With the rise of cloud services, users have more and more information stored in cloud services. The traditional text password mechanism has been unable to protect the user's account security. The use of the second factor authentication and two-stage authentication has gradually become a trend. This article introduces the Google authenticator, a two-stage authentication mechanism provided by Google, and the Universal Authentication Framework (UAF), Universal 2nd Factor (U2F), and FIDO2 mechanisms proposed by the FIDO Alliance.