Research On Transmission&File System Modules Of Smartcard Operating System

The UCard model, which contains several COSs(Card Operating System) in one card, is proposed by our lab, and the hardware simulation platform is ready, but we are still stay at theoretical stage for certain issues. So the focus of this papers is on the research of the operating system of smartcards, a real operating system is expect to developed to test these theoretical.Typically, COS include flow control module, communication interface module, security management module, command explain module and file system module. The function of each module is analyzed, then the data transmission module and file system module will be discussed in detail.For the data transmission module, the activation of smartcard and the transmit of ATR are the must steps before the whole system works, the key implement is the control of time sequence and standards data transmit flow. Then the T=0 protocol is focused, T=0 is defined in the ISO7816-3, which is one kind of characters protocol. T = 0 transmission protocol, including smartcard ends and terminal ends, whose hierarchical structure is similar to the network, is also divided into physical layer, data link layer, transport layer and terminal application layer . Each layer is analyzed in detail. The physical transmit of characters, the assemble of commands frame and the structure of commands are studied.The file system module, including files, files chain, and file operation commands. There are two methods to realize the files chain: direct links and unconspicuous links. Direct links method is introduced to realize the files chain, and the data structure,left child-right sibling, is selected to achieve the tree logic structure of the file system. The file is divided to the file head and file body. The structure of the file head is researched. Then the file operation commands are abstracted, some definitions are given, and the file operation commands are analyzed from the angle of semantic to guide the detail program.The dynamic program downloading is supported by the multi-application smartcards. Usually, in the process of allocation space to download new procedures, and process to delete procedures,many times of writing to the EEPROM is needed to maintenance the storage management information, but the operation of writing EEPROM is very time-consuming. RAM mapping of storage is constructed to avoid the numerous EEPROM write operations, these storage section will be managed directly by CPU.