The first device, which utilize a cipher, generates device unique data by a PUF, and the second device generates one pair of helper data and a device unique ID on the basis of the generated device unique data. The device unique data has fluctuations caused by the generation environment, and regarding the fluctuations as an error to the device unique ID, the helper data serves as correction data for correcting the error. The second device generates a Hash function from the device unique ID and the encryption key. The second device writes one of the helper data and the Hash function to the first device first, and after authenticating the first device by the write, the other of the helper data and the Hash function is written in the first device. Decrypting the encryption key, the first device is allowed to utilize the cipher.