Efficient composable Oblivious Transfer from CDH in the Global Random Oracle Model

Bernardo David, Rafael Dowsley

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Oblivious Transfer (OT) is a fundamental cryptographic protocol that finds a number of applications, in particular, as an essential building block for two-party and multi-party computation. We construct the first universally composable (UC) protocol for oblivious transfer secure against active static adversaries based on the Computational Diffie-Hellman (CDH) assumption. Our protocol is proven secure in the observable Global Random Oracle model. We start by constructing a protocol that realizes an OT functionality with a selective failure issue, but shown to be sufficient to instantiate efficient OT extension protocols. In terms of complexity, this protocol only requires the computation of 6 modular exponentiations and the communication of 5 group elements, five binary strings of security parameter length, and two binary strings of message length. Finally, we lift this weak construction to obtain a protocol that realizes the standard OT functionality (without any selective failures) at an additional cost of computing 9 modular exponentiations and communicating 4 group elements, four binary strings of security parameter length and two binary strings of message length. As an intermediate step before constructing our CDH based protocols, we design generic OT protocols from any OW-CPA secure public-key encryption scheme with certain properties, which could potentially be instantiated from more assumptions other than CDH.

Original languageEnglish
Title of host publicationCryptology and Network Security
Subtitle of host publication19th International Conference, CANS 2020 Vienna, Austria, December 14–16, 2020 Proceedings
EditorsStephan Krenn, Haya Shulman, Serge Vaudenay
Place of PublicationCham Switzerland
Number of pages20
ISBN (Electronic)9783030654115
ISBN (Print)9783030654108
Publication statusPublished - 2020
EventInternational Conference on Cryptology and Network Security 2020 - Vienna, Austria
Duration: 14 Dec 202016 Dec 2020
Conference number: 19th
https://link.springer.com/book/10.1007/978-3-030-65411-5 (Proceedings)
https://cans2020.at (Webpage)

Publication series

NameLecture Notes in Computer Science
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


ConferenceInternational Conference on Cryptology and Network Security 2020
Abbreviated titleCANS 2020
Internet address

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