PKI, certificates

Question

I'm trying to understand how public key encryption works, or better how the authentication process works.

As far as I understand the CA are here to pin a certain public key to a certain organization or person so that on one hand a person that signed anything with its private key can't say "this is not my public key" (non repudiation), and on the other hand that no attacker can send his public key and say its from someone else (otherwise you would encrypt your message with the attackers key).

But now the whole security depends on:

• browser developers that add certificates to the browser
• CA that create certificates

Isn't this a very low standard? I've read articles about governments forcing CA's to distribute false certificates (for example https://en.wikipedia.org/wiki/DigiNotar) or maybe the CA's get hacked themselves. And it puts the CA's in a very powerful position, which is never a good thing. Then the browser developers make decisions which certificates go into the browser.

Besides from this, it seems that the problem is just moved, since we need to get the public key of the CA to verify the certificate which in turn can also be a public key from an attacker (like Thomas Pomin wrote here: how digital signature verification process works) He says the problem is also concentrated which makes sense, but still, I can't really see how this should be trustworthy.

So to have authentication you necessary have some shared secret before the actual communication starts, which is not possible when you don't know the other person (Internet, etc). Therefore "real" public key authentication doesn't exist, right? Or better formulated, you can't protect yourself from a sophisticated attacker.

I've also read that many problems with SSL are mainly due to users that are not well educated in this topic (for example you could use client certificates that the server also knows who he is talking to, but it would be too complicated for the average user). But the key distribution seems also technically unsolvable, what do you think?

Answer 1

And it puts the CA's in a very powerful position, which is never a good thing.

CAs role is to protect their secret keys and also ensure secure protocol for generating the certs for browsers (so the secret keys are not spilled). And also to validate when they issue cert to the domain that domain belongs to the requester.

That's their business model and sole purpose. They must be responding also to new types of hacks and keep improving standards.

Since their scope is limited to these secret keys, this is manageable and with little invention they can prevent massive leaks as number of secret information is not big and not spread. This is why this way these companies can be trusted.

Another thing is, that today most of browsers are getting automated updates (as of second half of 2016, web browsers including mobile devices).

There were single incidents of private keys theft like Comodo and the world didn't end.

Regarding browser, it just depends on the source code control and software distribution. The source code is protected from tampering with Git for example, so there's control over source and what certs are included. Then, the browser is built in secure environment with no external access and known, secure binaries, and then checksum-ed and signed. So then, they can monitor their distribution channels whatever the binaries are signed well and are having good checksum.