U2F is an open authentication standard that strengthens and simplifies two-factor authentication using specialized USB or NFC devices based on similar security technology found in smart cards.
U2F provides two-factor authentication by combining something you know (a username and password) with something you have (a hardware security key). It's designed to be easy to use and does not require a battery or network connectivity, so it works even in situations where your phone or computer might not have power or an internet connection.
The FIDO Alliance, which is behind the U2F standard, says that it's more secure than two-factor authentication systems that rely on SMS messages or one-time codes generated by an app, because those can be intercepted by attackers.
U2F-compatible security keys are available from a number of different manufacturers, and they all work with a growing number of online services. Google, Dropbox, GitHub, and Facebook are among the companies that support U2F. What does U2F stand for? The Universal 2nd Factor (U2F) protocol was created by the FIDO Alliance with the goal of providing a simpler and more secure way to authenticate to online services. U2F uses public key cryptography to verify the user's identity, and it supports multiple authentication factors, including physical tokens, biometrics, and one-time codes. U2F is designed to be interoperable, so that any U2F-enabled device can be used with any U2F-enabled service.
What are U2F keys?
U2F keys are physical devices that can be used to authenticate a user to an online service. The user plugs the U2F key into a USB port on their computer and enters their username and password into the service's login page. If the credentials are correct, the U2F key will emit a signal that allows the user to access the service.
U2F keys are designed to be more secure than traditional password-based authentication methods. They are difficult to clone and can be configured to only work with specific online services. This makes them less likely to be compromised by phishing attacks or other forms of malware.
U2F keys are not currently widely used, but they are gaining popularity as a more secure alternative to traditional authentication methods.
How do U2F keys work?
U2F keys are physical devices that can be used to authenticate a user to an online service. A U2F key typically takes the form of a USB key or a smart card, and is designed to be used in conjunction with a corresponding software application.
When a user attempts to log in to a service that supports U2F authentication, they will be prompted to insert their U2F key into a USB port or to swipe their smart card. Once the key is detected, the software will generate a challenge, which will be signed by the key. The signature will be verified by the service, and if it is valid, the user will be granted access.
U2F keys are designed to be highly secure, and to protect against a number of different attack vectors, including phishing and man-in-the-middle attacks.
Is FIDO2 the same as U2F?
FIDO2 is a new standard that includes both the W3C's Web Authentication specification (WebAuthn) and the FIDO Alliance's Client to Authenticator Protocol (CTAP). FIDO2 devices can be used for both passwordless authentication as well as two-factor authentication (2FA).
U2F is an older standard that was developed by the FIDO Alliance. U2F devices can only be used for two-factor authentication (2FA).
What if I lose my YubiKey?
If you lose your YubiKey, you will no longer be able to access any services that require YubiKey authentication. This includes any services that you use your YubiKey to log into, as well as any services that use your YubiKey to provide two-factor authentication (2FA).
If you use your YubiKey for 2FA, you will need to contact each service that you use and update your account to use a different 2FA method. Many services will allow you to use a mobile app for 2FA in lieu of a YubiKey.
If you use your YubiKey to log into any services, you will need to contact the service provider and update your account to use a different login method. Many service providers will allow you to log in with an email and password combination.