Your top comment on HN. What's part am I missing that if we used hash(long_key pair + emp_key pair) protects us if the long term is known by an attacker? Why c

Your top comment on HN. What's part am I missing that if we used hash(long_key pair + emp_key pair) protects us if the long term is known by an attacker? Why couldn't the attacker intercept the emp_keys. I'm assuming there's no key signing done here.