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If you use Google Authenticator to log into sites using 2 Factor Authentication, how do you log in after you lose your phone?

Can you install Google Authenticator on another device?

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You can install Google Authenticator on another device. However, that new application will not have access to the prior secret shared between the server and your phone.

In Google's case, they recommend printing out backup passwords and keeping them somewhere safe in the event anything happens. It is up to other sites using Google Authenticator as a means of 2FA authentication to provide similar ways of recovering from such a loss. The HOTP and TOTP algorithms themselves do not allow for any recovery.

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During the enrolment procedure Google provides you with a set of 8-digit "one-time scratch codes" which you should print out and keep in a safe place. If you lose your phone, you can use these scratch-codes to log in to your infrastructure and to enrol a new device.

  • According to security.stackexchange.com/a/167580/10390 these codes are account specific though, so they help you recover access to your Google account, but not to other accounts set up to use Google Authenticator. I'm not 100% sure as to whether that is correct though. – Highly Irregular Sep 27 '17 at 21:49

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