Efficient analog verification against Trojan states using divide and contraction method

Abstract

Identifying and removing the undesired stable operating point (also called "Trojan state" in analog circuit) is one of the most important problems in circuit design. In this paper, an innovative divide and contraction verification method against Trojan states is proposed. Unlike the traditional methods to find all operating points, it only targets searching the voltage interval containing undesired stable operating point. Based on this, a monotonic divide and contraction algorithm (MDC) is proposed, it could verify the existence of Trojan state in high efficiency. Simulation results show that this method is effective and efficient in identifying Trojan states and verifying the efficacy of Trojan state Elimination (TSE) circuits which is commonly termed start-up circuits.

Challenges and Opportunities in Analog and Mixed Signal (AMS) Integrated Circuit (IC) Security

“…With the help of DDG, a few strongly connected components (SCCs) are identified in the circuit and then graph theory is utilized to detect positive feedback loops and identify the set of node points to be removed. Another theory proposed in [70,71] explains homotopy methods which convert the circuit into graphical formats with the respective nodes and branches and detect the positive feedback loop (PFL). The PFL is then broken and a voltage source is inserted at the break point which is then swept within a predetermined sweep range to obtain the unwanted DC states (Trojan states).…”

Undesired Operating Points and Hardware Trojans in High-Speed Operational Amplifier Microcircuits

“…In particular, circuit engineering methods of increasing the slew rate (SR), associated with a dynamic increase in the output currents of the input stage, lead to Trojan states of high-speed Op-Amps [3][4][5][6][7]. In [8][9][10][11], several effective methods were proposed for detecting positive feedback loops (PFLs), as well as detecting all Trojan states in analog circuits. In [12], a new method for identifying PFLs in an analog circuit is shown.…”

“…In [16][17][18] the main stages of development and supply of microcircuits are presented, in which Trojans can be introduced (intentionally or not) during circuit design, creation of topologies, copying and counterfeiting, and provides an overview of some existing topological solutions that have Trojan states.…”

Hardware Trojan vulnerability

“…In other works, continuous/homotopy methods have been used to track DC solutions [22]. In [23], a break-loop homotopy method was proposed and it finds all stable operating points for CMOS circuits with one positive feedback loop by breaking the positive feedback loop in the circuit at the gate of a transistor, inserting a voltage source at the break point, and sweeping the voltage to create a return map. From the return map, the stable equilibrium points can be obtained.…”