2PC ⇒ Malicious OT

Fully-black-box reduction · standard model · folklore · security loss: none

Statement

A protocol that securely computes every polynomial-time two-party functionality with abort against a malicious adversary (2PC), run on the functionality $((x_0,x_1),c)\mapsto (\perp ,x_c)$ with the honest receiver outputting the $c$-th entry of a fixed default pair after an abort, is an OT protocol with malicious security — folklore.

Sketch

A corrupted receiver’s abort withholds only the sender’s output $\perp$, so the 2PC simulator serves as the OT simulator. The simulator for a corrupted sender receives only $\perp$ from the trusted party before deciding whether to abort, so that decision does not depend on $c$ and can be replaced by submitting the default pair — standard.