\begin{frame}
  \frametitle{How is trust established on the web?}
  \centering
  \includegraphics<1>[height=0.85\textheight]{img/chrome-http}
  \includegraphics<2>[height=0.85\textheight]{img/chrome-https}
\end{frame}

\begin{frame}
  \frametitle{What is the meaning of the padlock?}
  \begin{columns}
    \begin{column}{0.69\textwidth}
      \begin{description}
        \item[\tyes] Communication is encrypted
        \item[\tyes] Communication is not tampered with
        \item[\tyes] Server identity is verified
      \end{description}
    \end{column}
    \begin{column}{0.29\textwidth}
      \centering
      \includegraphics[width=0.9\textwidth]{img/padlock}
    \end{column}
  \end{columns}
\end{frame}

\begin{frame}
  \frametitle{Server verification relies on certificate issuance}
  \centering
  \includegraphics[height=0.85\textheight]{img/chrome-cert}
\end{frame}

\begin{frame}
  \frametitle{Tracking certificate issuance is a mess}
  \centering
  \includegraphics[height=0.8\textheight,width=0.7\textwidth]{img/ca-mess}
  \scriptsize{\url{https://www.eff.org/files/colour_map_of_cas.pdf}}
\end{frame}

\begin{frame}
  \frametitle{Certificate issuance gone wrong...}
  \centering
  \begin{tabular}{cc|l}
    Year  & Issuer & Mis-issued certificates affected e.g. \\
    \toprule
    2010 & Versign        & Unkown \\
    2011 & Comodo         & Google, Mozilla, Yahoo \\
    2011 & DigiNotar      & Google\footnote{These certificates were used to attack $\approx100,000$ gmail users in Iran}, Skype, Tor... \\
    2012 & Trustwave      & Enterprise employees \\
    2012 & T\"{u}rkTrust  & Google \\
    2013 & ANSSI          & Google \\
    2013 & Thawte         & Google \\
    2016 & Let's Encrypt  & Facebook \\
    ...  &  ...           & ... \\
  \end{tabular}
\end{frame}