[PROBLEMS] To prevent leak of information because loss or theft judgement is made whether or not read control information stored in a predetermined read control information storage area of an external storage is proper. If the judgment result shows that it is invalid, virtualized data stored in the external storage is decrypted, and genuine read control information virtualized in the virtualized data is extracted. Next judgement is made whether or not the extracted genuine read control information is proper. If the extracted genuine read control information is proper, the virtualized genuine data in the virtualized data along with the genuine read control information is made usable by decrypting and creating the virtualized data, and improper read control information is stored in the read control information storage area.