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I know this question has been asked before - or similar. I really don't understand Google Authenticator. If I have set up 2FA on my old phone and can no longer use my old phone - how do I login to these various websites (e.g. cryptocurrency exchanges) with my new phone?

I think I misunderstood Backup Codes - I thought if I downloaded these backup codes I would be able to use them to access my favourite crypto website. But these are 8-digit codes, and my crypto websites require 6-digit 2fa codes.

Some websites will help you if you don't have access to your 2fa. I thought the point in the backup codes was to enter with new 6-digit codes, but clearly not. Is it possible to see on a new phone all the logins I had previously set up on my old phone? I mean, if I had 15 logins set up on old phone - How can recover all that entire set-up?

Chris

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Solving the Existing Problem

Hopefully, you still have the old phone. Google Authenticator is not meant to be transferred, but you could use a backup utility (possibly requiring root access) to back up the data files from the old phone, and restore them on the new one. Also, many sites offer SMS as a backup way of verifying a login (even though this is not as secure), so you may be able to access some accounts this way, if set up.

If you can't exercise either above option, you will likely need to recover those accounts (possibly using backup codes; if they don't fit where you put the 2FA token, perhaps there is a "use a backup code" button like some sites have).

Preventing This Next Time

Google Authenticator, as mentioned, does not have backup capabilities at time of writing. The only other solution would be to use a 3rd party 2FA app. There are probably many options in the app store, but the main ones I'm familiar with are Authy, which syncs your tokens to the cloud (supposedly encrypted and only recoverable by you, but can you trust them?), or the open source AndOTP, which lets you import/export the data. However, I'd suggest you do your own research.

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I really don't understand Google Authenticator

This is my understanding:

Google Authenticator uses Time-based One-Time Password algorithm (TOTP) along with a secret key and the current time (rounded to nearest 30 second mark), to generate a 6 digit code. You can add to it multiple accounts (an account name, and a secret key) and that's all there is to it. There's no need for it to do any network requests or connect to other services through the network. The generation of the 6 digit codes happens only on your phone using the secret keys stored by the app on your phone and nowhere else. The way a website accepts or declines the 6 digit code you submit to it, is by going through the exact same process as what your google authenticator app is doing, generating the same 6 digit code (by way of using the same secret key, stored against your account with them, and the current time) and then comparing that with the code you submit to it when you log in.

The secret key for each account in your google authenticator app made its way onto your phone when you scanned a QR code presented to you on the screen when you register for 2FA with the service. That service may then optionally decide to provide you with backup codes but those codes will only be any good for that same service.

This means you would be able to create your own backup/recovery option that would also port to new phones, if you saved a screenshot of the QR code during registrations (you can also just save the secret key itself, which is sometimes displayed below the QR code or accessible via an 'Enter code manually' option)

Be aware that this exposes you to the risk of losing or having your saved QR codes compromised, hence the other solutions (such as the backup options provided by Authy as suggested by multithr3at3d) would probably be the way to go.

Hope this helps

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I am assuming that you used the old phone to log in to various websites using your 'Google' account. If that is so, you need to simply log into your Google account using your new phone. If you have 2-factor authentication set up, you will need those Google backup codes to log into that Google account. Once you have successfully logged into your Google account using your new phone, you can redownload the Google Authenticator app in your new device and access those various websites using your Google account as before.

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