ELECTRONIC KEY REGISTRATION SYSTEM

PROBLEM TO BE SOLVED: To provide an electronic key registration system capable of permitting the registration of a regular key only on an after-replacement control device when a control device is replaced therewith.SOLUTION: Notice of an on-vehicle equipment ID in a before-replacement ECU when replaced with a replacement ECU 24 to be mounted on a vehicle is given through a registration tool 19 to a center 20. The center 20 refers to databases 21, 22 on the basis of the on-vehicle equipment ID in the before-replacement ECU, and extracts a cryptographic key Kcr registered on the before-replacement ECU. The center 20 encrypts the extracted cryptographic key Kcr with an on-vehicle equipment center key Kvc coordinated with the replacement ECU 24, and outputs this SEED code SC to the replacement ECU 24. The replacement ECU 24 decrypts the acquired SEED code SC with its on-vehicle equipment center key Kvc to generate the cryptographic key Kcr which is written and stored in a memory 24a together with an electronic key ID.