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Problem Set 4!

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Nadim Kobeissi 2025-06-27 21:49:36 +02:00
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@ -334,6 +334,56 @@
\end{itemize}
\end{frame}
\begin{frame}{Cipher Suites: The building blocks of TLS security}
\begin{itemize}[<+->]
\item \textbf{What is a cipher suite?}
\begin{itemize}
\item A combination of cryptographic algorithms used together
\item Defines exactly how data will be secured
\item Like a recipe: specifies all ingredients for secure communication
\end{itemize}
\item \textbf{Four components of a cipher suite}:
\begin{enumerate}
\item \textbf{Key exchange algorithm}: How to establish shared keys (RSA, ECDHE, DHE)
\item \textbf{Authentication algorithm}: How to verify identity (RSA, ECDSA)
\item \textbf{Bulk encryption algorithm}: How to encrypt data (AES, ChaCha20)
\item \textbf{MAC algorithm}: How to ensure integrity (SHA256, SHA384, Poly1305)
\end{enumerate}
\item \textbf{Example}: \texttt{TLS\_ECDHE\_RSA\_WITH\_AES\_128\_GCM\_SHA256}
\begin{itemize}
\item \texttt{ECDHE}: Elliptic Curve Diffie-Hellman Ephemeral (key exchange)
\item \texttt{RSA}: RSA signatures (authentication)
\item \texttt{AES\_128\_GCM}: AES with 128-bit keys in GCM mode (encryption + MAC)
\item \texttt{SHA256}: SHA-256 for handshake integrity
\end{itemize}
\end{itemize}
\end{frame}
\begin{frame}{Common cipher suites in practice}
\begin{itemize}[<+->]
\item \textbf{TLS 1.2 cipher suites} (verbose naming):
\begin{itemize}
\item \texttt{TLS\_ECDHE\_RSA\_WITH\_AES\_256\_GCM\_SHA384}
\item \texttt{TLS\_ECDHE\_ECDSA\_WITH\_AES\_128\_GCM\_SHA256}
\item \texttt{TLS\_RSA\_WITH\_AES\_128\_CBC\_SHA256}
\item \texttt{TLS\_DHE\_RSA\_WITH\_AES\_256\_CBC\_SHA256}
\end{itemize}
\item \textbf{TLS 1.3 cipher suites} (simplified naming):
\begin{itemize}
\item \texttt{TLS\_AES\_128\_GCM\_SHA256}
\item \texttt{TLS\_AES\_256\_GCM\_SHA384}
\item \texttt{TLS\_CHACHA20\_POLY1305\_SHA256}
\end{itemize}
\item \textbf{Why TLS 1.3 names are shorter}:
\begin{itemize}
\item Key exchange is always (EC)DHE (forward secrecy mandatory)
\item Authentication tied to certificate type
\item Only specifies symmetric crypto algorithms
\end{itemize}
\item \textbf{Cipher suite negotiation}: Client proposes, server chooses
\end{itemize}
\end{frame}
\begin{frame}{The TLS handshake: Basic flow}
\begin{columns}[c]
\begin{column}{0.6\textwidth}