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\section*{Homework 1}

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\item {\bf (Optional)} If you want to have a look at the code
  presented in the lectures, install \texttt{Node.js} available (for free) from
\begin{center}
\url{http://nodejs.org}
\end{center}

It needs also the Node-packages Express, Cookie-Parser,
Body-Parser and Crypto. They can be easily installed using the
Node package manager \texttt{npm}.


\item Practice thinking like an attacker. Assume the following situation:

  \begin{quote}\it
    Prof.~V.~Nasty gives the following final exam question (closed books, closed notes):\bigskip

    \noindent
    \begin{tabular}{@ {}l}
      Write the first 100 digits of pi:\\
      3.\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
    \end{tabular}
  \end{quote}

\noindent
Think of ways how you can cheat in this exam? How would you defend
against such cheats.

\item Here is another puzzle where you can practice thinking
      like an attacker: Consider modern car keys. They
      wirelessly open and close the central locking system of
      the car. Whenever you lock the car, the car ``responds''
      by flashing the indicator lights. Can you think of a
      security relevant purpose for that? (Hint: Imagine you
      are in the business of stealing cars. What attack would
      be easier to perform if the lights do not flash?)
      Should the car also make a ``beep noise'' when it
      unlocks the doors? Which threat could be thwarted
      by that?

\item And another one: Imagine you have at home a broadband
      contract with TalkTalk. You do not like their service
      and want to switch to Virgin, say. The procedure
      between the Internet providers is that you contact
      Virgin and set up a new contract and they will
      automatically inform TalkTalk to terminate the old
      contract. TalkTalk will then send you a letter to
      confirm that you want to terminate. If they do not hear
      from you, they will proceed with terminating
      the contract and will request any outstanding
      cancellation fees. Virgin on the other hand sends you a
      new router and paperwork about the new contract.
      Obviously this way of doing things is meant to make
      switching as convenient as possible. Still can
      you imagine situations in which this way of switching
      providers can cause you a lot of headaches? For
      this consider that TalkTalk needs approximately 14 days
      to reconnect you and might ask for reconnection fees.
      
\item And another one: A water company installed devices that
      transmit meter readings when their company car drives
      by. How can this transmitted data be abused, if not
      properly encrypted? If you identified an abuse, then how
      would you encrypt the data so that such an abuse is
      prevented. Hint: Consider the fact that every person
      uses approximately 120l of water every day.

%\item And another one: Nowadays everybody and their
%      grandmother seems to be scared about a bomb going off at
%      a big event, say a football game. To mitigate such a
%      threat, you order expensive metal detectors and hire a
%      security team that will staff these detectors at each
%      game. Think whether people are really safer at a
%      football game with metal detectors or not. Hint: People
%      certainly might *\emph{feel}* safer by going through
%      metal detectors, but the question is whether they
%      *\emph{are}* safer. Hint: Consider how people arrive at
%      such an event: within a relative short amount of time,
%      thousands, if not more, spectators will arrive at your
%      football game.

%% CYA security - cover-your-ass
% It's an attitude I've seen before: "Something must 
% be done. This is something. Therefore, we must do it." 
% Never mind if the something makes any sense or not.
    
\item And another one: Imagine you are researching security
      products (e.g.~CCTV, alarms etc) on a helpful website.
      They ask you for your address details? Think about
      whether this can be bad for you.


%\item Imagine there was recently a break in where computer criminals
%  stole a large password database containing 

\item Explain what hashes and salts are. Describe how they can be used
  for ensuring data integrity and storing password information.

\item What is the difference between a brute force attack and a 
  dictionary attack on passwords? 
  
\item Even good passwords consisting of 8 characters, can be
      broken in around 50 days (obviously this time varies a
      lot and also gets shorter and shorter over time). Do you
      think it is good policy to require users to change their
      password every 3 months (as King's did until recently)?
      Under which circumstance should users be required to
      change their password?

\item What are good uses of cookies (that is browser cookies)?

\item Why is making bank customers liable for financial fraud a bad
design choice for credit card payments?

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