ELECTRONIC-KEY REGISTRATION METHOD AND ELECTRONIC-KEY REGISTRATION SYSTEM

This electronic-key registration method, in which a plurality of electronic keys (2) including an initially registered first electronic key and a second electronic key to be registered additionally are registered with a control device (6) for a communication target, is provided with the following steps: an additional-key manufacturing step in which an additional-encryption-key generation code (SC-9) unique to the second electronic key and an additional encryption key (K-9) used in authentication of the second electronic key are stored in the second electronic key; and an additional-key registration step in which, if identifying information (VID-A) unique to the communication target is stored in the second electronic key, the additional-encryption-key generation code (SC-9) is obtained from the second electronic key, an additional encryption key (K-9) is generated by additional-encryption-key generation logic (g) using the additional-encryption-key generation code (SC-9) and the aforementioned identifying information (VID-A), and said additional encryption key is stored in the control device (6).