Research On Cognition And Reconstruction Of Computer Electromagnetic Emanation

Computer equipments and peripheral components usually emanate elec-tromagnetic emanation which may contain compromising information. This information, encrypted or unencrypted, may be eavesdropped by hackers in a remote region and cause information security problems. Threaten from these security problems has become growing concern by each country. In this re-search, supported by National Natural Science Foundation of China, we work on the process of the electric equipments’ radiation based on their electromag-netic characteristics. We try to figure out how to distinguish the EM emanating source and reconstruct the information eavesdropped based on the EM emis-sion from these sources. Studies in this paper include three parts mainly.In the first part we discuss theoretically on the regularity of equipments emanation. We focus on the emanation from the computers’I/O ports, single data wire and the whole random wire bundles. The geometry of the wires has also been taken into consideration. When building the model, tensor method was used and we took the different structures of wire as kinds of antenna and calculated the electric and magnetic fields from them. Based on method of time domain and frequency domain, we also take account of the waveform and the spectrum and extract the characteristic from it, these sampled data and the characteristic of it can be used as the input of the pattern recognition machine used for identifying the emanated targets.In the second part we focus on time domain waveform transmitted and the reception curve captured in measurement. Inspire by the fact that periodical signal waveform can be considered as the sum of simple sinusoidal waveforms, we use the accumulation of basic waveforms to simulate the radioactive source and analyze the transformational characteristics. We discuss on the topics of that how the change of the factors, such as frequency, amplitude of the vary-ing current and the geometries of the path the current follows, affects on the radiations and receptions, and we try to find out the relations between them. Expressions of both the varying current on the circuits, antennas and the volt-age of radiation, reception are studied. We also make a measurement under office environment to support our studies.The third part mainly introduces the studies of the identification using support vector machine(SVM). The targets identified include the emanating sources, the content eavesdropped, etc. Especially, in the part of emanating source recognition, liquid crystal display (LCD) monitors were used as the targets. Measurements of reception are taken under normal environment but not semi-anechoic chamber. We extract the parameters such as the magnitude from the spectrum and use them to train of SVM. We also carry out experiments on recognition of waveform in time domain. Bits sequence are divided into groups and are also identified using SVM, in this way the information is reconstructed.The main innovations of this study are as following:●Monopole model is used to analyze the geometries of emanating source, emanation models of computer I/O ports, arbitrary wire are built to ana-lyze using tensor method;●Using equivalent waveform components to simulate the real radiation in time domain to simplify both the emanation models and the machine train-ing calculation.●Identification and reconstruction using pattern recognition technique is introduced in this study and a high accuracy method to both distinguish the source and reconstructing the information is outlined.