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%
% Title page
%
% Hi everyone. Welcome to our talk "privacy-preserving and incrementally
% deployable support for Certificate Transparency in Tor". I'm Rasmus, a PhD
% student at Karlstad University. This is joint work together with
% Tobias Pulls from Karlstad University,
% Tom Ritter from Mozilla, and
% Paul Syverson from the US Naval Research Laboratory.
%
\begin{frame}
%
% To get started I would like to remind us of the past.
%
% The year is 2011. Summer just arrived, and we are located in the northern
% parts of Netherlands. The offices of DigiNotar appear to be operating as
% usual. Had we been there at the time, we probably wouldn't have thought
% they'd be out of business in September.
%
\vfill
\begin{columns}
\begin{column}{0.45\textwidth}
\mktitle{A flash-back into the past}
\begin{itemize}
\item June, 2011
\item Netherlands, Beverwijk
\item DigiNotar
\end{itemize}
\end{column}
\begin{column}{0.55\textwidth}
\centering
\includegraphics[width=\columnwidth]{img/beverwijk}
\burl{https://creativecommons.org/licenses/by-sa/3.0/}
% https://commons.wikimedia.org/wiki/File:Nzkanaal2.jpg
\end{column}
\end{columns}
\end{frame}
\begin{frame}
%
% What happened?
%
% Let me give you the backdrop.
%
% DigiNotar was a so-called certificate authority that issued certificates
% for the web. Your browser uses these certificates to verify that you are
% really visiting the website that you intended to and not some attacker.
%
% Sounds great! What's the catch?
% Well.
% You have to trust that no Certificate Authority is going to mess up the
% certificate issuance process. Any failure in this process may result in a
% mis-issued certificate, which in turn may result in insecure connections.
%
% Okay. So,
% I think most of you know what happened. DigiNotar was hacked. They
% mis-issued certificates for Google, Mozilla, Tor, and many others.
%
% This was actually detected by DigiNotar.
% In response, they decided to be silent and cover it up.
%
% The main reason why we, the public, detected that DigiNotar was no longer
% operating in good faith is because of a large scale attack in Iran. Some
% of the mis-issued certificates were used to intercept network traffic of
% 300k gmail users. Perhaps we were actually lucky to detect the attack at
% all. If the attacker had been more stealthy, DigiNotar might still have
% been in operation today. That is a scary though. Can we do better?
%
% Fortunately, the answer is yes. We can do better. The overall ecosystem
% improved significantly since 2011. This talk covers one such improvement:
% - Certificate Transparency
%
\vfill
\begin{columns}
\begin{column}{0.45\textwidth}
\mktitle{What happened?}
\begin{itemize}
\item DigiNotar issued web certificates
\item Did not live up to expectations
\item Then tried to cover it up\footnotemark
\end{itemize}
\end{column}
\begin{column}{0.55\textwidth}
\centering
\includegraphics[width=\columnwidth]{img/diginotar}
\burl{https://www.bbc.com/news/technology-14989334}
\end{column}
\end{columns}
\vfill
\pause
\centering\alert{A stealthy attacker might have gotten away with it!}
\footnotetext[1]{%
\tiny{
FoxIT.
Black Tulip: Report of the investigation into the DigiNotar Certificate
Authority breach.
Page 3.
}
}
\end{frame}
\begin{frame}
%
% Just to make sure that we are on the same page.
%
% A large scale attack should not be necessary to detect if a trusted party
% like DigiNotar misbehaves. And it is not like we are only talking about a
% single isolated incident. The real problem is that we have hundreds of
% Certificate Authorities that claim to issue certificates only to the
% rightful domain owners. Every now and then, someone gets it wrong. What
% we are left with is an incident that endangers our digital safety,
% sometimes even our physical safety depending on the real-world context.
%
% What Certificate Transparency brings to the table is the ability to detect
% mis-issued certificates. The basic idea is that every issued certificate
% must be disclosed in a public log that anyone can inspect.
%
% Usually, Certificate authorities are the ones doing the logging. Websites
% then serve the issued certificate together with some proofs of logging.
% The browser verifies these proofs before accepting the certificate as
% valid.
%
% This is actually great, because now a website can look for certificates
% that match their domain name in the log. If something shows up that they
% did not ask for - well - now they are aware of that. They probably
% wouldn't have been without the log. In response, you might question the
% certificate authority, initiate a revocation process, and so forth.
%
\vfill
\begin{columns}
\begin{column}{0.5\textwidth}
\mktitle{Larger problem and solution?}
\begin{itemize}
\item Digitar was not a one-time incident\footnotemark
\item Many other parties can get it wrong
\item Add visibility into issued certificates\footnotemark
\end{itemize}
\end{column}
\begin{column}{0.5\textwidth}
\input{img/ct}
\end{column}
\end{columns}
\footnotetext[2]{\burl{https://sslmate.com/certspotter/failures}}
\footnotetext[3]{\burl{https://certificate.transparency.dev/}}
\end{frame}
\begin{frame}
%
% Certificate Transparency, or CT for short, has been - and is still being -
% gradually rolled-out by Google and others. For example, every certificate
% must be CT compliant to validate in Google Chrome and Apple's Safari.
%
% CT compliance basically means that at least two logs must have "promised"
% to make that certificate available to the public. Such a promise is
% usually called an SCT and it is hard-coded into the issued certificate.
%
% Browsers currently use SCTs as proofs of logging. It is possible to
% verify that these promises are in fact true. That is an important part to
% ensure that blind trust is not shifted from Certificate Authorities to CT
% logs. However, such verification is challenging because of the added
% complexity and possible privacy concerns.
%
% For example, to verify that a certificate is in fact included in a log,
% you need to interact with the log ecosystem. Such interactions leak
% a user's browsing patterns to the logs and that is kind of problematic.
%
\mktitle{Certificate Transparency (CT) compliance\footnotemark}
\begin{columns}
\begin{column}{0.25\textwidth}
\end{column}
\begin{column}{0.25\textwidth}
\centering\includegraphics[width=.67\columnwidth]{img/chrome}
\end{column}
\begin{column}{0.25\textwidth}
\centering\includegraphics[width=.7\columnwidth]{img/safari}
\end{column}
\begin{column}{0.25\textwidth}
\end{column}
\end{columns}
\vfill
``Two logs promised that they will make the certificate public''
\footnotetext[4]{%
\burl{https://github.com/chromium/ct-policy/blob/master/ct_policy.md}
\&
\burl{https://support.apple.com/en-us/HT205280}%
}
\end{frame}
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