https://www.grc.com/sn/sn-996-notes.pdf (page 18) https://twit.tv/shows/security-now/episodes/996
(It's really not too difficult.)
--edit--
Looking at the linked page that would be super trivial to implement.
https://www.grc.com/sn/sn-996-notes.pdf (page 18) https://twit.tv/shows/security-now/episodes/996