Winning the 'Race to the Bottom' by Changing the Rules: Inhibiting Malicious Hardware Activation through Attack Incompatibility

Many hardware trojans depend on (a) the ability of an attacker to have an accurate model of the target system and of key software used on that system and (b) identification of one or more deterministic trigger conditions with low observability (i.e., conditions that evade detection by traditional scan- or ATPG-based testing methodologies but that can be exercised on demand via external stimuli). We call this class of trojans deterministic, externally-triggered (DET) trojans. This work introduces a class of software-based general purpose countermeasures to the DET class of trojans. We propose a set of tools by which the software engineer can transform the source code of system & application software to automatically obfuscate communication channels. The tools take as input two things: (a) the source code of communicating software components, and (b) a specification of obfuscating transformations on the communication; from these is generated the transformed source code. The resulting system does not adhere to the behavioral model assumed when building the trojan. Thus an adversary's assault is rendered less effective via "attack incompatibility": trigger conditions have been altered such that the malicious behavior cannot be reliably instigated.