[tynes]

Proof of Work solves that by preventing Sybil attacks - it's costly to mine (which is equivalent to signing off on, because it wouldn't make sense to sign an invalid block, you would get rewarded). It's the only signature scheme known to be dynamic and allow for an arbitrary participant size. The point is that you can trust the chain with the most proof of work. As long as you maintain a diverse set of peers and validate blocks, you can know the state of the network.

[EGreg]

It doesn’t solve this problem at all. The site says:

How do you know that Google's public key is actually Google's public key? When you make that first request to Google, an intermediate network may have intercepted your request and returned a fake public key for Google. CAs attempt to solve this problem. CAs are trusted third parties that verify the authenticity of public keys for websites.

How does proof of work ensure that google.com really goes to Google and not someone who paid $2,000 to mine something?

[troquerre]

A miner wouldn’t be able to do that. Only the private key owner of Google could do that. At most a miner could do a double spend attack (would cost a lot more than $2000), but that wouldn’t change the DNS record for Google.

[EGreg]

The question is how do you know that the owner of the private key is the “owner of GOOGLE”. That’s what CA’s solve. Blockchain doesn’t solve this problem.