we don't actually use any signs in elliptic curve calculations since we are using modular arithmetic. for example if prime is 7 then we have
4 ≡ 11 ≡ 18 ≡ -3 ≡ -10 (mod 7)
by a "contract" we only use the smallest positive number meaning "4"
You points are all well taken. Very good information for the more technical savvy in the audience.
I'm trying to follow you guys, however, its quite difficult since I don't have any background knowledge. Its definitely quite interesting. Is there any good literature you could recommend to start with?
There are ton of books on Elliptic curves, but they are not Bitcoin related. Best tutorial is famous 4-part series: Elliptic Curve Cryptography: a gentle introduction.