An idea to help with this would be a new resource record type, with an opaque value that changes only when the domain changes hands (yes, it is up to the regist

An idea to help with this would be a new resource record type, with an opaque value that changes only when the domain changes hands (yes, it is up to the registrar to decide when to change the value). The resource records would live underneath registry.arpa, which has delegations that correspond to delegations at the DNS root; so to find out if example.com has changed, you can query: $ delv example.com.registry.arpa OWNER example.com.registry.arpa. 3660 IN OWNER "MEpnFkIk4sKW_oLPEl-R7WxFSAnWvgZnLYmRtn-3BkY" You could put other stuff in there too, such as the start-date of the current registration... this is starting to sound like whois but structured and machine readable. Why on earth did that never take off! An interesting related thing is the approach adopted by iSCSI, which constructs iSCSI Qualified Name (IQN)s by qualifying the domain name with the dates of registration. So iqn.2003-05.com.example is a different identity to iqn.2021-01.com.example.