Patent ID: 7716477

Claim:
A data processing method performed by a first processing device and a second processing device when the first data processing device holds first authentication key data and encryption key data and the second data processing device holds second authentication key data corresponding to the first authentication key data and decryption key data corresponding to the encryption data, comprising: a first step by which the first data processing device uses the first authentication key data, wherein the first authentication key data is from an integrated circuit (“IC”) device and had been generated using key data designated by key designation data, and the second processing device uses the second authentication key data, wherein the second authentication key data is generated in the second data processing device using the key data designated by the key designation data which has been communicated to the second data processing device and is from the IC device, and authentication is performed between the first data processing device and the second data processing device; a second step by which, when the second data processing device verifies the first data processing device by the authentication in the first step, the first processing device uses the encryption key data for encryption and the second processing device decrypts encrypted data provided to the second data processing device by using the decryption key data, and a third step by which, when the second data processing device judges that decryption data obtained by the decryption in the second step is decrypted adequately, the second data processing device uses the decryption data as the data that is effective.