The Hardware System Design Of Preventing Compromising Emanations From DVI Display System

In this paper, the author discusses the background and the trend of electromagnetic eavesdropping of computer displays system, and then analyses the basic principle, signal characteristic, encoding of DVI. The filter which was used in analog system does not apply to digital system, because of the bandwidth. The signal-to-noise ratio is very important to compromising emanations. On the side of digital signal, the author proposes a new method-randomizing, and simulates its effectiveness.Based on the simulation analysis, the author provides a blue print about how to randomize the digital signal by hardware. In this paper, the author designs pseudo random number generator by FPGA, and the digital video data are displaced by the pseudo random number, so the digital video itself becomes a white noise. There are two kinds of pseudo random number generator in this paper. Finally, these two generators were accomplished by FPGA. This hardware consists of three parts: TMDS decoding, FPGA randomizing, and TMDS encoding.Since the DVI signal requires a faster rise time and real-time processing, the hardware must be designed carefully. The author optimized the FPGA program to reach the required timing standard, and then utilized the relevant knowledge in signal integrity, power integrity to design the PCB. In the end, after the testing of the hardware system of preventing compromising emanations from DVI displays, the system satisfies the demand of the design.