Design And Implementation Of USB Key File System

With the rapid development of e-commerce and e-government,information security has attracted more and more attention from all walks of life.Due to the reason that traditional method of simple username/password authorization can no longer meet the high security demand of some special systems,much safer PKI digital authentication system is emerged.As the storage equipment of digital certificate and hardware encryption devices,USB key has achieved rapid development and wide application.Hardware resources of Intelligent USB key are becoming more and more rich,and its storage capacity increases gradually.Moreover,it can provide support for development from a single application to multiple applications.The physical properties and applications requirements of intelligent USB key demand for unique file system for its chip operating system.Currently,though the logical structure of the file system of intelligent USB key is designed according to ISO7816 standard,but this standard for the storage method and the data structure of the document is not clearly defined,and the realization of security access control is also not required.Hence it requires all manufacturers to develop unique COS file system according to particular application and the characteristics of specific chip independently.In his paper,the requirements of the hardware characteristics and application of USB key has been analyzed,and the design and implementation of the secure file system based on SSX1209 chips are also be given.In this paper,we first introduce the principle of USB key and the structure of its chip operating system.Inspired by the implementation of the popular flash file system,according to the application and physical characteristics,we have design a file system for the USB key.The design of the file system architecture,the method of physical space's allocation and management,the design of the data structure and interface,and the power down protection mechanism are presented respectively.Secondly,by combining cryptographic technology with Mandatory Access control(MAC)and Role Based Access Control(RBAC),we propose a file security control scheme based on the secret key.The proposed scheme can provide a sort of secret key protection for each file operation by applying deliberative access control.The security strategy combines the SM1 algorithm with PIN code to provide multiple protections for files and the file access control method,the file encryption/decryption and checking process are given.Finally,the experiment of file system has tested the basic functions of file system,the security of file access and the rate of file encryption and decryption respectively.The results show that the file system achieves the basic functions,meets the security demand of file data and operation,and improves the rate of entire file system's encryption and decryption effectively.