[Rhapso]

This is a better summary then I can hack together: http://namecoin.info/

I have issues with their implementation, but in general the message is right.

[dfc]

How does Alice attest to Carol's key so that Bob (who trusts Alice) can identify/use Carol's key for communication?

[Rhapso]

Alice just signs Carols name. Bob looks up Carol's name in the blockchain. The primary application is TLS style authentication, so the user ideally already knows the name of their intended recipient.