Fermat's last theorem

Yeah.. that is the name of the book I am reading currently at my usual snail pace.
For the less-informed : Fermat was a great (amateur) French mathematician whose last theorem :
x^n + y^n = z^n has no solution for n>2
has intrigued the mathematicians world wide. Only recently someone has been able to prove this theorem.
In the book, Fermat is portrayed as an amateur who liked to hide to proofs of his theorems to 'challenge' other mathematician come up with a proof instead. Nasty.
But I am sure he never would have thought that his theorems would play such a crutial part in modern computer cryptography and security. (I am sure no one could even have imagined a computer by then!!!)