Analysis of information leakage from display devices with LCD

This study confirms the possibility of information leakage from two typical display devices with liquid crystal display (LCD). The compromising electromagnetic emanations are measured by log periodic antenna and wideband receiver in various distances. Frequency bands of leaked signal related to display on monitor exist in the range of several hundred megahertz with about ten megahertz bandwidth, which are different as display devices. Measured emanated signal is recovered as display by signal processing technique using software. In this process, timing parameters that necessary to composition of display are detected and clear recovered image is achieved by averaging multiple frames. The tendency of information leakage according to distance and display composition is analyzed by recovering emanated electromagnetic waves.