It is an object of the present invention to more strongly protect data to be distributed from being illegally plagiarized, and further, to add an electronic watermark function necessary to protect the copyright to all reproduction means apparatuses. In order to achieve the above-described objects, according to the present invention, data targeted for protection is encrypted, and an encryption key required for decrypting this encrypted data and reproduction control data for protecting the copyright are embedded in encrypted data through the use of the electronic watermark. Thus, when reproducing the data, the electronic watermark is detected, and the encryption key required for decrypting the cryptogram and the reproduction control data for protecting the copyright are restored. Through the use of the restored encryption key, the cryptogram is decrypted. Thus, through the use of the reproduction control data restored, the reproduction of the data targeted for protection is controlled.