A vehicular system includes a first electronic control device that manages an encryption key, and a second electronic control device that uses the encryption key. The first electronic control device is configured to create the encryption key in response to that an owner of a vehicle has changed, and output the encryption key to the second electronic control device. The second electronic control device is configured to store a first encryption key and a third encryption key, receive a second encryption key, switch the encryption key being used, and update the first encryption key to the second encryption key.