I had designed "Moodle OTP Registration & Authentication Plugin" for my client. This plugin offering an email-based self-registration and a new authentication method via one-time password (OTP).
I had also designed highest quality document/specification with process diagram, state machine, use cases,
requirements, error handling, and screen mockups is available.
You contact me on firstname.lastname@example.org or Skype: magento.experts for more details.