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Paper 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.

Note: Minor error fix.

Metadata
Available format(s)
PDF
Category
Cryptographic protocols
Publication info
Preprint. MINOR revision.
Keywords
secret sharingthreshold cryptographyblockchains
Contact author(s)
sm2686 @ cornell edu
History
2019-10-02: last of 5 revisions
2019-01-09: received
See all versions
Short URL
https://ia.cr/2019/017
License
Creative Commons Attribution
CC BY
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