COMMUNICATION SYSTEM, COMMUNICATION DEVICE, KEY MANAGEMENT APPARATUS, AND COMMUNICATION METHOD

A communication system includes a first communication device, a second communication device, and a key management apparatus. The second communication device generates a random number, generates encrypted data using an encryption key, encrypts the random number, generates key information data, and transmits the key information data, identification information of the second communication device, and the encrypted data to the first communication device. The first communication device receives the key information data, the identification information, and the encrypted data, transmits the key information data and the identification information to the key management apparatus, receives the encryption key from the key management device, decodes the encrypted data and obtains the predetermined data using the received encryption key. The key management apparatus receives the key information data and the identification information, decodes the key information data, acquires the random number, and transmits the encryption key to the first communication device.