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Using a U2F (Universal 2nd Factor) device is currently one of the most secure authentication methods available to end-users. Its advantage comes from the hardware isolation. It’s impossible to steal keys from it or trigger authentication just using <a href="https://hackernoon.com/tagged/software" target="_blank">software</a>. Physical interaction is mandatory. U2F is resistant to phishing by design too. For instance you cannot be tricked to press the key and authenticate with a “fake” web page since authentication origin is also part of the process and the communication between the device and the web browser cannot be intercepted by a third party. A malicious person cannot ask for your “U2F codes” because there are no codes in play.