X-Git-Url: https://git.distorted.org.uk/~mdw/doc/ips/blobdiff_plain/41761fdc7bb8f1ed87f5e1116d389158513ee280..f6d1bf60edfd1c63abb27f891cdf741524d973d1:/auth-mac.tex

diff --git a/auth-mac.tex b/auth-mac.tex
index 40f466d..0c3e6e5 100644
--- a/auth-mac.tex
+++ b/auth-mac.tex
@@ -97,23 +97,6 @@
   \end{itemize}
 \end{slide}
 
-%% IFF systems
-\begin{exercise}
-  %% A nice open-ended question.  Need to sort out IFF details (e.g.,
-  %% aircraft numbering or whatever.
-  An \emph{identify friend-or-foe} (IFF) system works as follows.  Each
-  `friendly' aircraft knows a common secret key.  When a new aircraft is
-  detected, a \emph{challenge} $x$ is sent.  If a correct \emph{response} is
-  returned, the new aircraft is presumed friendly; otherwise it is attacked.
-  Discuss the security requirements of IFF systems and construct a formal
-  model.  Decide which primitive is best suited to the job and relate the
-  security notions.  What sorts of resource constraints can be imposed on
-  adversaries attacking an IFF system?
-  \answer%
-  No prizes for guessing that a MAC is what's wanted, this being the MAC
-  section.  
-\end{exercise}
-
 \xcalways\subsection{Basic results}\x
 
 \begin{slide}