# CSE 127: Lecture 5

The topics covered in this lecture are
Euler Phi function
buffer overflows
*under construction*
Euler's theorem showed that for all `x` in `{1, ..., n-1}`:
`
x`^{phi(n)} = 1 mod n

where phi(n) is defined as follows:
Write `n = prod`_{i} p_{i}^{ei},
where `p`_{i} =/= p_{j} if `i =/= j`.
(I.e., express `n` as its prime factorization, with multiple
occurences of primes in the factorization coalesced and expressed as
exponents.) Then
`
phi(n) = prod`_{i} p_{i}^{ei-1}(p_{i}-1)
So in RSA where `n=p*q`, where `p` and `q` are
primes, `phi(n) = (p-1)(q-1)`.

Anatomy of a Unix process's stack. Stack frames, environment
variables, argument lists. (Windows is not very different.)
Task: use gdb commands (info reg, x/x `addr`) to figure
out where a process's stack is and look at the environment. You
should write a ``hello world'' program, run gdb on it, set a break
point, e.g., "break main", run the program until it hits the break
point, then use the info and x commands to explore.

## Links

These are links additional security-related information. Exploring
them is optional unless otherwise stated.
Here is a New York Times article on
Warning
on Iraqi Hackers and U.S. Safety. Note the 2% success rate figure.

Hacking physical master keys.

You are required to read this web site on
electronic voting
machines.

New worm attack slows down the Internet. Read the
story at the
BBC, the
story
at CNN, and the
original CERT
advisory about the vulnerability, and the
current advisory
about the worm.

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bsy+cse127.w03@cs.ucsd.edu, last updated Sat Jan 25 15:06:55 PST 2003. Copyright 2003 Bennet Yee.

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