Constrained Pseudorandom Functions from Homomorphic Secret Sharing

A Constrained pseudorandom function (CPRF) is a pseudorandom function that provides fine-grained access to the evaluation of the function. In other words, for a (possibly super-polynomial) subset of inputs, a constrained pseudorandom function allows us to derive a constrained key that enables evaluating the function on that subset of inputs while learning nothing beyond. We propose and analyze a simple strategy for constructing 1-key constrained pseudorandom functions from homomorphic secret sharing (HSS) protocols. This relation, in particular, leads to instantiations of CPRFs for various constraints and from various assumptions. In this talk, I present this strategy and briefly go over one of the instantiations.