Modeling of Sneaky Hardware Trojan Using Spin-orbit Torque Assisted Magnetic Tunnel Junction for High Speed Digital Circuits

This work explores spin-orbit torque (SOT) assisted magnetic tunnel junction (MTJ) as a potential candidate for designing sneaky hardware Trojan (HT). The type of payload targeted is IC malfunction using an externally triggered activation mechanism with an external magnetic field. To make it sneakier, we designed the Trojan to have sufficient tolerance to stray magnetic fields and thermal stability to ensure better-hidden operation for temperature-based tests during system-on-a-chip (SoC) flow. For creating a smaller Trojan, the energy barrier height's effect must be considered. Therefore, an appropriate optimization for SOT-assisted MTJ is required. This work thus considers the effect of process variation in key MTJ parameters by using Monte-Carlo (MC) simulations, and the effect of temperature sweep is utilized to determine the operational ability of the Trojan. We also conclude the Trojan optimization design by analysing its behaviour for high-speed IC operation by performing eye-diagram tests and transient analysis measurements for more practical applications. This work shows that a 5% reduction in MTJ key dimensions for Trojan operation has around 58.87% reduction in the critical magnetic field required for triggering with sufficient tolerance to process variation. Thus, this work contributes towards optimization of hardware Trojan for more sneaky operation.