Encoding the state of integrated circuits: a proactive and reactive protection against hardware Trojans horses

Abstract

Hardware Trojan Horses (HTH) are a serious threat to semiconductor industry with significant economic impact. However, most of the research in HTH focuses on detection. We propose the concept of "encoded circuit", as a technique to protect HTH insertion. Encoded circuit is based on the theory of codes. It encodes the internal state with a chosen code of security parameter d, such that knowledge of less than d bits of the encoded state reveals no information about the actual state. This parameter stems from a similar notion introduced by Ishai, Sahai and Wagner at CRYPTO 2003 for the prevention of probing attacks. Usually d < 10 in probing attacks, whereas HTH are able to connect to more than 10 nets. In this paper, we discuss the theory behind "encoded circuits" and its practical demonstration on various HDL circuits.