Oh wait. I just realised that all integers belong to a finite integer field of [1, n-1].
So you have to do finite field math or whatever its called.
The tricky one is division; that is not division on the field of integers followed by a modulus operation. Instead, it involves finding the multiplicative inverse of a number; that is, given b, we find the field member b^−1 such that b×b^−1=1. Then, a/b=a×b^−1
so thats how k^-1 is calculated. someone please correct me if im wrong... or tell me if im right lol. im still not sure if thats correct