Research And Implementation Of A Client-based USB Encryption System

In recent years, software protection has attracted more and more attention, leading to the flourish of various techniques and means. The traditional method for computer software protection applies registration code to verify users iegitimacy, or shells the software. These operations, being executed directly on computer operating systems, are easy to observe by some debugging tools, making the crash relatively effortless. The utilization of hardware circuit on software protection can overcome such deficits to some extent, for such scheme requires analysis on hardware circuit and firmware program to crash, resulting in a higher cost. With the analysis on common techniques of software protection, a new solution is proposed within this paper: a USB-based software protection system.The research on USB criteria, composing of the detailed explanation on the architecture, the communication flow, the transmission filed and the transition formats, provides technical support for the design. Then a brief description is made on the encryption concepts and principles with expiration on the two typical encryption algorithms: DES and RSA. The analysis on encryption algorithms assures the data transmission safety.A DSP chip is adopted as the system micro processor. The selection of DSP chip is of great importance which defines the further peripheral circuit and other system circuits. The design of the DSP platform, consisting of design method and software programming procedure, is expounded in Chapter 3. Also the chip TMS320LF2407 adopted in this system is introduced. The first part of Chapter 4 introduces the USB bus interface controller which consists of the functions and interface settings of the chip ISP 1581 utilized in this system. The following section interprets the interface circuit composition. The software development is the key point and main difficulty of system design. The whole software is divided into three parts from the function point of view: firmware module, encryption algorithm module and USB facility driver module, full expiration in Chapter 5. The last section summarizes the whole paper and points out the future work directions.