path: root/slides/2021-padsec/src/body.tex

\begin{frame}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\mktitle{Outline}
			\begin{enumerate}
				\item Explore the problem area
				\item A bird's view of the design
				\item Revisit the problem area
				\item How to get involved
			\end{enumerate}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\includegraphics[width=\columnwidth]{img/rgdd}
			\burl{https://creativecommons.org/licenses/by-sa/4.0/}
		\end{column}
	\end{columns}
\end{frame}

%
% https://curl.se/download.html
%
\begin{frame}
	%
	% 1. Introduce the setup.  Daniel represents many software projects.
	% 2. How would you know if your private key got compromised?
	%
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\mktitle{Meet Daniel, the author of \texttt{curl}}
			\begin{itemize}
				\item Digital signing using \texttt{gpg}
				\item Long-term RSA public key
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\includegraphics[height=.75\textheight]{img/curl}
			\burl{https://creativecommons.org/licenses/by-sa/4.0/}
		\end{column}
	\end{columns}
\end{frame}

%%
%% signify: https://www.openbsd.org/papers/bsdcan-signify.html
%%
%% Locate next public key from the current OpenBSD, version 69.
%% 1. Download from mirror: https://cdn.openbsd.org/pub/OpenBSD/6.9/
%% 2. Unpack src.tar.gz
%% 3. See etc/signify/openbsd-70-base.pub
%%
%\begin{frame}
%	%
%	% 1. Introduce the setup.  A newer type of tooling than gpg.  Sort of built-
%	% in revocation by "ignoring the problem until it goes away".
%	% 2. However, you would still like to know if you have a problem or not.
%	%
%	\vfill
%	\begin{columns}
%		\begin{column}{0.5\textwidth}
%			\mktitle{Meet Puffy, the OpenBSD cartoon}
%			\begin{itemize}
%				\item Digital signing using \texttt{signify}
%				\item Basically an interface to use Ed25519
%				\item Public keys are rotated every release
%			\end{itemize}
%		\end{column}
%		\begin{column}{0.5\textwidth}
%			\centering
%			\includegraphics[width=\columnwidth]{img/openbsd}
%			\burl{https://www.openbsd.org/art4.html}
%		\end{column}
%	\end{columns}
%\end{frame}

%
% https://arxiv.org/pdf/2104.06020.pdf, page 6 for the challenge.
%
\begin{frame}
	%
	% 1. What is R-B.
	% 2. Challenge
	% 3. How I think that challenge could be approached
	%
	\vfill
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\mktitle{Meet the R-B project}
			\begin{itemize}
				\item Same input gives the same output
				\item Consensus of ``valid'' checksum?
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\includegraphics[width=\columnwidth]{img/rb}
			\burl{https://creativecommons.org/licenses/by-sa/4.0/}
		\end{column}
	\end{columns}
\end{frame}

\begin{frame}
	\mktitle{Problem summary}
	\vfill
	\begin{columns}
		\begin{column}{0.125\textwidth}
		\end{column}
		\begin{column}{0.75\textwidth}
			\begin{enumerate}
				\item What signatures were produced by a given private key?
				\item Consensus of checksums that should be considered valid?
			\end{enumerate}
		\end{column}
		\begin{column}{0.125\textwidth}
		\end{column}
	\end{columns}
	\vfill
\end{frame}

\begin{frame}
	%
	% 1. Introduce the system.  Think first two paragraphs in design.md
	%
	\mktitle{Our starting point}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\begin{itemize}
				\item Data publisher
				\item End-user
				\item Assumptions
					\begin{itemize}
						\item Public key can be located
						\item Signed data can be located
						\item End-user can install extra tooling
					\end{itemize}
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\input{img/before}
		\end{column}
	\end{columns}
	\vfill
	\pause
	\alert{The attacker can compromise the data publisher}\\
	\pause
	\alert{The goal is to detect unwanted key-usage}
\end{frame}

\begin{frame}
	%
	% 1. Our design is about transparency logs.  So, I need to explain briefly
	% what a transparency log is.
	% 2. Append-only Merkle tree.  You can think of the data as being stored in
	% the leaves.  Each leaf is hashed.  Parents concatenate their children
	% hashes to produces their own hash values.  Repeat until single root hash.
	% 3. The root hash is usually called a tree head.
	% 4. Tree head interesting because it fixes the structure and the content of
	% the tree.  Add/remove/modify -> new tree head.
	% 5. If the log signs the tree head, you can hold it accountable for its
	% structure and content.
	% 6. This is important because the attacker can control the log.
	% 7. So we cannot trust that the log is append-only.  We will need to verify
	% that.  To this end we have consistency proofs.  The intuition is that you
	% can force the log to reveal a number of cryptographic hashes.  These
	% hashes will prove that the tree head you see today is consistent with the
	% tree head you saw yesterday.
	% 8. You can also prove that something is in the log efficiently.  This is
	% called an inclusion proof.  The intuition is that you reveal a number of
	% hashes.  If you can use them to reconstruct the root of a globally
	% consistent tree head you can be sure that some data is in the log.
	% 8. Global consistency (as opposed to just consistency) is what prevents
	% the log from creating forks.  I will return to this later on because it is
	% an important part of our design.
	% (9. Not having global consistency would be like having a blockchain
	% without a consensus mechanism.)
	%
	\mktitle{A quick step back---Transparency log crash course}
	\input{img/mt}
	\vfill
	\begin{columns}
		\begin{column}{0.33\textwidth}
			\begin{itemize}
				\item Tree head
			\end{itemize}
		\end{column}
		\begin{column}{0.33\textwidth}
			\begin{itemize}
				\item Consistency proof
			\end{itemize}
		\end{column}
		\begin{column}{0.33\textwidth}
			\begin{itemize}
				\item Inclusion proof
			\end{itemize}
		\end{column}
	\end{columns}
	\vfill
	\pause
	\alert{The attacker can control the log}
\end{frame}

\begin{frame}
	\mktitle{Preparing a logging request}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\begin{itemize}
				\item Select a shard hint and checksum
				\item Sign using your private key
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\lstinputlisting[style=CStyle]{img/tree-leaf.trunnel}
		\end{column}
	\end{columns}
\end{frame}

\begin{frame}
	\mktitle{Submitting a logging request}
	\begin{columns}
		\begin{column}{0.2\textwidth}
			\underline{Key-value pairs:}
			\begin{itemize}
				\item Shard hint
				\item Checksum
				\item Signature
				\item Public key
				\item Domain hint
			\end{itemize}
		\end{column}
		\begin{column}{0.8\textwidth}
			\centering
			\input{img/log-request}
		\end{column}
	\end{columns}
\end{frame}

\begin{frame}
	\mktitle{Distributing proofs of public logging}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\begin{itemize}
				\item End-user will not talk to the log
				\item Proofs of logging
					\begin{itemize}
						\item Inclusion proof
						\item Tree head
					\end{itemize}
				\item Witness cosigning
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\input{img/after}
		\end{column}
	\end{columns}
	\pause
	\alert{The attacker can control a threshold of witnesses}
\end{frame}

\begin{frame}
	\mktitle{Summary and additional details}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\begin{itemize}
				\item Signed checksums
				\item Sharding
				\item Preserved data flows
				\item Anti-spam
				\item Global consistency
				\item Few simple parsers
				\item No cryptographic agility
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\includegraphics[width=\columnwidth]{img/clean}
		\end{column}
	\end{columns}
\end{frame}

\begin{frame}
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\mktitle{Remember Daniel?}
			\begin{itemize}
				\item (Cross-)sign with Ed25519
				\item Backwards compatible verification?
					\begin{enumerate}
						\item Verify RSA \texttt{gpg} signature
						\item Verify the rest with tlog tooling
					\end{enumerate}
				\item Monitor the log for your own leaves
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\includegraphics[height=.75\textheight]{img/curl}
			\burl{https://creativecommons.org/licenses/by-sa/4.0/}
		\end{column}
	\end{columns}
\end{frame}

%\begin{frame}
%	\vfill
%	\begin{columns}
%		\begin{column}{0.5\textwidth}
%			\mktitle{Remember Puffy?}
%			\begin{itemize}
%				\item No extra key-pair
%				\item Cross-sign for backwards compatibility
%				\item Possible end-user verification
%					\begin{enumerate}
%						\item Verify \texttt{signify} signature
%						\item Verify the rest with tlog tooling
%					\end{enumerate}
%			\end{itemize}
%		\end{column}
%		\begin{column}{0.5\textwidth}
%			\centering
%			\includegraphics[width=\columnwidth]{img/openbsd}
%			\burl{https://www.openbsd.org/art4.html}
%		\end{column}
%	\end{columns}
%\end{frame}

\begin{frame}
	\vfill
	\begin{columns}
		\begin{column}{0.5\textwidth}
			\mktitle{Remember the R-B project?}
			\begin{itemize}
				\item Sign and log the expected checksums
				\item Valid checksum is a logged checksum
				\item Rebuilders monitor the log
			\end{itemize}
		\end{column}
		\begin{column}{0.5\textwidth}
			\centering
			\includegraphics[width=\columnwidth]{img/rb}
			\burl{https://creativecommons.org/licenses/by-sa/4.0/}
		\end{column}
	\end{columns}
\end{frame}

\begin{frame}
	\vfill
	\begin{columns}
		\begin{column}{0.7\textwidth}
			\mktitle{Get involved}
			\begin{itemize}
				\item Feedback on our v0 design\footnotemark and API\footnotemark?
				\item Is this a service that you would use?  Why (not)?
				\item Want to run an experimental log or witness?
				\item Implementation and tooling is still early-days
				\item Reach out via slack\footnotemark, GitHub, or DM
			\end{itemize}
		\end{column}
		\begin{column}{0.3\textwidth}
			\centering
			\includegraphics[width=\columnwidth]{img/thanks}
		\end{column}
	\end{columns}
	\footnotetext[1]{\burl{https://github.com/system-transparency/stfe/blob/design/doc/design.md}}
	\footnotetext[2]{\burl{https://github.com/system-transparency/stfe/blob/design/doc/api.md}}
	\footnotetext[3]{\burl{https://communityinviter.com/apps/system-transparency/join}}
\end{frame}