This paper proposes a method that reconstructs the original video data signal from leaking electromagnetic emanations of multiple video signal sources using a software-defined radio (SDR). The results of the method give valuable insights into the potential risk of this threat of obtaining sensitive information in an everyday situation. The leaking emanations of co-located identical high definition liquid crystal displays are analyzed for possible data reconstruction using a SDR of a small form factor. It is proven that the leaked emanations of multiple identical active video display units (VDUs) can be separated from each other and that their separate video images can be reconstructed individually from one data acquisition. Moreover, this is done by recovering the synchronization frequencies and the image resolution by exploiting multiple leakage channels without having any foreknowledge of the VDU's properties. A multitude of leakage channels is investigated and analyzed for their radiation pattern and their signal-to-noise ratio, and is exploited to increase the quality of the reconstructed images employing multiple-input multiple-output based techniques. As far as we can see, our results and new insights in the nature and mechanisms of multiple compromising emanations are crucial for improving video data security.
Video display units (VDUs) using differential signaling technology significantly increase the risk of compromising video information security through leakage emissions. This paper shows that differential signaling cables act as substantial video leakage sources. A concept is proposed which explains the video leakage principles of VDUs using differential signal cables such as the HDMI (high-definition multimedia interface) cable, DVI (digital visual interface) cable and the LVDS (low-voltage differential signaling) cable. The emanations of the LVDS cable are closely examined by measuring simultaneously the differential video signal on the LVDS lines and its near-and far-field leakage emissions. From these measurements several conclusions are drawn which give new insights into the video eavesdropping risk of VDUs using differential signaling methods. Furthermore, a novel video image reconstruction method is proposed which exploits the compromising emanations of a video display unit (VDU) by using frequency demodulation techniques. This paper shows that leaked video emanations of VDUs using differential signaling cables are not only amplitude modulated (AM) but also frequency modulated (FM). This strongly implies that the possible algorithmic toolset of malicious video eavesdroppers is much larger than currently assumed. This paper investigates several VDU setups at a distance of 10 meters, including an ultra-high-definition video display, three different HDMI cables and two notebooks. Additionally, the AM-based and FM-based video image reconstruction results are discussed and compared.
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