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Knowledgebase: Validation
Alternative Methods of Domain Control Validation (DCV)
Posted by Leonard Grove on 14 December 2011 03:13 PM

All SSL.com certificates must pass through DCV (Domain Control Validation) before they are issued. DCV is a mechanism used to prove ownership or control of a registered domain name.

There are 3 mechanisms for DCV:
  1. eMail-based DCV (Traditional)

    You will be sent an email to an administrative contact for your domain. The email will contain a unique validation code and link. Clicking the link and entering the code will prove domain control.

  2. DNS CNAME-based

    This method requires you to create a CNAME entry in your domain’s DNS record that is pointed at comodoca.com. An MD5 hash as well as a SHA-256 hash of the CSR are required for this CNAME entry.  The CNAME entry should follow this formula:

    _<MD5 hash>.<domain> <TTL> IN CNAME <SHA-256 hash>.comodo.com

    Please notice the underscore at the beginning of the entry, which is required.  Additionally, because the SHA-256 hash is 64 characters long, it will need to be split into two 32-character subdomains.


  3. HTTP-based DCV

    The CSR you submit to SSL.com will be hashed. The hash values are provided to you and you must create a simple plain-text file and place this in the root of your webserver and served over HTTP-only!

    The file and it's content should be as follows:
    http://yourdomain.com/.well-known/pki-validation/<Upper case MD5 hash of CSR>.txt

    Content (as a plain text file):

    <SHA1 hash of CSR>

    Note: Serving the page over HTTPS or using an HTTP 302 redirect to an HTTPS will cause a failure of verification. Please use HTTP only for this procedure!

Additional Information

CSR hashes are provided to you once you submit the CSR as part of the ordering process.

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