DNS Certification Authority Authorization

CAA was drafted by computer scientists Phillip Hallam-Baker and Rob Stradling in response to increasing concerns about the security of publicly trusted certificate authorities. It is an Internet Engineering Task Force (IETF) proposed standard. A series of incorrectly issued certificates from 2001 onwards damaged trust in publicly trusted certificate authorities, and accelerated work on various security mechanisms, including Certificate Transparency to track misissuance, HTTP Public Key Pinning and DANE to block misissued certificates on the client side, and CAA to block misissuance on the certificate authority side. The first draft of CAA was written by Phillip Hallam-Baker and Rob Stradling, and submitted as an IETF Internet Draft in October 2010. This was progressively improved by the PKIX Working Group, and approved by the IESG as RFC 6844, a Proposed Standard, in January 2013. CA/Browser Forum discussion began shortly afterward, and in March 2017 they voted in favor of making CAA implementation mandatory for all certificate authorities by September 2017. At least one certificate authority, Comodo, failed to implement CAA before the deadline. A 2017 study by the Technical University of Munich found many instances where certificate authorities failed to correctly implement some part of the standard.