CRAFT: Composable Randomness Beacons and Output-Independent Abort MPC From Time

Carsten Baum; Bernardo David; Rafael Dowsley; Ravi Kishore; Jesper Buus Nielsen; Sabine Oechsner

Paper 2020/784

CRAFT: Composable Randomness Beacons and Output-Independent Abort MPC From Time

Carsten Baum, Technical University of Denmark, Denmark, Aarhus University, Denmark

Bernardo David, IT University of Copenhagen, Denmark

Rafael Dowsley, Monash University, Australia

Ravi Kishore

, IT University of Copenhagen, Denmark

Jesper Buus Nielsen, Aarhus University, Denmark

Sabine Oechsner, University of Edinburgh, United Kingdom

Abstract

Recently, time-based primitives such as time-lock puzzles (TLPs) and verifiable delay functions (VDFs) have received a lot of attention due to their power as building blocks for cryptographic protocols. However, even though exciting improvements on their efficiency and security (e.g. achieving non-malleability) have been made, most of the existing constructions do not offer general composability guarantees and thus have limited applicability. Baum et al. (EUROCRYPT 2021) presented in TARDIS the first (im)possibility results on constructing TLPs with Universally Composable (UC) security and an application to secure two party computation with output-independent abort (OIA-2PC), where an adversary has to decide to abort before learning the output. While these results establish the feasibility of UC-secure TLPs and applications, they are limited to the two-party scenario and suffer from complexity overheads. In this paper, we introduce the first UC constructions of VDFs and of the related notion of publicly verifiable TLPs (PV-TLPs). We use our new UC VDF to prove a folklore result on VDF-based randomness beacons used in industry and build an improved randomness beacon from our new UC PV-TLPs. We moreover construct the first multiparty computation protocol with punishable output-independent aborts (POIA MPC), i.e. MPC with OIA and financial punishment for cheating. Our novel POIA-MPC both establishes the feasibility of (non-punishable) OIA-MPC and significantly improves on the efficiency of state-of-the-art OIA-2PC and (non-OIA) MPC with punishable aborts.

Note: Simplified most of the Functionalities, Protocols and Proofs.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: A major revision of an IACR publication in PKC 2023
Keywords: Universal Composability Time Lock Puzzle Verifiable Delay Function Output Independent Abort Multiparty Computation Randomness Beacons Public Verifiability
Contact author(s): cabau @ dtu dk
bernardo @ bmdavid com
rafael @ dowsley net
rava @ itu dk
jbn @ cs au dk
s oechsner @ ed ac uk
History: 2023-02-13: last of 3 revisions; 2020-06-27: received; See all versions
Short URL: https://ia.cr/2020/784
License: CC BY

BibTeX

@misc{cryptoeprint:2020/784,
      author = {Carsten Baum and Bernardo David and Rafael Dowsley and Ravi Kishore and Jesper Buus Nielsen and Sabine Oechsner},
      title = {{CRAFT}: Composable Randomness Beacons and Output-Independent Abort {MPC} From Time},
      howpublished = {Cryptology {ePrint} Archive, Paper 2020/784},
      year = {2020},
      url = {https://eprint.iacr.org/2020/784}
}