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\usepackage{pgf}
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\mode<presentation> {
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}

\begin{document}

\begin{comment}
  \begin{frame}
    \vbox{}
    \vspace{-0.3cm}
    \begin{centering}
      \begin{beamercolorbox}[sep=8pt,center]{title}
	\bfseries
	%% TODO -- title here
	\usebeamerfont{title}Anonymity and Censorship Resistance\par%
      \end{beamercolorbox}%
      
      \vspace{1cm}

      %% TODO -- main image here
     \includegraphics[height=3.5cm]{tor-safe-path} \hspace{1cm} \includegraphics[height=3.5cm]{chacha.jpg}

     \vspace{1.5cm}

      \begin{beamercolorbox}[sep=8pt,center]{author}
        Steven J. Murdoch\\[0.2cm]
        \url{http://www.cl.cam.ac.uk/users/sjm217/}
      \end{beamercolorbox}

    \end{centering}
    \vfill
    \begin{flushright}
      %% TODO location here
      \fontsize{4}{4} \selectfont Part II Security, 14 November 2008, Cambridge, UK
    \end{flushright}
  \end{frame}
\end{comment}

  \begin{frame}
    \vbox{}
    \vspace{-0.3cm}
    \begin{centering}
      \begin{beamercolorbox}[sep=8pt,center]{title}
	\bfseries
	\usebeamerfont{title}Censorship, Anonymity, and Traffic Analysis\par%
      \end{beamercolorbox}%
      
      \vspace{0.5cm}

      %% TODO -- main image here
     \includegraphics[height=3.5cm]{tor-safe-path} \hspace{1cm} \includegraphics[height=3.5cm]{chacha.jpg}

     \vspace{0.5cm}

      \begin{beamercolorbox}[sep=8pt,center]{author}
	\underline{Steven J. Murdoch}\\[0.2cm]
        \url{http://www.cl.cam.ac.uk/users/sjm217/}
      \end{beamercolorbox}
      \begin{beamercolorbox}[sep=2pt,center]{institute}
	\usebeamerfont{institute}%
	\parbox[t]{4.9cm}{\raggedleft \fontfamily{psb} \selectfont \bfseries
          \vspace{1mm}\resizebox{3.46cm}{!}{\includegraphics{logo}}\\[1mm]}
	\hspace{2.5cm}
	\parbox[t]{3.46cm}{
	  \vspace{0mm}\resizebox{1.40cm}{!}{\includegraphics{tor-logo}}\\[-0.1mm]
          \mbox{\bfseries \hspace{-5.5mm}\color[HTML]{773795} \href{https://www.torproject.org/}{www.torproject.org}}}
      \end{beamercolorbox}
    \end{centering}
    \vfill
    \begin{flushright}
      %% TODO location here
      %\fontsize{4}{4} \selectfont Anonymity Research Meet-up, 28 November 2008, London, UK
    \end{flushright}
  \end{frame}

%% \begin{frame}
%% \frametitle{Construction of the Internet}
%% \begin{itemize}
%% \item Internet Service Providers (ISPs) give people access to the Internet, and allow people to host services such as websites
%% \item ISPs connect to other ISPs so the customers of one ISP can communicate with those of others
%% \item Some ISPs have international connections, others use those of the bigger ISPs
%% \item ISPs are typically based in one country and governed by the laws of that country
%% \item Often governments control international Internet connections, either directly or via regulation
%% \end{itemize}
%% \end{frame}

%% \begin{frame}
%% \frametitle{Construction of the Internet}
%% \begin{center}
%% \includegraphics[width=10cm]{cnmap}
%% \end{center}
%%       \flushright

%%       \tiny Diagram: China Internet Network Information Center
%% \end{frame}


  \begin{frame}
    \frametitle{What is being blocked, and why}
    \begin{columns}[t]
      \column{7cm}
     \setbeamercovered{transparent}

      \begin{itemize}
      \item Out of the 40 countries studied by the OpenNet Initiative in 2006, 26 censored the Internet in some way
      \item The types of material censored varied depending on country, e.g.:
        \begin{itemize}
        \item<1-> Human Rights (blocked in China)
        \item<2-> Religion (blocked in Saudi Arabia, UAE, Iran, Bahrain)
        \item<3-> Pornography (blocked in Saudi Arabia, UAE, Iran, Bahrain, Singapore, Burma, \ldots)
        \end{itemize}
      \item Other issues censored include: military and militant websites; sex education, alcohol/drugs, music; gay and lesbian websites; news
      \end{itemize}
      \setbeamercovered{invisible}
      \column{5cm}
      \vbox{}
      \begin{overlayarea}{5cm}{10.5cm}
        \only<1>{\resizebox{5cm}{!}{\includegraphics{hrichina}}}
        \only<2>{\resizebox{5cm}{!}{\includegraphics{islameyat}}}
        \only<3>{\resizebox{5cm}{!}{\includegraphics{playboy}}}
      \end{overlayarea}
    \end{columns}
  \end{frame}

\begin{frame}
\frametitle{Blocking with technology}
\begin{itemize}
\item When a country's government controls international connectivity, they can block requests for banned websites
\item There are a number of different approaches (DNS blocking, IP address blocking, etc.)
\item Software may be produced in-country, but often is an adapted commercial product
\item These companies not only make the software, but provide a continuously updated list of websites to be blocked
\end{itemize}

\end{frame}

\begin{comment}

  \begin{frame}
    \frametitle{Normal web browsing}

    \begin{centering}
    \vbox{}

    \includegraphics[clip, trim=1cm 4cm 1cm 2.2cm, width=10cm]{no-proxy}
    \end{centering}

\vspace{-1cm}

      \flushright

      \tiny Diagram: Jane Gowan

  \end{frame}

  \begin{frame}
    \frametitle{DNS tampering}

    \begin{centering}
    \vbox{}

    \includegraphics[clip, trim=1cm 4cm 1cm 2.2cm, width=10cm]{dns}
    \end{centering}

\vspace{-1cm}

      \flushright

      \tiny Diagram: Jane Gowan

  \end{frame}

  \begin{frame}
    \frametitle{IP blocking}

    \begin{centering}
    \vbox{}

    \includegraphics[clip, trim=1cm 4cm 1cm 2.2cm, width=10cm]{ip}
    \end{centering}

\vspace{-1cm}

      \flushright

      \tiny Diagram: Jane Gowan

  \end{frame}

\end{comment}

\begin{frame}
\frametitle{Tradeoffs in blocking systems}
\begin{itemize}
\item DNS blocking
\begin{itemize}
\item Easy and cheap to implement
\item Blocks at domain name granularity -- overblocks protocols, webpages
\item Trivial to bypass
\end{itemize}
\item IP blocking
\begin{itemize}
\item Easy and cheap to implement
\item Blocks at IP address (perhaps port) -- overblocks virtual hosting
\end{itemize}
\item Proxy blocking
\begin{itemize}
\item Expensive to implement
\item Blocks at webpage level -- low overblocking
\end{itemize}
\item Hybrid blocking -- IP based redirection to proxy
\begin{itemize}
\item Tricky to get right, but cheap
\item Has some vulnerabilities
\item Blocks at webpage level -- low overblocking
\end{itemize}
\end{itemize}
\end{frame}

\begin{comment}
\begin{frame}
\frametitle{Blocking through regulation}
\begin{itemize}
\item ISPs may also be forced to implement their own blocking system, through regulation
\item Individuals may also be covered by laws
\item Governments can also force self-regulation by threatening more heavyweight legislation
\end{itemize}
\begin{columns}[t]
\column{6cm}
\vbox{}
%% http://farm1.static.flickr.com/150/347760599_fedfd250cb.jpg

\includegraphics[width=6cm]{kareem}
\column{6cm}
\vbox{}

Kareem Amer: An blogger to four years' prison in Egypt for insulting Islam and the president.

\textit{``I call on Egyptian government officials to take the necessary procedures to protect the Egyptian youth from the spread of subversive religious ideologies among them by permanently shutting down religious institutions in this country.''}
\end{columns}
\end{frame}
\end{comment}

\begin{frame}
  \frametitle{Even if a site is accessible, it may be removed from search engine results}
  \begin{center}
    \includegraphics[width=11cm]{tiananmen}
  \end{center}
  Searching for ``Tiananmen Square'' on Google.com and Google.cn
\end{frame}

\begin{frame}
\frametitle{Limitations of blocking}
     \begin{columns}[t]
      \column{7cm}
\begin{itemize}
\item Censorship systems block legitimate content and fail to block banned content
\item It is fairly easy for readers and publishers to circumvent the technical measures
\item Building and maintaining censorship systems is expensive
\item Blocking one type of content encourages other types to be blocked
\item Often the process of censorship is not transparent
\end{itemize}
      \column{5cm}
     \vbox{}
    \parbox{5cm}{\includegraphics[width=5cm]{david}}

    \flushright
    \tiny Photograph: \href{http://commons.wikimedia.org/wiki/Image:Michelangelos_David.jpg}{David Gaya}
    \end{columns}
\end{frame}

\begin{frame}
\frametitle{Blocking through laws, fear, and intimidation}
     \begin{columns}[t]
      \column{7cm}
     \begin{itemize}
\item ISPs may be forced to block sites themselves, or implement self-regulation
\item People can be intimidated into not testing rules through fear of detection and retribution
\item These may be through laws, social pressure or extra-legal punishment
\item All these approaches may be used at the same time, and complement each other
      \end{itemize}
      \column{5cm}
     \vbox{}
    \parbox{5cm}{\resizebox{3.5cm}{!}{\includegraphics{chacha}}}
    \parbox{5cm}{\resizebox{3.5cm}{!}{\includegraphics{kareem}}}
    \end{columns}
\end{frame}

%% \begin{frame}
%% \frametitle{Measuring censorship}
%% The OpenNet Initiative test and analyse Internet censorship

%% \begin{center}
%% \includegraphics[width=10cm]{censorship-map}
%% \end{center}

%% \url{http://opennet.net/}

%% \end{frame}

\begin{frame}
\frametitle{Censorship resistance systems}
\begin{itemize}
\item Software to resist censorship should
\begin{itemize}
 \item Hide where user is visiting (to prevent blocking)
 \item Hide who the user is (to protect them from intimidation)
\end{itemize}
\item These properties should be maintained even if the censorship resistance system is partially compromised
\end{itemize}

\begin{center}
\includegraphics[height=3cm]{tor-logo}\quad\includegraphics[height=3cm]{freenet-logo}\quad\includegraphics[height=3cm]{psiphon-logo}
\end{center}

\end{frame}

\begin{frame}
\frametitle{There are many other reasons why people might want privacy}
\begin{itemize}
\item Ordinary people
\begin{itemize}
\item To avoid personal information being sold to marketers
\item Protect themselves when researching sensitive topics
\end{itemize}
\item Militaries and law enforcement
\begin{itemize}
\item To carry out intelligence gathering
\item Protect undercover field agents
\item Offer anonymous tip lines
\end{itemize}
\item Journalists
\begin{itemize}
\item To protect sources, such as whistle blowers
\end{itemize}
\item Human rights workers
\begin{itemize}
\item To publicise abuses and protect themselves from surveillance
\item Blogging about controversial subjects
\end{itemize}
\item Businesses
\begin{itemize}
\item To observe their competition and build anonymous collaborations
\end{itemize}
\end{itemize}
\end{frame}

%% \begin{frame}
%% \frametitle{Limitations of censorship resistance}
%% \begin{itemize}
%% \item Censorship resistance is thought controversial -- especially by the censors
%% \item There is something for everyone to like, and something for everyone to dislike, going on with censorship resistance systems
%% \item Bad people do use them to do bad things (for many different definitions of bad people)
%% \item It is impossible to block bad uses, even if we could come up with a common definition of bad content
%% \item The systems are not perfect, so it is possible some people will be caught
%% \end{itemize}
%% \end{frame}

%\begin{comment}

\begin{frame}
\frametitle{Anonymous communication}
\begin{itemize}
\item People have to hide in a crowd of other people (``anonymity loves company'')
\item The goal of the system is to make all users look as similar as possible, to give a bigger crowd
\item Hide who is communicating with whom
\item Layered encryption and random delays hide correlation between input traffic and output traffic
\end{itemize}

\begin{center}
\includegraphics[width=11cm]{mix}
\end{center}

\end{frame}

\begin{frame}
\frametitle{Remailers}

\begin{center}
\includegraphics[width=11cm]{remailer}
\end{center}

\end{frame}

%\end{comment}

\begin{frame}
\frametitle{Tor is a low-latency anonymity system}
\begin{itemize}
\item Based on technology developed in the Onion Routing project
\item Commonly used for web browsing (works for any TCP traffic)
\item Originally built as a pure anonymity system (hides who is talking to whom)
\item Now designed to resist censorship too (hides whether someone is using the system at all)
\item Centralised directory authorities publish a list of all servers
%%\item (First version developed as Part II project by Matej Pfajfar)
\end{itemize}
\end{frame}

  \begin{frame}
    \frametitle{Tor hides communication patterns by relaying data through volunteer servers}
    \begin{center}
      \begin{overlayarea}{9cm}{6cm}
      \only<1>{\includegraphics[width=9cm]{tor-network}}
      \only<2>{\includegraphics[width=9cm]{tor-safe-selection}}
      \only<3>{\includegraphics[width=9cm]{tor-safe-path}}
      \end{overlayarea}
      \flushright

      \tiny Diagram: Robert Watson
    \end{center}
  \end{frame}

%\begin{comment}
  \begin{frame}
    \frametitle{Tor uses two types of encryption}

    \begin{center}
    \begin{overlayarea}{11cm}{5cm}
      \includegraphics<1>[width=11cm]{tor-keys1}
      \includegraphics<2>[width=11cm]{tor-keys2}
      \includegraphics<3>[width=11cm]{tor-keys3}
    \end{overlayarea}
    \end{center}

  \begin{overlayarea}{12cm}{1cm}
  \only<1-3>{Circuit encryption unlinks data entering and leaving a server}

  \only<2-3>{Link encryption (TLS) disguises individual circuits}

  \only<3>{But data rate is unchanged so traffic analysis can correlate flows}
  \end{overlayarea}

  \end{frame}
%\end{comment}

%%   \begin{frame}
%%   \frametitle{Tor hidden services allow censorship resistant hosting of services}
%%   \begin{center}
%%     \includegraphics[width=11cm]{wikileaks}
%%   \end{center}
%%   \end{frame}

  \begin{frame}
    \frametitle{Freenet is an anonymous content distribution network}
    \begin{columns}[t]
      \column{7cm}
      \begin{itemize}
      \item While Tor allows access to the Internet, Freenet creates a private network
      \item Users can create websites, share files and send/receive emails between other members of the network
      \item Content is hosted by sharing it amongst users of the network
      \item Users cannot select what content they host, and it is stored in an encrypted form
      \end{itemize}
      \column{5cm}
      \vbox{}
      \begin{overlayarea}{5cm}{10cm}
        \resizebox{5cm}{!}{\includegraphics{freenet}}
      \end{overlayarea}
    \end{columns}
  \end{frame}

  \begin{frame}
    \frametitle{Psiphon a is censorship resistance system with different tradeoffs to Tor}
    \begin{columns}[t]
      \column{7cm}
      \begin{itemize}
      \item There is no centralized control, so it is hard to block but also hard for user to find a server
      \item Users do not have to download software, but this limits the strength of protection
      \item If the user cannot modify browser settings or install software, Psiphon is still usable
      \item Users within a censored country can ask someone they trust outside of the country to install the Psiphon server
      \end{itemize}
      \column{5cm}
      \vbox{}
      \begin{overlayarea}{5cm}{10cm}
        \resizebox{5cm}{!}{\includegraphics{psiphon}}
      \end{overlayarea}
    \end{columns}
  \end{frame}

\begin{frame}
\frametitle{Further information}
    \begin{columns}[t]
      \column{9cm}

      \setlength{\parskip}{\bigskipamount}

``Tools and Technology of Internet Filtering'', a chapter in ``Access Denied''. \url{http://opennet.net/accessdenied}

``Security Engineering'', 2nd Edition (Chapter 23). \url{http://www.cl.cam.ac.uk/~rja14/book.html}

The anonymity bibliography \url{http://www.freehaven.net/anonbib/}

The Tor Project website \url{https://www.torproject.org/}

%A copy of these slides will be available \url{http://www.cl.cam.ac.uk/~sjm217/}
      
      \column{3cm}
      \vbox{}

      \center
      \includegraphics[width=3cm]{access-denied}
      \medskip

      \includegraphics[width=3cm]{tor-logo}

    \end{columns}
\end{frame}

%% \begin{frame}
%% \frametitle{Ethical issues in censorship resistance}
 
%% \begin{overlayarea}{\textwidth}{6cm}
%% \begin{itemize}
%% \item People take risks in using censorship resistance systems, and contributing to them -- many of these risks are not well understood
%% \item Censorship resistance systems are used for evil, as well as for good -- does the latter outweigh the former
%% \item Censorship does serve a useful purpose for some people -- when is it acceptable
%% \item Is it appropriate to develop censorship software, deploying in countries with poor human right records, building list of blocked sites, designing surveillance systems
%% \end{itemize}
%% \begin{center}
%% \only<2>{\fbox{Discuss}}
%% \end{center}
%% \end{overlayarea}
%% \end{frame}

\end{document}
