Non-Invasive Hardware Trojans Modeling and Insertion: A Formal Verification Approach

In modern chip designs, shared resources are used extensively. Arbiters usage is crucial to settle conflicts when multiple requests compete for these shared resources. Making sure these arbiter circuits work correctly is vital not just for their proper functionality, but also for security reasons. The work in this paper introduces a method based on formal verification to thoroughly assess the proper functional aspects of various arbiter setups. This is achieved through SystemVerilog assertions and model checking. Additionally, we explore a non-invasive method for the modeling and insertion of different types of hardware Trojans. These Trojans, with their unique triggers and payloads, are modeled formally without the need for any alterations to the actual circuit. The results provide a detailed analysis of the cost involved in running the formal verification environment on versions of arbiters that are free from Trojans. This analysis is carried out using Questa PropCheck formal analysis tool, which offers valuable insights into the time and memory resources required. Furthermore, the results highlights how the formally modeled and inserted Trojans interfere with hold criteria of the arbiters’ properties, where at least a single property fires due to the inserted Trojan. This work can be extended to be a generic approach with the potential to validate both the proper operation and security aspects of complex systems.