Sometimes mobile user may forget the sPIN. There are two ways to resolve this trouble. User can either register the service and keys again or user can try to recover the lost sPIN. When the sPIN recovery is wanted, a special PUK (Personal Unlocking Key) is needed. There can be two kinds of PUK codes – pre-generated or on-board generated PUK.
The problem with the pre-generated PUK is that PUK code storage and delivery is at least as high sensitive as the registration process itself. Therefore, storing a pre-generated PUK code in the database and revealing the code when needed has to be done with the same rigor as with the registration procedure.
The on-board generated PUK codes (OBG-PUK) do not have the same problems as pre-generated PUK codes. The OBG-PUK is generated after the mobile user has generated the sPIN and visible only for the mobile user. Mobile operator does not need to store or deliver any PUK codes.