Google Two Factor Authentication - Changing Authentication Device
I've just upgraded my phone, but did not want to just restore the old backup on the new phone, so have set it up again from scratch.
Unfortunately, however, there is no way to suck just the Google Authenticator data from the phone (in my case both iPhones, but I suspect this is just the same for Androids) and put it on the new phone. So the Google Authenticator config was lost and needed recreating... except you cannot get the authenticator seed info back from Google, so you have to reset that too.
So you need to modify your authentication config for the new device.
To do this:-
* Go to your google account (since you are using 2 factor auth you will need to login with user/pass plus additional auth code).
* Find the Using 2-step verification entry and click Edit (you may be prompted again for your password)
* On the Mobile application line click Remove
* 2 Factor auth will be switched off the account (temporarily).
* If you do not have a number set up for SMS auth then you will be guided through setting this up. (this tends to include yet another re-auth stage).
* Set up authentication for your phone/device again - you can probably use the 2d barcode to set your device up (make sure you can tell the new entry from the old - which you will need to delete now or later).
* and after working through this you have working 2 factor auth again
The upside of this is that your old emergency 2 factor auth password (given to you when you first set it up - also displayable from within the 2 factor auth setup screens) are not changed.
Also any application passwords you set up (ie email IMAP/SMTP access, google reader sync etc), also continue working OK without change.
Obviously if you were doing this because you believed your config was compromised then you would need to invalidate all of these too.
Overall this was a bit of a faff, but less painful than I was expecting.