In the answer here: Verification of identity by certification authority, it states that for European eIdentity you must provide your passport or ID card, but that

this practice is quite different for SSL certificates (which makes up the biggest part) or software signing certificates.

I'm interested in that case. The comment below the answer is pointing to a reference which I don't exactly understand.

So the question is, if I own a web domain www.croraf.com and I apply to the registration authority for certification, how will they verify that I'm really in control of the domain?

EDIT: I'm asking about domain validated (DV) SSL certificates as extended validation (EV) SSL certificates include a human element in the verification.

  • $\begingroup$ You might want to have this question migrated to Security.SE, which focuses more on the overall usage rather than the cryptographic details. $\endgroup$ – DannyNiu Oct 29 '17 at 9:20
  • $\begingroup$ I'm actually interested in the how and why the communication with RA ensures the ownership of domain. $\endgroup$ – croraf Oct 29 '17 at 9:44
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    $\begingroup$ @croraf Related to the comment you deleted a few secs after I posted mine: Sorry to say so, but not liking users at a specific SE site doesn’t make it on-topic at Crypto.SE. For your convenience, I would have migrated this Q&A to Security.SE as that’s where it Q&A belongs – but as it turns out, you’re currently blocked from asking there, which prevents migration (and raises the suspicion you might have asked here to circumvent you have been blocked from asking at Security.SE). $\endgroup$ – e-sushi Oct 29 '17 at 15:17
  • $\begingroup$ I think this can fit cryptography, moreso because you have pki and tls tags. And Im new user in both crypto and security as can be seen so you can be more polite. $\endgroup$ – croraf Oct 29 '17 at 15:26
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    $\begingroup$ @croraf Not really according to our help center. Besides, the mere existance of some tags doesn’t mean anything fitting such a tag is on-topic here. For example: TLS and/or PKI coding questions would be off-topic just like security-related TLS and/or PKI questions. As a matter a fact, if you check those tags you will notice questions like “Compromising a CA, how is it achieved” (which also uses the pki) have been migrated accordingly too. $\endgroup$ – e-sushi Oct 29 '17 at 15:31

The answer these days is the Ten Blessed Methods

Public CAs for the Web PKI (the PKI of the Internet's SSL/TLS services) are trusted by various entities, but by far the most important are the Web Browser vendors, who in practice are also more or less the Operating System vendors. These are Microsoft, Apple, Mozilla (who stand in for all the Free Unix systems), and Google. Trust by these organizations means certificates from the CA are trusted by web browsers ordinary people use, which is in effect necessary to get much done.

These trust stores, and almost all public CAs, take part in a standing meeting between the two groups call the CA/Browser Forum or CA/B for short. The meeting agrees requirements documents, which set down what CAs must do in order to remain trusted by any of the browser members. The most important these days are the Baseline Requirements or BRs.

Historically the BRs said that CAs could use "any method" to validate that the applicant controls the name requested if they were confident that it was "equivalent" to a list of methods commonly known to be used. It had become apparent that CAs weren't very good at actually judging if their methods were effective, and so this requirement was unsatisfactory.

Last year a sub-committee of the CA/B agreed a revision to the BRs called "Ballot 169" which listed exactly ten concrete methods by which a public CA could verify the DNS name in a trustworthy certificate. Although the ballot passed, a ridiculous series of events occurred which led to it not taking effect yet. However CA/B BRs are just the baseline so Mozilla as part of its own requirements on top demanded that CAs begin using only these methods which folks involved tend to call the ten blessed methods.

At time of writing they're listed in Section "Validation of Domain Authorization or Control" of the newest BR documents and they are: Validating the Applicant as a Domain Contact Email, Fax, SMS, or Postal Mail to Domain Contact Phone Contact with Domain Contact Constructed Email to Domain Contact Domain Authorization Document Agreed‐Upon Change to Website DNS Change IP Address Test Certificate TLS Using a Random Number

So, today a public CA must use one of those exact methods (each is discussed in detail in the BRs, use the newest available version to catch any errata) to confirm that a DNS name is controlled by the applicant before creating a certificate. They're allowed to do more, but they are required to do at least that.

For example Let's Encrypt, one of the most popular CAs, offers to let applicants use either, or

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  • $\begingroup$ ' CAs could use "any method" '- do you mean any method to confirm the digital certificate applicant (which is called domain contact?) is who he pretends to be? $\endgroup$ – croraf Oct 29 '17 at 11:55
  • $\begingroup$ Any method which, in their sole opinion, was adequate for this purpose. Yes, prior to the Ten Blessed Methods that was the case. $\endgroup$ – tialaramex Oct 29 '17 at 12:13
  • $\begingroup$ Also the applicant may not be the domain contact. Assuring themselves of this is one of the goals of most methods. $\endgroup$ – tialaramex Oct 29 '17 at 12:15
  • $\begingroup$ I will adjust the answer to make that clearer. $\endgroup$ – tialaramex Oct 29 '17 at 12:18
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    $\begingroup$ Indeed it does, however it also says those are examples. is pretty technical, so probably anybody who understands how it works isn't going to be reading an introductory text like that. Let's Encrypt call their implementation of "tls-sni-01" if you need to find evidence of that ("http-01" is and "dns-01" is $\endgroup$ – tialaramex Oct 29 '17 at 12:27

I've managed my company's own x509 DV certificate, so I'll tell you based on my own experience.

Basically, you provide the CA with an administration email address in your certficate signing request (CSR), typically webmaster@ or admin@ <your-domain-name>. Then, CA sends you an email, and you follow the links or instructions in the mail and approve your own CSR.

OV and EV might involve other procedures.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – e-sushi Dec 17 '17 at 13:48

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