
diff -r be35ff24cccc -r d1d07f05325a slides/slides09.tex
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/slides/slides09.tex	Sun Sep 22 15:22:11 2013 +0100
@@ -0,0 +1,554 @@
+\documentclass[dvipsnames,14pt,t]{beamer}
+\usepackage{proof}
+\usepackage{beamerthemeplainculight}
+\usepackage[T1]{fontenc}
+\usepackage[latin1]{inputenc}
+\usepackage{mathpartir}
+\usepackage{isabelle}
+\usepackage{isabellesym}
+\usepackage[absolute,overlay]{textpos}
+\usepackage{ifthen}
+\usepackage{tikz}
+\usepackage{courier}
+\usepackage{listings}
+\usetikzlibrary{arrows}
+\usetikzlibrary{positioning}
+\usetikzlibrary{calc}
+\usepackage{graphicx} 
+\usetikzlibrary{shapes}
+\usetikzlibrary{shadows}
+\usetikzlibrary{plotmarks}
+
+
+\isabellestyle{rm}
+\renewcommand{\isastyle}{\rm}%
+\renewcommand{\isastyleminor}{\rm}%
+\renewcommand{\isastylescript}{\footnotesize\rm\slshape}%
+\renewcommand{\isatagproof}{}
+\renewcommand{\endisatagproof}{}
+\renewcommand{\isamarkupcmt}[1]{#1}
+
+% Isabelle characters
+\renewcommand{\isacharunderscore}{\_}
+\renewcommand{\isacharbar}{\isamath{\mid}}
+\renewcommand{\isasymiota}{}
+\renewcommand{\isacharbraceleft}{\{}
+\renewcommand{\isacharbraceright}{\}}
+\renewcommand{\isacharless}{$\langle$}
+\renewcommand{\isachargreater}{$\rangle$}
+\renewcommand{\isasymsharp}{\isamath{\#}}
+\renewcommand{\isasymdots}{\isamath{...}}
+\renewcommand{\isasymbullet}{\act}
+
+
+
+\definecolor{javared}{rgb}{0.6,0,0} % for strings
+\definecolor{javagreen}{rgb}{0.25,0.5,0.35} % comments
+\definecolor{javapurple}{rgb}{0.5,0,0.35} % keywords
+\definecolor{javadocblue}{rgb}{0.25,0.35,0.75} % javadoc
+
+\lstset{language=Java,
+	basicstyle=\ttfamily,
+	keywordstyle=\color{javapurple}\bfseries,
+	stringstyle=\color{javagreen},
+	commentstyle=\color{javagreen},
+	morecomment=[s][\color{javadocblue}]{/**}{*/},
+	numbers=left,
+	numberstyle=\tiny\color{black},
+	stepnumber=1,
+	numbersep=10pt,
+	tabsize=2,
+	showspaces=false,
+	showstringspaces=false}
+
+\lstdefinelanguage{scala}{
+  morekeywords={abstract,case,catch,class,def,%
+    do,else,extends,false,final,finally,%
+    for,if,implicit,import,match,mixin,%
+    new,null,object,override,package,%
+    private,protected,requires,return,sealed,%
+    super,this,throw,trait,true,try,%
+    type,val,var,while,with,yield},
+  otherkeywords={=>,<-,<\%,<:,>:,\#,@},
+  sensitive=true,
+  morecomment=[l]{//},
+  morecomment=[n]{/*}{*/},
+  morestring=[b]",
+  morestring=[b]',
+  morestring=[b]"""
+}
+
+\lstset{language=Scala,
+	basicstyle=\ttfamily,
+	keywordstyle=\color{javapurple}\bfseries,
+	stringstyle=\color{javagreen},
+	commentstyle=\color{javagreen},
+	morecomment=[s][\color{javadocblue}]{/**}{*/},
+	numbers=left,
+	numberstyle=\tiny\color{black},
+	stepnumber=1,
+	numbersep=10pt,
+	tabsize=2,
+	showspaces=false,
+	showstringspaces=false}
+
+% beamer stuff 
+\renewcommand{\slidecaption}{APP 09, King's College London, 27 November 2012}
+\newcommand{\dn}{\stackrel{\mbox{\scriptsize def}}{=}}% for definitions
+\newcommand{\bl}[1]{\textcolor{blue}{#1}}
+
+\begin{document}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}<1>[t]
+\frametitle{%
+  \begin{tabular}{@ {}c@ {}}
+  \\
+  \LARGE Access Control and \\[-3mm] 
+  \LARGE Privacy Policies (9)\\[-6mm] 
+  \end{tabular}}\bigskip\bigskip\bigskip
+
+  %\begin{center}
+  %\includegraphics[scale=1.3]{pics/barrier.jpg}
+  %\end{center}
+
+\normalsize
+  \begin{center}
+  \begin{tabular}{ll}
+  Email:  & christian.urban at kcl.ac.uk\\
+  Of$\!$fice: & S1.27 (1st floor Strand Building)\\
+  Slides: & KEATS (also homework is there)\\
+  \end{tabular}
+  \end{center}
+
+\end{frame}}
+ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Last Week}
+
+Recall, the Schroeder-Needham (1978) protocol is vulnerable to replay attacks.
+
+\begin{center}
+\begin{tabular}{@{}r@ {\hspace{1mm}}l@{}}
+\bl{$A \rightarrow S :$} & \bl{$A, B, N_A$}\\
+\bl{$S \rightarrow A :$} & \bl{$\{N_A, B, K_{AB},\{K_{AB}, A\}_{K_{BS}} \}_{K_{AS}}$}\\
+\bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A\}_{K_{BS}} $}\\
+\bl{$B \rightarrow A :$} & \bl{$\{N_B\}_{K_{AB}}$}\\
+\bl{$A \rightarrow B :$} & \bl{$\{N_B-1\}_{K_{AB}}$}\\
+\end{tabular}
+\end{center}\pause
+
+Fix: Replace messages 2 and 3 to include a timestamp:\bigskip
+
+\begin{minipage}{1.1\textwidth}
+\begin{center}
+\begin{tabular}{@{\hspace{-2mm}}r@ {\hspace{1mm}}l@{}}
+\bl{$S \rightarrow A :$} & \bl{$\{B, K_{\!AB}, T_S, \!\{K_{\!AB}, A, T_S\}_{K_{BS}} \}_{K_{AS}}$}\\
+\bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A, T_S\}_{K_{BS}} $}\\
+\end{tabular}
+\end{center}
+\end{minipage}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[t]
+\frametitle{Denning-Sacco Fix}
+
+Denning-Sacco (1981) suggested to add the timestamp, but omit the handshake:\bigskip
+
+\begin{minipage}{1.1\textwidth}
+\begin{center}
+\begin{tabular}{@{\hspace{-2mm}}r@ {\hspace{1mm}}l@{}}
+\bl{$A \rightarrow S :$} & \bl{$A, B$}\\
+\bl{$S \rightarrow A :$} & \bl{$\{B, K_{\!AB}, T_S, \!\{K_{\!AB}, A, T_S\}_{K_{BS}} \}_{K_{AS}}$}\\
+\bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A, T_S\}_{K_{BS}} $}\\
+\textcolor{lightgray}{$B \rightarrow A :$} & \textcolor{lightgray}{$\{N_B\}_{K_{AB}}$}\\
+\textcolor{lightgray}{$A \rightarrow B :$} & \textcolor{lightgray}{$\{N_B-1\}_{K_{AB}}$}\\
+\end{tabular}
+\end{center}
+\end{minipage}\bigskip
+
+they argue \bl{$A$} and \bl{$B$} can check that the messages are not replays of earlier 
+runs, by checking the time difference with when the protocol is last used
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[t]
+\frametitle{\begin{tabular}{@{}c@{}}Denning-Sacco-Lowe Fix of Fix\end{tabular}}
+
+Lowe (1997) disagreed and said the handshake should be kept, 
+otherwise:\bigskip 
+
+\begin{minipage}{1.1\textwidth}
+\begin{center}
+\begin{tabular}{@{\hspace{-7mm}}r@ {\hspace{1mm}}l@{}}
+\bl{$A \rightarrow S :$} & \bl{$A, B$}\\
+\bl{$S \rightarrow A :$} & \bl{$\{B, K_{\!AB}, T_S, \!\{K_{\!AB}, A, T_S\}_{K_{BS}} \}_{K_{AS}}$}\\
+\bl{$A \rightarrow B :$} & \bl{$\{K_{AB}, A, T_S\}_{K_{BS}} $}\\
+\bl{$I(A) \rightarrow B :$} & \bl{$\{K_{AB}, A, T_S\}_{K_{BS}} $}\hspace{5mm}\textcolor{black}{replay}\\
+\end{tabular}
+\end{center}
+\end{minipage}\bigskip
+
+When is this a problem?\pause\medskip
+
+Assume \bl{$B$} is a bank and the message is ``Draw \pounds{1000} from \bl{$A$}'s
+account and transfer it to \bl{$I$}.''
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[t]
+\frametitle{Privacy}
+
+\begin{minipage}{1.05\textwidth}
+\begin{itemize}
+\item we \alert{do} want that government data is made public (free maps for example)
+\item we \alert{do not} want that medical data becomes public (similarly tax data, school 
+records, job offers)\bigskip
+\item personal information can potentially lead to fraud 
+(identity theft)
+\end{itemize}\pause
+
+{\bf ``The reality'':}
+\only<2>{\begin{itemize}
+\item London Health Programmes lost in June unencrypted details of more than 8 million people
+(no names, but postcodes and details such as gender, age and ethnic origin)
+\end{itemize}}
+\only<3>{\begin{itemize}
+\item also in June Sony, got hacked: over 1M users' personal information, including passwords, email addresses, home addresses, dates of birth, and all Sony opt-in data associated with their accounts.
+\end{itemize}}
+\end{minipage}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+   
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Privacy and Big Data}
+
+Selected sources of ``Big Data'':\smallskip{}
+
+\begin{itemize}
+\item Facebook 
+\begin{itemize}
+\item 40+ Billion photos (100 PB)
+\item 6 Billion messages daily (5 - 10 TB)
+\item 900 Million users  
+\end{itemize}
+\item Common Crawl
+\begin{itemize}
+\item covers 3.8 Billion webpages (2012 dataset)
+\item 50 TB of data
+\end{itemize}
+\item Google
+\begin{itemize}
+\item 20 PB daily (2008)
+\end{itemize}
+\item Twitter
+\begin{itemize}
+\item 7 Million users in the UK
+\item a company called Datasift is allowed to mine all tweets since 2010
+\item they charge 10k per month for other companies to target advertisement
+\end{itemize}
+\end{itemize}\pause
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Cookies\ldots}
+
+``We have published a new cookie policy. It explains what cookies are 
+and how we use them on our site. To learn more about cookies and 
+their benefits, please view our cookie policy.\medskip
+
+If you'd like to disable cookies on this device, please view our information 
+pages on 'How to manage cookies'. Please be aware that parts of the 
+site will not function correctly if you disable cookies. \medskip
+
+By closing this 
+message, you consent to our use of cookies on this device in accordance 
+with our cookie policy unless you have disabled them.''
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Scare Tactics}
+
+The actual policy reads:\bigskip
+
+``As we explain in our Cookie Policy, cookies help you to get the most 
+out of our websites.\medskip
+
+If you do disable our cookies you may find that certain sections of our 
+website do not work. For example, you may have difficulties logging in 
+or viewing articles.''
+
+
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Netflix Prize}
+
+Anonymity is \alert{necessary} for privacy, but \alert{not} enough!\bigskip
+
+\begin{itemize}
+\item Netflix offered in 2006 (and every year until 2010) a 1 Mio \$ prize for improving their movie rating algorithm
+\item dataset contained 10\% of all Netflix users (appr.~500K)
+\item names were removed, but included numerical ratings as well as times of rating
+\item some information was \alert{perturbed} (i.e., slightly modified)
+\end{itemize}
+
+\hfill{\bf\alert{All OK?}}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Re-identification Attack}
+
+Two researchers analysed the data: 
+
+\begin{itemize}
+\item with 8 ratings (2 of them can be wrong) and corresponding dates that can have a margin 14-day error, 98\% of the
+records can be identified
+\item for 68\% only two ratings and dates are sufficient (for movie ratings outside the top 500)\bigskip\pause
+\item they took 50 samples from IMDb (where people can reveal their identity)
+\item 2 of them uniquely identified entries in the Netflix database (either by movie rating or by dates)
+\end{itemize}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{}
+
+\begin{itemize}
+\item Birth data, postcode and gender (unique for\\ 87\% of the US population)
+\item Preferences in movies (99\% of 500K for 8 ratings)
+\end{itemize}\bigskip
+
+Therefore best practices / or even law (HIPAA, EU): 
+
+\begin{itemize}
+\item only year dates (age group for 90 years or over), 
+\item no postcodes (sector data is OK, similarly in the US)\\
+\textcolor{gray}{no names, addresses, account numbers, licence plates}
+\item disclosure information needs to be retained for 5 years
+\end{itemize}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{How to Safely Disclose Information?}
+
+\only<1>{
+\begin{itemize}
+\item Assume you make a survey of 100 randomly chosen people.
+\item Say 99\% of the surveyed people in the 10 - 40 age group have seen the
+Gangnam video on youtube.\bigskip
+
+\item What can you infer about the rest of the population? 
+\end{itemize}}
+\only<2>{
+\begin{itemize}
+\item Is it possible to re-identify data later, if more data is released. \bigskip\bigskip\pause
+
+\item Not even releasing only  aggregate information prevents re-identification attacks.
+(GWAS was a public database of gene-frequency studies linked to diseases;
+you only needed partial DNA information  in order
+to identify whether an individual was part of the study --- DB closed in 2008) 
+\end{itemize}}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Differential Privacy}
+
+\begin{center}
+User\;\;\;\;    
+\begin{tabular}{c}
+tell me \bl{$f(x)$} $\Rightarrow$\\
+$\Leftarrow$ \bl{$f(x) + \text{noise}$}
+\end{tabular}
+\;\;\;\;\begin{tabular}{@{}c}
+Database\\
+\bl{$x_1, \ldots, x_n$}
+\end{tabular}
+\end{center}
+
+
+\begin{itemize}
+\item \bl{$f(x)$} can be released, if \bl{$f$} is insensitive to
+individual entries  \bl{$x_1, \ldots, x_n$}\\
+\item Intuition: whatever is learned from the dataset would be learned regardless of whether
+\bl{$x_i$} participates\bigskip\pause 
+
+\item Noised needed in order to prevent queries:\\ Christian's salary $=$ 
+\begin{center}
+\bl{\large$\Sigma$} all staff $-$  \bl{\large$\Sigma$} all staff $\backslash$ Christian
+\end{center} 
+\end{itemize}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{Adding Noise}
+
+Adding noise is not as trivial as one would wish:
+
+\begin{itemize}
+\item If I ask how many of three have seen the Gangnam video and get a result
+as follows 
+
+\begin{center}
+\begin{tabular}{l|c}
+Alice & yes\\
+Bob & no\\
+Charlie & yes\\
+\end{tabular}
+\end{center}
+
+then I have to add a noise of \bl{$1$}. So answers would be in the
+range of \bl{$1$} to \bl{$3$}
+
+\bigskip
+\item But if I ask five questions for all the dataset (has seen Gangnam video, is male, below 30, \ldots),
+then one individual can change the dataset by \bl{$5$}
+\end{itemize}
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[t]
+\frametitle{\begin{tabular}{@{}c@{}}Tor, Anonymous Webbrowsing\end{tabular}}
+
+\begin{itemize}
+\item initially developed by US Navy Labs, but then opened up to the world 
+\item network of proxy nodes
+\item a Tor client establishes a ``random'' path to the destination server (you cannot trace back where the information came from)\bigskip\pause
+\end{itemize}
+
+\only<2>{
+\begin{itemize}
+\item malicious exit node attack: someone set up 5 Tor exit nodes and monitored the traffic:
+\begin{itemize}
+\item a number of logons and passwords used by embassies (Usbekistan `s1e7u0l7c', while
+Tunesia `Tunesia' and India `1234')
+\end{itemize}
+\end{itemize}}
+\only<3>{
+\begin{itemize}
+\item bad apple attack: if you have one insecure application, your IP can be tracked through Tor
+\begin{itemize}
+\item background: 40\% of traffic on Tor is generated by BitTorrent
+\end{itemize}
+\end{itemize}}
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[t]
+\frametitle{\begin{tabular}{@{}c@{}}Skype Secure Communication\end{tabular}}
+
+\begin{itemize}
+\item Skype used to be known as a secure online communication (encryption cannot be disabled), 
+but \ldots\medskip
+
+\item it is impossible to verify whether crypto algorithms are correctly used, or whether  there are backdoors.\bigskip
+ 
+\item recently someone found out that you can reset the password of somebody else's
+account, only knowing their email address (needed to suspended the password reset feature temporarily)
+\end{itemize}
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{\begin{tabular}{@{}c@{}}Take Home Point\end{tabular}}
+
+According to Ross Anderson: \bigskip
+\begin{itemize}
+\item Privacy in a big hospital is just about doable.\medskip
+\item How do you enforce privacy  in something as big as Google
+or complex as Facebook? No body knows.\bigskip
+
+Similarly, big databases imposed by government
+\end{itemize}
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\mode<presentation>{
+\begin{frame}[c]
+\frametitle{\begin{tabular}{@{}c@{}}Next Week\end{tabular}}
+
+Homework: Which areas should I focus on?
+
+
+\end{frame}}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
+
+\end{document}
+
+%%% Local Variables:  
+%%% mode: latex
+%%% TeX-master: t
+%%% End: 
+




