The Initiative for Open Authentication (OATH) is based around the idea of authenticating with One-Time Passwords (OTPs) using a standard outlined in RFC 4226 which is referred to as Hash-based OTP (HOTP) and Time-based OTP (TOTP).
You can use Google Authenticator on your Android or Blackberry phone to provide second-factor authentication for Google accounts, Linux boxes, LastPass, and other services.
Google Authenticator
Google accounts
LastPass
PAM for UNIX
Amazon Web Services (AWS) accounts
Kenny Root
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