I might remember it now that I know KDF = key derivation function.
Since the GP mentions Django, it's worth remembering in this connection that there are extra security concerns with expensive KDF algorithms. There was a vuln in Django where people could submit 'passwords' of arbitrary size - a 20 character password isn't a problem, but 1MB worth of text being expensively hashed a few times at once could be used as a nice DoS vector.[0] So there's more to the problem than just bunging in PBKDF2/bcrypt and forgetting about it.
