slides04.tex
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     1 \documentclass[dvipsnames,14pt,t]{beamer}
       
     2 \usepackage{beamerthemeplainculight}
       
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    72 
       
    73 % beamer stuff 
       
    74 \renewcommand{\slidecaption}{APP 04, King's College London, 16 October 2012}
       
    75 
       
    76 
       
    77 \begin{document}
       
    78 
       
    79 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
    80 \mode<presentation>{
       
    81 \begin{frame}<1>[t]
       
    82 \frametitle{%
       
    83   \begin{tabular}{@ {}c@ {}}
       
    84   \\
       
    85   \LARGE Access Control and \\[-3mm] 
       
    86   \LARGE Privacy Policies (4)\\[-6mm] 
       
    87   \end{tabular}}\bigskip\bigskip\bigskip
       
    88 
       
    89   %\begin{center}
       
    90   %\includegraphics[scale=1.3]{pics/barrier.jpg}
       
    91   %\end{center}
       
    92 
       
    93 \normalsize
       
    94   \begin{center}
       
    95   \begin{tabular}{ll}
       
    96   Email:  & christian.urban at kcl.ac.uk\\
       
    97   Of$\!$fice: & S1.27 (1st floor Strand Building)\\
       
    98   Slides: & KEATS (also homework is there)\\
       
    99   \end{tabular}
       
   100   \end{center}
       
   101 
       
   102 
       
   103 \end{frame}}
       
   104  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
       
   105 
       
   106 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   107 \mode<presentation>{
       
   108 \begin{frame}[c]
       
   109 \frametitle{Unix-Style Access Control}
       
   110 
       
   111 \begin{itemize}
       
   112 \item Q: ``I am using Windows. Why should I care?'' \\ A: In Windows you have:
       
   113 
       
   114 \begin{center}
       
   115 \begin{tabular}{l}
       
   116 administrators group\\ 
       
   117 \hspace{5mm}(has complete control over the machine)\\
       
   118 authenticated users\\
       
   119 server operators\\
       
   120 power users\\
       
   121 network configuration operators\\
       
   122 \end{tabular}
       
   123 \end{center}\medskip
       
   124 
       
   125 \item Modern versions of Windows have more fine-grained AC; they do not have a setuid bit, but
       
   126 have \texttt{runas} (asks for a password).\pause
       
   127 
       
   128 \item OS provided access control can \alert{add} to your
       
   129 security.
       
   130 \end{itemize}
       
   131 
       
   132   
       
   133 \end{frame}}
       
   134 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   135 
       
   136 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   137 \mode<presentation>{
       
   138 \begin{frame}[c]
       
   139 \frametitle{\begin{tabular}{c}Network Applications:\\[-1mm] Privilege Separation\end{tabular}}
       
   140 
       
   141 
       
   142 \begin{center}
       
   143   \begin{tikzpicture}[scale=1]
       
   144   
       
   145   \draw[line width=1mm] (-.3, 0) rectangle (1.5,2);
       
   146   \draw (4.7,1) node {Internet};
       
   147   \draw (0.6,1.7) node {\footnotesize Interface};
       
   148   \draw (0.6,-0.4) node {\footnotesize \begin{tabular}{c}unprivileged\\[-1mm] process\end{tabular}};
       
   149   \draw (-2.7,-0.4) node {\footnotesize \begin{tabular}{c}privileged\\[-1mm] process\end{tabular}};
       
   150   
       
   151   \draw[line width=1mm] (-1.8, 0) rectangle (-3.6,2);
       
   152 
       
   153   \draw[white] (1.7,1) node (X) {};
       
   154   \draw[white] (3.7,1) node (Y) {};
       
   155   \draw[red, <->, line width = 2mm] (X) -- (Y);
       
   156  
       
   157   \draw[red, <->, line width = 1mm] (-0.6,1) -- (-1.6,1);
       
   158   \end{tikzpicture}
       
   159 \end{center}
       
   160 
       
   161 \begin{itemize}
       
   162 \item the idea is make the attack surface smaller and 
       
   163 mitigate the consequences of an attack
       
   164 \end{itemize}
       
   165 
       
   166 
       
   167 \end{frame}}
       
   168 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
       
   169 
       
   170 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   171 \mode<presentation>{
       
   172 \begin{frame}[c]
       
   173 \frametitle{Shared Access Control}
       
   174 
       
   175 \begin{center}
       
   176 \includegraphics[scale=0.7]{pics/pointsplane.jpg}
       
   177 \end{center}
       
   178 
       
   179 \begin{textblock}{11}(10.5,10.5)
       
   180 \small
       
   181 To take an action you\\[-1mm] 
       
   182 need either:
       
   183 \begin{itemize}
       
   184 \item 1 CEO\\[-5mm]
       
   185 \item 2 MDs\\[-5mm]
       
   186 \item 3 Ds
       
   187 \end{itemize}
       
   188 \end{textblock}
       
   189 
       
   190 \end{frame}}
       
   191 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   192 
       
   193 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   194 \mode<presentation>{
       
   195 \begin{frame}[c]
       
   196 \frametitle{Lessons from Access Control}
       
   197 
       
   198 \begin{itemize}
       
   199 \item if you have too many roles (i.e.~too finegrained AC), then 
       
   200 	hierarchy is too complex\\
       
   201 	\textcolor{gray}{you invite situations like\ldots let's be root}\bigskip
       
   202 
       
   203 \item you can still abuse the system\ldots
       
   204 
       
   205 \end{itemize}
       
   206 
       
   207 \end{frame}}
       
   208 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   209 
       
   210 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   211 \mode<presentation>{
       
   212 \begin{frame}[c]
       
   213 \frametitle{\begin{tabular}{@ {}c@ {}}A ``Cron''-Attack\end{tabular}}
       
   214 
       
   215 The idea is to trick a privileged person to do something on your behalf:
       
   216 
       
   217 \begin{itemize}
       
   218 \item root:\\\texttt{rm /tmp/*/*}\bigskip\bigskip\pause
       
   219 
       
   220 \footnotesize
       
   221 \begin{minipage}{1.1\textwidth}
       
   222 \textcolor{gray}{the shell behind the scenes:}\\
       
   223 \textcolor{gray}{\texttt{rm /tmp/dir$_1$/file$_1$ /tmp/dir$_1$/file$_2$ /tmp/dir$_2$/file$_1$ \ldots}}\bigskip\\
       
   224 
       
   225 \textcolor{gray}{this takes time}
       
   226 \end{minipage}
       
   227 \end{itemize}
       
   228 
       
   229 
       
   230 \end{frame}}
       
   231 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   232 
       
   233 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   234 \mode<presentation>{
       
   235 \begin{frame}[c]
       
   236 \frametitle{\begin{tabular}{@ {}c@ {}}A ``Cron''-Attack\end{tabular}}
       
   237 
       
   238 \begin{enumerate}
       
   239 \item attacker \textcolor{gray}{(creates a fake passwd file)}\\ 
       
   240 \texttt{mkdir /tmp/a; cat > /tmp/a/passwd}\medskip
       
   241 \item root \textcolor{gray}{(does the daily cleaning)}\\
       
   242 \texttt{rm /tmp/*/*}\medskip\\
       
   243 \hspace{2cm}\textcolor{gray}{\small records that \texttt{/tmp/a/passwd}}\\ 
       
   244 \hspace{2cm}\textcolor{gray}{\small should be deleted, but does not do it yet}\medskip\\
       
   245 
       
   246 \item attacker \textcolor{gray}{(meanwhile deletes the fake passwd file, and establishes a link to 
       
   247 the real passwd file)}\\
       
   248 \texttt{rm /tmp/a/passwd; rmdir /tmp/a;}\\\texttt{ln -s /etc /tmp/a}\\
       
   249 \item root now deletes  the real passwd file
       
   250 \end{enumerate}
       
   251 
       
   252 \only<2>{
       
   253 \begin{textblock}{11}(2,5)
       
   254 \begin{tikzpicture}
       
   255 \draw (0,0) node[inner sep=2mm,fill=cream, ultra thick, draw=red, rounded corners=2mm] 
       
   256 {\normalsize\color{darkgray}
       
   257 \begin{minipage}{9cm}\raggedright
       
   258 To prevent this kind of attack, you need additional
       
   259 policies.
       
   260 \end{minipage}};
       
   261 \end{tikzpicture}
       
   262 \end{textblock}}
       
   263 
       
   264 \end{frame}}
       
   265 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   266 
       
   267 
       
   268 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   269 \mode<presentation>{
       
   270 \begin{frame}[c]
       
   271 \frametitle{\begin{tabular}{@ {}c@ {}}Schneier Analysis\end{tabular}}
       
   272 
       
   273 \begin{itemize}
       
   274 \item What assets are you trying to protect?
       
   275 \item What are the risks to these assets?
       
   276 \item How well does the security solution mitigate those risks?
       
   277 \item What other risks does the security solution cause?
       
   278 \item What costs and trade-offs does the security solution impose?
       
   279 \end{itemize}
       
   280 
       
   281 \textcolor{gray}{There is no absolutely secure system and security almost never comes for free.}
       
   282 
       
   283 \end{frame}}
       
   284 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   285 
       
   286 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   287 \mode<presentation>{
       
   288 \begin{frame}[t]
       
   289 \frametitle{\begin{tabular}{@ {}c@ {}}Example: Credit Cards\end{tabular}}
       
   290 
       
   291 You might have the policy of not typing in your credit card online. Worthwhile or not?
       
   292 \begin{itemize}
       
   293 \item<2->What assets are you trying to protect?\\
       
   294 \only<2>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}your credit card number\end{tabular}}
       
   295 \item<3->What are the risks to these assets?\\
       
   296 \only<3>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   297 With credit cards you loose a fixed amount \pounds{50}. Amazon \pounds{50}. \end{tabular}}
       
   298 \item<4->How well does the security solution mitigate those risks?\\
       
   299 \only<4>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   300 Well, hackers steal credit cards from databases. They usually do not attack you individually.\end{tabular}}
       
   301 \item<5->What other risks does the security solution cause?
       
   302 \only<5>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright None (?)\end{tabular}}
       
   303 \item<6->What costs and trade-offs does the security solution impose?
       
   304 \only<6>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright Internet shopping is convenient and sometimes cheaper.\end{tabular}}
       
   305 \item<7>[]{\bf\large No!}
       
   306 \end{itemize}\pause\pause
       
   307 
       
   308 
       
   309 \end{frame}}
       
   310 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   311 
       
   312 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   313 \mode<presentation>{
       
   314 \begin{frame}[c]
       
   315 \frametitle{\begin{tabular}{@ {}c@ {}}Example: Firewall\end{tabular}}
       
   316 
       
   317 \begin{center}
       
   318 \includegraphics[scale=0.5]{pics/firewall.png}
       
   319 \end{center}
       
   320 
       
   321 A firewall is a piece of software that controls incoming and outgoing traffic according to some rules. 
       
   322 \end{frame}}
       
   323 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   324 
       
   325 
       
   326 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   327 \mode<presentation>{
       
   328 \begin{frame}[t]
       
   329 \frametitle{\begin{tabular}{@ {}c@ {}}Example: Firewall\end{tabular}}
       
   330 
       
   331 \begin{itemize}
       
   332 \item<1->What assets are you trying to protect?\\
       
   333 \only<1>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}Whatever is behind the firewall 
       
   334 (credit cards, passwords, blueprints, \ldots)\end{tabular}}
       
   335 \item<2->What are the risks to these assets?\\
       
   336 \only<2>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   337 With a small online shop you are already at risk. Pentagon, definitely.\end{tabular}}
       
   338 \item<3->How well does the security solution mitigate those risks?\\
       
   339 \only<3>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   340 Well, at home so not much. Everywhere else, if properly configurated then it does.\end{tabular}}
       
   341 \item<4->What other risks does the security solution cause?
       
   342 \only<4>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright There might be backdoors or bugs in the firewall,
       
   343 but generally they are secure. You choose to prevent certain traffic.\end{tabular}}
       
   344 \item<5->What costs and trade-offs does the security solution impose?
       
   345 \only<5>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright 
       
   346 Minimal to modest. Firewalls are part of free software. You need a knowledgeable 
       
   347 person to set them up.\end{tabular}}
       
   348 \item<7>[]{\bf\large Yes!}
       
   349 \end{itemize}\pause\pause
       
   350 
       
   351 
       
   352 \end{frame}}
       
   353 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   354 
       
   355 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   356 \mode<presentation>{
       
   357 \begin{frame}[t]
       
   358 \frametitle{\begin{tabular}{@ {}c@ {}}Ex: Two-Factor Authentication\end{tabular}}
       
   359 
       
   360 Google uses nowadays two-factor authentication. But it is an old(er)
       
   361 idea. It is used for example in Germany and Netherlands for online transactions.
       
   362 
       
   363 \begin{center}
       
   364 \includegraphics[scale=0.6]{pics/tan1.jpg}\hspace{5mm}
       
   365 \includegraphics[scale=0.2]{pics/tan2.jpg}
       
   366 \end{center}
       
   367 
       
   368 \pause
       
   369 Or nowadays by SMS (restricts the validity of the numbers) or with a secure generator
       
   370 
       
   371 \begin{center}
       
   372 \includegraphics[scale=0.08]{pics/pinsentry.jpg}
       
   373 \end{center}
       
   374 
       
   375 \end{frame}}
       
   376 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   377 
       
   378 
       
   379 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   380 \mode<presentation>{
       
   381 \begin{frame}[t]
       
   382 \frametitle{\begin{tabular}{@ {}c@ {}}Ex: Two-Factor Authentication\end{tabular}}
       
   383 
       
   384 \begin{itemize}
       
   385 \item<1->What assets are you trying to protect?\\
       
   386 \only<1>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}Your bank account.\end{tabular}}
       
   387 \item<2->What are the risks to these assets?\\
       
   388 \only<2>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   389 Nowadays pretty high risk.\end{tabular}}
       
   390 \item<3->How well does the security solution mitigate those risks?\\
       
   391 \only<3>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   392 It prevents problems when passwords are stolen. Man-in-the-middle attacks 
       
   393 still possible.\end{tabular}}
       
   394 \item<4->What other risks does the security solution cause?
       
   395 \only<4>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright Your mobile phone or creditcard/pin might 
       
   396 be stolen. SIM card become valuable.\end{tabular}}
       
   397 \item<5->What costs and trade-offs does the security solution impose?
       
   398 \only<5>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright 
       
   399 Banks need to establish an infrastructure. For you it might be inconvenient.\end{tabular}}
       
   400 \item<7>[]{\bf\large Yes!}
       
   401 \end{itemize}
       
   402 
       
   403 
       
   404 \end{frame}}
       
   405 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   406 
       
   407 
       
   408 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   409 \mode<presentation>{
       
   410 \begin{frame}[t]
       
   411 \frametitle{\begin{tabular}{@ {}c@ {}}Security Seals\end{tabular}}
       
   412 
       
   413 According to Ross Anderson: ``\ldots is a tamper-indicating device 
       
   414 designed to leave non-erasable, unambiguous evidence of unauthorized 
       
   415 entry or tampering.''
       
   416 
       
   417 \begin{center}
       
   418 \includegraphics[scale=0.45]{pics/seal.jpg}
       
   419 \end{center}\mbox{}\\[-12mm]
       
   420 
       
   421 They also need some quite sophisticated policies (seal regiment).
       
   422 \end{frame}}
       
   423 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   424 
       
   425 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   426 \mode<presentation>{
       
   427 \begin{frame}[t]
       
   428 \frametitle{\begin{tabular}{@ {}c@ {}}Security Seals (2)\end{tabular}}
       
   429 
       
   430 \begin{itemize}
       
   431 \item at the Argonne National Laboratory they tested 244 different security seals (including 19\%
       
   432 that were used for safeguard of nuclear material)
       
   433 \begin{itemize}
       
   434 \item mean time to break the seals for a trained person: 100 s 
       
   435 \end{itemize}\bigskip
       
   436 
       
   437 \item Andrew Appel defeated all security seals which were supposed to keep 
       
   438 voting machines safe.
       
   439 \end{itemize}
       
   440 
       
   441 
       
   442 \only<2>{
       
   443 \begin{textblock}{11}(1,1)
       
   444 \begin{tikzpicture}
       
   445 \draw (0,0) node[inner sep=2mm,fill=cream, ultra thick, draw=red, rounded corners=2mm] 
       
   446 {\normalsize
       
   447 \begin{minipage}{11cm}\raggedright\small
       
   448 \begin{center}
       
   449 \includegraphics[scale=0.25]{pics/appelseals.jpg}
       
   450 \end{center}
       
   451 \begin{center}
       
   452 \begin{minipage}{10.5cm}
       
   453 \begin{itemize}
       
   454 \item The tamper-indicating tape can be lifted using a heat gun.
       
   455 \item The security screw cap can be removed using a screwdriver, then the
       
   456 serial-numbered top can be replaced (undamaged) onto a fresh (unnumbered) base.
       
   457 \item The wire seal can be defeated using a \#4 wood screw.
       
   458 \item The plastic strap seal can be picked using a jeweler's screwdriver.
       
   459 \end{itemize}
       
   460 \end{minipage}
       
   461 \end{center}
       
   462 \end{minipage}};
       
   463 \end{tikzpicture}
       
   464 \end{textblock}}
       
   465 
       
   466 \end{frame}}
       
   467 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   468 
       
   469 
       
   470 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
       
   471 \mode<presentation>{
       
   472 \begin{frame}[t]
       
   473 \frametitle{\begin{tabular}{@ {}c@ {}}Ex: Security Seals\end{tabular}}
       
   474 
       
   475 \begin{itemize}
       
   476 \item<1->What assets are you trying to protect?\\
       
   477 \only<1>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}Voting machines, doors.\end{tabular}}
       
   478 \item<2->What are the risks to these assets?\\
       
   479 \only<2>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright Casual thiefs, insider attacks.\end{tabular}}
       
   480 \item<3->How well does the security solution mitigate those risks?\\
       
   481 \only<3>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright
       
   482 Needs a quite complicated security regiment.\end{tabular}}
       
   483 \item<4->What other risks does the security solution cause?
       
   484 \only<4>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright You might not notice tampering.\end{tabular}}
       
   485 \item<5->What costs and trade-offs does the security solution impose?
       
   486 \only<5>{\begin{tabular}{@{\hspace{1cm}}p{9cm}}\raggedright 
       
   487 The ``hardware'' is cheap, but indirect costs can be quite high.\end{tabular}}
       
   488 \item<7>[]{\bf\large No!} {\textcolor{gray}{Though in some areas they work: airport.}}
       
   489 \end{itemize}
       
   490 
       
   491 
       
   492 \end{frame}}
       
   493 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
       
   494 
       
   495 
       
   496 \end{document}
       
   497 
       
   498 %%% Local Variables:  
       
   499 %%% mode: latex
       
   500 %%% TeX-master: t
       
   501 %%% End: 
       
   502