
diff -r 20d0a65b47f2 -r 6ebdaef3e4f1 slides07.tex
--- a/slides07.tex	Tue Nov 13 14:10:23 2012 +0000
+++ b/slides07.tex	Tue Nov 13 14:21:09 2012 +0000
@@ -945,14 +945,24 @@
   \begin{frame}[c]
   \frametitle{Another Challenge-Response}
 
-\bl{$A$} and \bl{$B$} share the key \bl{$K_{AB}$} and want to identify
-each other\bigskip
+Unfortunately, an intruder \bl{$I$} can impersonate \bl{$B$}.
 
- \begin{itemize}
- \item \bl{$A \,\text{sends}\, B :  A, N_A$} 
- \item \bl{$B\,\text{sends}\, A : \{N_A, K'_{AB}\}_{K_{AB}}$}
- \item \bl{$A \,\text{sends}\, B : \{N_A\}_{K'_{AB}}$}
- \end{itemize}
+\begin{center}
+\begin{tabular}{@{\hspace{-7mm}}c@{\hspace{1mm}}c@{}}
+\begin{tabular}{@{}l@{}}
+\onslide<1->{\bl{$A \,\text{sends}\, I :  A, N_A$}}\\ 
+\onslide<4->{\bl{$I \,\text{sends}\, A :  \{N_A,\!K'_{\!AB}\}_{K_{\!AB}}$}}\\ 
+\onslide<5->{\bl{$A \,\text{sends}\, I : \{N_A\}_{K'_{AB}}$}}\\
+\end{tabular}
+&
+\begin{tabular}{@{}l@{}}
+\onslide<2->{\bl{$I \,\text{sends}\, A :  B, N_A$}}\\ 
+\onslide<3->{\bl{$A \,\text{sends}\, I :  \{N_A,\!K'_{\!AB}\}_{K_{\!AB}}$}}\\ 
+\onslide<6->{\bl{$I \,\text{sends}\, A : \{N_A\}_{K'_{AB}}$}}\\
+\end{tabular}
+\end{tabular}
+\end{center}
+
   \end{frame}}
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%          
      




