* Passwordless single factor with AD integration (couldn't this already be done by storing your password on the key?)
* 2factor auth with the token as one of the factors.
From the article:
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Single Factor: This only requires possession of the Security Key to log in, allowing for a passwordless tap-and-go experience.
Second-Factor: In a two-factor authentication scenario, such as the current Google and Facebook FIDO U2F implementations, the Security Key by Yubico is used as a strong second factor along with a username and password.
Multi-Factor: This allows the use of the Security Key by Yubico with an additional factor such as a PIN (instead of a password), to meet the high-assurance requirements of operations like financial transactions, or submitting a prescription.