TOTP security tokens and 2-Step Verification

Time-based One-time Password Algorithm (TOTP) is an algorithm that computes a  one-time password  from a  shared secret key  and the current time. The most popular implementation of this solution is Google Authenticator.

This application that implements  TOTP   security tokens . Usually is branded as “ Two-step verification {.mw-redirect}” (or 2-Step Verification). Authenticator provides a six- to eight-digit  one-time password  which users must provide in addition to their username and password to log into various services or other sites.