Time-based One-time Password Algorithm

Acronym

TOTP

Quote

"A variant of the HOTP algorithm specifying the calculation of a one-time password value, based on a representation of the counter as a time factor."

Url

https://tools.ietf.org/html/rfc6238

About

TOTP is an time-based extension of the HMAC-based One-Time Password (HTOP) algorithm. Where HTOP truncates a HMAC-SHA-1 hash of a shared secret and a counter value, TOTP is the truncation of either a HMAC-SHA-1, HMAC-SHA-256 or HMAC-SHA-512 hash of a shared secret and an integer representing the number of time steps between an initial counter time and the current Unix time.