FSM Inspired Unconventional Hardware Watermark Using Field-Assisted SOT-MTJ

Abstract

The globalization of the Integrated Circuits supply chain has increased threats from untrusted entities involved in the process. Several mechanisms, such as logic locking, watermarking and split manufacturing, are widely used to ensure hardware security. This study describes a novel method for creating hardware watermarks inspired by finite-state machines. It makes use of the unique physical property of magnetic tunnel junctions that are based on spin-orbit torque. The design strategy is described in detail, including the use of an EDA tool to analyze and take advantage of the unique switching properties of MTJ, their non-volatility, and their reliance on an external magnetic field to direct information through a predetermined order of states in a manner akin to an FSM. Furthermore, the performance prospects are analyzed using Monte Carlo simulations. For the 5% and 10% of process variation in the key MTJ parameters, the accuracy of 100% and 99.80%, respectively, are achieved. In control signal voltage variation, a tolerance of 9% (0.91V) is observed. The required state transition is not altered, demonstrating a tolerable sensitivity to temperature variation from 250K to 350K. The security aspects and methodology for the approach are explained to ensure a more robust and practical application, and finally, a comparison is made with other FSM-based watermarks.

Keywords

• Hardware watermarks
• hardware security
• spintronics
• spin-orbit torque (SOT)
• magnetic tunnel junction (MTJ)
• finite-state machine (FSM)