How do you collect Federal Tax ID's for commissions?


How do you guys collect your affiliates tax ID information for sending 1099's etc?
I was going to setup a separate secure form where the data could be store using AES encryption.
But then I would have to setup a separate method to authenticate there account info etc...

How do you guys handle this?

Or How about this..
Give them a link to a PDF then have them fax and sign in the agreement?