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\renewcommand{\slidecaption}{SEN 05, King's College London}

\begin{document}

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\begin{frame}[t]

\frametitle{%

  \begin{tabular}{@ {}c@ {}}

  \\

  \LARGE Security Engineering (6)\\[-3mm] 

  \end{tabular}}\bigskip\bigskip\bigskip

  \normalsize

  \begin{center}

  \begin{tabular}{ll}

  Email:  & christian.urban at kcl.ac.uk\\

  Office: & N7.07 (North Wing, Bush House)\\

  Slides: & KEATS (also homework is there)\\

  \end{tabular}

  \end{center}

\end{frame}

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\begin{frame}[c]

\frametitle{Topical Slide}

\begin{itemize}

\item DoS attack agains some US webpages (hijacked IoT devives, like

  cameras,\ldots)

\item funny cow attack (privilege escalation attack) 

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{Trusted Third Parties}

Simple protocol for establishing a secure connection via a

mutually trusted 3rd party (server):

\begin{center}

\begin{tabular}{r@ {\hspace{1mm}}l}

\bl{$A \rightarrow S :$} & \bl{$A, B$}\\

\bl{$S \rightarrow A :$} & \bl{$\{K_{AB}, \{K_{AB}\}_{K_{BS}} \}_{K_{AS}}$}\\

\bl{$A \rightarrow B :$} & \bl{$\{K_{AB}\}_{K_{BS}} $}\\

\bl{$A \rightarrow B :$} & \bl{$\{m\}_{K_{AB}}$}\\

\end{tabular}

\end{center}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI: The Main Idea}

\begin{itemize}

\item the idea is to have a certificate authority (CA)

\item you go to the CA to identify yourself

\item CA: ``I, the CA, have verified that public key 

  \bl{$P^{pub}_{Bob}$} belongs to Bob''\bigskip

\item CA must be trusted by everybody\medskip

\item certificates are time limited, and can be revoked

\item What happens if CA issues a false certificate? Who pays in case of loss? (VeriSign 

explicitly limits liability to \$100.)

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI: Chains of Trust}

\begin{center}

  \begin{tikzpicture}[scale=1,

                      node/.style={

                      rectangle,rounded corners=3mm,

                      very thick,draw=black!50,minimum height=18mm, minimum width=23mm,

                      top color=white,bottom color=black!20}]

  \node (A) at (0,0)  [node] {};

  \node [below right] at (A.north west) 

  {\small\begin{tabular}{@{}l}CA\\Root Cert.\end{tabular}};

  \node (B) at (4,0)  [node] {};

  \node [below right=1mm] at (B.north west) 

 {\mbox{}\hspace{-1mm}\small

  \begin{tabular}{@{}l}Subordinate\\ CA\end{tabular}};

  \node (C) at (8,0)  [node] {};

  \node [below right] at (C.north west) 

  {\small\begin{tabular}{@{}l}Server\\ Bank.com\end{tabular}};

  \draw [->,line width=4mm] (A) -- (B); 

  \draw [->,line width=4mm] (B) -- (C); 

  \node (D) at (6,-3)  [node] {};

  \node [below right] at (D.north west) 

  {\small\begin{tabular}{@{}l}Browser\\ Root Store\end{tabular}};

  \node (E) at (2,-3)  [node] {};

  \node [below right] at (E.north west) 

  {\small\begin{tabular}{@{}l}Browser\\ Vendor\end{tabular}};

  \draw [->,line width=4mm] (E) -- (D); 

  \end{tikzpicture}

\end{center}

\begin{itemize}

\item CAs make almost no money anymore, because of stiff

  competition

\item browser companies are not really interested in security;

  only in market share

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI: Weaknesses}

CAs just cannot win (make any profit):\medskip

\begin{itemize}

\item there are hundreds of CAs, which issue millions of

      certificates and the error rate is small

\item users (servers) do not want to pay or pay as little as

      possible\bigskip

\item a CA can issue a certificate for any domain not needing

      any permission (CAs are meant to undergo audits,

      but\ldots DigiNotar)

\item if a CA has issued many certificates, it ``becomes too

      big to fail'' 

\item Can we be sure CAs are not just frontends of some 

      government organisation?  

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI: Weaknesses}

\begin{itemize}

\item many certificates are issued via Whois, whether you own

      the domain\ldots if you hijacked a domain, it is easy to

      obtain certificates\medskip

\item the revocation mechanism does not work (Chrome has given

      up on general revocation lists)\medskip

\item lax approach to validation of certificates 

  (Have you ever bypassed certification warnings?)\medskip

\item sometimes you want to actually install invalid

      certificates (self-signed)

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI: Attacks}

\begin{itemize}

\item Go directly after root certificates 

  \begin{itemize}

  \item governments can demand private keys\smallskip

  \item 10 years ago it was estimated that breaking a 1024 bit

        key takes one year and costs 10 - 30 Mio \$; this is now

        reduced to 1 Mio \$

   \end{itemize} 

\item Go after buggy implementations of certificate

      validation\smallskip

\item Social Engineering 

  \begin{itemize}

    \item in 2001 somebody pretended to be 

    from Microsoft and asked for two code-signing 

    certificates

    \end{itemize}\bigskip

\end{itemize}

\small The eco-system is completely broken (it relies on

thousands of entities to do the right thing). Maybe DNSSEC

where keys can be attached to domain names is a way out.

\end{frame}

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\begin{frame}[c]

\frametitle{Real Attacks}

\begin{itemize}

\item In 2011, DigiNotar (Dutch company) was the first CA that

      got compromised comprehensively, and where many

      fraudulent certificates were issued to the wild. It

      included approximately 300,000 IP addresses, mostly

      located in Iran. The attackers (in Iran?) were likely

      interested ``only'' in collecting gmail passwords.\medskip

\item The Flame malware piggy-bagged on this attack by

      advertising malicious Windows updates to some targeted

      systems (mostly in Iran, Israel, Sudan).

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{PKI is Broken}

\begin{itemize}

\item PKI and certificates are meant to protect you against

      MITM attacks, but if the attack occurs your are 

      presented with a warning and you need to decide whether

      you are under attack.\medskip

\item Webcontent gets often loaded from 3rd-party servers,

      which might not be secured\medskip

\item Misaligned incentives: browser vendors are not

      interested in breaking webpages with invalid

      certificates     

\end{itemize}

\end{frame}

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\begin{frame}[c]

Why are there so many invalid certificates?\bigskip

\begin{itemize}

\item insufficient name coverage (www.example.com should

include example.com)

\item IoT: many appliances have web-based admin interfaces; 

  the manufacturer cannot know under which IP and domain name

  the appliances are run (so cannot install a valid certificate)

\item expired certificates, or incomplete chains of trust

      (servers are supposed to supply them)

\end{itemize}

\end{frame}

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%

%

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%\begin{frame}[c]

%\frametitle{Best Practices}

%

%{\bf Principle 1:} Every message should say what it means: the

%interpretation of a message should not depend on the

%context.\bigskip\pause

%

%{\bf Principle 2:} If the identity of a principal is essential

%to the meaning of a message, it is prudent to mention the

%principal’s name explicitly in the message (though

%difficult).\bigskip

%

%\end{frame}

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%

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%\begin{frame}[c]

%\frametitle{Best Practices}

%

%{\bf Principle 3:} Be clear about why encryption is being

%done. Encryption is not wholly cheap, and not asking precisely

%why it is being done can lead to redundancy. Encryption is not

%synonymous with security.
%

%

%\small

%\begin{center}

%Possible Uses of Encryption
%

%

%\begin{itemize}

%\item Preservation of confidentiality: \bl{$\{X\}_K$} only those that have \bl{$K$} may recover \bl{$X$}.
%\item Guarantee authenticity: The partner is indeed some particular principal.
%\item Guarantee confidentiality and authenticity: binds two parts of a message --- 

%\bl{$\{X,Y\}_K$} is not the same as \bl{$\{X\}_K$} and \bl{$\{Y\}_K$}.

%\end{itemize}

%\end{center}

%

%\end{frame}

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%

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%\begin{frame}[c]

%\frametitle{Best Practices}

%

%{\bf Principle 4:} The protocol designers should know which

%trust relations their protocol depends on, and why the

%dependence is necessary. The reasons for particular trust

%relations being acceptable should be explicit though they will

%be founded on judgment and policy rather than on

%logic.\bigskip

%

%
%Example Certification Authorities: CAs are trusted to certify

%a key only after proper steps have been taken to identify the

%principal that owns it.

%

%\end{frame}

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%

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%\begin{frame}[c]

%\frametitle{Formal Methods}

%

%Ross Anderson about the use of Logic:\bigskip

%

%\begin{quote}

%Formal methods can be an excellent way of finding 

%bugs in security protocol designs as they force the designer 

%to make everything explicit and thus confront difficult design 

%choices that might otherwise be fudged. 

%\end{quote}

%

%\end{frame}

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%

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\begin{frame}[c]

\frametitle{Mid-Term}

\begin{itemize}

\item homework, handouts, programs\ldots

\end{itemize}\bigskip\bigskip\bigskip

\begin{center}

{\huge\bf\alert{Any Questions?}}

\end{center}

\end{frame}

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\begin{frame}[c]

\frametitle{Security Engineering}

  \begin{center}

  \begin{tabular}{cc}

  \raisebox{-0.8mm}{\includegraphics[scale=0.28]{../pics/flight.jpg}} &

  \includegraphics[scale=0.31]{../pics/airbus.jpg}\\

  \small Wright brothers, 1901 & \small Airbus, 2005 \\ 

  \end{tabular}

  \end{center}

  \end{frame}

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\begin{frame}[c]

\frametitle{1st Lecture}

\begin{itemize}

\item chip-and-pin, banks vs.~customers

\begin{quote}\small\rm

 the one who can improve security should also be 

 liable for the losses 

\end{quote}\pause\bigskip

\item hashes and salts to guarantee data integrity\medskip

\item storing passwords (you should know the difference between

brute force attacks and dictionary attacks; how do salts help?)

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{1st Lecture: Cookies}

\begin{itemize}

\item good uses of cookies?\medskip

\item bad uses of cookies: snooping, tracking, profiling\ldots

      the ``disadvantage'' is that the user is in

      \alert{control}, because you can delete them 

          \begin{center} ``Please track me using cookies.''

          \end{center}\bigskip\pause

\item fingerprinting beyond browser cookies

  \begin{quote}\small\rm

  Pixel Perfect: Fingerprinting Canvas in HTML5\\ 

  (a research paper from 2012)\\

  \footnotesize

  \url{http://cseweb.ucsd.edu/~hovav/papers/ms12.html}      

  \end{quote}      

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{1st Lecture: Cookies}

\begin{itemize}

\item a bit of JavaScript and HTML5 + canvas\medskip

\begin{center}

\begin{tabular}{cc}

Firefox & Safari\\

\includegraphics[scale=0.31]{../pics/firefox1.png} &

\includegraphics[scale=0.31]{../pics/safari1.png} \\

\tiny

\pcode{55b2257ad0f20ecbf927fb66a15c61981f7ed8fc} &

\tiny

\pcode{17bc79f8111e345f572a4f87d6cd780b445625d3}

\end{tabular}

\end{center}\bigskip

\item\small no actual drawing needed\pause

\item\small in May 2014 a crawl of 100,000 popular 

webpages revealed 5.5\% already use canvas 

fingerprinting\smallskip

\begin{center}\scriptsize

\url{https://securehomes.esat.kuleuven.be/~gacar/persistent/the_web_never_forgets.pdf}

\end{center}

\end{itemize}

\end{frame}

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\begin{frame}[c]

\frametitle{1st Lecture: Cookies}

Remember the small web-app I showed you where a cookie 

protected a counter?\bigskip 

\begin{itemize}

\item NYT, the cookie looks the ``resource'' - harm\medskip

\item imaginary discount unlocked by cookie - no harm

\end{itemize}

\end{frame}

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