Detection mechanisms for unauthorized wireless transmissions

With increasing diversity of supply chains from design to delivery, there is an increasing risk that unauthorized changes can be made within an IC. One of the motivations for this type of change is to learn important information (such as encryption keys, spreading codes) from the hardware, and transmit this information to a malicious party. To evade detection, such unauthorized communication can be hidden within legitimate bursts of transmit signal. In this article, we present several signal processing techniques to detect unauthorized transmissions which can be hidden within the legitimate signal. We employ a scheme where the legitimate transmission is configured to emit a single sinusoidal waveform. We use time and spectral domain analysis techniques to explore the transmit spectrum. Since every transmission, no matter how low the signal power is, must have a spectral signature, we identify unauthorized transmission by eliminating the desired signal from the spectrum after capture. Experiment results show that when spread spectrum techniques are used, the presence of an unauthorized signal can be determined without the need for decoding the malicious signal. The proposed detection techniques need to be used as enhancements to the regular testing and verification procedures if hardware security is a concern.