First demonstration of federated learning with homomorphic encryption using vertically-stacked ferroelectric tunnel junction

Abstract

A novel vertical ferroelectric tunnel junction (VFTJ) array enabling hardware-level implementation of homomorphic encryption (HE) for secure federated learning (FL) is proposed. A highly integrated 4-stack TiN/SiO2 structure with vertically etched hole-type architecture was fabricated. Distinct ferroelectric and ionic switching induced by interfacial TiOx formation significantly enhanced tunneling electroresistance (TER) and switching reliability. The intrinsic randomness of devices enabled the realization of polynomial samplers (ternary, Gaussian, uniform) essential for HE schemes. The proposed VFTJ-based FL achieves accuracy comparable to the software baseline, exhibiting less than 4% accuracy reduction under highly non-IID conditions