What about password reclamation - do I keep the answers to their grandmothers maiden name in the same database? What about adding a new email address to the list of ones I will mail a password reset token to - do I force them to prove ownership of the first email address before adding the second ? Or will a SMS to their phone do?
I am sure I am missing a hundred items and none of them are to do with bcrypt vs scrypt. Thus is hard stuff and I am avoiding most of it with the magic words "Mozilla persona" but I still don't know how to do sso well. I can do not badly but not well.
Edit: I am being a bit snipy and I apologise but I know I am in deep waters and would be happier if NIST were producing reference implementations. Perhaps actually they have - there is kerberos. If you want a key visit room 303 with your passport