Nowadays, Hardware Trojan threats have become inevitable due to the growing complexities of Integrated Circuits (ICs) as well as the current trend of Intellectual Property (IP)-based hardware designs. An adversary can insert a Hardware Trojan during any of its life cycle phases — the design, fabrication or even at manufacturing phase. Once a Trojan is inserted into a system, it can cause an unwanted modification to system functionality which may degrade system performance or sometimes Trojans are implanted with the target to leak secret information. Once Trojans are implanted, they are hard to detect and impossible to remove from the system as they are already fabricated into the chip. In this paper, we propose three stealthy Trojan models which affect the coherence mechanism of Chip Multiprocessors’ (CMPs) cache system by arbitrarily modifying the cache block state which in turn may leave the cache line states as incoherent. We have evaluated the payload of such modeled Trojans and proposed a cellular automaton (CA)-based solution for detection of such Trojans.
Cellular automata (CAs) are simple mathematical models that are effectively being used to analyze and understand the behavior of complex systems. Researchers from a wide range of fields are interested in CAs due to their potential for representing a variety of physical, natural and real-world phenomena. Three-neighborhood one-dimensional CAs, a special class of CAs, have been utilized to develop various applications in the field of very large-scale integration (VLSI) design, error-correcting codes, test pattern generation, cryptography and others. A thorough analysis of a three-neighborhood cellular automaton (CA) with two states per cell is presented in this paper. A graph-based tool called the next-state rule minterm transition diagram (NSRTD) is presented for analyzing the state transition behavior of CAs with fixed points. A linear time mechanism has been proposed for synthesizing a special class of irreversible CAs referred to as single length cycle two-attractor CAs (TACAs), having only two fixed points.
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