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by nsheridan 3356 days ago
There's noting stopping you from scanning the barcode multiple times
1 comments

Didn't it change the web page on your computer browser after you successfully added it into Google Authenticator?

I suppose you could always take a photo of the QR code and then rescan that. Text seems simpler.

edit: Anyone else remember this behavior? Old version? Browser specific?

It changes when you input current code. You can scan it multiple times, print it, and then input the code from one of your devices.
Also, if you have a rooted device, you can get the original secret from the SQLite database of the authenticator app.
"can get the original secret" is a phrase which should worry a security-conscious person
rooting their phone is not something a security-conscious person would do, either.

Edit: maybe I should have explained my position. There are a few security issues with rooting a phone, e.g.:

- rooting usually requires unlocking the bootloader. Once it's unlocked, anyone can flash or boot a custom recovery and modify your system partition. Enrolling your own keys in the recovery and re-locking the bootloader, while possible, is an undocumented and complex process that just about nobody uses, see https://mjg59.dreamwidth.org/31765.html . You're also screwed if a system update replaces the recovery. Once the bootloader is unlocked, anyone with physical access to your phone can mess with your system in malicious ways.

- it circumvents the system's permission model. A malicious app that tricks the user into granting it root rights (maybe for a legitimate reason) could access information it shouldn't have, install a keylogger, etc.

Even without root. Just run a backup and extract it from that. You can do it with just adb or helium.
That doesn't work for Google Authenticator. Apps can opt-out of being able to be backed up, which even prevents adb/helium backups (unless you're rooted).