Patent ID: 8683227

Claim:
A communication system comprising: an information processing device; and a management device configured to update old data stored in the information processing device by outputting new data to the information processing device, wherein the management device comprises: a challenge input device that inputs challenge data output by the information processing device; an old data input device that inputs the old data; a first new data input device that inputs the new data; an encryption device that encrypts combination data comprising the new data and the challenge data by utilizing the old data as a key; and a new data output device that outputs the encrypted combination data to the information processing device, wherein the information processing device comprises: a challenge output device that outputs the challenge data to the management device; a challenge storage that stores the challenge data output by the challenge output device; an old data storage that stores the old data; a second new data input device that inputs the encrypted combination data output by the management device; a decryption device that decrypts the encrypted combination data by utilizing the old data stored in the old data storage as a key; and an updating device that compares the challenge data included in the decrypted combination data and the challenge data stored in the challenge storage, wherein, when the decrypted challenge data and the stored challenge data are identical, the updating device updates the old data stored in the old data storage to the new data included in the decrypted combination data, and, when the decrypted challenge data and the stored challenge data are not identical, the updating device does not update the old data stored in the old data storage.