Advancing the State-of-the-Art in Hardware Trojans Design

TL;DR

This paper reveals the vast landscape of hardware Trojan designs beyond known benchmarks, introduces new design principles, and demonstrates a novel Trojan example, emphasizing the need for more comprehensive detection methods.

Contribution

It identifies crucial properties of HTs leading to an exponentially large class of Trojans, and proposes a new Trojan design based on these principles as a proof-of-concept.

Findings

Existing HT detection techniques are limited to known benchmarks.

A new class of HTs can be designed using discovered principles.

The proposed XOR-LFSR Trojan exemplifies the new design approach.

Abstract

Electronic Design Automation (EDA) industry heavily reuses third party IP cores. These IP cores are vulnerable to insertion of Hardware Trojans (HTs) at design time by third party IP core providers or by malicious insiders in the design team. State of the art research has shown that existing HT detection techniques, which claim to detect all publicly available HT benchmarks, can still be defeated by carefully designing new sophisticated HTs. The reason being that these techniques consider the HT landscape to be limited only to the publicly known HT benchmarks, or other similar (simple) HTs. However the adversary is not limited to these HTs and may devise new HT design principles to bypass these countermeasures. In this paper, we discover certain crucial properties of HTs which lead to the definition of an exponentially large class of Deterministic Hardware Trojans $H_D$ that an adversary can (but is not limited to) design. The discovered properties serve as HT design principles, based on which we design a new HT called 'XOR-LFSR' and present it as a 'proof-of-concept' example from the class $H_D$. These design principles help us understand the tremendous ways an adversary has to design a HT, and show that the existing publicly known HT benchmarks are just the tip of the iceberg on this huge landscape. This work, therefore, stresses that instead of guaranteeing a certain (low) false negative rate for a small constant set of publicly known HTs, a rigorous HT detection tool should take into account these newly discovered HT design principles and hence guarantee the detection of an exponentially large class (exponential in number of wires in IP core) of HTs with negligible false negative rate.