Protecting Computations against Continuous Bounded-Communication Leakage

We consider the question of protecting a general computation device, modeled by a stateful Boolean circuit, against leakage of partial information about its internal wires. Goyal et al. (FOCS 2016) obtained a solution for the case of bounded-communication leakage, where the wires are partitioned into two parts and the leakage can be any function computed using t bits of communication between the parts. However, this solution suffers from two major limitations: (1) it only applies to a one-shot (stateless) computation, mapping an encoded input to an encoded output, and (2) the leakage-resilient circuit consumes fresh random bits, whose number scales linearly with the circuit complexity of the computed function. In this work, we eliminate the first limitation and make progress on the second. Concretely: - We present the first construction of stateful circuits that offer information-theoretic protection against continuous bounded-communication leakage. As an application, we extend a two-party “malware-resilient” protocol of Goyal et al. to the continuous-leakage case. - For simple types of bounded-communication leakage, which leak t parities or t disjunctions of circuit wires or their negations, we obtain a deterministic variant that does not require any fresh randomness beyond the randomness in the initial state. Here we get computational security based on a subexponentially secure one-way function. This is the first deterministic leakage-resilient circuit construction for any nontrivial class of global leakage.