Simultaneous information flow security and circuit redundancy in Boolean gates

High assurance systems require strict guarantees on information flow security and fault tolerance or else face catastrophic consequences. Recently, Gate Level Information Flow Tracking (GLIFT) has been proposed to monitor information flows at the level of Boolean logic. At this level, all flows are explicit which makes it possible to detect security violations, even those that occur due to difficult to detect timing channels. In this paper, we show that the encoding technique used in previous GLIFT generation methods includes redundant encoding states, which leads to large overheads in area, delay and verification time. We present a new encoding technique with fewer encoding states by leveraging an inherent property of GLIFT. By denoting don't-care input conditions to logic synthesis tools, smaller GLIFT logic for dynamic information flow tracking is obtained and shorter simulation time for static information flow security verification is achieved. Experimental results using the IWLS benchmarks show average reductions of 39.8%, 31.1% and 57.5% in area, delay and simulation time respectively. Furthermore, the new encoding technique enables the GLIFT tracking logic to function both as information flow tracking and redundant logic. As a result, information flow security and fault tolerance can be simultaneously enforced with the same logic.