption + \item Available for Outlook, Android, Enigmail + \item Spies \& spam filters can no longer inspect content + \end{itemize}\vfill\pause + With GNU Taler: + \begin{itemize} + \item Peer-to-peer payments via e-mail + \item If unsolicited sender, hide messages from user \& + automatically request payment from sender + \item Sender can attach payment to be moved to inbox + \item Receiver may grant refund to sender + \end{itemize} +\end{frame} + + +\begin{frame} + \vfill + \begin{center} + {\bf Where might this get us exactly?} + \end{center} + \vfill +\end{frame} + + +\begin{frame}{Visions} + \begin{itemize} + \item Be paid to read advertising, starting with spam + \item Give welfare without intermediaries taking huge cuts +% \item Forster regional trade via regional currencies + \item Eliminate corruption by making all income visible + \item Stop the mining by making crypto-currencies useless for + anything but crime + \end{itemize} +\end{frame} + + +\section{Competitor analysis} +\begin{frame}{Competitor 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} + \vfill + \begin{center} + {\bf Technology} + \end{center} + \vfill +\end{frame} + + +\begin{frame}{How does it work?} +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}{Exchange setup: Create a denomination key (RSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Pick random primes $p,q$. + \item Compute $n := pq$, $\phi(n) = (p-1)(q-1)$ + \item Pick small $e < \phi(n)$ such that + $d := e^{-1} \mod \phi(n)$ exists. + \item Publish public key $(e,n)$. + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance=1em and 1em, inner sep=0em, outer sep=.3em]; + \node (origin) at (0,0) {\includegraphics[width=0.2\textwidth]{dice.pdf}}; + \node (primes) [draw=none, below = of origin] at (0,0) {$(p, q)$}; + \node (seal) [def, draw=none, below left=of primes]{\includegraphics[width=0.15\textwidth]{seal.pdf}}; + \node (hammer) [def, draw=none, below right=of primes]{\includegraphics[width=0.15\textwidth]{hammer.pdf}}; + + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (primes) -- (origin) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (seal) -- (primes) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (hammer) -- (primes) node [midway, above, sloped] (TextNode) {}; + \end{tikzpicture} +% \includegraphics[width=0.4\textwidth]{seal.pdf} + \end{minipage} +\end{frame} + + +\begin{frame}{Merchant: Create a signing key (EdDSA)} + \begin{minipage}{6cm} + \begin{itemize} + \item pick random $m \mod o$ as private key + \item $M = mG$ public key + \end{itemize} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 1em and 1em, inner sep=0em, outer sep=.3em]; + \node (origin) at (0,0) {\includegraphics[width=0.2\textwidth]{dice.pdf}}; + \node (m) [draw=none, below = of origin] at (0,0) {$m$}; + \node (seal) [draw=none, below=of m]{M}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (m) -- (origin) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (seal) -- (primes) node [midway, above, sloped] (TextNode) {}; + \end{tikzpicture} + \end{minipage} + \parbox[t]{3cm}{{\bf Capability:} $m \Rightarrow$ } + \raisebox{\dimexpr-\height+\baselineskip}{\includegraphics[width=0.1\textwidth]{merchant-sign.pdf}} +\end{frame} + + +\begin{frame}{Customer: Create a planchet (EdDSA)} + \begin{minipage}{8cm} + \begin{itemize} + \item Pick random $c \mod o$ private key + \item $C = cG$ public key + \end{itemize} + \end{minipage} + \begin{minipage}{4cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 1em and 1em, inner sep=0em, outer sep=.3em]; + \node (origin) at (0,0) {\includegraphics[width=0.2\textwidth]{dice.pdf}}; + \node (c) [draw=none, below = of origin] at (0,0) {$c$}; + \node (planchet) [draw=none, below=of c]{\includegraphics[width=0.4\textwidth]{planchet.pdf}}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (c) -- (origin) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (planchet) -- (c) node [midway, above, sloped] (TextNode) {}; + \end{tikzpicture} + \end{minipage} + \parbox[t]{3cm}{{\bf Capability:} $c \Rightarrow$ } + \raisebox{\dimexpr-\height+\baselineskip}{\includegraphics[width=0.1\textwidth]{planchet-sign.pdf}} +\end{frame} + + +\begin{frame}{Customer: Blind planchet (RSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Obtain public key $(e,n)$ + \item Compute $f := FDH(C)$, $f < n$. + \item Pick blinding factor $b \in \mathbb Z_n$ + \item Transmit $f' := f b^e \mod n$ + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 2em and 0.5em, inner sep=0em, outer sep=.3em]; + \node (origin) at (0,0) {\includegraphics[width=0.2\textwidth]{dice.pdf}}; + \node (b) [def, draw=none, below = of origin] at (0,-0.2) {$b$}; + \node (blinded) [def, draw=none, below right=of b]{\includegraphics[width=0.2\textwidth]{blinded.pdf}}; + \node (planchet) [def, draw=none, above right=of blinded]{\includegraphics[width=0.15\textwidth]{planchet.pdf}}; + \node (exchange) [node distance=4em and 0.5em, draw, below =of blinded]{Exchange}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (b) -- (origin) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (blinded) -- (planchet) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (blinded) -- (b) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (exchange) -- (blinded) node [midway, above, sloped] (TextNode) {{\small transmit}}; + \end{tikzpicture} + \end{minipage} +\end{frame} + + +\begin{frame}{Exchange: Blind sign (RSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Receive $f'$. + \item Compute $s' := f'^d \mod n$. + \item Send signature $s'$. + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 2em and 0.5em, inner sep=0em, outer sep=.3em]; + \node (hammer) [def, draw=none] at (0,0) {\includegraphics[width=0.15\textwidth]{hammer.pdf}}; + \node (signed) [def, draw=none, below left=of hammer]{\includegraphics[width=0.2\textwidth]{sign.pdf}}; + \node (blinded) [def, draw=none, above left=of signed]{\includegraphics[width=0.15\textwidth]{blinded.pdf}}; + \node (customer) [node distance=4em and 0.5em, draw, below =of signed]{Customer}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (signed) -- (hammer) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (signed) -- (blinded) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (customer) -- (signed) node [midway, above, sloped] (TextNode) {{\small transmit}}; + \end{tikzpicture} + \end{minipage} +\end{frame} + + +\begin{frame}{Customer: Unblind coin (RSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Receive $s'$. + \item Compute $s := s' b^{-1} \mod n$ % \\ + % ($(f')^d = (f b^e)^d = f^d b$). + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 2em and 0.5em, inner sep=0em, outer sep=.3em]; + \node (b) [def, draw=none] at (0,0) {$b$}; + \node (coin) [def, draw=none, below left=of b]{\includegraphics[width=0.2\textwidth]{coin.pdf}}; + \node (signed) [def, draw=none, above left=of coin]{\includegraphics[width=0.15\textwidth]{sign.pdf}}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (coin) -- (b) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (coin) -- (signed) node [midway, above, sloped] (TextNode) {}; + \end{tikzpicture} + \end{minipage} +\end{frame} + + +\begin{frame}{Customer: Build shopping cart} + \begin{center} + \begin{tikzpicture} + \tikzstyle{def} = [node distance= 1em and 1em, inner sep=0em, outer sep=.3em]; + \node (origin) at (0,0) {\includegraphics[width=0.2\textwidth]{shop.pdf}}; + \node (cart) [draw=none, below=of m]{\includegraphics[width=0.2\textwidth]{cart.pdf}}; + \node (merchant) [node distance=4em and 0.5em, draw, below =of cart]{Merchant}; + \tikzstyle{C} = [color=black, line width=1pt]; + \draw [<-, C] (cart) -- (origin) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (merchant) -- (cart) node [midway, above, sloped] (TextNode) {{\small transmit}}; + \end{tikzpicture} + \end{center} +\end{frame} + + +\begin{frame}{Merchant: Propose contract (EdDSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Complete proposal $D$. + \item Send $D$, $EdDSA_m(D)$ + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance=2em and 0.5em, inner sep=0em, outer sep=.3em]; + \node (cart) [def, draw=none] at (0,0) {\includegraphics[width=0.15\textwidth]{cart.pdf}}; + \node (proposal) [def, draw=none, below right=of cart]{\includegraphics[width=0.5\textwidth]{merchant_propose.pdf}}; + \node (customer) [node distance=4em and 0.5em, draw, below =of proposal]{Customer}; + \tikzstyle{C} = [color=black, line width=1pt]; + \node (sign) [def, draw=none, above right=of proposal] {$m$}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (proposal) -- (sign) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (proposal) -- (cart) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (customer) -- (proposal) node [midway, above, sloped] (TextNode) {{\small transmit}}; + \end{tikzpicture} + \end{minipage} +\end{frame} + + +\begin{frame}{Customer: Spend coin (EdDSA)} + \begin{minipage}{6cm} + \begin{enumerate} + \item Receive proposal $D$, $EdDSA_m(D)$. + \item Send $s$, $C$, $EdDSA_c(D)$ + \end{enumerate} + \end{minipage} + \begin{minipage}{6cm} + \begin{tikzpicture} + \tikzstyle{def} = [node distance=2em and 0.4em, inner sep=0em, outer sep=.3em]; + \node (proposal) [def, draw=none] at (0,0) {\includegraphics[width=0.15\textwidth]{merchant_propose.pdf}}; + \node (contract) [def, draw=none, below right=of cart]{\includegraphics[width=0.3\textwidth]{contract.pdf}}; + \node (c) [def, draw=none, above=of contract] {$c$}; + \node (merchant) [node distance=4em and 0.5em, draw, below=of contract]{Merchant}; + \node (coin) [def, draw=none, right=of contract]{\includegraphics[width=0.2\textwidth]{coin.pdf}}; + \tikzstyle{C} = [color=black, line width=1pt] + + \draw [<-, C] (contract) -- (c) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (contract) -- (proposal) node [midway, above, sloped] (TextNode) {}; + \draw [<-, C] (merchant) -- (contract) node [midway, above, sloped] (TextNode) {{\small transmit}}; + \draw [<-, C] (merchant) -- (coin) node [midway, below, sloped] (TextNode) {{\small transmit}}; + \end{tikzpicture} + \end{minipage} +\end{frame} + + +\begin{frame}{Merchant and Exchange: Verify coin (RSA)} + \begin{minipage}{6cm} + \begin{equation*} + s^e \stackrel{?}{\equiv} FDH(C) \mod n + \end{equation*} + \end{minipage} + \begin{minipage}{6cm} + \begin{minipage}{0.2\textwidth} + \includegraphics[width=\textwidth]{coin.pdf} + \end{minipage} + $\stackrel{?}{\Leftrightarrow}$ + \begin{minipage}{0.2\textwidth} + \includegraphics[width=\textwidth]{seal.pdf} + \end{minipage} + \end{minipage} +\end{frame} + + +\begin{frame}{Technology} +GNU Taler additionally offers: +\begin{itemize} +\item Giving change, can provide refunds +\item Integration with HTTP, handles network failures +\item High performance +\item Bounded losses on key compromise +\item Formal security proofs +\item ... +\end{itemize} +\begin{center} +\includegraphics[width=0.5\textwidth]{provable-security.png} +\end{center} +More information at \url{https://taler.net/}. +\end{frame} + + +\begin{frame}{Conclusion} + \begin{center} + {\bf What can we do?} + \end{center} + \vfill +\begin{itemize} + \item{Suffer mass-surveillance enabled by credit card oligopolies with high fees, and} + \item{Engage in arms race with deliberately unregulatable blockchains, and} + \item{Enjoy the ``benefits'' of cash \\ + \hfill \includegraphics[height=0.3\textheight]{atm-rupee.jpg} \hfill} +\end{itemize} +\vfill +\begin{center} + {\bf OR} +\end{center} +\vfill +\begin{itemize} + \item{Establish free software alternative balancing social goals!} +\end{itemize} +\vfill +\end{frame} + + +\begin{frame} +\frametitle{Do you have any questions?} +\vfill +References: +{\tiny + \begin{enumerate} + \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}{The Distraction: Bitcoin} + +\begin{itemize} +\item Unregulated payment system and currency: +\item[] $\Rightarrow$ lack of regulation is a feature! +\item Implemented in free software +\item Decentralised peer-to-peer system \pause +\item Decentralised banking requires solving Byzantine consensus +\item Creative solution: tie initial accumulation to solving consensus \pause +\item[] $\Rightarrow$ Proof-of-work advances ledger +\item[] $\Rightarrow$ Very expensive banking +\end{itemize} +\end{frame} + + +\begin{frame} + \frametitle{\includegraphics[height=0.5cm]{pics/bitcoin.jpeg}?} + \centering +\noindent +\includegraphics[width=\textwidth]{pics/btc-transaction-cost.png} + +Current average transaction value: $\approx$ 1000 USD +\end{frame} + + +\begin{frame} + \vfill + \begin{center} + {\bf What is there?} + \end{center} + \vfill +\end{frame} + + +\begin{frame}{Components} + \begin{itemize} + \item REST APIs, C APIs + \item Command-line, WebExtension (Firefox, Chrome, Chromium, Brave) and Android wallet + \item GLS bank integration (libeufin, WiP) + \item Escrow/backup solution (Anastasis, WiP) + \item Merchant backend \& backoffice (needs improvements) + \item WooCommerce plugin (needs update) + \item Taler-enabled vending machine (MDB) + \item Sample Web frontends + \end{itemize} +\end{frame} + + +\end{document} + + + + +\begin{frame}{Taler {\tt /withdraw/sign}} +% Customer withdrawing coins with blind signatures +% \bigskip + \begin{figure}[th] + \begin{minipage}[b]{0.45\linewidth} + \begin{center} + \begin{tikzpicture}[scale = 0.4, + transform shape, + msglabel/.style = { text = Black, yshift = .3cm, + sloped, midway }, + okmsg/.style = { ->, color = MidnightBlue, thick, + >=stealth }, + rstmsg/.style = { ->, color = BrickRed, thick, + >=stealth } + ] + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h1) at (-4, 0) {}; + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h2) at (4, 0) {}; + \node[above = 0cm of h1] {Wallet}; + \node[above = 0cm of h2] {Exchange}; + + \path[->, color = MidnightBlue, very thick, >=stealth] + (-5, 4.5) edge + node[rotate=90, text = Black, yshift = .3cm] {Time} + (-5, -4.5); + \path[okmsg, dashed] + ($(h1.east)+(0, 4.0)+(0, -1.0)$) edge + node[msglabel] {SEPA(RK,A)} + ($(h2.west)+(0, 3.5)+(0, -1.0)$); + \path[okmsg] + ($(h1.east)+(0, -1.0)$) edge + node[msglabel] {POST {\tt /withdraw/sign} $S_{RK}(DK, B_b(C))$} + ($(h2.west)+(0, -1.5)$); + \path[okmsg] + ($(h2.west)+(0, -2.0)$) edge + node[msglabel] {200 OK: $S_{DK}(B_b(C))$)} + ($(h1.east)+(0, -2.5)$); + \path[rstmsg] + ($(h2.west)+(0, -3.5)$) edge + node[msglabel] {402 PAYMENT REQUIRED: $S_{RK}(DK, B_b(C))$)} + ($(h1.east)+(0, -4)$); + \node at (5.3, 0) {}; + \end{tikzpicture} + \end{center} + Result: $\langle c, S_{DK}(C) \rangle$. + \end{minipage} + \hspace{0.5cm} + \begin{minipage}[b]{0.45\linewidth} + \tiny + \begin{description} + \item[$A$] Some amount, $A \ge A_{DK}$ + \item[$RK$] Reserve key + \item[$DK$] Denomination key + \item[$b$] Blinding factor + \item[$B_b()$] RSA-FDH blinding % DK supressed + \item[$C$] Coin public key $C := cG$ + \item[$S_{RK}()$] EdDSA signature + \item[$S_{DK}()$] RSA-FDH signature + \end{description} + \end{minipage} + \end{figure} +\end{frame} + + +\begin{frame}[t]{Taler {\tt /deposit}} +Merchant and exchange see only the public coin $\langle C, S_{DK}(C) \rangle$. +\bigskip + \begin{figure}[th] + \begin{minipage}[b]{0.45\linewidth} + \begin{center} + \begin{tikzpicture}[scale = 0.4, + transform shape, + msglabel/.style = { text = Black, yshift = .3cm, + sloped, midway }, + okmsg/.style = { ->, color = MidnightBlue, thick, + >=stealth }, + rstmsg/.style = { ->, color = BrickRed, thick, + >=stealth } + ] + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h1) at (-4, 0) {}; + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h2) at (4, 0) {}; + \node[above = 0cm of h1] {Merchant}; + \node[above = 0cm of h2] {Exchange}; + + \path[->, color = MidnightBlue, very thick, >=stealth] + (-5, 4.5) edge + node[rotate=90, text = Black, yshift = .3cm] {Time} + (-5, -4.5); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h1.east)+(0,3)$) edge + node[text = Black, yshift = .3cm, sloped] {POST {\tt /deposit} $S_{DK}(C), S_{c}(D)$} + ($(h2.west)+(0,2)$); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h2.west)+(0,0.5)$) edge + node[text = Black, yshift = .3cm, sloped] {200 OK: $S_{SK}(S_{c}(D))$} + ($(h1.east)+(0,-0.5)$); + \path[rstmsg] + ($(h2.west)+(0, -2.5)$) edge + node[msglabel] {409 CONFLICT: $S_{c}(D')$} + ($(h1.east)+(0, -3.5)$); + \node at (5.3, 0) {}; + \end{tikzpicture} + \end{center} + \end{minipage} + \hspace{0.5cm} + \begin{minipage}[b]{0.45\linewidth} + \tiny + \begin{description} + \item[$DK$] Denomination key + \item[$S_{DK}()$] RSA-FDH signature using $DK$ + \item[$c$] Private coin key, $C := cG$. + \item[$S_{C}()$] EdDSA signature using $c$ + \item[$D$] Deposit details + \item[$SK$] Exchange's signing key + \item[$S_{SK}()$] EdDSA signature using $SK$ + \item[$D'$] Conficting deposit details $D' \not= D$ + \end{description} + \end{minipage} + \end{figure} +\end{frame} + + +\begin{frame}{Taler {\tt /refresh/melt}} + \begin{figure}[th] + \begin{minipage}[b]{0.45\linewidth} + \begin{center} + \begin{tikzpicture}[scale = 0.4, + transform shape, + msglabel/.style = { text = Black, yshift = .3cm, + sloped, midway }, + okmsg/.style = { ->, color = MidnightBlue, thick, + >=stealth }, + rstmsg/.style = { ->, color = BrickRed, thick, + >=stealth } + ] + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h1) at (-4, 0) {}; + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h2) at (4, 0) {}; + \node[above = 0cm of h1] {Customer}; + \node[above = 0cm of h2] {Exchange}; + + \path[->, color = MidnightBlue, very thick, >=stealth] + (-5, 4.5) edge + node[rotate=90, text = Black, yshift = .3cm] {Time} + (-5, -4.5); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h1.east)+(0,3)$) edge + node[text = Black, yshift = .3cm, sloped] {POST {\tt /refresh/melt} $S_{DK}(C), S_c({\cal DK}, {\cal T},{\cal B})$} + ($(h2.west)+(0,2)$); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h2.west)+(0,0.5)$) edge + node[text = Black, yshift = .3cm, sloped] {200 OK: $S_{SK}(H({\cal T}, {\cal B}),\gamma)$} + ($(h1.east)+(0,-0.5)$); + \path[rstmsg] + ($(h2.west)+(0, -2.5)$) edge + node[msglabel] {409 CONFLICT: $S_{C}(X), \ldots$} + ($(h1.east)+(0, -3.5)$); + \node at (5.3, 0) {}; + \end{tikzpicture} + \end{center} + \end{minipage} + \hspace{0.5cm} + \begin{minipage}[b]{0.45\linewidth} + \tiny + \begin{description} + \item[$\kappa$] System-wide security parameter, usually 3. + \\ \smallskip + \item[$\cal DK$] $:= [DK^{(i)}]_i$ \\ List of denomination keys \\ + $D + \sum_i A_{DK^{(i)}} < A_{DK}$ + \item[$t_j$] Random scalar for $j<\kappa$ + \item[${\cal T}$] $:= [T_j]_\kappa$ where $T_j = t_j G$ + \item[$k_j$] $:= c T_j = t_j C$ is an ECDHE + \item[$b_j^{(i)}$] $:= KDF_b(k_j,i)$ % blinding factor + \item[$c_j^{(i)}$] $:= KDF_c(k_j,i)$ % coin secret keys + \item[$C_j^{(i)}$] $: = c_j^{(i)} G$ % new coin publics % keys + \item[${\cal B}$] $:= [H( \beta_j )]_\kappa$ where \\ + $\beta_j := \left[ B_{b_j^{(i)}}(C_j^{(i)}) \right]_i$ + \\ \smallskip + \item[$\gamma$] Random value in $[0,\kappa)$ +% \\ \smallskip +% \item[$X$] Deposit or refresh + \end{description} + \end{minipage} + \end{figure} +\end{frame} + + +\begin{frame}{Taler {\tt /refresh/reveal}} + \begin{figure}[th] + \begin{minipage}[b]{0.45\linewidth} + \begin{center} + \begin{tikzpicture}[scale = 0.4, + transform shape, + msglabel/.style = { text = Black, yshift = .3cm, + sloped, midway }, + okmsg/.style = { ->, color = MidnightBlue, thick, + >=stealth }, + rstmsg/.style = { ->, color = BrickRed, thick, + >=stealth } + ] + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h1) at (-4, 0) {}; + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h2) at (4, 0) {}; + \node[above = 0cm of h1] {Customer}; + \node[above = 0cm of h2] {Exchange}; + + \path[->, color = MidnightBlue, very thick, >=stealth] + (-5, 4.5) edge + node[rotate=90, text = Black, yshift = .3cm] {Time} + (-5, -4.5); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h1.east)+(0,3)$) edge + node[text = Black, yshift = .3cm, sloped] {POST {\tt /refresh/reveal} $H({\cal T}, {\cal B}), {\tilde{\cal T}}, \beta_\gamma$} + ($(h2.west)+(0,2)$); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h2.west)+(0,0.5)$) edge + node[text = Black, yshift = .3cm, sloped] {200 OK: $\cal S$} + ($(h1.east)+(0,-0.5)$); + \path[rstmsg] + ($(h2.west)+(0, -2.5)$) edge + node[msglabel] {400 BAD REQUEST: $Z$} + ($(h1.east)+(0, -3.5)$); + \node at (5.3, 0) {}; + \end{tikzpicture} + \end{center} + \end{minipage} + \hspace{0.5cm} + \begin{minipage}[b]{0.45\linewidth} + \tiny + \begin{description} + \item[$\cal DK$] $:= [DK^{(i)}]_i$ + \item[$t_j$] .. \\ \smallskip + + \item[$\tilde{\cal T}$] $:= [t_j | j \in \kappa, j \neq \gamma]$ \\ \smallskip + + \item[$k_\gamma$] $:= c T_\gamma = t_\gamma C$ + \item[$b_\gamma^{(i)}$] $:= KDF_b(k_\gamma,i)$ + \item[$c_\gamma^{(i)}$] $:= KDF_c(k_\gamma,i)$ + \item[$C_\gamma^{(i)}$] $: = c_\gamma^{(i)} G$ + + \item[$B_\gamma^{(i)}$] $:= B_{b_\gamma^{(i)}}(C_\gamma^{(i)})$ + \item[$\beta_\gamma$] $:= \big[ B_\gamma^{(i)} \big]_i$ + \item[$\cal S$] $:= \left[ S_{DK^{(i)}}( B_\gamma^{(i)} ) \right]_i$ \\ \smallskip + + \item[$Z$] Cut-and-choose missmatch information + \end{description} + \end{minipage} + \end{figure} +\end{frame} + + +\begin{frame}{Taler {\tt /refresh/link}} + \begin{figure}[th] + \begin{minipage}[b]{0.45\linewidth} + \begin{center} + \begin{tikzpicture}[scale = 0.4, + transform shape, + msglabel/.style = { text = Black, yshift = .3cm, + sloped, midway }, + okmsg/.style = { ->, color = MidnightBlue, thick, + >=stealth }, + rstmsg/.style = { ->, color = BrickRed, thick, + >=stealth } + ] + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h1) at (-4, 0) {}; + \node[draw = MidnightBlue, + fill = CornflowerBlue, + minimum width = .3cm, + minimum height = 10cm + ] (h2) at (4, 0) {}; + \node[above = 0cm of h1] {Customer}; + \node[above = 0cm of h2] {Exchagne}; + + \path[->, color = MidnightBlue, very thick, >=stealth] + (-5, 4.5) edge + node[rotate=90, text = Black, yshift = .3cm] {Time} + (-5, -4.5); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h1.east)+(0,3)$) edge + node[text = Black, yshift = .3cm, sloped] {POST {\tt /refresh/link} $C$} + ($(h2.west)+(0,2)$); + \path[->, color = MidnightBlue, thick, >=stealth] + ($(h2.west)+(0,0.5)$) edge + node[text = Black, yshift = .3cm, sloped] {200 OK: $T_\gamma$} + ($(h1.east)+(0,-0.5)$); + \path[rstmsg] + ($(h2.west)+(0, -2.5)$) edge + node[msglabel] {404 NOT FOUND} + ($(h1.east)+(0, -3.5)$); + \node at (5.3, 0) {}; + \end{tikzpicture} + \end{center} + \end{minipage} + \hspace{0.5cm} + \begin{minipage}[b]{0.45\linewidth} + \tiny + \begin{description} + \item[$C$] Old coind public key \\ \smallskip + \item[$T_\gamma$] Linkage data $\cal L$ at $\gamma$ + \end{description} + \end{minipage} + \end{figure} +\end{frame} + + +\begin{frame}{Operational security} + \begin{center} + \resizebox{\textwidth}{!}{ +\begin{tikzpicture}[ + font=\sffamily, + every matrix/.style={ampersand replacement=\&,column sep=2cm,row sep=2cm}, + source/.style={draw,thick,rounded corners,fill=green!20,inner sep=.3cm}, + process/.style={draw,thick,circle,fill=blue!20}, + sink/.style={source,fill=green!20}, + datastore/.style={draw,very thick,shape=datastore,inner sep=.3cm}, + dots/.style={gray,scale=2}, + to/.style={->,>=stealth',shorten >=1pt,semithick,font=\sffamily\footnotesize}, + every node/.style={align=center}] + + % Position the nodes using a matrix layout + \matrix{ + \node[source] (wallet) {Wallet}; + \& \node[process] (browser) {Browser}; + \& \node[process] (shop) {Web shop}; + \& \node[sink] (backend) {Taler backend}; \\ + }; + + % Draw the arrows between the nodes and label them. + \draw[to] (browser) to[bend right=50] node[midway,above] {(4) signed contract} + node[midway,below] {(signal)} (wallet); + \draw[to] (wallet) to[bend right=50] node[midway,above] {(signal)} + node[midway,below] {(5) signed coins} (browser); + \draw[<->] (browser) -- node[midway,above] {(3,6) custom} + node[midway,below] {(HTTPS)} (shop); + \draw[to] (shop) to[bend right=50] node[midway,above] {(HTTPS)} + node[midway,below] {(1) proposed contract / (7) signed coins} (backend); + \draw[to] (backend) to[bend right=50] node[midway,above] {(2) signed contract / (8) confirmation} + node[midway,below] {(HTTPS)} (shop); +\end{tikzpicture} +} +\end{center} +\end{frame} -- cgit v1.2.3