Auto Provisioning - General Question

[CraigFox]

OK, This is a lob into the community for a recommendation on how to setup an auto-provisioning solutions.

GOAL-1: A zero touch solution to provision phones to register on the phone system.
GOAL-2: Provide the ability to Authenticate the Phone to the provisioning system (e.g. username/password)
GOAL-3: Encrypt the provisioning information during transport (e.g. ftps, https, etc)

Solution-1: TFTP - no authentication mechanism, not encryption mechanism
Solution-2: FTP/HTTP - no encryption mechanism, Problem, how to get the username/password for the site to the phone automatically?
Solution-3: FTPS/FTPES/SFTP/HTTPS - Problem, How to get the username/password to the phone automatically. Not sure it's supported by Yealink

Any solutions, ideas, comments would be greatly appreciated