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Documents authored by Ren, Ling

Document
DOI: 10.4230/LIPIcs.DISC.2024.30
Granular Synchrony

Authors: Neil Giridharan, Ittai Abraham, Natacha Crooks, Kartik Nayak, and Ling Ren

Published in: LIPIcs, Volume 319, 38th International Symposium on Distributed Computing (DISC 2024)

Abstract
Today’s mainstream network timing models for distributed computing are synchrony, partial synchrony, and asynchrony. These models are coarse-grained and often make either too strong or too weak assumptions about the network. This paper introduces a new timing model called granular synchrony that models the network as a mixture of synchronous, partially synchronous, and asynchronous communication links. The new model is not only theoretically interesting but also more representative of real-world networks. It also serves as a unifying framework where current mainstream models are its special cases. We present necessary and sufficient conditions for solving crash and Byzantine fault-tolerant consensus in granular synchrony. Interestingly, consensus among n parties can be achieved against f ≥ n/2 crash faults or f ≥ n/3 Byzantine faults without resorting to full synchrony.
Cite as

Neil Giridharan, Ittai Abraham, Natacha Crooks, Kartik Nayak, and Ling Ren. Granular Synchrony. In 38th International Symposium on Distributed Computing (DISC 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 319, pp. 30:1-30:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{giridharan_et_al:LIPIcs.DISC.2024.30,
  author =	{Giridharan, Neil and Abraham, Ittai and Crooks, Natacha and Nayak, Kartik and Ren, Ling},
  title =	{{Granular Synchrony}},
  booktitle =	{38th International Symposium on Distributed Computing (DISC 2024)},
  pages =	{30:1--30:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-352-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{319},
  editor =	{Alistarh, Dan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2024.30},
  URN =		{urn:nbn:de:0030-drops-212566},
  doi =		{10.4230/LIPIcs.DISC.2024.30},
  annote =	{Keywords: Timing model, synchrony, asynchrony, consensus, blockchain, fault tolerance}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2021.5
Good-Case and Bad-Case Latency of Unauthenticated Byzantine Broadcast: A Complete Categorization

Authors: Ittai Abraham, Ling Ren, and Zhuolun Xiang

Published in: LIPIcs, Volume 217, 25th International Conference on Principles of Distributed Systems (OPODIS 2021)

Abstract
This paper studies the good-case latency of unauthenticated Byzantine fault-tolerant broadcast, which measures the time it takes for all non-faulty parties to commit given a non-faulty broadcaster. For both asynchrony and synchrony, we show that n ≥ 4f is the tight resilience threshold that separates good-case 2 rounds and 3 rounds. For asynchronous Byzantine reliable broadcast (BRB), we also investigate the bad-case latency for all non-faulty parties to commit when the broadcaster is faulty but some non-faulty party commits. We provide matching upper and lower bounds on the resilience threshold of bad-case latency for BRB protocols with optimal good-case latency of 2 rounds. In particular, we show 2 impossibility results and propose 4 asynchronous BRB protocols.
Cite as

Ittai Abraham, Ling Ren, and Zhuolun Xiang. Good-Case and Bad-Case Latency of Unauthenticated Byzantine Broadcast: A Complete Categorization. In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, pp. 5:1-5:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{abraham_et_al:LIPIcs.OPODIS.2021.5,
  author =	{Abraham, Ittai and Ren, Ling and Xiang, Zhuolun},
  title =	{{Good-Case and Bad-Case Latency of Unauthenticated Byzantine Broadcast: A Complete Categorization}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{5:1--5:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-219-8},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{217},
  editor =	{Bramas, Quentin and Gramoli, Vincent and Milani, Alessia},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2021.5},
  URN =		{urn:nbn:de:0030-drops-157806},
  doi =		{10.4230/LIPIcs.OPODIS.2021.5},
  annote =	{Keywords: Byzantine broadcast, asynchrony, synchrony, latency, good-case, optimal}
}
Document
DOI: 10.4230/LIPIcs.DISC.2021.32
Optimal Communication Complexity of Authenticated Byzantine Agreement

Authors: Atsuki Momose and Ling Ren

Published in: LIPIcs, Volume 209, 35th International Symposium on Distributed Computing (DISC 2021)

Abstract
Byzantine Agreement (BA) is one of the most fundamental problems in distributed computing, and its communication complexity is an important efficiency metric. It is well known that quadratic communication is necessary for BA in the worst case due to a lower bound by Dolev and Reischuk. This lower bound has been shown to be tight for the unauthenticated setting with f < n/3 by Berman et al. but a considerable gap remains for the authenticated setting with n/3 ≤ f < n/2. This paper provides two results towards closing this gap. Both protocols have a quadratic communication complexity and have different trade-offs in resilience and assumptions. The first protocol achieves the optimal resilience of f < n/2 but requires a trusted setup for threshold signature. The second protocol achieves near optimal resilience f ≤ (1/2 - ε)n in the standard PKI model.
Cite as

Atsuki Momose and Ling Ren. Optimal Communication Complexity of Authenticated Byzantine Agreement. In 35th International Symposium on Distributed Computing (DISC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 209, pp. 32:1-32:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{momose_et_al:LIPIcs.DISC.2021.32,
  author =	{Momose, Atsuki and Ren, Ling},
  title =	{{Optimal Communication Complexity of Authenticated Byzantine Agreement}},
  booktitle =	{35th International Symposium on Distributed Computing (DISC 2021)},
  pages =	{32:1--32:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-210-5},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{209},
  editor =	{Gilbert, Seth},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2021.32},
  URN =		{urn:nbn:de:0030-drops-148341},
  doi =		{10.4230/LIPIcs.DISC.2021.32},
  annote =	{Keywords: Byzantine Agreement, Communication Complexity, Lower Bound}
}
Document
DOI: 10.4230/LIPIcs.DISC.2020.28
Improved Extension Protocols for Byzantine Broadcast and Agreement

Authors: Kartik Nayak, Ling Ren, Elaine Shi, Nitin H. Vaidya, and Zhuolun Xiang

Published in: LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020)

Abstract
Byzantine broadcast (BB) and Byzantine agreement (BA) are two most fundamental problems and essential building blocks in distributed computing, and improving their efficiency is of interest to both theoreticians and practitioners. In this paper, we study extension protocols of BB and BA, i.e., protocols that solve BB/BA with long inputs of l bits using lower costs than l single-bit instances. We present new protocols with improved communication complexity in almost all settings: authenticated BA/BB with t < n/2, authenticated BB with t < (1-ε)n, unauthenticated BA/BB with t < n/3, and asynchronous reliable broadcast and BA with t < n/3. The new protocols are advantageous and significant in several aspects. First, they achieve the best-possible communication complexity of Θ(nl) for wider ranges of input sizes compared to prior results. Second, the authenticated extension protocols achieve optimal communication complexity given the current best available BB/BA protocols for short messages. Third, to the best of our knowledge, our asynchronous and authenticated protocols in the setting are the first extension protocols in that setting.
Cite as

Kartik Nayak, Ling Ren, Elaine Shi, Nitin H. Vaidya, and Zhuolun Xiang. Improved Extension Protocols for Byzantine Broadcast and Agreement. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 28:1-28:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{nayak_et_al:LIPIcs.DISC.2020.28,
  author =	{Nayak, Kartik and Ren, Ling and Shi, Elaine and Vaidya, Nitin H. and Xiang, Zhuolun},
  title =	{{Improved Extension Protocols for Byzantine Broadcast and Agreement}},
  booktitle =	{34th International Symposium on Distributed Computing (DISC 2020)},
  pages =	{28:1--28:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-168-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{179},
  editor =	{Attiya, Hagit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.28},
  URN =		{urn:nbn:de:0030-drops-131064},
  doi =		{10.4230/LIPIcs.DISC.2020.28},
  annote =	{Keywords: Byzantine agreement, Byzantine broadcast, extension protocol, communication complexity}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2020.47
Brief Announcement: Byzantine Agreement, Broadcast and State Machine Replication with Optimal Good-Case Latency

Authors: Ittai Abraham, Kartik Nayak, Ling Ren, and Zhuolun Xiang

Published in: LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020)

Abstract
This paper investigates the problem good-case latency of Byzantine agreement, broadcast and state machine replication in the synchronous authenticated setting. The good-case latency measure captures the time it takes to reach agreement when all non-faulty parties have the same input (or in BB/SMR when the sender/leader is non-faulty) and all messages arrive instantaneously. Previous result implies a lower bound showing that any Byzantine agreement or broadcast protocol tolerating more than n/3 faults must have a good-case latency of at least Δ. Our first result is a matching tight upper bound for a family of protocols we call 1Δ. We propose a protocol 1Δ-BA that solves Byzantine agreement in the synchronous and authenticated setting with optimal good-case latency of Δ and optimal resilience f < n/2. We then extend our protocol and present 1Δ-BB and 1Δ-SMR for Byzantine fault tolerant broadcast and state machine replication, respectively, in the same setting and with the same optimal good-case latency of Δ and f < n/2 fault tolerance.
Cite as

Ittai Abraham, Kartik Nayak, Ling Ren, and Zhuolun Xiang. Brief Announcement: Byzantine Agreement, Broadcast and State Machine Replication with Optimal Good-Case Latency. In 34th International Symposium on Distributed Computing (DISC 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 179, pp. 47:1-47:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{abraham_et_al:LIPIcs.DISC.2020.47,
  author =	{Abraham, Ittai and Nayak, Kartik and Ren, Ling and Xiang, Zhuolun},
  title =	{{Brief Announcement: Byzantine Agreement, Broadcast and State Machine Replication with Optimal Good-Case Latency}},
  booktitle =	{34th International Symposium on Distributed Computing (DISC 2020)},
  pages =	{47:1--47:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-168-9},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{179},
  editor =	{Attiya, Hagit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.47},
  URN =		{urn:nbn:de:0030-drops-131259},
  doi =		{10.4230/LIPIcs.DISC.2020.47},
  annote =	{Keywords: Byzantine broadcast, synchrony, latency, state machine replication}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2017.25
Solida: A Blockchain Protocol Based on Reconfigurable Byzantine Consensus

Authors: Ittai Abraham, Dahlia Malkhi, Kartik Nayak, Ling Ren, and Alexander Spiegelman

Published in: LIPIcs, Volume 95, 21st International Conference on Principles of Distributed Systems (OPODIS 2017)

Abstract
The decentralized cryptocurrency Bitcoin has experienced great success but also encountered many challenges. One of the challenges has been the long confirmation time. Another chal- lenge is the lack of incentives at certain steps of the protocol, raising concerns for transaction withholding, selfish mining, etc. To address these challenges, we propose Solida, a decentralized blockchain protocol based on reconfigurable Byzantine consensus augmented by proof-of-work. Solida improves on Bitcoin in confirmation time, and provides safety and liveness assuming the adversary control less than (roughly) one-third of the total mining power.
Cite as

Ittai Abraham, Dahlia Malkhi, Kartik Nayak, Ling Ren, and Alexander Spiegelman. Solida: A Blockchain Protocol Based on Reconfigurable Byzantine Consensus. In 21st International Conference on Principles of Distributed Systems (OPODIS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 95, pp. 25:1-25:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{abraham_et_al:LIPIcs.OPODIS.2017.25,
  author =	{Abraham, Ittai and Malkhi, Dahlia and Nayak, Kartik and Ren, Ling and Spiegelman, Alexander},
  title =	{{Solida: A Blockchain Protocol Based on Reconfigurable Byzantine Consensus}},
  booktitle =	{21st International Conference on Principles of Distributed Systems (OPODIS 2017)},
  pages =	{25:1--25:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-061-3},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{95},
  editor =	{Aspnes, James and Bessani, Alysson and Felber, Pascal and Leit\~{a}o, Jo\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2017.25},
  URN =		{urn:nbn:de:0030-drops-86409},
  doi =		{10.4230/LIPIcs.OPODIS.2017.25},
  annote =	{Keywords: Cryptocurrency, Blockchain, Byzantine fault tolerance, Reconfiguration}
}
Document
Brief Announcement
DOI: 10.4230/LIPIcs.DISC.2017.41
Brief Announcement: Practical Synchronous Byzantine Consensus

Authors: Ittai Abraham, Srinivas Devadas, Kartik Nayak, and Ling Ren

Published in: LIPIcs, Volume 91, 31st International Symposium on Distributed Computing (DISC 2017)

Abstract
This paper presents new protocols for Byzantine state machine replication and Byzantine agreement in the synchronous and authenticated setting. The PBFT state machine replication protocol tolerates f Byzantine faults in an asynchronous setting using n = 3f + 1 replicas. We improve the Byzantine fault tolerance to n = 2f + 1 by utilizing the synchrony assumption. Our protocol also solves synchronous authenticated Byzantine agreement in fewer expected rounds than the best existing solution (Katz and Koo, 2006).
Cite as

Ittai Abraham, Srinivas Devadas, Kartik Nayak, and Ling Ren. Brief Announcement: Practical Synchronous Byzantine Consensus. In 31st International Symposium on Distributed Computing (DISC 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 91, pp. 41:1-41:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{abraham_et_al:LIPIcs.DISC.2017.41,
  author =	{Abraham, Ittai and Devadas, Srinivas and Nayak, Kartik and Ren, Ling},
  title =	{{Brief Announcement: Practical Synchronous Byzantine Consensus}},
  booktitle =	{31st International Symposium on Distributed Computing (DISC 2017)},
  pages =	{41:1--41:4},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-053-8},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{91},
  editor =	{Richa, Andr\'{e}a},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2017.41},
  URN =		{urn:nbn:de:0030-drops-79703},
  doi =		{10.4230/LIPIcs.DISC.2017.41},
  annote =	{Keywords: consensus, agreement, Byzantine fault tolerance, replication, synchrony}
}
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