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\section*{Handout 2 (E-Voting)}

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 (let's 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 more in the category of being
unsolvable with current technology. This is not just my
opinion, but also shared by many security researchers amongst
them Alex Halderman, who is the world-expert on this subject
and from whose Coursera 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 to change votes and also emitted radio signals
      revealing how you voted.

\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 The US used mechanical machines since the 1930s, later punch
  cards, now DREs and optical scan voting machines.  But there is a
  lot of evidence that DREs and optical scan voting machines are not
  as secure as they should be. Some states experimented with Internet
  voting, but all experiments have been security failures. One
  exceptional election happened just after hurrican Sandy in 2012 when
  some states allowed emergency electronic voting. Voters downloaded
  paper ballots and emailed them back to election officials.

\item Estonia used since 2007 the Internet for national
      elections. There were earlier pilot studies for voting
      via Internet in other countries.

\item The Australian parliament ruled in 2014 that e-voting is
      highly vulnerable to hacking and will not use it any time
      soon. That is because it is still not as secret and 
      secure as paper ballots, the parliamentary committee 
      in charge concluded.

\item India uses e-voting devices since at least 2003. They
      use ``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. 
\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 for voting in general
are:

\begin{itemize}
\item {\bf Integrity} 
  \begin{itemize}
  \item By this we mean that the outcome of the vote matches
        with the voters' intend. Note that it does not say
        that every vote should be counted as cast. This might
        be surprising, but even counting paper ballots will
        always have an error rate: people after several hours
        looking at ballots will inevitably miscount votes. But
        what should be ensured is that the error rate does not
        change the outcome of the election. Of course if
        elections continue to be on knives edges we need to
        strive for rather small error rates. 
          
  \item There might be gigantic sums at stake and need to be
        defended against. The problem with this is that if
        the incentives are great and enough resources are
        available, then maybe it is feasible to mount a DoS
        attack against the voting server and by bringing the
        system to its knees, change the outcome of an
        election. Not to mention to hack the complete
        system with malware and change votes undetectably.                
  \end{itemize}

\item {\bf Ballot Secrecy}
  \begin{itemize}
  \item Nobody can find out how you voted. This is to avoid
        that voters can be coerced to vote in a certain way
        (for example by relatives, employers etc).
         
     \item (Stronger) Even if you try, you cannot prove how
           you voted. The reason for this is that you want to
           avoid vote coercion, but also vote selling. That
           this can be a problem is proved by the fact that
           some jokers in the recent Scottish referendum tried
           to make money out of their vote. \end{itemize}

\item {\bf Voter Authentication}
  \begin{itemize}
  \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}
  \item Authorised voters should have the opportunity to vote.
        This can, for example, be a problem if you make the
        authorisation dependent on an ID card, say a driving
        license. Then everybody who does not have a license
        cannot vote. While this sounds an innocent
        requirement, in fact some parts of the population for
        one reason or another just do not have driving
        licenses. They are now excluded. Also if you insist on
        paper ballots you have to have special provisions for
        blind people. Otherwise they too cannot vote.
 \end{itemize}
  
\item {\bf Availability}
  \begin{itemize}
  \item The voting system should accept all authorised votes
        and produce results in a timely manner. If you move
        an election online, you have to guard against DoS 
        attacks for example.
   \end{itemize}
\end{itemize}

\noindent While these requirements seem natural, the problem 
is that they often clash with each other. For example

\begin{center}
integrity vs.~ballot secrecy\\
authentication vs.~enfranchisement
\end{center}

\noindent If we had ballots with complete voter
identification, then we can improve integrity because we can
trace back the votes to the voters. This would be good when
verifying the results or when recounting. But such an
identification would violate ballot secrecy (you can prove to
somebody else how you voted). In contrast, if we remove all
identification for ensuring ballot secrecy, then we have to
ensure that no ``vote-stuffing'' occurs. Similarly, if we
improve authentication by requiring to be present at the
polling station with an ID card, then we exclude absentee
voting.

To tackle the problem of e-voting, we should first have a look
into the history of voting and how paper-based ballots
evolved. Because also good-old-fashioned paper ballot voting
is not entirely trivial and immune from being hacked. We know
for sure that elections were held in Athens as early as 600
BC, but might even date to the time of Mesopotamia and also in
India some kind of republics might have existed before the
Alexander the Great invaded it. Have a look at Wikipedia about
the history of democracy for more information. These elections
were mainly based on voting by show of hands. While this
method of voting satisfies many of the requirements stipulated
above, the main problem with hand voting is that it does not
guaranty ballot secrecy. As far as I know the old Greeks and
Romans did not perceive this as a problem, but the result was
that their elections favoured rich, famous people who had
enough resources to swing votes. Even using small coloured
stones, which were also used at that time, did not really
mitigate the problem with ballot secrecy. The problem of
authorisation was solved by friends or neighbours vouching for
you to prove you are eligible to vote (there were no ID cards
in ancient Greece and Rome).

Starting with the French Revolution and the US constitution,
people began to value a more egalitarian approach to voting
and electing officials. This was also the time where paper
ballots started to become the prevailing form of casting
votes. While more resistant against voter intimidation, paper
ballots need a number of security mechanisms to avoid fraud.
For example you need voting booths for being able to fill out
the ballot in secret. Also transparent ballot boxes are often
used in order to easily detect and prevent vote stuffing
(prefilling the ballot box with false votes). 

\begin{center}
\includegraphics[scale=2.5]{../pics/ballotbox.jpg}
\end{center}

\noindent Another security mechanism is to guard the ballot
box against any tampering during the election until counting.
The counting needs to be done by a team potentially involving
also independent observers. 

One interesting attack against completely anonymous paper
ballots is called \emph{chain vote attack}. It works if the
paper ballots are given out to each voter at the polling
station. Then an attacker can give the prefilled ballot to a
voter. The voter uses this prefilled ballot to cast the vote,
and then returns the empty ballot paper back to the attacker who now
compensates the voter. The blank ballot can be reused for the
next voter. 

To sum up, the point is that paper ballots have evolved over some time 
and no single best method has emerged for preventing fraud.
But the involved technology is well understood in order to
provide good enough security with paper ballots.

\subsection*{E-Voting}

If one is to replace paper ballots by some electronic
mechanism, one should always start from simple premise taken
from an Australian white paper about e-voting:

\begin{quote} \it ``Any electronic voting system should
provide at least the same security, privacy and transparency
as the system it replaces.''
\end{quote}

\noindent Whenever people argue in favour of e-voting they
seem to be ignoring this basic premise.\bigskip

\noindent After the debacle of the Florida presidential
election in 2000, many voting pre\-cincts in the US used
Direct-Recording Electronic voting machines (DREs) or optical
scan machines. One popular model of DREs was sold by a
company called Diebold. In hindsight they were a complete
disaster: the products were inadequate and the company
incompetent. Direct recording meant that there was no paper
trail, the votes were directly recorded on memory cards. Thus
the voters had no visible assurance whether the votes were
correctly cast. Even if there is a printout provided;
it does not give any guaranty about what is recorded on
the memory card.

The machines behind these DREs were ``normal'' Windows
computers, which could be used for anything, for example for
changing votes. Why did nobody at Diebold think of that? I
have no idea. But that this was eventually done undetectably
is the result of the determination of ethical hackers like
Alex Halderman. His group thoroughly hacked Diebold's DREs
showing that election fraud with them is easily possible. They
even managed to write a virus that infected the whole system
by having only access to a single machine.

\begin{figure}[t]
\begin{center}
\begin{tabular}{c}
\includegraphics[scale=0.45]{../pics/dre1.jpg}\; 
\includegraphics[scale=0.40]{../pics/dre2.jpg}\smallskip\\
\includegraphics[scale=0.5]{../pics/opticalscan.jpg} 
\end{tabular}
\end{center}
\caption{Direct-Recording Electronic voting machines above;
an optical scan machine below.\label{machines}}
\end{figure}

What made matters worse was that Diebold tried to hide their
incompetence and the inferiority of their products by
requiring that election counties must not give the machines up
for independent review. They also kept their source code
secret. This meant Halderman and his group had to obtain a
machine not through the official channels. They then had to
reverse engineer the source code in order to design their
attack. What all this showed is that a shady security design
is no match for a determined hacker. 

Apart from the obvious failings (for example no paper trail),
this story also told another side. While a paper ballot box
need to be kept secure from the beginning of the election
(when it needs to be ensured it is empty) until the end of the
day, electronic voting machines need to be kept secure the
whole year. The reason is of course that one cannot see
whether somebody has tampered with the program a computer is
running. Such a 24/7 security is costly and often even
impossible, because voting machines need to be
distributed---usually the day before the election---to the
polling stations. These are often schools where the voting
machines are kept unsecured overnight. The obvious solution of
putting seals on computers did not work: in the process of
getting these DREs discredited (involving court cases) it was
shown that seals can easily be circumvented. The moral of this
story is that election officials were incentivised with money
by the central government to obtain new voting equipment and
in the process fell prey to pariahs which sold them a
substandard product. Diebold was not the only pariah in this
area, but one of the more notorious ones.

Optical scan machines are slightly better from a security
point of view but by no means good enough. Their main idea
is that the voter fills out a paper ballot, which is then 
scanned by a machine. At the very least the paper ballot can 
serve as a paper trail in cases an election result needs to
be recounted. But if one takes the paper ballots as the 
version that counts in the end, thereby using the optical 
scan machine only as a device to obtain quickly preliminary
results, then why not sticking with paper ballots in the 
first place?\bigskip 

\noindent An interesting solution for e-voting was designed in
India. Essentially they designed a bespoke voting device,
which could not be used for anything else. Having a bespoke
device is a good security engineering decision because it
makes the attack surface much smaller. If you have a
full-fledged computer behind your voting system, then you can
do everything a computer can do\ldots{}and that is a lot,
including a lot of abuse. What was bad about the devices in
India was that these machines did not have the important paper
trail: that means if an election was tampered with, nobody
would find out. Even if they had by their bespoke design a
very small attack surface, ethical hackers were still able to
tamper with them. The moral with Indian's voting machines is
that even if very good security design decisions are taken,
e-voting is very hard to get right.\bigskip 


\noindent This brings us to the case of Estonia, which held in
2007 the worlds first general election that used the Internet.
Again their solution made some good choices: for example voter
authentication is done via the Estonian ID card, which
contains a chip like on credit cards. They also made most of
their source code public for independent scrutiny. Of course
this openness means that people (hackers) will look at your
fingers and find code such as this snippet.

{\footnotesize\lstinputlisting[language=Python,numbers=none]
{../progs/estonia.py}}

\noindent If you want to have a look at their code it can be
downloaded from their github
repository.\footnote{\url{https://github.com/vvk-ehk/evalimine/}}
Also their system is designed such that Internet voting is
used before the election: votes can be changed an unlimited
amount of times; always the last vote is tabulated. You can
even change your vote on the polling day in person. This is an
important security mechanism guarding against vote coercion,
which of course is an important problem if you are allowed to
vote via Internet.

However, the weak spots in any Internet voting system are the
voters' computers and the central server. Unfortunately, their
system is designed such that they needs to trust the integrity
of voters’ computers, central server components and also the
election staff. In 2014, a group of independent observers around
Alex Halderman were able to scrutinise the election process in
Estonia. They found many weaknesses, for example careless
handling of software updates on the servers. They also
simulated an election with the available software and were
able to covertly manipulate results by inserting malware on
the voters' computers. Overall, their recommendation is 
to abandon Internet voting and to go back to an entirely
paper-based voting process. In face of state-sponsored
cyber-crime (for example NSA), Internet voting cannot be made
secure with current technology. They have a small video
clip with their findings at

\begin{center}
\url{https://estoniaevoting.org}
\end{center}

\noindent This brings us to the question, what could be a
viable electronic voting process in
\underline{\smash{\textbf{\emph{theory}}}} with current technology?
In the literature one can find proposals such as this one:

\begin{enumerate}
\item Alice prepares and audits some ballots, then casts an
      encrypted ballot, which requires her to authenticate to
      a server.

\item A bulletin board posts Alice's name and encrypted
      ballot. Anyone, including Alice, can check the bulletin
      board and find her encrypted vote posted. This is to
       make sure the vote was received by the server.

\item When the election closes, all votes are shuffled and the
      system produces a non-interactive proof of a correct
      shuffling---correct in the sense that one cannot determine
       anymore who has voted for what. This will require a 
       shuffling procedure based on zero-knowledge-proofs.

\item After a reasonable complaint period, let auditors
      check the shuffling, all shuffled ballots are decrypted,
      and the system provides a decryption proof for each
      decrypted ballot. Again this will need a 
      zero-knowledge-proof-type of method.

\item Perform a tally of the decrypted votes.

\item An auditor can download the entire (shuffled) election
      data and verify the shuffle, decryptions and tally.
\end{enumerate}

\noindent As you can see, the whole process is not trivial at
all and leaves out a number of crucial details (such as how to
best distribute public keys for encryption). It even depends
on a highly sophisticated process called
\emph{zero-knowledge-proofs}. They essentially allow one to
convince somebody else to know a secret without actually
revealing what the secret is. This is a kind of cryptographic
``magic'', like the Hellman-Diffie protocol which can be used
to establish a secret even if you can only exchange postcards
with your communication partner. We will look at
zero-knowledge-proofs in a later lecture in more detail. 

The point of these theoretical/hot-air musings is to show that
such an e-voting procedure is far from convenient: it takes
much more time to allow, for example, scrutinising whether the
votes were cast correctly. Very likely it will also not pass
the benchmark of being understandable to Joe Average. This was
a standard, a high court ruled, that needs to be passed in the
German election process. 

The overall conclusion is that an e-voting process involving
the Internet cannot be made secure with current technology.
Voting has just too high demands on integrity and ballot
secrecy. This is different from online banking where the whole
process is designed around authentication. If fraud occurs,
you try to identify who did what (somebody’s account got zero;
somewhere the money went). Even if there might be more 
gigantic sums at stake in online banking than with voting,
it can be solved. That does not mean there are no problems
with online banking. But with enough thought, they can
usually be overcome with technology we have currently. This
is different with e-voting: even the best have not come
up with something workable yet.


This conclusion does not imply that in some special cases
of Internet voting cannot be made to work securely. Just in a
general election where stakes are very high, it does not work.
For example a good-enough and workable in-lecture online
voting system where students' votes are anonymous and students
cannot tamper with the outcome, I am sure, can be implemented. 


\subsubsection*{Further Reading}

If you want to know more about e-voting, I recommend
the highly entertaining online course by Alex Halderman at
Coursera.

\begin{center}
\url{https://www.coursera.org/course/digitaldemocracy}
\end{center}

\noindent There is also an entertaining TEDtalk by Barbara
Simons called ``Why can I bank online but not vote online?''

\begin{center}
\url{https://www.youtube.com/watch?v=Wv3VuGZzdK8}
\end{center}

\noindent At the beginning she describes the complete break-in
by the group of Alex Halderman at the try-out voting at
Washington D.C. Halderman's amusing paper about this break in 
including pictures is at

\begin{center}
\url{https://jhalderm.com/pub/papers/dcvoting-fc12.pdf}
\end{center}

\noindent
Another passionate plea to not use electronic voting is the youtube
video

\begin{center}
\url{https://www.youtube.com/watch?v=w3_0x6oaDmI}
\end{center}

\noindent
Two researchers from Galois, Inc., present an interesting 
attack against home routers which silently alters pdf-based
voting ballots. This shows that the vote submission via
an unencrypted pdf-file is highly unsafe.

\begin{center}
\url{http://galois.com/wp-content/uploads/2014/11/technical-hack-a-pdf.pdf}
\end{center}

\end{document}

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