How to construct a leakage-resilient (stateless) trusted party

Trusted parties and devices are commonly used in the real world to securely perform computations on secret inputs. However, their security can often be compromised by side-channel attacks in which the adversary obtains partial leakage on intermediate computation values. This gives rise to the following natural question: To what extent can one protect the trusted party against leakage? Our goal is to design a hardware device T that allows m≥ 1 parties to securely evaluate a function f(x₁, …, x_m) of their inputs by feeding T with encoded inputs that are obtained using local secret randomness. Security should hold even in the presence of an active adversary that can corrupt a subset of parties and obtain restricted leakage on the internal computations in T. We design hardware devices T in this setting both for zero-knowledge proofs and for general multi-party computations. Our constructions can unconditionally resist either AC⁰ leakage or a strong form of “only computation leaks” (OCL) leakage that captures realistic side-channel attacks, providing different tradeoffs between efficiency and security.