A simple example would be separating usernames and passwords, having an outer and inner password (think Truecrypt/Veracrypt) or even personal quirks. Again, it

A simple example would be separating usernames and passwords, having an outer and inner password (think Truecrypt/Veracrypt) or even personal quirks. Again, it depends how much the attacker knows, but even today you can still do the classic "hash my master key with site name" for a password that you wouldn't store anywhere.