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So today I got Authy, (because I wanted 2FA on my google account).

Anyway, it works grand, and I scanned the google QR code and all works well.

One thing is weird though, I have coinbase on my iPhone as I buy bitcoins sometimes. When I launched the Authy app it immediately offered Coinbase codes as well as google codes.

The thing is I didn't use google 2FA for Coinbase, my coinbase account is totally separate from google.

So, minus the fact that I had the coinbase app on my iPhone (and iPhone apps are supposed to be completely sandboxed and don't communicate), how did Authy know I had a coinbase account?

Bonus question, which is the weirdest thing ever, when I went to sign into Coinbase (after having downloaded the authy app), rather than sending me an SMS to my phone, Coinbase ASKED for the Authy code...

Also the Authy app sent me a push notification on my phone to suggest I open it to get my code. How is this POSSIBLE?

I didn't link Authy and coinbase, the ONLY link is my coinbase user name is my google email address... please help explain.

  • There's no Google Codes and Authy Codes. There's only 2FA. Both Authy and Google Authenticator will use exactly the same keys and generate exactly the same codes. They will get the current timestamp down to half-minutes, hash it with your key, and generate a code. You can even do it by hand if you want. – ThoriumBR Feb 26 '17 at 1:54
  • @ThoriumBR, sure but that doesn't explain how Authy knew I had coinbase, is linked with Coinbase without scanning a QR code or how it knows when I'm signing into coinbase. – Woodstock Feb 26 '17 at 10:04
  • Do Authy and Coinbase both have the same registered phone number? – Arminius Feb 28 '17 at 0:00
  • @Arminius - yes they do, but I didn't permission sharing on either side? – Woodstock Feb 28 '17 at 7:16
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Have a look at the Authy integration guide in the Coinbase docs:

  • Install the app on your phone (the exact procedure may vary depending on your device).
  • Launch the Authy app. When prompted during setup, enter the phone number you have verified on Coinbase and press OK.
  • Choose to receive either a phone call or SMS to retrieve a verification code.
  • Check your phone for the SMS or voice message sent by Authy. Note that the number that the code comes from may vary.
  • Enter the registration pin that was sent to you via SMS/voice into the Authy app.
  • Your phone is now a secure token for your Coinbase account and the Authy app should now have a Coinbase entry. Your Coinbase account will be synced with Authy through your phone number.
  • The setup process is now complete. 2-step verification codes will be available under the Coinbase entry in the Authy app and can no longer be sent via SMS or Voice.

(Emphasis my own)

There is no explicit permission step where you authorize Authy to generate tokens for Coinbase. Authy associates your account based on the same confirmed phone number for both Authy and Coinbase.

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