What is a common use case for the HOTP protocol?

The HOTP (HMAC-based One-Time Password) protocol is commonly utilized in two-factor authentication implementations. It generates a one-time password based on a secret key and a counter, making it particularly effective for enhancing security when accessing sensitive information or services.

In two-factor authentication, users provide something they know (like a password) and something they have (like a device generating a one-time password). HOTP serves as the second factor, ensuring that even if a password is compromised, unauthorized access is still prevented without the unique one-time code. This dual requirement significantly strengthens the security posture against unauthorized access.

While generating secure passwords for cloud services and providing real-time user authentication are relevant to security practices, these functions do not specifically capture the defining characteristics and primary use of the HOTP protocol. Similarly, although generating time-sensitive codes for transactions is relevant to many authentication methods, HOTP relies on a counter rather than time-based elements. Hence, its main and most effective use case aligns with two-factor authentication.