IACR News item: 14 June 2015
Rafail Ostrovsky, Silas Richelson, Alessandra Scafuro
ePrint ReportA rich line of work [IKLP06, Hai08, CDSMW09, IKOS07, PW09] has shown that the non- black-box use of the cryptographic primitive in secure two-party computation is not necessary by providing black-box constructions matching basically all the feasibility results that were previously demonstrated only via non-black-box protocols.
All such constructions however are far from being round optimal. The reason is that they are based on cut-and-choose mechanisms where one party can safely take an action only after the other party has successfully completed the cut-and-choose phase, therefore requiring additional rounds.
A natural question is whether round-optimal constructions do inherently require non-black- box access to the primitives, and whether the lower bound shown by Katz and Ostrovsky can only be matched by a non-black-box protocol.
In this work we show that round-optimality is achievable even with only black-box access to the primitives. We provide the first 4-round black-box oblivious transfer based on any enhanced trapdoor permutation. Plugging a parallel version of our oblivious transfer into the black- box non-interactive secure computation protocol of [IKO+11] we obtain the first round-optimal black-box two-party protocol in the plain model for any functionality.
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