Critals- how do they work?

Backstabs and Ripostes do huge damage, but I want to know what how they decide their damage, do they go by ???% weapon damage times ???% critical rating minus enemy armour rating, do they get stronger with a certain stat or stat scaling etc.

So in short how can I maximise my criticals? and critcal defence if possible?

Criticals do damage based on their weapons based stat, mltiplied by a factor decided by their critical factor. Its hard to pin down exactly what this factor is (it may be a percent increase in AR but its hard to be sure) since no definitive testing has been done. The best defence is learning to avoid them.

Welcome to the forums btw!