Oblivious Transfer Is Symmetric

KEISUKE TANAKA, 井上, 大輔, Inoue, Daisuke

Stefan Wolf, Jürg Wullschleger

Abstract. We show that oblivious transfer of bits from A to B can be obtained from a single instance of the same primitive from B to A. Our reduction is perfect and shows that oblivious transfer is in fact a symmetric functionality. This solves an open problem posed by Crépeau and Sántha in 1991. 1

Claude Crépeau, Miklós Sántha

Douglas Stebila, Stefan Wolf

In 1997, Crepeau proved that the important cryptographic primitive of oblivious transfer can be efficiently realized by using a binary-symmetric channel with symbol-error probability less than 0.1982. We show that this restriction is unnecessary: Oblivious transfer can be realized as efficiently based on any non-trivial binary-symmetric channel between the involved parties.

So Suda, Shun Watanabe, Haruya Yamaguchi

We revisit the oblivious transfer (OT) capacities of noisy channels against the passive adversary, which have been identified only for a limited class of channels. In the literature, the general construction of oblivious transfer has been known only for generalized erasure channels (GECs); for other channels, we first convert a given channel to a GEC via alphabet extension and erasure emulation, and then apply the general construction for GEC. In this paper, we derive an improved lower bound on the OT capacity of the binary symmetric channel (BSC) and binary symmetric erasure channel (BSEC) by proposing a new protocol; by using interactive communication between the sender and the receiver, our protocol emulates erasure events recursively in multiple rounds. We also discuss a potential necessity of multiple rounds interactive communication to attain the OT capacity.

Mehrad Jaberi, Hamid Mala