Mobile phones can be used for authentication via One Time Password (OTP) or Challenge-Response (CR or Y/N) delivered via Interactive Voice Response (IVR). This is a less-secure form of strong authentication because it is vulnerable to man-in-the-middle (MITM) attacks.
- IVR OTP places a voice call to the user, who listens to the OTP. Then the user enters the OTP into their login authentication and is approved.
- IVR Challenge-Response places a voice call to the user, who listens to a question asking if the authorization attempt is approved. If the user replies “Yes”, authentication is completed and the user is logged in. If the user replies “No”, authentication is failed and the user is not logged in.
For organizations with visually-impaired users, IVR Challenge/Response enables compliance with the Americans with Disabilities Act (ADA). However, IVR authentication is not compliant with NIST-based regulatory regimes due to its security vulnerability.