BRAINS2022 presentation update

1 files changed, 58 insertions, 209 deletions

diff --git a/pres-brains22/presentation.tex b/pres-brains22/presentation.tex
index 72050a1..9ad6d6a 100644
--- a/pres-brains22/presentation.tex
+++ b/pres-brains22/presentation.tex
@@ -9,7 +9,7 @@
 
 \title{Depolymerization}
 \subtitle{Integrating GNU Taler with blockchain-based cryptocurrencies}
-\author{Antoine d'Aligny}
+\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}}
@@ -134,106 +134,59 @@
     \end{center}
 \end{frame}
 
-\begin{frame}{Blockchain-based cryptocurrencies}{What is a blockchain?}
-    \begin{center}
-        \begin{tikzpicture}[
-                block/.style={rectangle,draw=black,fill=black!10,minimum size=7mm},
-                ar/.style={-stealth},
-                nconf/.style={dotted},
-            ]
-            \node[block](1){};
-            \node[block,right=5mm of 1](2){$T_0$};
-            \node[block,right=5mm of 2](3){};
-            \node[block,right=5mm of 3](4){$T_1$};
-            \node[block,right=5mm of 4](5){};
-            \node[block,right=5mm of 5](6){};
-            \node[block,nconf,right=5mm of 6](7){$T_2$};
-            \draw[ar] (1) -- (2);
-            \draw[ar] (2) -- (3);
-            \draw[ar] (3) -- (4);
-            \draw[ar] (4) -- (5);
-            \draw[ar] (5) -- (6);
-            \draw[ar] (6) -- (7);
-        \end{tikzpicture}
-    \end{center}
-    \begin{center}
-    Append-only database composed of a list of linked blocks
-    \end{center}
-\end{frame}
-
-\begin{frame}{Blockchain-based cryptocurrencies}{Distributed Ledger}
-    \begin{center}
-        \begin{tikzpicture}[
-                block/.style={rectangle,draw=black,fill=black!10,minimum size=7mm},
-                ar/.style={-stealth},
-                pink/.style={draw=teal, fill=teal!10},
-                tan/.style={draw=orange, fill=orange!10},
-                blue/.style={draw=magenta, fill=magenta!10},
-                node/.style={circle, minimum size=7mm},
-            ]
-            % Common
-            \node[block](2){};
-            \node[block,right=5mm of 2](3){};
-            \node[block,pink,right=5mm of 3](4){};
-            \draw[ar] (2) -- (3);
-            \draw[ar] (3) -- (4);
-
-            % Center
-            \node[block,pink,right=5mm of 4](5){B};
-            \draw[ar] (4) -- (5);
-            
-            % Top
-            \node[block,blue,above=7mm of 5](5t){A};
-            \draw[ar] (4.east) -- (5t.west);
-
-            % Bottom
-            \node[block,tan,below=7mm of 4](4b){};
-            \node[block,tan,below=7mm of 5](5b){C};
-            \draw[ar] (3.east) -- (4b.west);
-            \draw[ar] (4b) -- (5b);
-
-            % Network
-            \node[node,blue,above left=0.1cm and 2cm of 2](A) {A};
-            \node[node,pink,below left=1cm and 0.45cm of A](B) {B};
-            \node[node,tan,below right=1cm and 0.45cm of A](C) {C};
-            \draw (A) -- (B);
-            \draw (B) -- (C);
-            \draw (C) -- (A);
-        \end{tikzpicture}
-        \begin{center}
-            Peer-to-peer network of nodes reaching consensus
-        \end{center}
-    \end{center}
-\end{frame}
-
-\begin{frame}{Blockchain-based cryptocurrencies}{Consensus protocol}
-    \begin{itemize}
-        \item Enforce a delay between blocks
-        \item Require coordinated effort to create new block
-        \item The longest chain is the consensus 
-    \end{itemize}
+\begin{frame}{Blockchain-based cryptocurrencies}
     \begin{columns}
         \column{0.4\paperwidth}
         \begin{block}{\textbf{BTC} Bitcoin}
             \begin{itemize}
                 \item Proof of Work
-                \item new block every 10 min
-                \item 4 txs per sec
+                \item new block every $\simeq$10 min
+                \item $\simeq$4 txs per sec
             \end{itemize}
         \end{block}
         \column{0.4\paperwidth}
         \begin{block}{\textbf{ETH} Ethereum}
             \begin{itemize}
                 \item Proof of Stake
-                \item new block every 12 sec
-                \item 14 txs per sec
+                \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 - Credit}
+        \begin{itemize}
+            \item Transactions from code
+            \item Only 32B + URI
+            \item \textbf{OP\_RETURN}
+        \end{itemize}
+    \end{block}
+    \begin{block}{Bitcoin - Debit}
+        \begin{itemize}
+            \item Transactions from common wallet software
+            \item Only 32B
+            \item \textbf{Fake Segwit Addresses}
+        \end{itemize}
+    \end{block}
+\end{frame}
 
-\begin{frame}{Distributed Ledger limitations}{Chain reorganization}
+\begin{frame}{Storing metadata}{Ethereum}
+    \begin{block}{Smart contract ?}
+        \begin{itemize}
+            \item Logs in smart contract is the recommend 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},
@@ -248,137 +201,42 @@
             \draw[ar] (2) -- (3);
 
             % Current
-            \only<-2>{
-                \node[block,right=5mm of 3](4){};
-                \node[block,right=5mm of 4](5){$T$};
-                \node[block,nconf,right=5mm of 5](6){};
-                \draw[ar] (5) -- (6);
-            }
-            \only<3->{
-                \node[block,replaced,right=5mm of 3](4){};
-                \node[block,replaced,right=5mm of 4](5){$T$};
-            }
+            \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);
           
 
-            \only<2->{
-                % Fork
-                \node[block,above=7mm of 4](4p){};
-                \only<-3>{
-                    \node[block,right=5mm of 4p](5p){};
-                }
-                \only<4->{
-                    \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<3>{$T$}
-                };
-                \draw[ar] (3.east) -- (4p.west);
-                \draw[ar] (4p) -- (5p);
-                \draw[ar] (5p) -- (6p);
-                \draw[ar] (6p) -- (7p);
-            }
-
-            % Indication
-            \only<2->{
-                \node [right=2mm of 7p]{\emph{
-                    \only<2>{
-                        new
-                    }
-                    \only<3->{
-                        active
-                    }
-                }};
-            }
-            \node [right=14mm of 6]{\emph{
-                \only<-2>{
-                    active
-                }
-                \only<3->{
-                    fork
-                }
-            }};
-        \end{tikzpicture}
-    \end{center}
-    \begin{center}
-        \only<1>{
-            We have a chain with an important transaction
-        }
-        \only<2>{
-            We may discover a new longer chain
-        }
-        \only<3>{
-            The important transaction is now pending
-        }
-        \only<4>{
-            A conflict can invalidate the transaction
-        }
-    \end{center}
-\end{frame}
-
-\begin{frame}{Distributed Ledger limitations}{Confirmation delay}
-    \begin{center}
-        \begin{tikzpicture}[
-                block/.style={rectangle,draw=black,fill=black!10,minimum size=7mm},
-                conf/.style={draw=black!60!green,fill=black!60!green!10},
-                nconf/.style={dotted},
-                err/.style={draw=black!60!red,fill=black!60!red!10},
-                ar/.style={-stealth}
-            ]
-            % Common
-            \node[block,conf](2){};
-            \node[block,conf,right=5mm of 2](3){$T_0$};
-            \draw[ar] (2) -- (3);
-
-            % Current
-            \only<1>{
-                \node [block,nconf,right=5mm of 3](4){};
-            }
-            \only<2->{
-                \node [block,conf,right=5mm of 3](4){\only<3>{$T_3$}};
-            }
-            \node[block,nconf,right=5mm of 4](5){};
-            \node[block,nconf,right=5mm of 5](6){$T_1$};
-            \draw[ar] (3) -- (4);
-            \draw[ar] (4) -- (5);
-            \draw[ar] (5) -- (6);
-
             % Fork
-            \only<-2>{
-                \node [block,nconf,above=7mm of 4](4p){};
+            \node[block,above=7mm of 4](4p){};
+            \only<1>{
+                \node[block,right=5mm of 4p](5p){};
             }
-            \only<3>{
-                \node [block,dashed,err,above=7mm of 4](4p){$T_3'$};
+            \only<2>{
+                \node[block,err,right=5mm of 4p](5p){$T'$};
             }
-            \node[block,nconf,right=5mm of 4p](5p){$T_2$};
-            \node[block,nconf,right=5mm of 5p](6p){};
-            \node[block,nconf,right=5mm of 6p](7p){};
+            \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{new}};
-            \node [right=17mm of 6]{\emph{active}};
+            \node [right=5mm of 7p]{\emph{active}};
+            \node [right=29mm of 5]{\emph{fork}};
         \end{tikzpicture}
     \end{center}
     \begin{center}
-        \only<1>{Confirmation delay}
-        \only<2>{Handling harmless reorganizations}
-        \only<3>{Handling harmful reorganizations}
+        \only<1>{Reorganization can remove transaction from the chain}
+        \only<2>{A conflict can invalidate the transaction}
     \end{center}
 \end{frame}
 
-\begin{frame}{Distributed Ledger limitations}{Stuck transactions}
-    \begin{block}{Transaction fees}
-        \begin{itemize}
-            \item Block production incentive
-            \item Variable by design
-        \end{itemize}
-    \end{block}
+\begin{frame}{Stuck transactions}
     \begin{center}
         \begin{tikzpicture}[
             dot/.style={circle,fill,inner sep=1pt,}
@@ -411,7 +269,7 @@
             \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 contain any amount you can send without losing money 
+            \item truncated at $10^{-8}$ ETH it can still represent any amount you can send without losing money 
         \end{itemize}
     \end{block}
 \end{frame}
@@ -431,18 +289,9 @@
     \end{itemize}
 \end{frame}
 
-\begin{frame}{Conclusion}{Future work}
-    \begin{itemize}
-        \item  Wallet-to-wallet payments are WIP
-        \item  Legal concerns around known-your-customer with cryptocurrencies
-    \end{itemize}
-
-    \begin{block}{Availability}
-    An experimental public Depolymerization exchange is available at
-    \url{https://bitcoin.ice.bfh.ch/}. To use the service, one only needs
-    to install a GNU Taler wallet from \url{https://wallet.taler.net/} and
-    instruct it to use this exchange to withdraw coins.
-    \end{block}
+\begin{frame}{Conclusion}{Demo}
+    An experimental public Depolymerization exchange is available at \url{https://bitcoin.ice.bfh.ch/}. You can try it by installing a GNU Taler wallet from \url{https://wallet.taler.net/} and instruct it to use this exchange to withdraw coins.
+    % Replace with demo
 \end{frame}
 
 \end{document}