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Documents authored by Christ, Miranda

Document
DOI: 10.4230/LIPIcs.AFT.2025.12
How Much Public Randomness Do Modern Consensus Protocols Need?

Authors: Joseph Bonneau, Benedikt Bünz, Miranda Christ, and Yuval Efron

Published in: LIPIcs, Volume 354, 7th Conference on Advances in Financial Technologies (AFT 2025)

Abstract
Modern blockchain-based consensus protocols aim for efficiency (i.e., low communication and round complexity) while maintaining security against adaptive adversaries. These goals are usually achieved using a public randomness beacon to select roles for each participant. We examine to what extent this randomness is necessary. Specifically, we provide tight bounds on the amount of entropy a Byzantine Agreement protocol must consume from a beacon in order to enjoy efficiency and adaptive security. We first establish that no consensus protocol can simultaneously be efficient, be adaptively secure, and use O(log n) bits of beacon entropy. We then show this bound is tight and, in fact, a trilemma by presenting three consensus protocols that achieve any two of these three properties.
Cite as

Joseph Bonneau, Benedikt Bünz, Miranda Christ, and Yuval Efron. How Much Public Randomness Do Modern Consensus Protocols Need?. In 7th Conference on Advances in Financial Technologies (AFT 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 354, pp. 12:1-12:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{bonneau_et_al:LIPIcs.AFT.2025.12,
  author =	{Bonneau, Joseph and B\"{u}nz, Benedikt and Christ, Miranda and Efron, Yuval},
  title =	{{How Much Public Randomness Do Modern Consensus Protocols Need?}},
  booktitle =	{7th Conference on Advances in Financial Technologies (AFT 2025)},
  pages =	{12:1--12:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-400-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{354},
  editor =	{Avarikioti, Zeta and Christin, Nicolas},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2025.12},
  URN =		{urn:nbn:de:0030-drops-247310},
  doi =		{10.4230/LIPIcs.AFT.2025.12},
  annote =	{Keywords: Consensus, Randomness Beacon}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.1
Accountable Secret Leader Election

Authors: Miranda Christ, Kevin Choi, Walter McKelvie, Joseph Bonneau, and Tal Malkin

Published in: LIPIcs, Volume 316, 6th Conference on Advances in Financial Technologies (AFT 2024)

Abstract
We consider the problem of secret leader election with accountability. Secret leader election protocols counter adaptive adversaries by keeping the identities of elected leaders secret until they choose to reveal themselves, but in existing protocols this means it is impossible to determine who was elected leader if they fail to act. This opens the door to undetectable withholding attacks, where leaders fail to act in order to slow the protocol or bias future elections in their favor. We formally define accountability (in weak and strong variants) for secret leader election protocols. We present three paradigms for adding accountability, using delay-based cryptography, enforced key revelation, or threshold committees, all of which ensure that after some time delay the result of the election becomes public. The paradigm can be chosen to balance trust assumptions, protocol efficiency, and the length of the delay before leaders are revealed. Along the way, we introduce several new cryptographic tools including re-randomizable timed commitments and timed VRFs.
Cite as

Miranda Christ, Kevin Choi, Walter McKelvie, Joseph Bonneau, and Tal Malkin. Accountable Secret Leader Election. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 1:1-1:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{christ_et_al:LIPIcs.AFT.2024.1,
  author =	{Christ, Miranda and Choi, Kevin and McKelvie, Walter and Bonneau, Joseph and Malkin, Tal},
  title =	{{Accountable Secret Leader Election}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{1:1--1:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-345-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{316},
  editor =	{B\"{o}hme, Rainer and Kiffer, Lucianna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.1},
  URN =		{urn:nbn:de:0030-drops-209378},
  doi =		{10.4230/LIPIcs.AFT.2024.1},
  annote =	{Keywords: Consensus Protocols, Single Secret Leader Election, Accountability}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.14
SoK: Zero-Knowledge Range Proofs

Authors: Miranda Christ, Foteini Baldimtsi, Konstantinos Kryptos Chalkias, Deepak Maram, Arnab Roy, and Joy Wang

Published in: LIPIcs, Volume 316, 6th Conference on Advances in Financial Technologies (AFT 2024)

Abstract
Zero-knowledge range proofs (ZKRPs) allow a prover to convince a verifier that a secret value lies in a given interval. ZKRPs have numerous applications: from anonymous credentials and auctions, to confidential transactions in cryptocurrencies. At the same time, a plethora of ZKRP constructions exist in the literature, each with its own trade-offs. In this work, we systematize the knowledge around ZKRPs. We create a classification of existing constructions based on the underlying building techniques, and we summarize their properties. We provide comparisons between schemes both in terms of properties as well as efficiency levels, and construct a guideline to assist in the selection of an appropriate ZKRP for different application requirements. Finally, we discuss a number of interesting open research problems.
Cite as

Miranda Christ, Foteini Baldimtsi, Konstantinos Kryptos Chalkias, Deepak Maram, Arnab Roy, and Joy Wang. SoK: Zero-Knowledge Range Proofs. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 14:1-14:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{christ_et_al:LIPIcs.AFT.2024.14,
  author =	{Christ, Miranda and Baldimtsi, Foteini and Chalkias, Konstantinos Kryptos and Maram, Deepak and Roy, Arnab and Wang, Joy},
  title =	{{SoK: Zero-Knowledge Range Proofs}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{14:1--14:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-345-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{316},
  editor =	{B\"{o}hme, Rainer and Kiffer, Lucianna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.14},
  URN =		{urn:nbn:de:0030-drops-209504},
  doi =		{10.4230/LIPIcs.AFT.2024.14},
  annote =	{Keywords: Range proofs, zero knowledge}
}
Document
DOI: 10.4230/LIPIcs.AFT.2024.17
Cornucopia: Distributed Randomness at Scale

Authors: Miranda Christ, Kevin Choi, and Joseph Bonneau

Published in: LIPIcs, Volume 316, 6th Conference on Advances in Financial Technologies (AFT 2024)

Abstract
We propose Cornucopia, a protocol framework for distributed randomness beacons combining accumulators and verifiable delay functions. Cornucopia generalizes the Unicorn protocol, using an accumulator to enable efficient verification by each participant that their contribution has been included. The output is unpredictable as long as at least one participant is honest, yielding a scalable distributed randomness beacon with strong security properties. Proving this approach secure requires developing a novel property of accumulators, insertion security, which we show is both necessary and sufficient for Cornucopia-style protocols. We show that not all accumulators are insertion-secure, then prove that common constructions (Merkle trees, RSA accumulators, and bilinear accumulators) are either naturally insertion-secure or can be made so with trivial modifications.
Cite as

Miranda Christ, Kevin Choi, and Joseph Bonneau. Cornucopia: Distributed Randomness at Scale. In 6th Conference on Advances in Financial Technologies (AFT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 316, pp. 17:1-17:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{christ_et_al:LIPIcs.AFT.2024.17,
  author =	{Christ, Miranda and Choi, Kevin and Bonneau, Joseph},
  title =	{{Cornucopia: Distributed Randomness at Scale}},
  booktitle =	{6th Conference on Advances in Financial Technologies (AFT 2024)},
  pages =	{17:1--17:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-345-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{316},
  editor =	{B\"{o}hme, Rainer and Kiffer, Lucianna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AFT.2024.17},
  URN =		{urn:nbn:de:0030-drops-209533},
  doi =		{10.4230/LIPIcs.AFT.2024.17},
  annote =	{Keywords: Randomness beacons, accumulators}
}
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