Factors to consider

There are a number of criteria to consider in selecting a second-factor, including:

Second-factor assurance levels

Any 2FA protection provides a higher assurance level than a static password alone affords. Within the realm of 2FA options, some options provide a higher level of security than others. The threshold for the security level appropriate for a given application that is protected with 2FA will vary with the risk posed to that application. As such, for applications that require a sufficiently high assurance level, less secure 2FA options will not be allowed.

Preferred second-factor option

The preferred option is the Duo Mobile app.


Duo Mobile System Requirements

  • Android: the current version of Duo Mobile supports Android 7.0 and greater. Duo recommends upgrading to the most recent version of Android available for your device. We cannot ensure compatibility of Duo Mobile with custom variants or distributions of Android.

  • iPhone: The current version of Duo Mobile supports iOS 11.0 and greater. Support for older Duo Mobile versions on iOS 10.0 ended July 28, 2019.

Alternative options

Hardware tokens

Tokens for students

Tokens for employees

Phone call

SMS

Device management instructions

For steps on enrolling in Duo 2FA using one of the above alternate second-factor methods, please see the Device management instructions page.

Second-factor criteria comparison 

Second-factor option

Self-serve enrollment?

Phone number required?

Cellular network connection required?

Wi-Fi connection required?

Duo Mobile app

Yes

No

No

No (only for enrollment)

U2F token

Yes

No

No

Yes

OTP token

No 

No

No

No

Combined U2F/OTP token

Yes (U2F)

No

No

No

SMS

Yes

Yes

Yes

No

Phone call

Yes

Yes

Yes (or landline)

No

Assurance levels

Second-factor option

Assurance level

Duo Mobile App

High

U2F token

High

OTP token

Moderate - high

SMS

Low

Phone call

Low

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