From Privacy-Only to Simulatable OT: Black-Box, Round-Optimal, Information-Theoretic

We present an information-theoretic transformation from any 2-round OT protocol with only game-based security in the presence of malicious adversaries into a 4-round (which is known to be optimal) OT protocol with simulation-based security in the presence of malicious adversaries. Our transform is the first satisfying all of the following properties at the same time: It is in the plain model, without requiring any setup assumption. It only makes black-box usage of the underlying OT protocol. It is information-theoretic, as it does not require any further cryptographic assumption (besides the existence of the underlying OT protocol). Additionally, our transform yields a cubic improvement in communication complexity over the best previously known transformation.