Cryptology ePrint Archive: Report 2019/017
CHURP: Dynamic-Committee Proactive Secret Sharing
Sai Krishna Deepak Maram and Fan Zhang and Lun Wang and Andrew Low and Yupeng Zhang and Ari Juels and Dawn Song
Abstract: We introduce CHURP (CHUrn-Robust Proactive secret sharing). CHURP enables secure secret-sharing in dynamic settings, where the committee of nodes storing a secret changes over time. Designed for blockchains, CHURP has lower communication complexity than previous schemes: $O(n)$ on-chain and $O(n^2)$ off-chain in the optimistic case of no node failures.
CHURP includes several technical innovations: An efficient new proactivization scheme of independent interest, a technique (using asymmetric bivariate polynomials) for efficiently changing secret-sharing thresholds, and a hedge against setup failures in an efficient polynomial commitment scheme. We also introduce a general new technique for inexpensive off-chain communication across the peer-to-peer networks of permissionless blockchains.
We formally prove the security of CHURP, report on an implementation, and present performance measurements.
Category / Keywords: cryptographic protocols / secret sharing, threshold cryptography, blockchains
Original Publication (in the same form): ACM CCS'19
DOI: 10.1145/3319535.3363203
Date: received 6 Jan 2019, last revised 1 Oct 2019
Contact author: sm2686 at cornell edu
Available format(s): PDF | BibTeX Citation
Note: Final CCS version, minor error fixes.
Version: 20191002:023949 (All versions of this report)
Short URL: ia.cr/2019/017
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