What factors of authentication does Usher offer?

Usher is a true multi-factor authentication solution, leveraging the following security factors:

• Knowledge factor, or “something you know” – passcode-protected app and/or device
• Inherence factor, or “something you are” – integration with Touch ID 
• Possession factor, or “something you have” – the phone itself, with its unique cryptographic certificate used to communicate with the Usher server