handouts/ho05.tex
changeset 274 1e1008403f17
parent 273 03321ef4349a
child 275 06a04b3b2dda
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273:03321ef4349a 274:1e1008403f17
   360 \item you could only have generated your answer after I send
   360 \item you could only have generated your answer after I send
   361       you my initial message (since my $N$ is always new, it
   361       you my initial message (since my $N$ is always new, it
   362       could not have been a message that was generated before
   362       could not have been a message that was generated before
   363       I myself knew what $N$ is)
   363       I myself knew what $N$ is)
   364 
   364 
   365 \item if only you and me know the key $K_{IY$, the message
   365 \item if only you and me know the key $K_{IY}$, the message
   366       must have come from you
   366       must have come from you
   367 \end{itemize}
   367 \end{itemize}
   368 
   368 
   369 \noindent Even if this does not seem much information I can
   369 \noindent Even if this does not seem much information I can
   370 glean from such an exchange, it is in fact the basic building 
   370 glean from such an exchange, it is in fact the basic building 
   635 of $H_1$ and $H_2$, respectively $M_1$ and $M_2$ and can
   635 of $H_1$ and $H_2$, respectively $M_1$ and $M_2$ and can
   636 decrypt the corresponding messages.
   636 decrypt the corresponding messages.
   637 
   637 
   638 Now the big question is, why on earth does this splitting
   638 Now the big question is, why on earth does this splitting
   639 of messages in half and additional message exchange help
   639 of messages in half and additional message exchange help
   640 with defending agains person-in-the-middle attacks? Well,
   640 with defending against person-in-the-middle attacks? Well,
   641 lets try to be such an attacker. As before we intercept
   641 lets try to be such an attacker. As before we intercept
   642 the messages where public keys are exchanged and inject
   642 the messages where public keys are exchanged and inject
   643 our own.
   643 our own.
   644 
   644 
   645 \begin{center}
   645 \begin{center}
   781 
   781 
   782 If you want to know more about how cars can be hijacked,
   782 If you want to know more about how cars can be hijacked,
   783 the paper  
   783 the paper  
   784 
   784 
   785 \begin{center}
   785 \begin{center}
   786 \url{http://www.cs.ru.nl/~rverdult/Gone_in_360_Seconds_Hijacking_with_Hitag2-USENIX_2012.pdf}}
   786 \url{http://www.cs.ru.nl/~rverdult/Gone_in_360_Seconds_Hijacking_with_Hitag2-USENIX_2012.pdf}
   787 \end{center}
   787 \end{center}
   788 
   788 
   789 \noindent is quite amusing to read. Obviously an even more
   789 \noindent is quite amusing to read. Obviously an even more
   790 amusing paper would be ``Dismantling Megamos Crypto: 
   790 amusing paper would be ``Dismantling Megamos Crypto: 
   791 Wirelessly Lockpicking a Vehicle Immobilizer'' but because
   791 Wirelessly Lockpicking a Vehicle Immobilizer'' but because