Every security technology needs a certain deployment base in order to be effective. With many other security measures already at our disposal restricting the set of Certificate Authorities that may issue a X.509 certificate for a given domain is just another step. The standard for doing so, is RFC 6844 specifying the DNS Certificate Authority Authorization (CAA) Resource Record. Specifying a special DNS RR it allows any complying CA to check, if the owner of the domain (actually: The one in control of the DNS) wishes any given CA to issue certificates for this domain.
Given the CAA DNS RR is quite new, the question arose, if there are any deployments yet.
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