What I want to know is WHY every student is allowed to access every locker. If opening and closing lockers is completely permission less, what prevents student 1 from walking back and changing the state of all lockers one more time? Can the students collude? What if one student intentionally leaves a locker in an ambiguous state to grief the next student? Isn’t it better for all lockers to be controlled by a TEE so that their behavior is more predictable? I wouldn’t recommend hiring anyone who answered “something something perfect squares” without thinking about these deeper issues