Two Factor Authentication
TFA = Two Factor Auth
OTP = One Time Password
For Mobile: FreeOTP
Warning: encrypt your HD if you are going to put the auth system on your PC!
For windows: Winauth
For Linux: OTP on linux client side and OAUTH
How to set up SSH for TFA
How to back up your TFA on Android and how to set it up for Paypal
Remember to write down your keys and keep them somewhere safe: losing them means no more access to your system!