About one-time passwords (OTP)
A one-time password (OTP) is a temporary and unique passcode, that is generated by an algorithm to authenticate users to digital resources. There are different types of one-time passwords (OTP), as defined by the Initiative for Open Authentication (OATH):
Time-based OTP (TOTP): A TOTP is renewed after a fix amount of time, for example 30 seconds. The algorithm that generates each password uses the current time of day as one of its factors, ensuring that each password is unique.
Event-based OTP (HOTP): An HOTP is valid per authentication. After authentication a new OTP is generated.