We identify a subtle flaw in a protocol of Goyal, Mohassel, and Smith (Eurocrypt 2008) and show how to modify their original construction to obtain security against covert adversaries.
We present generic compilers that transform arbitrary passively secure preprocessing protocols, i.e. protocols where the parties have no private inputs, into protocols that are secure against covert adversaries and publicly verifiable. Using our compiler, we construct the first efficient variants of the BMR and the SPDZ protocols that are secure and publicly verifiable against a covert adversary that corrupts all but one party and also construct variants with covert security and identifiable abort.
We observe that an existing impossibility result by Ishai, Ostrovsky, and Seyalioglu (TCC 2012) can be used to show that there exist certain functionalities that cannot be realized by parties, that have oracle-access to broadcast and arbitrary two-party functionalities, with information-theoretic security against a covert adversary.
Category / Keywords: cryptographic protocols / Covert Security, MPC protocols, Public Verifiability Date: received 18 Mar 2021 Contact author: luisa siniscalchi88 at gmail com,simkin@cs au dk,peter scholl@cs au dk Available format(s): PDF | BibTeX Citation Version: 20210322:192938 (All versions of this report) Short URL: ia.cr/2021/366