N-variant IC design: Methodology and applications

We propose the first method for designing N-variant sequential circuits. The flexibility provided by the N-variants enables a number of important tasks, including IP protection, IP metering, security, design optimization, self-adaptation and fault-tolerance. The method is based on extending the finite state machine (FSM) of the design to include multiple variants of the same design specification. The state transitions are managed by added signals that may come from various triggers depending on the target application. We devise an algorithm for implementing the N-variant IC design. We discuss the necessary manipulations of the added signals that would facilitate the various tasks. The key advantage to integrating the heterogeneity in the functional specification of the design is that we can configure the variants during or post-manufacturing, but removal, extraction or deletion of the variants is not viable. Experimental results on benchmark circuits demonstrate that the method can be automatically and efficiently implemented. Because of its lightweight, N-variant design is particularly well-suited for securing embedded systems. As a proof-of-concept, we implement the N-variant method for content protection in portable media players, e.g., iPod. We discuss how the N-variant design methodology readily enables new digital rights management methods.