Oblivious Transfer

Definition

Oblivious transfer (OT) is a two-party protocol between a sender and a receiver, by which the sender transfers some information to the receiver, the sender remaining oblivious, however, to what information the receiver actually obtains.

Theory

The most basic form of oblivious transfer, as introduced by Rabin [4], is a protocol achieving the following functionality. The sender uses one bit b as its private input to the protocol; the receiver does not provide any private input to the protocol. At the completion of the protocol, the receiver gets either the bit b or an undefined value $\infty$. Both cases occur with probability 50%, and the receiver knows whether it gets b or $\infty$. However, the sender does not know whether bit b was transferred successfully or not.

Despite its somewhat strange functionality, OT turns out to be sufficiently powerful to construct a secure multiparty computation for anycomputable function, as follows from the completeness result proved...