[phelmig]

Couldn't they create a challenge/response type authentication that proofs that liz has the private key for her public key?

Liz wants to authenticate. Keybase sends her a challenge, which she encrypts using her private key. Keybase uses her public key to verify that liz owns the private key for her public PGP key. Easy peasy.

[dfox]

Keybase seems to want identity proofs to be independently verifiable, which would not work with challenge/response mechanism.

[phelmig]

Yeah, I know this is somehow the point. On the other hand it (maybe?) would be more useful if they would just verify that certain online-personas (e.g. github, pgp, blog) are the same person, which you could do.

I want to know that liz, is the liz that blogs and liz who forks on github, not necessary her facebook/linkedin/real name.

[SomeoneWeird]

This is exactly what Keybase does.