Two-Round Maliciously-Secure Oblivious Transfer with Optimal Rate.

We give a construction of a two-round batch oblivious transfer (OT) protocol in the CRS model that is UC-secure against malicious adversaries and has (near) optimal communication cost. Specifically, to perform a batch of k oblivious transfers where the sender’s inputs are bits, the sender and the receiver need to communicate a total of 3k+o(k)·poly(λ) bits. We argue that 3k bits are required by any protocol with a black-box and straight-line simulator. The security of our construction is proven assuming the hardness of Quadratic Residuosity (QR) and the Learning Parity with Noise (LPN).