Universal 2nd Factor (U2F) is an open authentication standard originally developed by Google, Yubico, and NXP Semiconductors that strengthens and simplifies two-factor authentication using a specialized NFC, Bluetooth, or a USB security device such as the Yubikey or Ledger Wallet.
A U2F security key can be used as an additional method of strong, easy to use, and a highly private second factor of verification before performing logins, password changes, API key creation, account modifications, changes to sensitive security measures, and confirming withdrawals.
One Time Password (OTP) fallback
If your account has both U2F and Google Authenticator, you can activate a One Time Password (OTP) fallback option. If you have lost or misplaced your U2F key, the option will grant you access to your Bitfinex account through the Google Authentication code.
