commit a5767d94f785e27cce6d9f450997fe6c8d3ed883
parent 6676e056f5fee77e183fc58bc4a0e94a94b0f370
Author: Antoine A <>
Date: Sun, 11 Dec 2022 18:34:16 +0100
Merge branch 'master' of git+ssh://git.taler.net/depolymerization
Diffstat:
2 files changed, 305 insertions(+), 0 deletions(-)
diff --git a/pres-brains22/electrum.jpg b/pres-brains22/electrum.jpg
Binary files differ.
diff --git a/pres-brains22/presentation.tex b/pres-brains22/presentation.tex
@@ -0,0 +1,305 @@
+\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}
