Cryptology ePrint Archive: Report 2022/315

Low-Communication Multiparty Triple Generation for SPDZ from Ring-LPN

Damiano Abram and Peter Scholl

Abstract: The SPDZ protocol for multi-party computation relies on a correlated randomness setup consisting of authenticated, multiplication triples. A recent line of work by Boyle et al. (Crypto 2019, Crypto 2020) has investigated the possibility of producing this correlated randomness in a silent preprocessing phase, which involves a “small” setup protocol with less communication than the total size of the triples being produced. These works do this using a tool called a pseudorandom correlation generator (PCG), which allows a large batch of correlated randomness to be compressed into a set of smaller, correlated seeds. However, existing methods for compressing SPDZ triples only apply to the 2-party setting. In this work, we construct a PCG for producing SPDZ triples over large prime fields in the multi-party setting. The security of our PCG is based on the ring-LPN assumption over fields, similar to the work of Boyle et al. (Crypto 2020) in the 2-party setting. We also present a corresponding, actively secure setup protocol, which can be used to generate the PCG seeds and instantiate SPDZ with a silent preprocessing phase. As a building block, which may be of independent interest, we construct a new type of 3-party distributed point function supporting outputs over arbitrary groups (including large prime order), as well as an efficient protocol for setting up our DPF keys with active security.

Category / Keywords: cryptographic protocols / PCG, SPDZ, DPF, MPC

Original Publication (with major differences): IACR-PKC-2022

Date: received 7 Mar 2022

Contact author: damiano abram at cs au dk, peter scholl at cs au dk

Available format(s): PDF | BibTeX Citation

Version: 20220307:125206 (All versions of this report)

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