TOTP (Time-Based One-Time Password)

An algorithm defined in RFC 6238 that generates short-lived numeric codes from a shared secret key and the current Unix time, typically producing a 6-digit code valid for 30 seconds. TOTP is the basis for authenticator apps such as Google Authenticator and Authy. Because codes are time-bound and generated offline, TOTP provides stronger phishing resistance than SMS-based OTP while remaining accessible without internet connectivity.