Transmitter trojan channel reveals data leaks and detection tradeoffs
The Transmitter Trojan Channel: Achievable Rates and Error Exponents
Information Theory
Summary
Sometimes, tiny changes inside communication devices can sneak out secret messages without being noticed. The authors study how these hidden messages affect normal transmissions and how well they can be detected by the receiver. They look at how fast secret and normal messages can be sent, how often errors happen, and how likely the secret messages are to be spotted. They tested their ideas with common communication models to show the tradeoffs between hiding data and staying reliable.
What this means in practice
- •For hardware security engineers: Design detection methods to identify hidden data leaks caused by malicious hardware modifications in transmitters.
- •For communication protocol developers: Incorporate tradeoff insights between legitimate and rogue message rates to improve protocol robustness against hidden channel attacks.
Authors
Maryam Farahnak-Ghazani, Aria Nosratinia
Abstract
Experiments have shown that modifications in communication hardware can enable unauthorized exfiltration of data from transmitters. We study the resulting Transmitter Trojan channel, in which a malicious encoder embedded within a legitimate transmitter perturbs the transmitted codeword on a symbol-by-symbol basis. The model reflects the limited footprint, delay, and computational complexity available to such hardware modifications. We derive achievable rogue message rate and achievable rates for the legitimate message under the mismatch induced by the Trojan. We also analyze decoding error exponents for the legitimate and rogue receivers, including operational exponent lower bounds obtained through channel-resolvability transfer arguments. Finally, we study Trojan detection at the legitimate receiver under different levels of statistical knowledge, including likelihood-ratio detection when the ensemble-averaged induced channel is known and goodness-of-fit detection when only the nominal channel is known. The resulting detection error exponents, together with the achievable rate and decoding error exponents, quantify tradeoffs among rogue message rate, legitimate message rate, decoding reliability, and Trojan detectability. We specialize the analysis to the binary symmetric channel and the additive white Gaussian noise channel, and illustrate the resulting tradeoffs numerically.