THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. 2016 Sep.; 27(9), 844 853. http://dx.doi.org/10.5515/kjkiees.2016.27.9.844 ISSN 1226-3133 (Print) ISSN 2288-226X (Online) LCD Analysis of the Electromagnetic Leakage from Liquid Crystal Display Monitors 이호성 심규홍 오승섭 육종관 Ho seong Lee Kyuhong Sim* Seungsub Oh* Jong-Gwan Yook 요약 LCD(Liquid Crystal Display). LCD... LCD,.,,. Abstract Generally, the compromising electromagnetic emanations are generated from LCD(Liquid Crystal Display) monitor which is typical output component of computer. Because display information transmitted to LCD monitor is included in these emanations, there are risks about information leakage of monitor by eavesdropping of leaked signal. So, analysis about possibility of information leakage is necessary because electromagnetic security through the electromagnetic emanations is being at issue. In this paper, the possibility of display information leakage are demonstrated by analyzing the electromagnetic emanations from desktop and laptop monitors. The characteristics of leaked signal from LCD monitor is verified by analyzing display mechanism and the electromagnetic emanations are measured in the long distance by eavesdropping experiment. Also, threat of information leakage is confirmed by recovering display information with several signal processing technique and comprising with target display. Key words: Information Leakage, Compromising Electromagnetic Emanations, LCD Monitor, TEMPEST. 서론, (Electromagnetic interference) [1]., 2016 LIG. (School of Electrical & Electronic Engineering, Yonsei University) *LIG (LIG Nex1) Manuscript received July 13, 2016 ; Revised September 2, 2016 ; Accepted September 20, 2016. (ID No. 20160713-077) Corresponding Author: Jong-Gwan Yook (e-mail: jgyook@yonsei.ac.kr) 844 c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved.
LCD. 1985 [2].,. (TEMPEST).,,.... CRT(Cathode Ray Tube),, [3]. LCD(Liquid Crystal Display) [4]. LCD [5].,, VGA(Video Graphics Array) DVI (Digital Visual Interface) [6],[7]., 1 m [8]. RF 1 m LCD 그림 1. TEMPEST Fig. 1. Configuration of TEMPEST about monitor display.,., 1.. 비디오인터페이스와 LCD 모니터에대한분석 LCD., VGA. DVI HDMI(High Definition Multimedia Interface),.,. 3,,, 3. 3 2. (pixel),. 845
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep. 2016. 표 1. / Table 1. Display/timing parameter. ( ) 그림 2. Fig. 2. Composition and sequence of display. (visible pixel) (invisible pixel), visible pixel (display width) (display height). Invisible pixel, (total display width) (total display height). (display parameter), 1. (horizontal synchronous frequency).,. (vertical synchronous frequency),., (pixel frequency). (timing parameter), 1. VESA(Video Electronics Standards Association),., 표 2. VESA Table 2. VESA standard of monitor display. (Hz) (khz) (MHz) 1,024 768 60.004 48.363 65.000 1,344 806 1,024 768 75.029 60.023 78.750 1,312 800 1,280 1,024 60.020 63.981 108.000 1,688 1,066 1,280 1,024 75.025 79.976 135.000 1,688 1,066 1,600 1,200 60.000 75.000 162.000 2,160 1,250 1,600 1,200 75.000 93.750 189.000 2,160 1,250 1,280 1,024, 60 Hz 63.981 khz, 1,688 1,066. 2. LCD.,,. (video processor) (display controller) IC(Integrated Circuit)-chip. LVDS(Low Voltage Differential Signal) FPD(Flat Panel Display)-Link, 846
LCD 표 3. Table 3. Characteristics of experimental equipment. Video signal Video processor Main board Display controller LVDS/ FPD-Link 그림 3. LCD Fig. 3. Typical structure of an LCD monitor. Display panel Antenna Log-periodic dipole array antenna 20 3000 MHz - RF receiver RF wideband receiver 20 Hz 3.6 GHz 60 MHz 표 4. LCD Table 4. Characteristics of LCD monitor. Desktop monitor Laptop monitor TRL-170 E8020 1,280 1,024 60 Hz 그림 4. Fig. 4. Experimental setup.. LCD,, LVDS/FPD-link... 누설전자파측정 LCD RF. 4 RF. log-periodic dipole array, 20 3,000 MHz. RF, 60 MHz., RF down-converter. RF 3. LCD. VGA, 1,280 1,024 60 Hz. LCD 4. 1 m 3 m, 200 ms. 60 Hz 10.,.. LCD 5 그림 5. Fig. 5. Target display. 847
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep. 2016. 표 5. LCD Table 5. Experimental parameter. (m) 1, 3 (ms) 200 50, 30, 12 : : 55 (16) (RGB). 55 (16) RGB, [4]. 5.. RF 1 m, 6 7.,. 2 LCD, 300 500 MHz. 6 그림 7. Fig. 7. Frequency spectrum of leaked signal from laptop monitor. 411.164 MHz, 7 377.8 MHz. 20 MHz.,. 60 MHz. 60 MHz RF. 108 MHz,.. 누설신호탐지및복원 그림 6. Fig. 6. Frequency spectrum of leaked signal from desktop monitor.. 8.,. (low-pass filtering). /. 848
LCD 그림 8. Fig. 8. Flow chart of leakage information recovery... 1 m LCD.. 20 MHz. 10 MHz. 9., 50 db. (signal- to-noise ratio). /. (auto-correlation). 그림 9. Fig. 9. Frequency spectrum of received and filtered signal.,., /. 10 /. 64.034 khz 60.018 Hz /. 1,280 1,024 60 Hz, 2 VESA 63.981 khz 60.020 Hz...,. 849
THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep. 2016. (a) (a) Detection of vertical synchronous frequency 그림 11. Fig. 11. Recovered display of single frame. (b) (b) Detection of horizontal synchronous frequency 그림 10. Fig. 10. Autocorrelation to detect synchronous frequency.., (cross-correlation).,... 11, 12 그림 12. Fig. 12. Recovered display using frame averaging technique..,. 12 1 m LCD. 5., VESA. 64.034 khz, VESA 63.981 khz 850
LCD 그림 13. 3 m Fig. 13. Recovered display of leaked signal from desktop monitor on 3 meter. 그림 14. 1 m Fig. 14. Recovered display of leaked signal from laptop monitor on 1 meter.., 1,688. VESA. 13 3 m LCD. 14 15 1 m 3 m LCD.,. 그림 15. 3 m Fig. 15. Recovered display of leaked signal from laptop monitor on 3 meter. 3 m. 3 m log-periodic antenna, RF,. RF.. 결론 LCD. LCD,.,.. LCD. 851
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