Two-Stage Adaptive Data Recovery Method From Electromagnetic Emanations Using Error Detection Codes

This article presents a two-stage adaptive bit recovery method utilizing error detection codes for information recovery via electromagnetic emanations from encoded data transmission systems. Traditional TEMPEST primarily targets human interface devices where contextual information enables error correction; however, in encoded data, even single-bit errors can propagate through the decoding process, rendering entire information blocks irrecoverable. In the first stage, our proposed method performs exhaustive threshold searching utilizing packet-embedded error detection codes to achieve complete recovery of packets transmitted under favorable electromagnetic environments. In the second stage, statistical amplitude distribution profiles constructed from successfully recovered packets are used to identify error candidate bits in packets transmitted under degraded environments, enabling error correction through limited combinatorial searches. Experimental validation using a USB 2.0 webcam demonstrated successful complete recovery of Motion JPEG-encoded 640 × 480 resolution images (59 packets/frame), proving the feasibility of encoded data recovery under time-varying electromagnetic environments. The objective of this study is to conservatively quantify—from an adversary's standpoint—the amount of information that can be recovered via electromagnetic leakage, and to feed the result back to EMC/security engineers as a design-time risk-assessment guideline.