We are working on U2F support. NFC sounds good in theory but did you actually used it? It has compatibility issues and only works with certain phone vendors, depending on your dongle vendor. Not talking about the general issue of how to secure an unsecure connection. Remember Yubikey's recent security flaw which allows an attacker to easily disable the PIN? However, we are watching that space and may implement NFC or another wireless protocol in the future.

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