# HG changeset patch
# User Christian Urban <christian dot urban at kcl dot ac dot uk>
# Date 1353420369 0
# Node ID 807393d1efff4bee29d399b41b1553e62d6018b1
# Parent  2eaca58f9bcc86791d2fbc68e65681b05fded75b
updated

diff -r 2eaca58f9bcc -r 807393d1efff slides08.pdf
Binary file slides08.pdf has changed
diff -r 2eaca58f9bcc -r 807393d1efff slides08.tex
--- a/slides08.tex	Tue Nov 20 11:58:23 2012 +0000
+++ b/slides08.tex	Tue Nov 20 14:06:09 2012 +0000
@@ -286,7 +286,9 @@
 \item timing attacks
 \item parallel session attacks
 \item binding attacks (public key protocols)
-\item changing environment / changing assumptions
+\item changing environment / changing assumptions\bigskip
+
+\item (social engineering attacks)
 \end{itemize}
 \end{frame}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
@@ -395,7 +397,7 @@
 \end{tabular}
 \end{center}\bigskip\pause
 
-Assume nonces are represented as bit-sequences of the same length
+Assume nonces are represented as bit-sequences of the same length as keys
 \begin{center}
 \begin{tabular}{@{}l@{}}
 \bl{$A \rightarrow B :$} \bl{$A, \{N_A\}_{K_{AB}}$}\\
@@ -424,7 +426,7 @@
 \end{tabular}
 \end{center}\bigskip\pause
 
-but nothing is for free: then you need to synchronise time and possibly become victim to
+but nothing is for free: then you need to synchronise time and possibly become a victim to
 timing attacks
 
 \end{frame}}
@@ -470,7 +472,7 @@
 \end{tabular}
 \end{center}\bigskip
 
-\bl{$A$} knows \bl{$K^{prig}_A$} and can verify the message came from \bl{$CA$}
+\bl{$A$} knows \bl{$K^{priv}_A$} and can verify the message came from \bl{$CA$}
 in response to \bl{$A$}'s message and trusts \bl{$K^{pub}_{B}$} is \bl{$B$}'s public key
 
 
@@ -506,7 +508,7 @@
 
 There are plenty of other protocols and attacks. This could go on ``forever''.\pause\bigskip
 
-attacks because of changing environment
+We look here on one more kind of attacks that are because of a changing environment.
 
 \end{frame}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
@@ -536,14 +538,15 @@
 
 \only<4>{
 \begin{itemize}
-\item But suddenly the environment changed: rail transport got privatised creating many companies
-cheating each other
-\item revenue from monthly tickets was distributed according to a formula where the ticket was bought
+\item but suddenly the environment changed: rail transport got privatised creating many 
+competing companies
+potentially cheating each other
+\item revenue from monthly tickets was distributed according to a formula involving where the ticket was bought\ldots
 \end{itemize}}
 
 \only<5>{
 \begin{itemize}
-\item apart from bad outsiders (passengers) you also had bad insiders (rail companies)
+\item apart from bad outsiders (passengers), you also had bad insiders (rail companies)
 \item chaos and litigation ensued
 \end{itemize}}
 
@@ -590,19 +593,43 @@
 \end{frame}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \mode<presentation>{
 \begin{frame}[c]
-\frametitle{Good Practices}
+\frametitle{Problems with WEP (Wifi)}
 
 \begin{itemize}
-\item explicit principles (you authenticate all data you might rely on)
-\item the one who can fix a system should also be liable for the losses  
+\item a standard ratified in 1999
+\item the protocol was designed by a committee not including cryptographers
+\item it used the RC4 encryption algorithm which is a stream cipher requiring a unique nonce
+\item WEP did not allocate enough bits for the nonce
+\item for authenticating packets it used CRC checksum which can be easily broken
+\item the network password was used to directly encrypt packages (instead of a key negotiation protocol)\bigskip
+\item encryption was turned of by default
 \end{itemize}
 
 \end{frame}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Protocols are Difficult}
+
+\begin{itemize}
+\item even the systems designed by experts regularly fail\medskip
+\item try to make everything explicit (you need to authenticate all data you might rely on)\medskip
+\item the one who can fix a system should also be liable for the losses\medskip
+\item cryptography is not {\bf the} answer\bigskip\bigskip  
+\end{itemize}
+
+Logic is one way protocols are studied in academia
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \mode<presentation>{
 \begin{frame}[c]