Check your resolvers: KSK-2010 trust anchor phased out

Following the successful rollover of the root KSK pair last year, all that remains is to phase out the old trust anchor. ICANN, the administrator of the root zone, is currently making the final preparations for deletion of the old key pair. Validating resolver operators should therefore verify that the old trust anchor has in fact been deleted from their systems.


The actual rollover of the KSK pair for the root zone took place last autumn. Since 11 October 2018, the old digital signature (KSK-2010) has not been used to validate the DNSSEC chain, and the new signature (KSK-2017) has been used instead.

The switch to the new signature was the most critical point in the entire process, because validating resolvers needed to have a (guaranteed identical) copy of the new signature installed as a trust anchor in order to continue validating the signatures linked to DNS records after 11 October. It was due to fears that not all resolvers might be ready that the switch was postponed for a year. And it was with good reason that, during the actual rollover, SIDN Labs monitored the performance of DNSSEC on a minute-by-minute basis through the Root Canary project. The initial evaluation by ICANN, the administrator of the zone, was published earlier this month.



Following the successful rollover, what remains is the phase-out of the old KSK-2010 trust anchor. The old key was officially revoked on 11 January 2019. Validating resolvers that support RFC 5011 should by now have automatically deleted the revoked trust anchor. On 22 March 2019, KSK-2010 will be completely removed from the root zone. That is unlikely to cause any problems, since the key pair has not been used to sign DNS records since 11 October last year. In the months since, the KSK-2010 will have been completely removed from ICANN's HSMs, enabling completion of the entire rollover process after three years.

For validating resolver operators, it is therefore important to verify that the old trust anchor has indeed been deleted from their systems. Although the KSK-2010 private key has never left the HSMs and has not been compromised (as far as anyone can tell), the presence of old key material is inevitably liable to be a source of future insecurity and confusion.


For advice on checking the trust anchors currently in use, tailored to the various DNS resolvers, refer to the article that we published in the weeks prior to the actual rollover. If the old KSK-2010 (key ID 19036) is still present and active as a trust anchor, it will need to be deleted manually. For guidance on how to do that, refer to our article on installation of the new trust anchor.


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