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\section*{Handout 1 (Security Engineering)}

Much of the material and inspiration in this module is taken
from the works of Bruce Schneier, Ross Anderson and Alex
Halderman. I think they are the world experts in the area of
security engineering. I especially like that they argue that a
security engineer requires a certain \emph{security mindset}.
Bruce Schneier for example writes:

\begin{quote} 
\it ``Security engineers --- at least the good ones --- see
the world differently. They can't walk into a store without
noticing how they might shoplift. They can't use a computer
without wondering about the security vulnerabilities. They
can't vote without trying to figure out how to vote twice.
They just can't help it.''
\end{quote}

\begin{quote}
\it ``Security engineering\ldots requires you to think
differently. You need to figure out not how something works,
but how something can be made to not work. You have to imagine
an intelligent and malicious adversary inside your system
\ldots, constantly trying new ways to
subvert it. You have to consider all the ways your system can
fail, most of them having nothing to do with the design
itself. You have to look at everything backwards, upside down,
and sideways. You have to think like an alien.''
\end{quote}

\noindent In this module I like to teach you this security
mindset. This might be a mindset that you think is very foreign to you
(after all we are all good citizens and not ahck into things). I beg
to differ: You have this mindset already when in school you were
thinking, at least hypothetically, about in which ways you can cheat in an
exam (whether it is about hiding notes or looking over the shoulders
of your fellow pupils). Right? To defend a system, you need to have
this kind mindset and be able to think like an attacker. This will
include understanding techniques that can be used to compromise
security and privacy in systems. This will many times result in
insights where well-intended security mechanisms made a system actually
less secure.\smallskip

{\Large\bf Warning!} However, don’t be evil! Using those
techniques in the real world may violate the law or King’s
rules, and it may be unethical. Under some circumstances, even
probing for weaknesses of a system may result in severe
penalties, up to and including expulsion, fines and
jail time. Acting lawfully and ethically is your
responsibility. Ethics requires you to refrain from doing
harm. Always respect privacy and rights of others. Do not
tamper with any of King's systems. If you try out a technique,
always make doubly sure you are working in a safe environment
so that you cannot cause any harm, not even accidentally.
Don't be evil. Be an ethical hacker.\smallskip


In this lecture I want to make you familiar with the security mindset
and dispel the myth that encryption is the answer to all security
problems (it is certainly often part of an answer, but almost always
never a sufficient one). This is actually an important thread going
through the whole course: We will assume that encryption works
perfectly, but still attack ``things''. By ``works perfectly'' we mean
that we will assume encryption is a black box and, for example, will
not look at the underlying mathematics and break the 
algorithms.\footnote{Though fascinating it might be.}
 
For a secure system it seems four requirements need to come together:
First a security policy (what is supposed to be achieved?); second a
mechanism (cipher, access controls, tamper resistance etc); third the
assurance we obtain from the mechanism (the amount of reliance we can
put on the mechanism) and finally the incentives (the motive that the
people guarding and maintaining the system have to do their job
properly, and also the motive that the attackers have to try to defeat
your policy). The last point is often overlooked, but plays an
important role. 

Lets look at an example. The questions is whether the Chip-and-PIN
system with credit cards is more secure than the older method of
signing receipts at the till. 



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