Thanks for this really interesting feedback – especially that the subdomain method could create more opportunities for cache poisoning. Interested to explore h

Thanks for this really interesting feedback – especially that the subdomain method could create more opportunities for cache poisoning. Interested to explore how a cache poisoning attack might be easier on a Domain Verification protocol TXT record compared to a DNS-01 TXT record. Given the scenario: an attacker is attempting to claim a domain (example.com) with service provider (SP1) who uses a DNS revolver (DR1) I don’t immediately see how the subdomain approach makes a cache poisoning attack easier. Couldn’t the attacker similarly keep asking DR1 for <rand>._acme-challenge.example.com and spam back NS delegation answers for _acme-challenge.example.com, with the goal that upon cache poisoning success, they could fraudulently claim example.com with SP1? I may have overlooked something here, if so please explain. With either method, DNSSEC would definitely seem the solution as you’ve suggested.