The DNSSEC Practice Statement for the Root Zone KSK Operator [1] section 6.5 says: After a RZ KSK has been removed from the key set, it will be retained after its operational period until the next scheduled key ceremony, when the private component will be destroyed in accordance with section 5.2.10. And section 5.2.10 says: When required, the RZ KSK Operator destroys RZ KSK private keys in a manner that reasonably ensures that there are no residual remains of the keys that could lead to the reconstruction of the keys. The RZ KSK Operator utilizes the zeroization function of its hardware security modules and other appropriate means to ensure the complete destruction of RZ KSK private keys. When performed, private key destruction activities are logged as part of a key ceremony. As I understand this, PTI is bound by the DPS to destroy the previous KSK at "the next scheduled key ceremony" or update the DPS to state otherwise. jakob [1] https://www.iana.org/dnssec/icann-dps.txt