REGISTRATION SYSTEM FOR ELECTRONIC KEY

PROBLEM TO BE SOLVED: To provide a registration system for an electronic key that eliminates the need to deliver on-vehicle equipment and an electronic key in a pair while ensuring security against crime.SOLUTION: A writing device 41 generates an encryption key according to a first encryption key generation program by using an ID code at the time of initial registration, and generates an encryption key according to a second encryption key generation program by using an ID code and the serial number of ECU 13 at the time of additional registration. The same process as in the writing device 41 is also performed in the ECU 13. At the time of the initial registration, only the ID code of an electronic key 12 is used to generate the encryption key. Accordingly, there is no need to deliver the electronic key 12 and the ECU 13 in a pair to a factory and the like at the time of initial registration. At the time of additional registration in the market and the like, only the electronic key 12 manufactured for the ECU 13 can be registered with the ECU 13. This provides security against crime.