path: root/pres-brains22/presentation.tex

\documentclass[aspectratio=169]{beamer}
\usepackage{tikz}
\usepackage{ragged2e}

\apptocmd{\frame}{}{\justifying}{}

\usetikzlibrary{positioning,fit,patterns}

\title{Depolymerization}
\subtitle{Integrating GNU Taler with blockchain-based cryptocurrencies}
\author{ Antoine d'Aligny \and Emmanuel Benoist \and Christian Grothoff}
\institute{Bern University of Applied Sciences}
\date{\today}
\titlegraphic{\includegraphics[width=2.5cm]{../docs/media/taler.png}}


\begin{document}

\begin{frame}
    \titlepage
\end{frame}

\begin{frame}{GNU Taler}{Overview}
    \begin{tikzpicture}[remember picture,overlay]
        \node (N1)[above right=22mm and 56mm of current page.center]    {\includegraphics[width=18mm]{./google_play_GNU_Taler.jpg}};
        \node [below=-2mm of N1]{wallet.taler.net};
    \end{tikzpicture}
    \begin{columns}
        \column{0.5\textwidth}
        \begin{tikzpicture}[
                rect/.style={circle, draw=black},
                sym/.style={-stealth, shorten >= 2pt, shorten <= 2pt}
            ]
            % Taler payment system
            \node[rect](1) {Exchange};
            \node[rect,below left=1.5cm and 0.7cm of 1](2) {Customer};
            \node[rect,below right=1.5cm and 0.7cm of 1](3) {Merchant};

            \draw[sym] (1) -- node [midway, above, sloped] {\tiny Withdraw coins} (2);
            \draw[sym] (2) -- node [midway, above, sloped] {\tiny Spend coins} (3);
            \draw[sym] (3) -- node [midway, above, sloped] {\tiny Deposit coins} (1);

            % Settlement layer
            \node[left=2cm of 1](E1){};
            \node[right=2cm of 1](E2){};
            \draw[sym] (E1) -- node [midway, above] {\tiny Deposit money} (1);
            \draw[sym] (1) -- node [midway, above] {\tiny Withdraw money} (E2);

            % Auditor
            \node[above= of 1](A){Auditor};
            \draw[sym] (A) -- node [midway, right] {\tiny Verify} (1);

            % Separator
            \node[below=1mm of E1] (S1S) {};
            \node[below=1mm of E2] (S1E) {};
            \node[above=6mm of E1] (S2S) {};
            \node[above=6mm of E2] (S2E) {};

            \draw[dotted] (S1S) -- (S1E);
            \draw[dotted] (S2S) -- (S2E);

            \node[below right=-2mm and -1.5mm of S2S] {\tiny{\emph{Settlement Layer}}};
            \node[below right=-2mm and -1.5mm of S1S] {\tiny{\emph{Taler payment system}}};
        \end{tikzpicture}
        \column{0.47\paperwidth}
       
        
        \begin{block}{Taler payment system}
            \begin{itemize}
                \item Tokenization
                \item Blind signatures (privacy)
            \end{itemize}
        \end{block}
        \begin{block}{Settlement layer}
            \begin{itemize}
                \item Designed for fiat currencies
                \item  BTC and ETH ?
            \end{itemize}
        \end{block}
    \end{columns}
\end{frame}

\begin{frame}{GNU Taler}{Blockchain settlement layer}
    \begin{tikzpicture}[remember picture,overlay]
        \node (N1)[above right=22mm and 56mm of current page.center]    {\includegraphics[width=18mm]{./google_play_GNU_Taler.jpg}};
        \node [below=-2mm of N1]{wallet.taler.net};
    \end{tikzpicture}
    \begin{center}
        \begin{tikzpicture}[
            rect/.style={rectangle, draw=black, minimum width=30mm},
            sym/.style={stealth-stealth, shorten >= 2pt, shorten <= 2pt},
            block/.style={rectangle,draw=black,fill=black!10,minimum size=7mm},
        ]
    
        %% Architecture
        \node(Tt){Taler};
        \node[rect,below=0cm of Tt](Tc){Exchange};
        \node[rect,fit={(Tt) (Tc)}](T){};
    
        \node[rect,below=7mm of Tc](D) {\textbf{Depolymerization}};
    
        \node[rect,below=7mm of D](Bc){Node};
        \node[below=0cm of Bc](Bt){Blockchain};
        \node[rect,fit={(Bt) (Bc)}](B){};
    
        \draw[sym] (T) -- (D);
        \draw[sym] (D) -- (B);
    
        %% Blockchain
        \node[block,right=8mm of B] (1){};
        \node[block,right=4mm of 1] (2){};
        \node[block,right=4mm of 2] (3){};
        \node[block,right=4mm of 3] (4){};
        \node[block,right=4mm of 4] (5){};
        \node[block,right=4mm of 5] (6){};
        \draw[-stealth] (1) -- (2);
        \draw[-stealth] (2) -- (3);
        \draw[-stealth] (3) -- (4);
        \draw[-stealth] (4) -- (5);
        \draw[-stealth] (5) -- (6);
    
        \node[left=4mm of 1] (S){};
        \node[right=4mm of 6] (E){};
        \draw[-stealth] (S) -- (1);
        \draw[-stealth] (6) -- (E);
    
        %% Taler
        \node[block, below right=-7.5mm and 20.5mm of T] (off){Off-chain transactions};
        \node[above=-0.5mm of off] {\includegraphics[height=7mm]{../docs/media/taler.png}};
    
        %% Depolymerization
        \node[right=12mm of D] {\small{Credit}};
        \node[right=55mm of D] {\small{Debit}};
        \draw[dashed,-stealth] (1.north) |- (off.west);
        \draw[dashed,-stealth] (off.east) -| (6.north);
    
        %% Separation
        \draw[dotted] (-2.1,-1.3) -- (9,-1.3);
        \draw[dotted] (-2.1,-2.5) -- (9,-2.5);
    \end{tikzpicture}
    \end{center}
\end{frame}

\begin{frame}{Blockchain-based cryptocurrencies}
    \begin{columns}
        \column{0.4\textwidth}
        \begin{block}{\textbf{BTC} Bitcoin}
            \begin{itemize}
                \item Proof of Work
                \item new block every $\simeq$10 min
                \item $\simeq$4 txs per sec
            \end{itemize}
        \end{block}
        \column{0.4\textwidth}
        \begin{block}{\textbf{ETH} Ethereum}
            \begin{itemize}
                \item Proof of Stake
                \item new block every $\simeq$12 sec
                \item $\simeq$14 txs per sec
            \end{itemize}
        \end{block}
    \end{columns}
\end{frame}

\begin{frame}{Storing metadata}{Bitcoin}
    \begin{block}{Bitcoin - Debit}
        \begin{itemize}
            \item Transactions from code
            \item Only 32B + URI
            \item \textbf{OP\_RETURN}
        \end{itemize}
    \end{block}
    \begin{block}{Bitcoin - Credit}
        \begin{itemize}
            \item Transactions from common wallet software
            \item Only 32B
            \item \textbf{Fake Segwit Addresses}
        \end{itemize}
    \end{block}
\end{frame}

\begin{frame}{Storing metadata}{Ethereum}
    \begin{block}{Smart contract ?}
        \begin{itemize}
            \item Logs in smart contract is the recommended way {\tiny (ethereum.org)}
            \item Expensive (additional storage and execution fees)
            \item Avoidable attack surface (error prone)
        \end{itemize}
    \end{block}
    \begin{block}{Custom input format}
        Use input data in transactions, usually used to call smart contract, to
        store our metadata.
    \end{block}
\end{frame}

\begin{frame}{Chain reorganization}
    \begin{center}
        \begin{tikzpicture}[
                block/.style={rectangle,draw=black,fill=black!10,minimum size=7mm},
                nconf/.style={dotted,fill=none},
                replaced/.style={pattern=north east lines,draw=black!60,fill opacity=0.3},
                err/.style={draw=black!60!red,fill=black!60!red!10,dashed},
                ar/.style={-stealth}
            ]
            % Common
            \node[block](2){};
            \node[block,right=5mm of 2](3){};
            \draw[ar] (2) -- (3);

            % Current
            \node[block,replaced,right=5mm of 3](4){};
            \node[block,replaced,right=5mm of 4](5){$T$};
            \draw[ar] (3) -- (4);
            \draw[ar] (4) -- (5);
          

            % Fork
            \node[block,above=7mm of 4](4p){};
            \only<1>{
                \node[block,right=5mm of 4p](5p){};
            }
            \only<2>{
                \node[block,err,right=5mm of 4p](5p){$T'$};
            }
            \node[block,right=5mm of 5p](6p){};
            \node[block,nconf,right=5mm of 6p](7p){
                \only<1>{$T$}
            };
            \draw[ar] (3.east) -- (4p.west);
            \draw[ar] (4p) -- (5p);
            \draw[ar] (5p) -- (6p);
            \draw[ar] (6p) -- (7p);
            

            % Indication
            \node [right=5mm of 7p]{\emph{active}};
            \node [right=29mm of 5]{\emph{fork}};
        \end{tikzpicture}
    \end{center}
    \begin{center}
        \only<1>{Reorganization can remove transaction from the chain}
        \only<2>{A conflict can invalidate the transaction}
    \end{center}
\end{frame}

\begin{frame}{Stuck transactions}
    \begin{center}
        \begin{tikzpicture}[
            dot/.style={circle,fill,inner sep=1pt,}
        ]
        \node (I) {\includegraphics[width=\textwidth]{../docs/media/fee.png}};
        \node [below left=-2.5mm and -1.5cm of I] (Tx) {\small Tx};
        \node [dot,above=8.4mm of Tx](D) {};
        \draw [dotted,thick] (Tx) -- (D);
        \node [left=-4.5cm of Tx] (C) {\small conf};
        \node [dot,above=8.4mm of C](D1) {};
        \draw [dotted,thick] (C) -- (D1);
        \end{tikzpicture}
    \end{center}
    \begin{center}
        Stuck transactions caused by transaction fees being a market-based value
    \end{center}
\end{frame}

\begin{frame}{Incompatible amount}
    GNU Taler amount follow RFC 8905:  $2^{53}$ unit and 8 decimal digits
    \begin{block}{\textbf{BTC} Bitcoin}
        \begin{itemize}
            \item 1 satoshi = $10^{-8}$ BTC
            \item capped at 21 000 000 BTC
            \item Fit perfectly
        \end{itemize}
    \end{block}
    \begin{block}{\textbf{ETH} Ethereum}
        \begin{itemize}
            \item 1 wei = $10^{-18}$ ETH
            \item actually more than 120 580 000 without cap
            \item average fee: 21 000 * 14 = 294 000 Gwei or 0.000295 ETH
            \item truncated at $10^{-8}$ ETH it can still represent any amount you can send without losing money 
        \end{itemize}
    \end{block}
\end{frame}

\begin{frame}{Implementation} 
    Download a wallet from \url{wallet.taler.net} and add our experimental bitcoin exchange at \url{bitcoin.ice.bfh.ch}
    
    \center\includegraphics[width=10.4cm]{./electrum.jpg}
\end{frame}


\begin{frame}{Conclusion}
    Distributed Ledgers can be used as a settlement layer for GNU Taler
    with Depolymerizer.

    \begin{itemize}
        \item [$-$] Trust exchange operators or auditors
        \item [$+$] Fast and cheap
        \item [$+$] Realtime, ms latency
        \item [$+$] Linear scalability
        \item [$+$] Ecological
        \item [$+$] Privacy when it can, transparency when it must (avoid tax evasion and money laundering)
    \end{itemize}
\end{frame}

\end{document}