Principle And Detection Of Conducted Compromising Emanations

Electromagnetic compromising emanation is an important risk in the field of information security,in which conducted emanation is a key problem.Compared with the emanations of free space radiation,the researches about mechanism and propagation of conducted emanations are still insufficient.With the rapid development of high-speed devices,the digital signal frequency of information technology equipment(ITE)is getting higher and higher,and the frequency range of emanations are also becoming wider and wider.The development of test equipment is far from meeting the needs of risk assessment of compromising emanations,especially the intermediate frequency bandwidth of measurement receiver.The electromagnetic compatibility(EMC)conducted interference test methods can not effectively test and evaluate the conduction emanations.So,it is urgent to propose a new test method to solve the testability problem of conducted emanations.Base on the practice demands of information security of electromagnetic leakage emission,this paper draws extensively on the research achievements in the field of EMC conducted interference,and studies and analyzes the conducted emanations of digital signals of ITE.In view of the two basic problems of radiation and coupling involved in conducted emanations,the paper focuses on three important issues of ITE digital signal conducted emanations' principle,test bandwidth and key measurement technologies.It is expected to gain insight into the physical properties of conducted electromagnetic emanations from the perspective of mechanism and model.The research contents of this paper are conducted emanation mechanism,key parameters of emanations test and conducted emanations test technoligies.The main research contents and contributions are as follows:1.This paper studies and analyzes different physical models such as quasi-static approximation,line-antenna radiation,transmission line(TL)theory,and enhanced transmission line(ETL)theory.The digital signal conducted emanation mechanism is given from TL radiation and coupling.The model and analysis method of emanations are proposed to deal with TL electrical dimensions.It can effectively reduce the calculation complexity and efficiency to making full use of the electrical dimension of the TL structure to select an analysis model reasonably.The difference between the commonmode and differential-mode current radiation of the TL is compared and analyzed.The principle analysis of the radiation induced by the common-mode and differential-mode current when the TL uniformity changes is given.Based on the principle of electromagnetic field reciprocity,the conversion method of TL radiation and coupling is studied and analyzed,so that the researches on the principle of conducted emanations can fully draw on the research achievements of electromagnetic interference(EMI)in the field of EMC.2.Based on the improved transmission line theory,the time-domain and frequencydomain of digital signal emanation simulation are carried out,and the research results of conduction leakage transmission mechanism are verified.In the time-domain,the simple multi-conductor transmission line(MTL)and the generalized MTL system are simulated by using the TL theory and the progressive theory method of ETL theory.The analysis results of the TL radiation and coupling principle are verified,and the radiation and coupled emanations are analyzed.In the frequency-domain,the attenuation laws of conducted emanations in the frequency-domain are given,and contrast and analyze the difference between the attenuation of the envelope of the digital signal and its emanation spectrum,and correct the previous misconception that the digital signal power spectrum is used as the radiated signal power in previous studies.Point out that this misunderstanding leads to an optimistic estimation of the radiation spectrum range.3.To overcome the problem of conducted emanation test,the influence of receiver bandwidth on receiving digital emanation signal is analyzed based on radiation impulse theory.The basic principle of signal-to-noise ratio(SNR)equivalent and narrow bandwidth SNR compensation method are proposed.The maximum SNR of wide-band signal can be measured by narrow-bandwidth electromagnetic compatibility test equipment,and the accurate results of emanation SNR can be obtained.According to the characteristics of radiation and conduction emission,the concept of digital signal "radiation impulse pairs" is proposed.The influence of impulse bandwidth and receiver resolution bandwidth on the receiving result of digital emanation signal is studied,analyzed and verified by simulation.The difference between square wave and impulse signal on maximum SNR output is compared,and the upper and lower bounds of SNR are given,which provides a theoretical basis for wide-band emanation measurements.4.In order to discriminate mixed red and black signals in compromising emanations detection,a general method of red and black signals recognition is proposed,which provides a feasible scheme for the system to solve the problem of red and black signals recognition.Independent component analysis(ICA)and sparse component analysis(SCA)are introduced into the scheme,and four recognition algorithms are proposed,which are spectrum feature discrimination,correlation discrimination,statistical independence discrimination and sparse representation discrimination.In the logical framework of red and black signals recognition method,independent component decomposition and sparse component decomposition of mixed signals can help realizing red and black signals discrimination through whitening processing and orthogonal transformation of received signals.According to different situations,four discrimination algorithms can be choosed to use.