Hardware Obfuscation Using Strong PUFs

Abstract

IC piracy is a significant security threat, where malicious manufacturers can produce unauthorized extra chips and/or steal the information of a design through reverse engineering attempts. As a countermeasure, hardware obfuscation schemes usually withhold a part of the design (which thereafter constitutes the "key") by replacing it with configurable modules. Enforcing the configurable module to be filled in with the withheld key information enables a post-manufacturing activation of each authenticate chip, albeit with a a need to state the threat of a leaked common key. To ensure that each chip has a unique key, Physically Unclonable Functions (PUFs) have been proposed to be integrated with hardware obfuscation. Such a paradigm is constrained to use weak PUFs, because, to uniquely set the key (the content of the configurable module) for each chip, the designer needs to fully characterize the PUFs for all the chips. In this paper, we argue that a powerful attacker in the position of a manufacturer can fully characterize all the weak PUFs, and use any leaked key to break the obfuscation framework. This paper proposes a strong PUF-based hardware obfuscation scheme to effectively prevent IC piracy even in the case of a leaked key from some activated chip.