I've been trying to research the privacy implications of using 2 factor authentication, specifically google authenticator. More generally I just want to gain an understanding of 2fa. I understand generally how it enhances security (one time passwords, requires access to your mobile). What I'm curious about is (1) what are the privacy implications of using Google Authenticator? (2) does Google Authenticator require a google account? (3) Are other 2fa apps (FreeOTP, etc) interoperable with google authenticator / sites designed to work with google authenticator? I haven't seen much talk about 2fa on Wilders so this might be a good place to start a general conversation on the topic as well.