LCD [2].,. (TEMPEST).,,.... CRT(Cathode Ray Tube),, [3]. LCD(Liquid Crystal Display) [4]. LCD [5].,, VGA(Video Graphics Array) DVI (Digital Visu

Transcription

1 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE Sep.; 27(9), ISSN (Print) ISSN X (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, (ID No ) Corresponding Author: Jong-Gwan Yook ( jgyook@yonsei.ac.kr) 844 c Copyright The Korean Institute of Electromagnetic Engineering and Science. All Rights Reserved.

2 LCD [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,,, (pixel),. 845

3 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep 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, , , , ,280 1, ,688 1,066 1,280 1, ,688 1,066 1,600 1, ,160 1,250 1,600 1, ,160 1,250 1,280 1,024, 60 Hz khz, 1,688 1, LCD.,,. (video processor) (display controller) IC(Integrated Circuit)-chip. LVDS(Low Voltage Differential Signal) FPD(Flat Panel Display)-Link, 846

4 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 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, 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, Hz. LCD 4. 1 m 3 m, 200 ms. 60 Hz 10.,.. LCD 5 그림 5. Fig. 5. Target display. 847

5 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep 표 5. LCD Table 5. Experimental parameter. (m) 1, 3 (ms) , 30, 12 : : 55 (16) (RGB). 55 (16) RGB, [4]. 5.. RF 1 m, 6 7.,. 2 LCD, MHz. 6 그림 7. Fig. 7. Frequency spectrum of leaked signal from laptop monitor MHz, 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

6 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 / khz Hz /. 1,280 1, Hz, 2 VESA khz Hz...,. 849

7 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep (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.., m LCD. 5., VESA khz, VESA khz 850

8 LCD 그림 m Fig. 13. Recovered display of leaked signal from desktop monitor on 3 meter. 그림 m Fig. 14. Recovered display of leaked signal from laptop monitor on 1 meter.., 1,688. VESA m LCD m 3 m LCD.,. 그림 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

9 THE JOURNAL OF KOREAN INSTITUTE OF ELECTROMAGNETIC ENGINEERING AND SCIENCE. vol. 27, no. 9, Sep TEMPEST.,,.,.. References [1],,, " RF (RFI) EMC ",, 25(10), pp , [2] Van Eck Wim, "Electromagnetic radiation from video display units: an eavesdropping risk?", Computers & Security 4.4, pp , [3] M. G. Kuhn, Ross J. Anderson, "Soft tempest: Hidden data transmission using electromagnetic emanations", Information Hiding, Springer Berlin Heidelberg, [4] M. G. Kuhn, "Compromising emanations: Eavesdropping risks of computer displays", Univ. Cambridge Comput. Lab., Cambridge, U.K., Tech. Rep. UCAM-CL-TR-577, Dec [5] M. G. Kuhn, "Compromising emanations of LCD TV sets", IEEE Trans. Electromagnetic Compatibility, vol. 55, no. 3, pp , Jun [6] Ho Seong Lee, Kyuhong Sim, and Jong-Gwan Yook, "Measurement and analysis of the electromagnetic emanations from video display interface", in Electrical Design of Advanced Packaging & Systems Symposium (EDAPS), pp , Dec [7] Tae-Lim Song, Yi-Ru Jeong, and Jong-Gwan Yook, "Modeling of leaked digital video signal and information recovery rate as a function of SNR", IEEE Trans. Electromagnetic Compatibility, vol. 57, no. 2, pp , Apr [8] Ho Seong Lee, Kyuhong Sim, and Jong-Gwan Yook, "An information recovery technique from radiated electromagnetic fields from display devices", 2016 Asia- Pacific International Symposium on Electromagnetic Compatibility(APEMC), pp , May : ( ) : [ 주관심분야 ] SI/PI/EMI/EMC, TEMPEST 1997 : ( ) 2014 : IT ( ) 1997: LIG [ 주관심분야 ], TEMP- EST 852

10 LCD 1989 : ( ) 1989: LIG [ 주관심분야 ], RF : ( ) : ( ) : University of Michigan () : University of Michigan Research Fellow : Qualcomm Inc. Senior Engineer : : : IEEE Distinguished Lecturer (EMC Society) [ 주관심분야 ],, RF MEMS, Bio-Radar and Sensors, Computational Electromagnetics, EMI/EMC, HEMP, TEMPEST 853