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\renewcommand{\slidecaption}{APP 11, King's College London}
\newcommand{\bl}[1]{\textcolor{blue}{#1}}

\begin{document}

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\begin{frame}[t]
\frametitle{%
  \begin{tabular}{@ {}c@ {}}
  \\
  \LARGE Access Control and \\[-3mm] 
  \LARGE Privacy Policies (11)\\[-6mm] 
  \end{tabular}}\bigskip\bigskip\bigskip

  \normalsize
  \begin{center}
  \begin{tabular}{ll}
  Email:  & christian.urban at kcl.ac.uk\\
  Office: & S1.27 (1st floor Strand Building)\\
  Slides: & KEATS (also homework is there)\\
  \end{tabular}
  \end{center}

\end{frame}
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\begin{frame}[c]

\begin{itemize}
\item you can still send me your homework\bigskip 
\item Unix AC question: use a terminal-based editor (vm, 
  vim)\bigskip 
\item exams: 2 out of 3 questions, 5 or so subquestions 
  each, you can fill in your answers on the question sheet
\end{itemize}

\end{frame}
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\begin{frame}[c]
\frametitle{Interlock Protocol}

The interlock protocol (``best bet'' against MITM):

\begin{center}
\begin{tabular}{ll@{\hspace{2mm}}l}
1. & \bl{$A \to B :$} & \bl{$K^{pub}_A$}\\
2. & \bl{$B \to A :$} & \bl{$K^{pub}_B$}\\
3. & & \bl{$\{A,m\}_{K^{pub}_B} \;\mapsto\; H_1,H_2$}\\
   & & \bl{$\{B,m'\}_{K^{pub}_A} \;\mapsto\; M_1,M_2$}\\
4. & \bl{$A \to B :$} & \bl{$H_1$}\\
5. & \bl{$B \to A :$} & \bl{$\{H_1, M_1\}_{K^{pub}_A}$}\\
6. & \bl{$A \to B :$} & \bl{$\{H_2, M_1\}_{K^{pub}_B}$}\\
7. & \bl{$B \to A :$} & \bl{$M_2$}
\end{tabular}
\end{center}\pause

\footnotesize
\bl{$m$} = How is your grandmother? \bl{$m'$} = How is the
weather today in London?

\end{frame}
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\begin{frame}[c]

\begin{center}
\begin{tabular}{l@{\hspace{9mm}}l}
\begin{tabular}[t]{@{}l@{}}
\bl{$A \to C : K^{pub}_A$}\\
\bl{$C \to B : K^{pub}_C$}\\
\bl{$B \to C : K^{pub}_B$}\\
\bl{$C \to A : K^{pub}_C$}\medskip\\
\bl{$\{A,m\}_{K^{pub}_C} \;\mapsto\; H_1,H_2$}\\
\bl{$\{B,n\}_{K^{pub}_C} \;\mapsto\; M_1,M_2$}\bigskip\\
\bl{$\{C,a\}_{K^{pub}_B} \;\mapsto\; C_1,C_2$}\\
\bl{$\{C,b\}_{K^{pub}_A} \;\mapsto\; D_1,D_2$}
\end{tabular} &
\begin{tabular}[t]{@{}l@{}}
\bl{$A \to C : H_1$}\\
\bl{$C \to B : C_1$}\\
\bl{$B \to C : \{C_1, M_1\}_{K^{pub}_C}$}\\
\bl{$C \to A : \{H_1, D_1\}_{K^{pub}_A}$}\\
\bl{$A \to C : \{H_2, D_1\}_{K^{pub}_C}$}\\
\bl{$C \to B : \{C_2, M_1\}_{K^{pub}_B}$}\\
\bl{$B \to C : M_2$}\\
\bl{$C \to A : D_2$}
\end{tabular}
\end{tabular}
\end{center}

\end{frame}
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\begin{frame}[c]

\begin{itemize}
\item you have to ask something that cannot imitated 
  (requires \bl{$A$} and \bl{$B$} know each other)
\item what happens if \bl{$m$} and \bl{$n$} are voice
  messages?\bigskip  

\item the moral: establishing a secure connection from ``zero'' is
almost impossible---you need to rely on some established 
trust\medskip

\item that is why we rely on certificates, which however are
badly, badly realised (just today a POODLE attack against SSL)

\end{itemize}

\end{frame}
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\end{document}


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