Patent ID: 7593900

Claim:
A system for exchanging information with a memory card, the system comprising: The memory card including a usable area for saving user data, and a security area for storing secret data, the memory card changing the capacity of the usable area by changing the capacity of the security area, the system being accessible with the security area only when the system is authenticated according to executing two-way authentication with the memory card; a central processing unit including a charge management module configured to receive payment of a charge corresponding to an increased amount of a usable area when a capacity of the usable area of the memory card for saving user data is increased, and pay out a charge corresponding to the reduced amount of the usable area when the capacity of the usable area is reduced; and a transmission module configured to transmit an area changing command to instruct an increase or a reduction of the usable area in accordance with the charge to the memory card.