David Reichmuth, Heriot-Watt University
One-out-of-two (1-2) oblivious transfer is a cryptographic primitive, in which a sender holds two bits, x0 and x1, and a receiver receives one of them, in such a way that the receiver does not know both bits, and the sender does not know which bit the receiver obtained. While information-theoretical security for quantum versions of such protocols is not possible, it is of interest to examine possible security bounds, which previous work has shown to be set at 0.749 in “complete” protocols employing pure symmetric states.