Step-up authentication is a security measure used to verify the identity of a user during high-risk transactions or when accessing sensitive information. It involves requesting additional authentication steps beyond the initial login process, such as asking for a second factor of authentication, such as a fingerprint, facial recognition, or a security code sent to a user's mobile device.

The primary use of step-up authentication is to provide an additional layer of security that can help prevent unauthorized access to sensitive information or fraudulent activities. By requiring users to provide additional authentication factors, it becomes more difficult for attackers to gain access to the user's account or information, even if they have somehow obtained the user's login credentials.

Step-up authentication is commonly used in industries such as banking, healthcare, and e-commerce, where sensitive data is often transmitted and accessed. It can help organizations meet compliance requirements and protect their customers from data breaches and identity theft.

In general, step-up authentication should be used judiciously and only when necessary, as it can create additional friction and inconvenience for the user. The timing and circumstances for step-up authentication will depend on the specific security requirements of the system and the risk associated with different types of transactions or activities.