HMAC-Based One-Time Password
HMAC-Based One-Time Password (HOTP) is a cryptographic algorithm that generates one-time passwords (OTPs) using a hash-based message authentication code (HMAC) and a counter. It provides a secure method for two-factor authentication (2FA) by creating unique, time-limited codes that are difficult to predict or reuse. HOTP is standardized in RFC 4226 and is widely used in authentication systems to enhance security beyond simple passwords.
Developers should learn and use HOTP when implementing two-factor authentication (2FA) in applications that require enhanced security, such as banking systems, enterprise logins, or sensitive data access. It is particularly useful in scenarios where offline authentication is needed, as it relies on a counter rather than time synchronization, making it suitable for hardware tokens or environments with limited connectivity. HOTP helps prevent unauthorized access by ensuring that passwords are valid for only a single use, reducing the risk of replay attacks.