On: Primer on elliptic curve cryptography

[acjohnson55]

I've usually heard it referred to as http://en.wikipedia.org/wiki/Fermat%27s_little_theorem

[wging → acjohnson55]

Fermat's little theorem is Euler's theorem in the special case that m is prime. The condition on Euler's theorem is that x and m must be relatively prime... which is certainly true if m is prime.