To protect the copyright of digital data, to prevent unauthorized copying and to allow only an authorized user to recognize the contents of the digital data.

By providing a means 4 for error correction/encoding of information data (image data for one screen for instance) and a means 5 for ciphering only the error correction code of a part (for instance, error correction-encoded image data recorded in one track) included in the error correction-encoded information data, data are not completely restored in a device without a constitution for performing deciphering corresponding to the ciphering, the copyright of digital data is protected, and the unauthorized copying is prevented. Also, a part to which the ciphering has not been executed is processed, even if the constitution for deciphering is not provided so that the contents of the information data can be partially confirmed.