Recognition and reconstruction of liquid crystal display monitor electromagnetic emanation signals

摘要

Computer electronic equipment will emit unintentional electromagnetic (EM) signals in the working state, especially liquid crystal display (LCD) monitors (desktop and laptop). The monitor emit unintentional EM signals across the Radio Frequency (RF) spectrum making it error-prone, time consuming, and difficult to find the relatively few emanations that obtain hidden information. In this paper, the characteristics of emitted signals which emanations by LCD monitor is verified by analyzing display mechanism, the EM emanations are received and reconstructed by the eavesdropping experiment. According to the principle of LCD, the study shows that refresh rate, horizontal frequency, and pixel frequency are confirmed as key factors to reconstruct image of LCD compromising emanations (CE). In addition, this study promotes the reconstitution quality of LCD CE based on wavelet transform spatial correlation filtering denoising method. Experimental results show that the method can effectively suppress noise and improve the reconstruction quality of weak leakage signal.