When will re-registration occur for a Subscriber?

Re-registration for a Subscriber in a Public Key Infrastructure (PKI) context typically occurs after they have been initially registered. This is an important step to ensure that all information associated with the Subscriber, such as their identity and public keys, remains current and accurate.

While it's possible for re-registration to occur under other circumstances, such as when there are changes to a Subscriber's details, these situations are not the primary conditions for initiating re-registration. For instance, re-registration might not occur specifically after a security breach unless the breach directly impacts the Subscriber's credentials or information.

Regular re-registration every year or at any time during their service may apply in certain policies, but the foundational principle is that initial registration must take place first. Therefore, the correct answer emphasizes the necessity of the initial registration as a prerequisite for any further action regarding a Subscriber's credentials in a PKI system.