From 3ffb4a79ee779e422679cc53277781cbf9b266cd Mon Sep 17 00:00:00 2001
From: eneller <erikneller@gmx.de>
Date: Thu, 7 May 2026 13:46:07 +0200
Subject: [PATCH] update

---
 crypto.bib | 14 ++++++++++++++
 crypto.tex | 46 ++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/crypto.bib b/crypto.bib
index e2521ce..d687e5d 100644
--- a/crypto.bib
+++ b/crypto.bib
@@ -45,3 +45,17 @@
   year={1978},
   publisher={ACM New York, NY, USA}
 }
+@misc{ enwiki:ciphersuite,
+  author = "{Wikipedia contributors}",
+  title = "Cipher suite --- {Wikipedia}{,} The Free Encyclopedia",
+  year = "2026",
+  url = "https://en.wikipedia.org/w/index.php?title=Cipher_suite&oldid=1342766306",
+  note = "[Online; accessed 10-April-2026]"
+}
+@misc{ enwiki:mitm,
+  author = "{Wikipedia contributors}",
+  title = "Man-in-the-middle attack --- {Wikipedia}{,} The Free Encyclopedia",
+  year = "2026",
+  url = "https://en.wikipedia.org/w/index.php?title=Man-in-the-middle_attack&oldid=1347824570",
+  note = "[Online; accessed 10-April-2026]"
+}
\ No newline at end of file
diff --git a/crypto.tex b/crypto.tex
index 037bb0f..b69bccd 100644
--- a/crypto.tex
+++ b/crypto.tex
@@ -21,6 +21,8 @@
 \newacronym{DES}{DES}{Data Encryption Standard}
 \newacronym{AES}{AES}{Advanced Encryption Standard}
 \newacronym{RSA}{RSA}{Rivest–Shamir–Adleman}
+\newacronym{mitm}{MITM}{Man-in-the-middle attack}
+\newacronym{CA}{CA}{Certificate Authority}
 
 
 
@@ -156,19 +158,51 @@ confusion through substitution boxes (S-box) and
 diffusion through permutation boxes (P-box).
 \cite{enwiki:confusion-diffusion}
 
-\section{DES}\label{sec:des}
+\section{Symmetric Encryption}
+\subsection{DES}\label{sec:des}
 The \acrfull{DES} is a symmetric (or private-key) cipher developed in the 1970s at IBM as an archetypal block cipher.
 It takes in a block of 64 bits and transforms it to a ciphertext using a key of equal length.
 Despite suspicions of backdoors engineered into the algorithm due to the involvement of the NSA in the development of \acrshort{DES},
 it was approved as a federal standard in the USA in 1976 and only retired due to its short key length,
-for which the NSA however was directly responsible as well. \newline
+for which the NSA however was directly responsible as well.
 Nevertheless, it sparked public and scientific interest in the research of encryption algorithms, producing a large body of publications.
+Extended versions of \acrshort{DES} such as Triple-DES (or 3DES) are still in use in embedded applications (chipcards).
 
-\section{AES}
+In \acrshort{DES}, the message is encrypted in 16 rounds, as well as an initial and final permutation (IP and FP),
+which are inverses. IP and FP were included to facilitate hardware loading of blocks.
+Each round consists of several parts:
+\begin{itemize}
+    \item split the 64-Bit message into two 32-Bit blocks left (L) and right (R).
+    \item derive a 48-Bit \textit{round key} from the original 64-Bit \textit{main key} using a fixed \textit{key schedule}.
+    \item apply the \textit{Feistel function} to the R-block, which also applies the \textit{round key}.
+    \item XOR the right block to the left block.
+\end{itemize}
+A round key is then applied to the \textbf{R-Block} in a \textit{Feistel function}
+
+
+The decryption process uses the same algorithm with a reversed \textit{key schedule}.
+
+
+\subsection{AES}
 The \acrfull{AES} superseded \acrshort{DES} in 2001 after an official selection process.
 Unlike its predecessor, it does not use a Feistel network.
 
-\section{RSA}
+
+
+
+
+\section{Asymmetric Encryption}
+Symmetric encryption however historically suffered from a key exchange problem;
+because the same key is used for encryption and decryption, a secure channel is required to agree on a common key.
+This chicken-and-egg problem can be solved in two ways.
+
+\paragraph{The Difie-Hellman Key Exchange} is an algorithm allowing the communication parties to establish a shared secret using
+properties of the discrete logarithm.
+
+\paragraph{Asymmetric} Cryptography
+Both methods however are still vulnerable to a \acrfull{mitm}, thus also requiring a trusted \acrfull{CA} for authentication. \cite{enwiki:mitm}
+
+\subsection{RSA}
 \acrfull{RSA} is the first asymmetric (or public-key) cryptographic algorithm and can thus be used for encryption and digital signing.
 It was named after its eponymous inventors in \citeyear{rsa} after trying to disprove the existence of \textit{trapdoor functions},
 a concept introduced by \citeauthor{diffiehellman} in their appropriately named pivotal paper \citetitle{diffiehellman}.
@@ -186,6 +220,10 @@ The algorithm they came up with relies on modular arithmetic, which remains the
     \item For the private key, % TODO
 \end{enumerate}
 \clearpage
+
+\section{Conclusion}
+Complementary, 
+typical cipher suite: ECDHE-ECDSA-AES128-GCM-SHA256 \citetitle{enwiki:ciphersuite}
 %\printglossary[type=\acronymtype]
 %\printglossary
 \printbibliography