
diff -r 85521d542da4 -r 17cd7fdee7c8 slides/slides08.tex
--- a/slides/slides08.tex	Sat Oct 28 00:05:02 2017 +0100
+++ b/slides/slides08.tex	Mon Nov 06 10:40:23 2017 +0000
@@ -7,7 +7,7 @@
 \usetikzlibrary{shapes}
 
 % beamer stuff 
-\renewcommand{\slidecaption}{SEN 08, King's College London}
+\renewcommand{\slidecaption}{SEN 06, King's College London}
 \newcommand{\bl}[1]{\textcolor{blue}{#1}}
 
 \newcommand{\DOWNarrow}[3]{%
@@ -34,7 +34,7 @@
 \frametitle{%
   \begin{tabular}{@ {}c@ {}}
   \\
-  \LARGE Security Engineering (8)\\[-3mm] 
+  \LARGE Security Engineering (6)\\[-3mm] 
   \end{tabular}}\bigskip\bigskip\bigskip
 
   \normalsize
@@ -49,67 +49,17 @@
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
 
-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-% student prticipation
-%\begin{frame}
-%\frametitle{Bitcoins}
-%
-%P2P, 21 Mio, $10^-8$, Mt~Gox, value decreased?, anonymity, 
-%Silk Road, verification incentive, puzzle, SHA-256, slow 
-%transactions, 
-%
-%\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 bitcoins cannot get lost,
-  all transactions are recorded
-\end{bubble}
-\end{textblock}
+\frametitle{Over to you\ldots}
 
-\begin{textblock}{5}(3.5,4)
-\begin{bubble}[5cm]
-\it not regulated by any government
-\end{bubble}
-\end{textblock}
-
-\begin{textblock}{4}(2,9)
-\begin{bubble}[4cm]
-\it untracable spending of money?
-\end{bubble}
-\end{textblock}
+{\bf What do you know about Bitcoins:}
 
-\begin{textblock}{5.7}(3,13)
-\begin{bubble}[5.7cm]
-  \it fixed amount of bitcoins in circulation (no inflation)
-  
-\end{bubble}
-\end{textblock}
+\begin{itemize}
+\item ???
+\end{itemize}  
 
-\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}(11,2.3)
-\begin{bubble}[3cm]
-\it bitcoins are anonymous
-\end{bubble}
-\end{textblock}
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
@@ -152,7 +102,7 @@
 \item cloud-based (passwords)
 \item paper-based
 \end{itemize}
-and contains only the public-private key
+and contains only your private key(s)
 
 \item Bitcoins can be stolen or lost
 \item Mt.~Gox: hacked $\Rightarrow$ insolvent
@@ -172,8 +122,8 @@
 
 \begin{itemize}
 \item public-private key encryption\medskip
-\item digital signatures\medskip
-\item cryptographic hashing (SHA-256)
+\item cryptographic hashing (SHA-256)\medskip
+\item digital signatures
 \end{itemize}
 
 \begin{center}
@@ -195,7 +145,7 @@
 \begin{itemize}
 \item no-one else could have created that message
 \item Alice cannot deny the ``intend'' of sending Bob money\pause\bigskip
-\item Q: What is money?\\ 
+\item Q: What is crypto money?\\ 
   A: Well a string like above
   (or later messages like that)
 \end{itemize}
@@ -308,7 +258,7 @@
 \item I , Alice, am giving Bob one infocoin, with serial
       number 1234567. 
 \item I, Alice, am giving \alt<2->{\alert{Alice}}{Charlie} 
-      one infocoin with number 1234567.
+      one infocoin with number 1234567. 
 \end{itemize}
 \end{bubble}
 
@@ -373,7 +323,7 @@
 \frametitle{Solving Puzzles}
 
 Given a string, say \code{"Hello, world!"}, what is the 
-\alert{salt} so the hash starts with a long run of 
+\alert{salt} so that the hash starts with a long run of 
 zeros?\bigskip
 
 \begin{bubble}[10cm]
@@ -397,7 +347,7 @@
 
 If we want the output hash value to begin with 10 zeroes,
 say, then we will need, on average, to try $16^{10} \approx
-10^{12}$ different salts before we find a suitable nonce. 
+10^{12}$ different salts before we find a suitable salt. 
 
 Hardness can be controlled by setting a \alert{target} (maximum
 number).
@@ -530,7 +480,7 @@
 The rule is: if a fork occurs, people on the network keep
 track of all forks. But at any given time, miners only work
 to extend whichever fork is longest in their copy of the block
-chain.
+chain. \pause(It is actually not a rule, but an incentive!)
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
@@ -563,7 +513,7 @@
 \end{columns}\bigskip\bigskip\pause
 
 \small
-A transaction is ``confirmed'' if:\smallskip
+By convention, a transaction is ``confirmed'' if:\smallskip
 
 (1) it is part of a block in the longest fork, and (2) at
 least 5 blocks follow it in the longest fork. In this case we
@@ -587,10 +537,10 @@
 
 \small
 Many people join groups called mining pools that collectively
-work to solve blocks, and distribute rewards based on work
+work to solve blocks, and distribute rewards based on the work
 contributed. These act somewhat like lottery pools among
 co-workers, except that some of these pools are quite large,
-and comprise more than 20\% of all the computers in the
+and comprise more than 50\% of all the computers in the
 network.\medskip
 
 \footnotesize
@@ -651,7 +601,7 @@
 \frametitle{Dispute Mediation}
 
 \begin{itemize}
-\item say, client and (online) merchant do not trust 
+\item say, a client and an (online) merchant do not trust 
   each other\bigskip\pause
 
 \item 2-of-3: mutually trusted escrow service
@@ -661,10 +611,11 @@
   \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
+  \item if goods are defective, and merchant is nice,
+    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''
+  service who signs a transaction and sends it to ``winning''
   party 
  \end{enumerate}
 \end{itemize}
@@ -785,7 +736,7 @@
 \item you cannot meddle with the ``history''
 \end{itemize}\bigskip
 
-The system can be scaled to all world transactions. 
+The system can be scaled to all world transactions??
 
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
@@ -799,7 +750,7 @@
 \end{center}
 
 \only<1>{
-ledger is public ``forever''; everybody can inspect
+the ledger is public ``forever''; everybody can inspect
 how money was transferred from which address to
 which address; maybe not ideal for money laundering}
 \only<2>{
@@ -843,7 +794,7 @@
   
     
   \item only makes sense if the share is much more
-  valueable than just 1 Bc.          
+  valuable than just 1 Bc.          
 \end{itemize} 
 
 \end{frame}
@@ -922,7 +873,9 @@
 %\frametitle{Take Home Points}
 
   \begin{center}
-  Next 2 weeks by Jose Such
+    Next 4 weeks by Jose Such\bigskip\bigskip
+
+    You can still send me homework for weeks 1 - 6.
   \end{center}  
       
 




