132 lines
No EOL
4.7 KiB
TeX
132 lines
No EOL
4.7 KiB
TeX
\documentclass[11pt]{scrartcl}
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\usepackage[utf8]{inputenc}
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\usepackage[T1]{fontenc}
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\usepackage[ngerman]{babel}
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\usepackage{lmodern}
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\usepackage{graphicx}
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\usepackage{listings}
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\usepackage{xspace}
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\usepackage{amsmath}
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\usepackage{algorithm}
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\usepackage{algpseudocode}
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\usepackage{xifthen}
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\usepackage{xcolor}
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\usepackage[a4paper,lmargin={2cm},rmargin={2cm},tmargin={2.5cm},bmargin = {2.5cm},headheight = {4cm}]{geometry}
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\usepackage{amsmath,amssymb,amstext,amsthm}
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\usepackage[shortlabels]{enumitem}
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\usepackage[headsepline]{scrlayer-scrpage}
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\pagestyle{scrheadings}
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\usepackage{titling}
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\usepackage{etoolbox}
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\usepackage{tikz}
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\usetikzlibrary{shapes, arrows, calc, automata, arrows.meta, positioning,decorations.pathmorphing,backgrounds,decorations.markings,decorations.pathreplacing, graphs}
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\usetikzlibrary{matrix,shapes,arrows,positioning,chains, calc}
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\usetikzlibrary{arrows.meta,matrix,shapes,arrows,positioning,chains, calc}
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\tikzset{%
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initial text={},
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state/.style={circle, draw, minimum size=.6cm},
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every initial by arrow/.style={-stealth},
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every loop/.append style={-stealth},
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>=stealth
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}
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\ohead{\parbox[t]{.5\linewidth}{\raggedleft \theauthor}}
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\ihead{System Security, SoSe 24, Assignment \thesheetnr}
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% Sheet number
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\newcounter{sheetnr}
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\newcommand{\sheetnr}[1]{\setcounter{sheetnr}{#1}}
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% Exercise environments
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\newenvironment{exercise}[2][]{\section*{#2\expandafter\ifstrempty\expandafter{#1}{}{\ #1}}}{}
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\newenvironment{subexercises}{\begin{enumerate}[a), font=\bfseries, wide, labelindent=0pt]}{\end{enumerate}}
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\newenvironment{subsubexercises}{\begin{enumerate}[i), font=\bfseries, wide, labelindent=0pt]}{\end{enumerate}}
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% Makros
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% MACRO for whole diagram
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% #1: total width of diagram
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% #2: total height of diagram
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% #3: nodes, paths, ...
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\newcommand\protocolflow[3]{
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\begin{center}
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\begin{tikzpicture}[x=#1cm,y=#2cm]
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#3
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\end{tikzpicture}
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\end{center}
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}
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% MACRO for path line shortening
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% #1: start coordinate
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% #2: target coordinate
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% #3: text above arrow
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\newcommand{\package}[3]{
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\path[*-{latex[width=5pt, length=5pt]}] (#1) edge node [above] {#3} (#2);
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}
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% Anpassen --> %
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\author{Benjamin Haschka\\Sascha Tommasone\\Paul Zinselmeyer}
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\sheetnr{4}
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% <-- Anpassen %
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\begin{exercise}[Warm Up]{2.1.}
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\protocolflow{1.5}{0.75}{
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\node[] (A) at (0,0) {\textbf{Alice}};
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\node[] (E) at (3,0) {\textbf{Eve}};
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\node[] (S) at (7,0) {\textbf{Server}};
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\node[] (B) at (10,0) {\textbf{Bob}};
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\package{0,-1}{3,-1}{$Alice, Bob$}
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\package{3,-2}{7,-2}{$Alice, \textcolor{red}{Eve}$}
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\package{7,-3}{0,-3}{$\{ K \}_{K_{AT}}, \{ K \}_{\textcolor{red}{K_{ET}}}$}
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\package{0,-4}{3,-4}{$Trent, Alice, \{ K \}_{\textcolor{red}{K_{ET}}}$}
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\package{3,-5}{0,-5}{$\{ Hello\ Alice! \}_K$}
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}
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\textbf{Assumptions}
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\begin{itemize}
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\item[(1)] Eve ist Nutzer des Protokolls, damit ein \textit{Key Encryption Key} (KEK) $K_{ET}$ zwischen ihr und dem KDC existiert.
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\item[(2)] Eve unterliegt dem Angreifermodell \textit{aktiver MitM}.
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\end{itemize}
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\noindent
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\textbf{Attack}
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\begin{enumerate}
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\item Eve fängt die erste Nachricht [$Alice, Bob$] von Alice ab, ersetzt $Bob$ durch ihren eigenen Namen und leitet die Nachricht anschließend an den Server weiter.
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\item Der Server antwortet mit [$\{ K \}_{K_{AT}}, \{ K \}_{K_{ET}}$]. Eve lässt diese Nachricht durch.
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\item Nachdem Alice den Session Key erhalten hat, schickt sie den mit $K_{ET}$ verschlüsselten Session Key $K$ an Bob. Damit Bob weiß, mit wem der Session Key ist und wie dieser verschlüsselt ist, schickt Alice nicht nur das Chiffrat, sondern $Trent, Alice$ ebenfalls mit.
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\item Eve fängt die Nachricht [$Trent, Alice, \{ K \}_{K_{ET}}$] ab. Aus (1) folgt, dass Eve in Besitz von $K_{ET}$ ist und kann daher den Session Key $K$ entpacken. Um das Protokoll zu beenden, und Alice endgültig davon zu überzeugen, dass sie Bob ist, schickt Eve $\{ Hello\ Alice! \}_K$ an Alice zurück.
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\end{enumerate}
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\noindent
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\textbf{Evaluation}
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\begin{itemize}
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\item
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\end{itemize}
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\end{exercise}
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\newpage
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\begin{exercise}[Key Establishment]{2.2.}
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\protocolflow{1.5}{0.75}{
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\node[] (A) at (0,0) {\textbf{Alice}};
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\node[] (E) at (5,0) {\textbf{Eve}};
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\node[] (B) at (8,0) {\textbf{Bob}};
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\node[] (CA) at (-1,-4.5) {\text{check $N_A$}};
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\package{0,-1}{5,-1}{$ID_A, N_A$}
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\textcolor{red}{\package{5,-2}{0,-2}{$ID_A, N_A$}}
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\package{0,-3}{5,-3}{$\{ N_A, K'_{AB} \}_{K_{AB}}$}
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\textcolor{red}{\package{5,-4}{0,-4}{$\{ N_A, K'_{AB} \}_{K_{AB}}$}}
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\package{0,-5}{5,-5}{$\{ N_A \}_{K'_{AB}}$}
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\package{5,-6}{0,-6}{\textcolor{red}{$N'_B$}}
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}
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\end{exercise}
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\newpage
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\begin{exercise}[Authentication without Trusted Party]{2.3.}
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\end{exercise}
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\newpage
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\begin{exercise}[Authentication with Trusted Party]{2.4.}
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\end{exercise}
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\end{document} |