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Is it possible to use two-factor authentication on a Linux laptop running Kubuntu 18.04 without using a phone at all? If so, how?

I'm able to authenticate on my phone without any particular difficulty. But when I log into Coinbase under Kubuntu, I'm asked for a 2-step verification code. Running Authenticator under Kubuntu, I'm asked for a provider (presumably Coinbase), an account name (presumably my account name at Coinbase), and a 2FA token. It seems that both Authenticator and Coinbase are asking for codes, and neither of them are providing codes. It's like trying to connect a male plug to another male plug.

I would guess that I'm making a major conceptual error -- but what?

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  • FYI: Kubuntu 16.04 LTS being a flavor of Ubuntu had only 3 years of supported life (fridge.ubuntu.com/2019/03/01/ubuntu-16-04-6-lts-released) which ended 2019-April. Ubuntu 16.04 LTS Server (no desktop) or Desktop (Unity 7) or Ubuntu Kylin have 5 years of supported life and are still supported. Refer release notes, or use ubuntu-support-status or your own system to confirm this is the case. I suggest you move to a supported release of Kubuntu for security reasons, unless you're off-line or are aware of risks. – guiverc Dec 2 '20 at 5:40
  • How do you intend to use 2 factor authentication? At login, on Google or Amazon's web site etc? Yubikey gives you several choices for 2fa, a fidokey is cheaper. – ubfan1 Dec 2 '20 at 5:50
  • I need 2FA in order to log onto the Coinbase website. When I first set up my account there, 2FA wasn't required. – Paul A. Dec 2 '20 at 20:07
  • EarIier, I mistakenly said I was running Kubuntu 16.04. In fact, I'm running Kubuntu 18.04. – Paul A. Dec 3 '20 at 5:16
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Looks like Coinbase supports Yubikey. From https://help.coinbase.com/en/coinbase/getting-started/authentication-and-verification/2-factor-authentication-2fa-faq :

Coinbase supports all WebAuthN / Fido2 standard security keys. An option for a security key is Yubico's yubikey.

See Using security keys

The Yubikey plugs into a USB port, emulates a keyboard, and produces a security code when touched. Should work with Kubuntu 18.04.

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  • Yubikey is a hardware device, so it's probably only worth using for critical and valuable accounts. In this case I can always use my phone if need be. I was hoping there was a lightweight way to do this in Kubuntu without involving anything else. Using the website and the Kubuntu version of Authenticator would be ideal -- if I could get it to work. – Paul A. Dec 3 '20 at 21:47
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Another option is to use a password manager like KeePassXC that has a built-in 2FA function to create TOTP or "Time-Based One-Time Passwords". It allows you to store the secret you get from the service you set it up for, and then create a 2FA code whenever you need it, just like a Yubikey. The only difference is the secrets are stored on your PC (or whereever) in your password manager database, not on a hardware key. It's cheaper, but depending on your threat model may be less secure.

You only need to be sure the 2FA code you need is compatible - some sites use their own proprietary stuff. Anything that works with "Google Authenticator" is usually fine. Coinbase seems to do so.

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