Amen: TOTP should be on a device with a much much smaller attack surface and supply-chain vulnerabilities.
This was many years back, but I remember searching to see if there was some kind of hardened not-a-phone appliance, without much luck.
This was many years back, but I remember searching to see if there was some kind of hardened not-a-phone appliance, without much luck.
Like, it was way better.
I use a hardware thingy that I put my Dutch bank card into that generates numbers for logins and purchases. I have the option of using an app or the hardware card reader.
I use a one time generating password hardware keyfob to login to the Dutch Belastingdienst. They require it and I don't think there is an app I can use for this purpose.
Danish banks, because they use the national MitID authorisation, accept MFA via app, code generator, or a chip device:
https://www.mitid.dk/en-gb/get-started-with-mitid/mitid-auth...
I'm confused, that seems like it confuses two independent aspects:
1. Whether the TOTP code comes from a fob-device versus a phone-device.
2. Whether some interactive interface you're using gives you a chance to see/confirm what you're about to authorize or not.
A phone app can lie to you about the transaction you're about to authorize regardless of whether the TOTP code was transcribed from an external device, transcribed from another app on the same phone, or auto-filled by itself.
The threat model is: malicious actor posing as the bank website, but legitimate keyfob or legitimate app. With the keyfob, the website intercepts a valid password and a valid 2FA code; with the app, nothing happens because it doesn't receive push data from the true bank.
I hope it is more clear now!
I don't see how that feature matters to a man in the middle attack during logon, since:
1. User opens web browser at a phishing site, which is masquerading as their bank, and starts the login process.
2. Phishing site interacts with bank.
3. Bank sends push-notification to the phone# that's on-file for that user: "Hey, that you logging in right now? Press the Yes button if so."
4. User sees it, expects it, presses the button, and then proceeds to hand over their TOTP and password to the phishing site anyway.
I suppose it might help on a per-transaction basis if the phishing site tries to trigger a hidden transaction, but at that point the app is just a way to streamline: "We sent you a code by SMS, enter that code to confirm the transaction."