Patent ID: 6158004
Filing Date: 2000-12-05
Classification: G06F

Abstract:
An information storage medium comprising:a central processor;a memory device for storing data, said memory device including a plurality of addresses at which data may be stored;an interface circuit for exchanging data with a host apparatus, the data including file data having logical addresses in a first range of logical addresses for storage in said memory device and file management data having logical addresses in a second range of logical addresses, different from the first range, for storage in said memory device;a calculator circuit for encrypting the file data, but not the file management data, received from the host apparatus for storing in said memory device, and decrypting the file data stored in said memory device; anda bus switching circuit for validating said calculator circuit in response to a command received from the host apparatus, wherein the central processor distinguishes the file data from the file management data based upon the logical addresses of the data and said calculator circuit selectively encrypts the file data received from the host apparatus file-by-file.