Always-on hardware Trojans (HTs) pose a critical risk to trusted microelectronics, yet most side-channel detection methods rely on unavailable golden references. We present a reference-free approach that combines time-frequency EM analysis with Gaussian Mixture Models (GMMs). By applying Short-Time Fourier Transform (STFT) at multiple window sizes, we show that HT-free circuits exhibit fluctuating statistical structure, while always-on HTs leave persistent footprints with fewer, more consistent mixture components. Results on AES-128 demonstrate feasibility without requiring reference models.

翻译：常开硬件木马对可信微电子构成严重威胁，然而大多数旁路检测方法依赖于难以获取的黄金参考模型。本文提出一种无参考检测方法，该方法将时频电磁分析与高斯混合模型相结合。通过应用多窗口尺寸的短时傅里叶变换，我们发现无硬件木马的电路呈现波动的统计结构，而常开硬件木马则留下具有更少、更一致混合分量的持久特征。在AES-128上的实验结果验证了该方案无需参考模型的可行性。