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I was just wondering why there is a file on your computer implementing the trusted root CA's instead of something similar to DNS where there is a file on root servers that computers check against to retrieve the list of trusted CA's?

Thanks again, Francis

  • I think to avoid having a single point of failure. – Shurmajee Jan 9 '14 at 7:40
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There is no World Overlord because there are too many candidates for the post.

The whole X.509 protocol is completely up to the task of having a single root CA. However, there is no single root CA because people could not agree about who should thus be entrusted with complete power over all certificates.

Or, from another point of view, there is a Global Root. He is called Bill Gates. Internet Explorer will validate a certificate against a list of locally known and trusted root CA, and that list comes with Windows, and is updated through the official update mechanisms from Microsoft. Therefore, for 99.9% of the people (who don't fiddle with their locally installed root CA), Microsoft decides, ultimately, what root CA are trusted. In that sense, Microsoft is the Global Root (at least for all Windows users).

  • The overlord is the owner of the computer. They decide which roots are trusted - or in practice, they accept the vendor's judgement, and possibly add a few of their own. – Ben Jan 9 '14 at 20:27
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    There is a second overlord called Mozilla. Mozilla Firefox/Thunderbid won't ask the Microsoft overlord about what they should trust, but come with their own list instead (which is usually the basis for the cert store in *nix). And obviously, if you are on a Mac device, the root certificate store was defined by Apple :) – Ángel Sep 17 '14 at 21:25
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DigiNotar was a trusted CA, and it was broken into. The attackers were able to issue fraudulent certificates for sites they did not own. Browser vendors quickly removed DigiNotar's certificate from their trusted list.

What do you suppose would be the consequence, were there to instead be only one single global root, and it was successfully hacked?

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    Is that much worse than if someone hacked Verisign, Equifax/Geotrust or one of the other biggies that are used by many major companies and banks? It could take a long time for millions of certificates to be replaced, even if the browser vendors quickly replace the root certs. – Johnny Jan 9 '14 at 1:58
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    To be fair, even those vendors often have multiple certificates (presumedly in case one of them is compromised). If there was only one global root, even if they created another certificate immediately after a publicized breach, would we be able to trust it? On the other hand, with the current system, Google, Facebook, Microsoft, et al. could easily have their certificates replaced within the hour (or even less) by different, existing certificate authorities. – Stephen Touset Jan 9 '14 at 4:29
  • Verisign was hacked in 2010. Comodo was too. If you're big enough, the pain of removing your root cert lets you get away with murder. If you're smaller, like DigiNotar, you get hung out to dry. – Chris S Jan 9 '14 at 18:04
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Probably because it doesn't solve a problem that exists. Who do you trust to certify that everyone else is trustworthy? Microsoft? Mozilla? Canonical? Verisign? Thawte? At that level, what's the difference between pulling them out of a store and tracing their signatures up one more level?

Worse, how do you add a locally trusted root in such a system? For example, my employer has created their own CA Root, and they have pushed that certificate to all workplace-issued computers. Under a global system, how would you see them getting added to that global list? Would you have ExampleCo's certificate sign the One-True-Already-Self-Signed Global Root, and replace the global root with their own? How does that work when the Global Root is already self signed? And if you're going to allow two global roots in this case, what's the difference between that and three global roots, or even 172 root CAs?

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The Global Root is the owner of the computer.

They decide which roots are trusted - or in practice, they accept the vendor's judgement, and possibly add a few of their own.

But they can also remove items from the vendor list - many admins including me dropped diginotar for example even though MS retained them.

If on a network, your admins (perhaps this is you since you are reading S.SE) may also exercise their own judgement. Do I want my users trusting a Brazilian or Ukrainian CA? They might be fine but a) how do I know and b) why are my users on a Ukrainian or Brazilian website for work purposes anyway? Do we ever do business in those countries?

The ultimate controller is the administrator of the computer, not the World Government, not Microsoft, Google, the FireFox Commissariat or anyone else.

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