U2F / Yubikey

Investigate whether U2F would be useful to DC, and if it is, how to integrate it.

Some links:

In this case maybe the way to go is supporting TLS client authentication which should be possible using the PKCS#11 support of Yubikey.

Another option would be supporting SASL (as I think IRC does) with the OTP system, but that may be overkill and I’m unsure whether it’d work.