Analysing KESO's Master Key System

Context NB: This is a writeup of something I explored years ago. It’s not really structured, and it may not be 100% accurate, but I find it interesting to share nonetheless. Hope you enjoy it! Some big buildings (hospitals, big companies, universities, etc.) still use traditional physical locks. On big facilities, people may need to open (or close) 3 or 4 doors between the outside and their desk. The problem arises in not giving more rights than needed.