Binary file handouts/ho08.pdf has changed

--- a/handouts/ho08.tex	Wed Nov 11 01:26:19 2015 +0000
+++ b/handouts/ho08.tex	Thu Nov 12 08:25:22 2015 +0000
@@ -47,16 +47,16 @@
 \noindent is signed by Satoshi Nakamoto, which however is
 likely only a pen name. There is a lot of speculation who
 could be the inventor, or inventors, but we simply do not
-know. This part of Bitcoins is definitely anonymous so far. The paper
-above is from the end of 2008; the first Bitcoin transaction
-was made in January 2009. The rules in Bitcoin are set up so
-that there will only ever be 21 Million Bitcoins with the
-maximum reached around the year 2140. Currently there are
-already 11 Million Bitcoins in `existence'. Contrast this with
-traditional fiat currencies where money can be printed almost
-at will. The smallest unit of a Bitcoin is called a Satoshi,
-which is the $10^{-8}$th part of a Bitcoin. Remember a Penny
-is the $10^{-2}$th part of a Pound.
+know. This part of Bitcoins is definitely anonymous so far.
+The paper above is from the end of 2008; the first Bitcoin
+transaction was made in January 2009. The rules in Bitcoin are
+set up so that there will only ever be 21 Million Bitcoins
+with the maximum reached around the year 2140. Currently there
+are already 11 Million Bitcoins in `existence'. Contrast this
+with traditional fiat currencies where money can be printed
+almost at will. The smallest unit of a Bitcoin is called a
+Satoshi, which is the $10^{-8}$th part of a Bitcoin. Remember
+a Penny is the $10^{-2}$th part of a Pound.
 
 The two main cryptographic building blocks of Bitcoins are
 cryptographic hashing functions (SHA-256) and public-private
@@ -674,6 +674,9 @@
 night with their Bitcoin mining. If you want to read the
 complete story, google for ``My \$2375 Amazon EC2 Mistake''.
 
+\subsubsection*{Multi-Signature Transactions}
+
+To be explained.
 
 \subsubsection*{Anonymity with Bitcoins}
 

Binary file slides/slides08.pdf has changed

--- a/slides/slides08.tex	Wed Nov 11 01:26:19 2015 +0000
+++ b/slides/slides08.tex	Thu Nov 12 08:25:22 2015 +0000
@@ -61,6 +61,59 @@
 %\end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[t]
+\frametitle{Last Week's Survey}
+
+{\bf About Bitcoins:}
+
+\begin{textblock}{2.5}(11.5,10)
+\begin{bubble}[2.5cm]
+\it anonymous? 
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{5}(3.5,4)
+\begin{bubble}[5cm]
+\it cannot be controlled by the government?
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{4}(2,9)
+\begin{bubble}[4cm]
+\it untracable spending of money?
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{5.7}(3,13)
+\begin{bubble}[5.7cm]
+\it it takes 0..10 mins to pay with Bitcoins
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{5.6}(8,7)
+\begin{bubble}[5.6cm]
+\it Should one mine for Bitcoins?
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{2}(12,12.5)
+\begin{bubble}[2cm]
+\it mined by GPUs
+\end{bubble}
+\end{textblock}
+
+\begin{textblock}{3.6}(10,2.3)
+\begin{bubble}[3.6cm]
+\it can be lost or stolen
+\end{bubble}
+\end{textblock}
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
+
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
 \frametitle{Bitcoins from 10,000m}
@@ -71,7 +124,7 @@
   (max 21 Mio bitcoins---deflationary currency) 
 \item mined by solving special puzzles involving hashes
 \item transaction history (ledger/blockchain) is P2P distributed (12 GB)
-\item two ``mining pools'' produce\\ currently more than 50\% 
+\item three ``mining pools'' produce\\ currently more than 50\% 
   of bitcoins 
 \item can be stolen and also lost
 \item anonymous?\pause
@@ -140,7 +193,6 @@
 \begin{itemize}
 \item no-one else could have created that message
 \item Alice cannot deny the ``intend'' of sending Bob money\pause\bigskip
-\item forgery possible only after Alice created the string
 \item Q: What is money?\\ 
   A: Well a string like above
   (or later messages like that)
@@ -161,7 +213,7 @@
 
 \begin{itemize}
 \item Alice could keep sending Bob this message over and over
-      again (did she mean to send 10 ICs?)\pause
+      again (did she mean to send 10 ICs?)\bigskip\pause
 \item we need to have a serial number
 \begin{center}
 \bl{$\{\text{I, Alice, am giving Bob infocoin \#1234567.}\}_{K^{priv}_{Alice}}$}
@@ -178,14 +230,14 @@
 \begin{frame}[c]
 \frametitle{No Banks Please}
 
-With banks we could implement:
+With banks we could implement:\medskip
 
 \begin{itemize}
 \item Bob asks the bank whether the infocoin with that serial
       number belongs to Alice and
 \item Alice hasn’t already spent this infocoin.\bigskip 
 \item If yes, then Bob tells the bank he accepts the infocoin.
-\item The bank updates the records to show that the infocoin
+\item The bank updates the records (ledger) to show that the infocoin
       with that serial number is now in Bob’s possession and
       no longer belongs to Alice.
 \end{itemize}
@@ -262,7 +314,7 @@
 register)?\\[-10mm]\mbox{}\pause
 
 \begin{center}
-\hspace{15mm}\includegraphics[scale=0.35]{../pics/bitcoindisagreement.png}
+\hspace{15mm}\includegraphics[scale=0.31]{../pics/bitcoindisagreement.png}
 \end{center}
 
 \end{frame}
@@ -519,6 +571,7 @@
 \footnotesize
 BTCC, the largest mining pool, has limited its members to 
 not solve more than 6 blocks in a row.
+\hfill\url{https://blockchain.info/pools}
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
@@ -536,12 +589,65 @@
 this address
 
 \item there are $2^{160}$ possibilities\\ 
-(no check for duplicates)
+(no check for duplicates)\bigskip\pause
+
+\item transactions contain ``payment scripts''
+ (non-Turing-complete scripting language)\bigskip
+ 
+ \small simplest script: pay-to-public-key
 \end{itemize}
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[t]
+\frametitle{Multi-Signature Addresses}
+
+\begin{itemize}
+\item \ldots Bitcoin Improvement Proposal\bigskip\pause
+\item pay-to-public-key (explained so far)
+\item pay-to-script-hash (since 2012)\bigskip\pause
+
+can specify: requires \bl{M} out of \bl{N} signatures\medskip
+
+{\small for example\\
+1-of-2: me and my wife, or\\
+2-of-2 in banking/companies}
+
+\end{itemize}
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[t]
+\frametitle{Dispute Mediation}
+
+\begin{itemize}
+\item say, client and (online) merchant do not trust 
+  each other\bigskip\pause
+
+\item 2-of-3: mutually trusted escrow service
+  \begin{enumerate}
+  \item client sends money to 2-of-3 transaction
+  \item merchant sends out goods
+  \item if goods are OK, client sends signed transaction
+    to merchant, merchant can sign and receive the money
+    (publish in blockchain)
+  \item if goods are defective, merchant sends signed transaction
+    to client, client can sign and receive the money back
+  \item if client and merchant disagree, then they ask escrow
+  servive who signs a transaction and sends it to ``winning''
+  party 
+ \end{enumerate}
+\end{itemize}
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
 \frametitle{A Transaction Msg}
@@ -672,7 +778,7 @@
 how money was transferred from which address to
 which address; maybe not ideal for money laundering}
 \only<2>{
-You should use a new pp-pair for \alert{every} transaction;
+You should use a new PKI-pair for \alert{every} transaction;
 but few do (merchants). A design flaw(?): combining transactions.}
 
 \end{frame}
@@ -697,6 +803,28 @@
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+\begin{frame}[t]
+\frametitle{Other Cryto-Currencies}
+
+Coloured Coins:
+
+\begin{itemize}
+  \item record a 1 bitcoin transfer, say, and give it a
+        ``colour'' 
+        
+  \item the transaction stands for a share in ``Foo Inc, UK''.
+  
+    
+  \item only makes sense if the share is much more
+  valueable than just 1 Bc.          
+\end{itemize} 
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
 \frametitle{Bitcoin vs Gov}