A Quantitative Analysis of Compromising Emanation From TMDS Interface and Possibility of Sensitive Information Leakage

Abstract

This paper investigates the electromagnetic interference characteristics of the transition-minimized differential signaling (TMDS) scheme, which is a well-known technology of rapid serial data transmission, from a radio communication perspective. Such scrutiny regarding the leaking phenomenon inspires a pseudo model of the compromising signal model, which can simultaneously consider behavioral features of the software-defined radio with a simple RF front-end measuring the leakage. In this work, a conceptual explanation with mathematical formulations in implementing the pseudo model has been presented. Subsequently, by merging the model with various extra noises being in nature, the model can be utilized to facilitate and quantify the possibility of information extraction from the defected electromagnetic signatures. Furthermore, it is interesting to note that there are asynchronous problems due to inevitable timing errors in video display devices, even with a sophisticated acquisition system, and it turns out to be fatal for the frame-averaging scheme conducted before the signal demodulation. In view of these challenges, we have formulated a synchronizing scheme and verified the validity by utilizing the pseudo model with the extra noise to take into account the asynchronous problem. Moreover, the structural similarity (SSIM), a function of the signal-to-noise ratio, can provide the number of frames for the frame-averaging process and eventually give the minimum acquisition time to earn meaningful information from the compromising emanation. Finally, after the appropriate post-processing, the extracted information from the actual measurements is compared with the reconstruction from the pseudo-model results revealing excellent agreements.

Keywords

• TEMPEST
• LCD monitor
• information leakage
• electromagnetic interference (EMI)
• compromising emanations