International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

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

Authors:
Carsten Baum , Technical University of Denmark
Bernardo David , IT University of Copenhagen
Rafael Dowsley , Monash University
Ravi Kishore , IT University of Copenhagen
Sabine Oechsner , University of Edinburgh
Jesper Buus Nielsen , Aarhus University
Download:
DOI: 10.1007/978-3-031-31368-4_16
Search ePrint
Search Google
Presentation: Slides
Conference: PKC 2023
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 (\textit{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 \textit{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 \emph{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), \textit{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.
BibTeX
@inproceedings{pkc-2023-32724,
  title={CRAFT: Composable Randomness Beacons and Output-Independent Abort MPC From Time},
  publisher={Springer-Verlag},
  doi={10.1007/978-3-031-31368-4_16},
  author={Carsten Baum and Bernardo David and Rafael Dowsley and Ravi Kishore and Sabine Oechsner and Jesper Buus Nielsen},
  year=2023
}