MOE: Multiplication Operated Encryption with Trojan Resilience

Bronchain, Olivier [UCL] Faust, Sebastian Lallemand, Virginie Leander, Gregor Perrin, Léo Standaert, François-Xavier [UCL]

In order to lower costs, the fabrication of Integrated Circuits (ICs) is increasingly delegated to offshore contract foundries, making them exposed to mali-cious modifications, known as hardware Trojans. Recent works have demonstrated that a strong form of Trojan-resilience can be obtained from untrusted chips by exploiting secret sharing and Multi-Party Computation (MPC), yet with significant cost overheads. In this paper, we study the possibility of building a symmetric cipher enabling similar guarantees in a more efficient manner. To reach this goal, we exploit a simple round structure mixing a modular multiplication and a multiplication with a binary matrix. Besides being motivated as a new block cipher design for Trojan resilience, our research also exposes the cryptographic properties of the modular multiplication, which is of independent interest.