There are three (3) commonly accepted authentication factors:
~~ What You Have – fairly useless by itself as an object (like a key or card) works just as well for a thief as for you.
~~ What You Know – Information unique to your life experience. Have you ever heard: “it’s not ‘what’ you know, but ‘who’ you know” that assists success.
~~ What you Are – This is the terrifying one. When your fingerprint, voice print, iris scan, DNA analysis, etc. belong to a hacker, your identity is permanently compromised.
Combining any of the two (2) factors is much wiser. Example: a digital device has a unique ID authorized to you. Require recognition of your hidden childhood friend’s face and you enjoy easy TWO FACTOR AUTHENTICATION.