\documentclass{beamer}
\mode<presentation>
\usetheme{Boadilla}
\title{Tor: Online anonymity, privacy, and security.}
\author{Runa A. Sandvik \\ runa@torproject.org}
\date{12 September 2011}
\begin{document}

\begin{frame}
\maketitle  
\begin{center}
\includegraphics[height=3cm]{../images/2009-tor-logo}
\end{center}
\end{frame}

% Introduce myself, just to be nice
\begin{frame}
\frametitle{About Runa}
\begin{itemize}
\item Studied at the Norwegian University of Science and Technology
\item Worked for the Tor Project during Google Summer of Code in 2009
\item Developer, security researcher, translation coordinator
\end{itemize}
\end{frame}

% And here's what we'll talk about
\begin{frame}
\frametitle{What are we talking about?}
\begin{itemize}
\item Crash course on anonymous communications
\item Quick overview of Tor
\item Tor and circumvention
\item Future work
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{The Tor Project, Inc.}
501(c)(3) non-profit organization dedicated to the research and development of technologies for online anonymity and privacy
\begin{center}
\includegraphics[height=5cm]{../images/2009-oval_sticker_new}
\end{center}
\end{frame}

% Crash course on anonymous communications
\begin{frame}
\frametitle{What is anonymity?}
\includegraphics[width=10cm]{../images/2llg3ts}
\end{frame}

% What is the threat model here?
\begin{frame}
\frametitle{Threat model: what can the attacker do?}
\begin{overlayarea}{9cm}{6cm}
\only<1>{\includegraphics[height=7cm]{../images/single_hop_relay}}
\only<2>{\includegraphics[height=7cm]{../images/evil_single_hop_relay}}
\only<3>{\includegraphics[height=7cm]{../images/data_snooping_single_hop_relay}}
\end{overlayarea}
\end{frame}

\begin{frame}
\frametitle{Anonymity isn't cryptography}
\begin{itemize}
\item Cryptography protects the contents in transit
\item You still know who is talking to whom, how often, and how much data is sent.
\end{itemize}
\begin{center}
\includegraphics[width=5cm]{../images/encryption-cc-by-sa}
\end{center}
\end{frame}

\begin{frame}
\frametitle{Anonymity isn't steganography}
Attacker can tell Alice is talking to someone, how often, and how much data is sent.
\bigskip

\begin{center}
\includegraphics[width=5cm]{../images/steganography-cc-by-sa}
\end{center}
\end{frame}

\begin{frame}
\frametitle{Anonymity isn't just wishful thinking...}
\begin{itemize}
\item "You can't prove it was me!"
\pause \item "Promise you won't look"
\pause \item "Promise you won't remember"
\pause \item "Promise you won't tell"
\pause \item "I didn't write my name on it!"
\pause \item "Isn't the Internet already anonymous?"
\end{itemize}
\end{frame}

\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}
\end{frame}

\begin{frame}
\frametitle{Anonymity serves different interests for different user groups}
\begin{itemize}
\item Private citizens: it's privacy
\item Businesses: it's network security
\item Governments: it's traffic-analysis resistance
\item Human rights activists: it's reachability
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{What is Tor?}
\begin{itemize}
\item Online anonymity software and network
\pause \item Open source, freely available (3-clause BSD license)
\pause \item Active research environment: \\
Rice, UMN, NSF, NRL, Drexel, Waterloo, Cambridge UK, Bamberg Germany, Boston Univ, Harvard, MIT, RPI, Georgia Tech
\pause \item Funding from US DoD, EFF, Voice of America, Google, NLNet,
Human Rights Watch \\
\pause \item Increasingly diverse toolset: \\
Tor, Torbutton, Tor Browser Bundle, TAILS Anonymous Operating System,
Tor Weather, GetTor, Thandy, Orbot, Tor Check, Arm, Torouter, Tor Cloud
and more
\end{itemize}
\end{frame}

% And what makes Tor different?
\begin{frame}
\frametitle{How is Tor different from other systems?}
\begin{overlayarea}{9cm}{6cm}
\only<1>{\includegraphics[height=7cm]{../../website/images/htw1}}
\only<2>{\includegraphics[height=7cm]{../../website/images/htw2}}
\only<3>{\includegraphics[height=7cm]{../../website/images/htw3}}
\end{overlayarea}
\end{frame}

\begin{frame}
\frametitle{Tor uses a simple centralized directory protocol}
\begin{itemize}
\item Relays publish self-signed descriptors to directory authorities
\item Authorities publish a consensus list of all relay descriptors
\item Clients download latest consensus from a directory authority or a directory cache
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Bridges versus relays}
\begin{itemize}
\item A step forward in the blocking resistance race
\item Bridge relays (or "bridges" for short) are Tor relays that aren't listed in the main Tor directory
\item To use a bridge, you will need to locate one first (can be done using bridges.torproject.org, email, social media etc)
\item A bridge will act as the first hop in the circuit
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Hidden services}
\begin{itemize}
\item Tor makes it possible for users to hide their locations while offering various kinds of services, such a website or an im server
\item Using Tor "rendezvous points," other Tor users can connect to these hidden services, each without knowing the other's network identity
\item A hidden service will have an address that ends in .onion, e.g. http://duskgytldkxiuqc6.onion/
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Encryption}
\begin{itemize}
\item Tor uses the 128-bit AES cipher in counter mode to generate a cipher stream
\item And the signing keys are 1024-bit RSA
\item We used to use a 1024-bit safe prime from RFC 2409, section 6.2 as the DH parameter...
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{}
\includegraphics[scale=0.5]{../images/direct-users-2010-12-01-off-300-2011-01-15-ir}
\end{frame}

\begin{frame}
\frametitle{}
\includegraphics[scale=0.5]{../images/bridge-users-2010-11-01-300-2011-01-14-ir}
\end{frame}

\begin{frame}
\frametitle{Encryption}
\begin{itemize}
\item But then we made the DH parameter we use for TLS match the one from Apache's mod\_ssl...
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{}
\includegraphics[scale=0.5]{../images/direct-users-2011-01-01-off-300-2011-03-01-ir.png}
\end{frame}

\begin{frame}
\frametitle{}
\includegraphics[scale=0.5]{../images/bridge-users-2011-01-01-300-2011-03-01-ir.png}
\end{frame}

\begin{frame}
\frametitle{Keys}
\begin{itemize}
\item Each relay maintains a long-term identity key and a short term onion key:
\begin{itemize}
\item The identity key is used to sign relay descriptors
\item The directory authorities also use the identity key to sign the consensus 
\item The onion key is used to decrypt requests from clients to set up a circuit and negotiate ephemeral keys
\item The TLS protocol also establishes a short-term link key when communicating between relays
\end{itemize}
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Cells}
\includegraphics[width=10cm]{../images/cell-struct.png}
\begin{itemize}
\item Traffic passes along circuits in the Tor network in fixed-size
cells (512 bytes):
\begin{itemize}
\item The header includes a circuit identifier that specifies which
circuit the cell refers to
\item The command describes what to do with the cells payload
\item The entire contents of the header and payload is
encrypted/decrypted together as the relay cell moves along the circuit
\end{itemize}
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Tor on the wire}
\includegraphics[width=12cm]{../images/tor-keys3}
\end{frame}

\begin{frame}
\frametitle{How many people use Tor daily?}
\includegraphics[scale=0.5]{../images/direct-users-2010-09-11-off-300-2011-09-11-all}
\end{frame}

% Tor and circumvention
\begin{frame}
\frametitle{Attackers can block access to the network}
\begin{itemize}
\item By blocking access to the directory authorities
\item By blocking access to all the relays in the network
\item By blocking access to all known bridges in the network
\item By preventing users from finding the software
\end{itemize}
\end{frame}

% China
\begin{frame}
\frametitle{Tor and circumvention in China}
\includegraphics[scale=0.5]{../images/direct-users-2010-09-11-off-300-2011-09-11-cn}
\end{frame}

\begin{frame}
\frametitle{Tor and circumvention in China}
\includegraphics[scale=0.5]{../images/bridge-users-2010-09-11-300-2011-09-11-cn}
\end{frame}

% Egypt
\begin{frame}
\frametitle{Tor and circumvention in Egypt}
\includegraphics[scale=0.5]{../images/direct-users-2010-09-11-off-300-2011-09-11-eg}
\end{frame}

\begin{frame}
\frametitle{Tor and circumvention in Egypt}
\includegraphics[scale=0.5]{../images/bridge-users-2010-09-11-300-2011-09-11-eg}
\end{frame}

% Libya
\begin{frame}
\frametitle{Tor and circumvention in Libya}
\includegraphics[scale=0.5]{../images/direct-users-2010-09-11-off-300-2011-09-11-ly}
\end{frame}

\begin{frame}
\frametitle{Tor and circumvention in Libya}
\includegraphics[scale=0.5]{../images/bridge-users-2010-09-11-300-2011-09-11-ly}
\end{frame}

% Future work
\begin{frame}
\frametitle{Future work, part 1}
\begin{itemize}
\item The Torouter project: hardware project to provide an easy to setup Tor bridge or relay 
\item The Tor Cloud project: provides bridge-by-default and relay-by-default images for Amazon EC2
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Future work, part 2}
\begin{itemize}
\item Pluggable transports: a plug-in system that can evade many censorship systems by disguising Tor traffic as, for example, standard HTTP traffic
\item Obfuscated proxy: protocol obfuscation for TCP protocols prevent third party from identifying protocol based on message contents
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Future work, part 3}
\begin{itemize}
\item Censorship resistance research: reachability testing of the Tor network from within certain countries
\item IPv6: goal for Tor 0.2.3.x is for bridges to handle IPv6-only clients and exits can handle IPv6 addresses
\end{itemize}
\end{frame}

% Demonstration of TBB
\begin{frame}
\frametitle{Time for a demo}
Demonstration of Tor Browser Bundle
\end{frame}

\begin{frame}
\frametitle{}
\begin{center}
\large Questions? \\
\vspace{10 mm}
runa@torproject.org \\
https://www.torproject.org/
\end{center}
\end{frame}

\end{document}
