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Comment by agwa | Hacker News Reader

Only if you use a U2F hardware token. 2FA using SMS or a smartphone app merely raises the bar for phishing: the attacker can forward the password along to the real service, prompt the user for the 2FA code, forward that along too, and then get a session cookie which they can use to access the account later.

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I've been thinking about buying a YubiKey. Could you elaborate on how U2F protects against MitM and phishing?

U2F knows what domain you're using it with, and won't send an authentication token for google.com to phisher.com.

A password manager will do the same thing for you.

(I'm not arguing that PMs are >= to hardware 2FA, but they both will keep this exact thing from happening)

Indeed it will. In fact, I'm not convinced U2F adds any meaningful security over a good password manager.

You know when your U2F device has been stolen because it's not in your possession anymore. The hardware is meant to be at least tamper-evident, if not tamper-resistant, so an attacker can't just steal the internal secret and put the device back where they found it.

Bytes in a password manager are hard to steal, but if you do steal them, the legitimate owner won't necessarily ever know.

One key difference which made me appreciate the thought which went into U2F: people using password managers can still copy and paste the real password into the form, which they're somewhat trained to do by all of the large websites which don't have / don't have working single sign on.

With U2F that failure mode is impossible since you cannot get the private key to shoot yourself in the foot with, even if the phisher successfully convinces you to try.

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