--- a/hws/hw05.tex	Sat Sep 23 19:32:21 2017 +0100
+++ b/hws/hw05.tex	Sat Sep 23 19:39:53 2017 +0100
@@ -93,6 +93,16 @@
 \end{tabular}
 \end{center}
 
+\item Explain briefly the purpose of the certification authority in
+  the public-private key encryption scheme.
+
+\item Explain briefly what is meant by a certification authority
+  becoming ``too big to fail'' when it has issued a large number 
+  of certificates.
+
+\item In which situations does it make sense to install
+  invalid (self-signed) certificates?
+
 
 \item \POSTSCRIPT
 \end{enumerate}