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+\documentclass{article}
+\usepackage{../style}
+\usepackage{../langs}
+\usetikzlibrary{patterns,decorations.pathreplacing}
+
+\begin{document}
+
+\section*{Handout 5 (Protocols)}
+
+The protocols we are interested here are generic descriptions
+of how to exchange messages in order to achieve a goal, be it
+establishing a mutual secure connection or being able to
+authenticate to a system. Our notion of protocol is
+deliberately quite general: it includes situations like the
+messages send between a key fob and a car in order to open
+doors or the messages that participants need to exchange in
+order to mine Bitcoins (which is often already called Bitcoin
+\emph{protocol}).
+
+Unlike the distant past where for example we had to meet a
+person in order to authenticate him or her (via a passport for
+example), the problem we are facing is that on the Internet we
+cannot easily be sure who we are ``talking'' to. The obvious
+reason is that only some electrons arrive at our computer; we
+do not see the person, or computer, behind the incoming
+electrons. Often there are is also no person behind the
+messages, rather than a computer system.
+
+
+
+Keyfobs - protocol
+
+attack such protocols because they use weak ciphers (Oyster
+card)
+
+\end{document}
+
+%%% Local Variables: 
+%%% mode: latex
+%%% TeX-master: t
+%%% End: