Google Authenticator

[birr]

I am going to have to use Google Authenticator because some services on Bitsamp require it.  Never used it before, and I have a question.
What if, after using Bitstamp on my tablet, I turn off Google Authenticator on my tablet -- will I then be able to go to a different computer and log in to gmail without having to input an Authenticator code -- in other words, does Google Authenticator turn off entirely, or on just one machine?

[Aahzman]

if you install google authenticator on a mobile device, the tokens stay on that device (there are ways to move tokens between devices, but i have yet to see a clean/easy way to do so).  When you enable google 2-factor authentication on a site or service, the device you register that site's token on (by scanning the QR code on the site when you enable 2FA) is the device you will then have to use to log back into that site or service. 

If you change devices (ie, you upgrade your iPhone 4S to an iPhone 5S), you will have to first log into all the sites you are using 2FA on, disable 2FA, then install Google Authenticator on your new phone, and then re-enable 2FA on all those sites again (unless you can decipher the pain-in-the-ass process o moving your Google Authenticator tokens from one device to another).

[birr]

OK, to use a different machine I disable GA at Bitstamp, then re-enable on the new machine. 
When you say disable is it enough simply to turn GA off as explained in this google support instructions link?
https://support.google.com/accounts/answer/1064203?hl=en

[cesmak]

No you have to disable 2FA on every single account where you use it.

If you use on bitstamp you have to disable 2FA on bitstamp after loggining in.

Disable 2FA on google site works only for gmail.

Cheers

[Aahzman]

Google Authenticator is an app for mobile devices. what good would it do to have Google Authenticator on the same machine you use to access your 2FA-protected sites/accounts?

Every site you enable 2FA on and scan their QR code into Google Authenticator on your phone creates a unique token on your phone within the GA app. Turning on 2FA in GMail (or the google suite of web apps) doesn't magically enable 2FA on all the other sites you visit.

So, you have to enable 2FA on your Google account, your bitstamp account, your virtex account, your btc-camwhores account, etc. Every time you activate 2FA on a different site, you open up Google Authenticator on your phone and scan in that site's unique QR code, generated JUST FOR YOU.  Each site will have a separate entry in your GA list. Each site will have a unique code generated in Google Authenticator every 30 seconds.

birr, perhaps you should do a little more research into how to use 2FA in general, and Google Authenticator specifically before you end up locking yourself out of a bunch of things you really don't wanna be locked out of.

[birr]

Don't worry, I'm not gonna burn my fingers.
Hey, while I was investigating this, I found something pretty cool:
https://github.com/gbraad/html5-google-authenticator
check out the "deployed test version"
http://gauth.apps.gbraad.nl/
it works!
You can save the code and run it offline.
A thread here
http://superuser.com/questions/462478/is-there-a-google-authenticator-desktop-client
mentions some other GA utilities