Abstract: Disclosed is a user authentication card and a method for preventing data synchronization from being performed if information stored in the user authentication card is the same as that stored when a corresponding user equipment (UE) is powered off. The user authentication card includes a memory area for storing an electronic serial number of a UE, a memory area for storing a command defined for requesting the UE to transmit the electronic serial number and a memory area for storing a command defined for requesting transmission of the stored electronic serial number to the UE.

Abstract: A method of managing files of a portable information terminal and automatically upgrading a program installed on the portable information terminal to the most recent version. The method consists of comparing a memory size of files to be changed in the portable information terminal with a size of memory available in the portable information terminal, generating a list of files to be changed, updating information on a memory size of the portable information terminal in a master server when the files are to be changed in the portable information terminal, and storing the generated list of files in a specific directory of the master server and transferring the list of files to be changed to the portable information terminal when the files are transferred to the portable information terminal.