XF 1.4 SQL query to reset all passwords

In case this is still useful to people:

UPDATE xf_user_authenticate
SET data = BINARY 'a:0:{}', scheme_class = 'XenForo_Authentication_NoPassword'
WHERE user_id = 1
Thank you, Martin. Is there a way to reset the passwords of ALL users to a random (secure) string so that they have to reset their own password to get in? Thanks!