diff -r 55968b3205cc -r f10d905e947f handouts/ho02.tex
--- a/handouts/ho02.tex	Fri Sep 26 12:14:41 2014 +0100
+++ b/handouts/ho02.tex	Mon Sep 29 17:43:35 2014 +0100
@@ -6,74 +6,67 @@
 
 \section*{Handout 2 (E-Voting)}
 
-In security there are many counter-intuitive phenomena: for
-example I am happy (more or less) to use online banking every
-day, where if something goes wrong, I can potentially loose a
-lot of money, but I am staunchly against using electronic
-voting (lets call it e-voting for short). E-voting is an idea
-that is nowadays often promoted in order to counter low
-turnouts in elections\footnote{In my last local election where
-I was eligible to vote only 48\% of the population have cast
-their ballot. I was, I shamefully admit, one of the
-non-voters.} and generally sounds like a good idea. Right?
-Voting from the comfort of your own home, or on your mobile on
-the go, what could possibly go wrong? Even the UK's head of
-the Electoral Commission, Jenny Watson, argued in 2014 in a
-Guardian article that the UK should have e-voting. Her
-plausible argument is that 76\% of pensioners in the UK vote
-(in a general election?), but only 44\% of the under-25s. For
-which constituency politicians might therefore make more
-favourable (short-term) decisions is clear. So being not yet 
+In security engineering, there are many counter-intuitive phenomena:
+for example I am happy (more or less) to use online banking every day,
+where if something goes wrong, I can potentially lose a lot of money,
+but I am staunchly against using electronic voting (lets call it
+e-voting for short). E-voting is an idea that is nowadays often
+promoted in order to counter low turnouts in elections\footnote{In my
+  last local election where I was eligible to vote only 48\% of the
+  population have cast their ballot. I was, I shamefully admit, one of
+  the non-voters.} and generally sounds like a good idea. Right?
+Voting from the comfort of your own home, or on your mobile on the go,
+what could possibly go wrong? Even the UK's head of the Electoral
+Commission, Jenny Watson, argued in 2014 in a Guardian article that
+the UK should have e-voting. Her plausible argument is that 76\% of
+pensioners in the UK vote (in a general election?), but only 44\% of
+the under-25s. For which constituency politicians might therefore make
+more favourable (short-term) decisions is clear. So being not yet
 pensioner, I should be in favour of e-voting, no?
 
-Well, it turns out there are many things that can go wrong
-with e-voting, as I like to argue in this handout. E-voting in
-a ``secure way'' seems to be one of the things in computer
-science that are still very much unsolved. It is not on the 
-scale of Turing's halting problem, which is proved that it can 
-never be solved in general, but it is unsolved with current 
-technology. This is not just my opinion, but 
-from shared by Alex Halderman, who is the world-expert on this
-subject and from whose course on Securing Digital Democracy
-I have most of my information and inspiration. It is also
-a controversial topic in many countries:
+Well, it turns out there are many things that can go wrong with
+e-voting, as I like to argue in this handout. E-voting in a ``secure
+way'' seems to be one of the things in computer science that are still
+very much unsolved. It is not on the scale of Turing's halting
+problem, which is proved that it can never be solved in general, but
+more in the category of being unsolvable with current technology. This
+is not just my opinion, but also shared by many security researchers
+amogst them Alex Halderman, who is the world-expert on this subject
+and from whose course on Securing Digital Democracy I have most of my
+information and inspiration. It is also a controversial topic in many
+countries:
 
 \begin{itemize}
 \item The Netherlands between 1997--2006 had electronic voting
-      machines, but ``hacktivists'' had found they can be
-      hacked and also emitted radio signals revealing how you
-      voted.
+  machines, but ``hacktivists'' had found they can be hacked to change
+  votes and also emitted radio signals revealing how you voted.
 
-\item Germany had used them in pilot studies, but in 2007 a
-      law suit has reached the highest court and it rejected
-      electronic voting on the grounds of not being
-      understandable by the general public.
+\item Germany conducted pilot studies with e-voting, but in 2007 a law
+  suit has reached the highest court and it rejected e-voting on the
+  grounds of not being understandable by the general public.
 
-\item UK used optical scan voting systems in a few trail
-      polls, but to my knowledge does not use any e-voting in
-      elections. 
+\item UK used optical scan voting systems in a few trail polls, but to
+  my knowledge does not use any e-voting in elections.
       
-\item The US used mechanical machines since the 1930s, later
-      punch cards, now DREs and optical scan voting machines.
+\item The US used mechanical machines since the 1930s, later punch
+  cards, now DREs and optical scan voting machines.
 
 \item Estonia used since 2007 the Internet for national
-      elections. There were earlier pilot studies for voting
-      via Internet in other countries.
+  elections. There were earlier pilot studies for voting via Internet
+  in other countries.
 
-\item India uses e-voting devices since at least 2003. They
-      used ``keep-it-simple'' machines produced by a
-      government owned company.
+\item India uses e-voting devices since at least 2003. They used
+  ``keep-it-simple'' machines produced by a government owned company.
 
 \item South Africa used software for its tallying in the 1993
-      elections (when Nelson Mandela was elected)
-      and found that the tallying software was
-      rigged, but they were able to tally manually.      
+  elections (when Nelson Mandela was elected) and found that the
+  tallying software was rigged, but they were able to tally manually.
 \end{itemize}
 
 
-The reason that e-voting is such a hard problem is that we
-have requirements about the voting process that conflict with
-each other. The five main requirements are:
+The reason that e-voting is such a hard problem is that we have
+requirements about the voting process that conflict with each
+other. The five main requirements for voting in general are:
 
 \begin{itemize}
 \item {\bf Integrity} 
@@ -85,11 +78,15 @@
 \item {\bf Ballot Secrecy}
   \begin{itemize}
   \item Nobody can find out how you voted.
-  \item (Stronger) Even if you try, you cannot prove how you voted.
+  \item (Stronger) Even if you try, you cannot prove how you
+    voted. The reason is that you want to avoid vote selling as has
+    been tried, for example, by a few jokers in the recent 
+    Scottish referendum.    
   \end{itemize}
 \item {\bf Voter Authentication}
   \begin{itemize}
-  \item Only authorised voters can vote up to the permitted number of votes.
+  \item Only authorised voters can vote up to the permitted number of votes
+    (in order to avoid the ``vote early, vote often'').
   \end{itemize}
 \item {\bf Enfranchisement}
   \begin{itemize}