Study On Practical Technology Of Computer Radiation Information Interception

Research shows that information could be obtained by intercepting emit energy of information equipment in various forms, such as electrical currents, heat, light, conducting and radiating electromagnetic waves, sound and vibrations. So the energy emitted can be a serious computer security threat. As information equipments grow day by day, the harm and defending effectiveness of information security that caused by energy emission has become one of the most impending problems in information field, and the studies on certain key technologies have attracted more attention in developed countries.Supported by National Natural Science Foundation of China, this paper aims at the studies of key technologies about interception and reconstruction of video and print image information by electromagnetic (EM) emission leakage arising from computer. A low cost EM information interception demo platform was designed and a practical technology of video and print information interception was developed. In addition, the NONSTOP technology was discussed in the paper. The main work and innovations included in this dissertation are as follows:1、The time domain and frequency domain characteristics of video signal are analyzed, after that its "Electromagnetic Fingerprint" is proposed. Then an equivalent system model of computer video information leakage, reception, demodulation and decoding is established. Those above are the theory foundation of automatic identification and extraction of video information by EM emission leakage from computer.2、A software definition radio platform using public equipments, such as broadband antenna, oscilloscope, and spectrum analyzer is set up, which could recover the text image from EM leakage of computers in the office environment effectively. 3. Transient EM leakage mechanism of print text messages is analyzed, then technologies about interception and reconstruction of print text information by EM emission leakage arising from printer are proposed. In addition, a low cost text recovery system is set up.4、The NONSTOP mechanism of computer video information is analyzed, and a video signal propagation model in the Local Area Network (LAN) is established. Compared with wireless interception distance, the video signal transmission distance in LAN is calculated and analyzed. Based on this mechanism, a new NONSTOP technology is proposed, then test examples of print signal NONSTOP leakage caused by Voice over Internet Protocol (VoIP) system and Global System for Mobile communications(GSM) are given, proving that this new NONSTOP leakage could threaten information security. The video information of computer is recovered from LAN and power line in office environment, indicating that the network equipments and power outlets cannot effectively block the computer TEMPEST signal transmission.