Comment by mcdoug

For those interested in how TOTP is implemented, here it is in Python [1] and Ruby [2]. It is really simple and understandable. Oh, and did you know you can secure your SSH connections using TOTP [3]?

This stuff is no more complicated than storing password hashes. Having a nice client app is good, but Google Authenticator is good enough. So instead of using authy and relying on a third party, why not get something like [4] and be done with it?

[1] https://github.com/nathforge/pyotp

[2] https://github.com/mdp/rotp

[3] http://delyan.me/securing-ssh-with-totp/

[4] https://github.com/mtigas/django-twofactor