Triggering Trojans in SRAM circuits with X-propagation

Over the past several years, there has been growing concern regarding the possibility that Hardware Trojan Horse circuits may be present in 3rd party IP. In this paper, we focus specifically on 3rd party IP related to Static Random-Access Memories (SRAMs), and we demonstrate that some Trojans in production-worthy SRAM circuits can easily evade standard verification techniques. We then describe a novel Trojan detection mechanism based on X-propagation during functional simulation of verification vectors. Our experiments from a silicon-worthy verification environment illustrate that our techniques can be significantly more effective at Trojan detection than standard SRAM verification practices.