PORTABLE DEVICE REGISTRATION SYSTEM AND PORTABLE DEVICE REGISTRATION METHOD

An immobilizer ECU (6) generates an encryption key using key generating logic, from a SEED code included in an ID code signal sent from an electronic key (2), and registers the encryption key to the immobilizer ECU (6). The immobilizer ECU (6) receives an instruction from a registration and deletion tool (8) and sends, to the electronic key (2), a deletion request signal that requests the deletion of the SEED code. The electronic key (2) deletes the SEED code from the electronic key (2) if a deletion request signal has been received.