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Documents authored by Nayak, Kartik


Document
Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption

Authors: Sravya Yandamuri, Ittai Abraham, Kartik Nayak, and Michael K. Reiter

Published in: LIPIcs, Volume 253, 26th International Conference on Principles of Distributed Systems (OPODIS 2022)


Abstract
Agreement protocols for partially synchronous networks tolerate fewer than one-third Byzantine faults. If parties are equipped with trusted hardware that prevents equivocation, then fault tolerance can be improved to fewer than one-half Byzantine faults, but typically at the cost of increased communication complexity. In this work, we present results that use small trusted hardware without worsening communication complexity assuming the adversary controls a fraction of the network that is less than one-half. In particular, we show a version of HotStuff that retains linear communication complexity in each view, leveraging trusted hardware to tolerate a minority of corruptions. Our result uses expander graph techniques to achieve efficient communication in a manner that may be of independent interest.

Cite as

Sravya Yandamuri, Ittai Abraham, Kartik Nayak, and Michael K. Reiter. Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption. In 26th International Conference on Principles of Distributed Systems (OPODIS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 253, pp. 24:1-24:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{yandamuri_et_al:LIPIcs.OPODIS.2022.24,
  author =	{Yandamuri, Sravya and Abraham, Ittai and Nayak, Kartik and Reiter, Michael K.},
  title =	{{Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption}},
  booktitle =	{26th International Conference on Principles of Distributed Systems (OPODIS 2022)},
  pages =	{24:1--24:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-265-5},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{253},
  editor =	{Hillel, Eshcar and Palmieri, Roberto and Rivi\`{e}re, Etienne},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2022.24},
  URN =		{urn:nbn:de:0030-drops-176448},
  doi =		{10.4230/LIPIcs.OPODIS.2022.24},
  annote =	{Keywords: communication complexity, consensus, trusted hardware}
}
Document
Optimal Good-Case Latency for Rotating Leader Synchronous BFT

Authors: Ittai Abraham, Kartik Nayak, and Nibesh Shrestha

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


Abstract
This paper explores the good-case latency of synchronous Byzantine Fault Tolerant (BFT) consensus protocols in the rotating leader setting. We first present a lower bound that relates the latency of a broadcast when the sender is honest and the latency of switching to the next sender. We then present a matching upper bound with a latency of 2Δ (Δ is the pessimistic synchronous delay) with an optimistically responsive change to the next sender. The results imply that both our lower and upper bounds are tight. We implement and evaluate our protocol and show that our protocol obtains similar latency compared to state-of-the-art stable-leader protocol Sync HotStuff while allowing optimistically responsive leader rotation.

Cite as

Ittai Abraham, Kartik Nayak, and Nibesh Shrestha. Optimal Good-Case Latency for Rotating Leader Synchronous BFT. In 25th International Conference on Principles of Distributed Systems (OPODIS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 217, pp. 27:1-27:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{abraham_et_al:LIPIcs.OPODIS.2021.27,
  author =	{Abraham, Ittai and Nayak, Kartik and Shrestha, Nibesh},
  title =	{{Optimal Good-Case Latency for Rotating Leader Synchronous BFT}},
  booktitle =	{25th International Conference on Principles of Distributed Systems (OPODIS 2021)},
  pages =	{27:1--27:19},
  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.2021.27},
  URN =		{urn:nbn:de:0030-drops-158022},
  doi =		{10.4230/LIPIcs.OPODIS.2021.27},
  annote =	{Keywords: Distributed Computing, Byzantine Fault Tolerance, Synchrony}
}
Document
Brief Announcement
Brief Announcement: Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption

Authors: Sravya Yandamuri, Ittai Abraham, Kartik Nayak, and Michael Reiter

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


Abstract
Small trusted hardware primitives can improve fault tolerance of Byzantine Fault Tolerant (BFT) protocols to one-half faults. However, existing works achieve this at the cost of increased communication complexity. In this work, we explore the design of communication-efficient BFT protocols that can boost fault tolerance to one-half without worsening communication complexity. Our results include a version of HotStuff that retains linear communication complexity in each view and a version of the VABA protocol with quadratic communication, both leveraging trusted hardware to tolerate a minority of corruptions. As a building block, we present communication-efficient provable broadcast, a core broadcast primitive with increased fault tolerance. Our results use expander graphs to achieve efficient communication in a manner that may be of independent interest.

Cite as

Sravya Yandamuri, Ittai Abraham, Kartik Nayak, and Michael Reiter. Brief Announcement: Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption. In 35th International Symposium on Distributed Computing (DISC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 209, pp. 62:1-62:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


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@InProceedings{yandamuri_et_al:LIPIcs.DISC.2021.62,
  author =	{Yandamuri, Sravya and Abraham, Ittai and Nayak, Kartik and Reiter, Michael},
  title =	{{Brief Announcement: Communication-Efficient BFT Using Small Trusted Hardware to Tolerate Minority Corruption}},
  booktitle =	{35th International Symposium on Distributed Computing (DISC 2021)},
  pages =	{62:1--62:4},
  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.2021.62},
  URN =		{urn:nbn:de:0030-drops-148647},
  doi =		{10.4230/LIPIcs.DISC.2021.62},
  annote =	{Keywords: communication complexity, consensus, trusted hardware}
}
Document
Perfectly Oblivious (Parallel) RAM Revisited, and Improved Constructions

Authors: T-H. Hubert Chan, Elaine Shi, Wei-Kai Lin, and Kartik Nayak

Published in: LIPIcs, Volume 199, 2nd Conference on Information-Theoretic Cryptography (ITC 2021)


Abstract
Oblivious RAM (ORAM) is a technique for compiling any RAM program to an oblivious counterpart, i.e., one whose access patterns do not leak information about the secret inputs. Similarly, Oblivious Parallel RAM (OPRAM) compiles a parallel RAM program to an oblivious counterpart. In this paper, we care about ORAM/OPRAM with perfect security, i.e., the access patterns must be identically distributed no matter what the program’s memory request sequence is. In the past, two types of perfect ORAMs/OPRAMs have been considered: constructions whose performance bounds hold in expectation (but may occasionally run more slowly); and constructions whose performance bounds hold deterministically (even though the algorithms themselves are randomized). In this paper, we revisit the performance metrics for perfect ORAM/OPRAM, and show novel constructions that achieve asymptotical improvements for all performance metrics. Our first result is a new perfectly secure OPRAM scheme with O(log³ N/log log N) expected overhead. In comparison, prior literature has been stuck at O(log³ N) for more than a decade. Next, we show how to construct a perfect ORAM with O(log³ N/log log N) deterministic simulation overhead. We further show how to make the scheme parallel, resulting in an perfect OPRAM with O(log⁴ N/log log N) deterministic simulation overhead. For perfect ORAMs/OPRAMs with deterministic performance bounds, our results achieve subexponential improvement over the state-of-the-art. Specifically, the best known prior scheme incurs more than √N deterministic simulation overhead (Raskin and Simkin, Asiacrypt'19); moreover, their scheme works only for the sequential setting and is not amenable to parallelization. Finally, we additionally consider perfect ORAMs/OPRAMs whose performance bounds hold with high probability. For this new performance metric, we show new constructions whose simulation overhead is upper bounded by O(log³ /log log N) except with negligible in N probability, i.e., we prove high-probability performance bounds that match the expected bounds mentioned earlier.

Cite as

T-H. Hubert Chan, Elaine Shi, Wei-Kai Lin, and Kartik Nayak. Perfectly Oblivious (Parallel) RAM Revisited, and Improved Constructions. In 2nd Conference on Information-Theoretic Cryptography (ITC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 199, pp. 8:1-8:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


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@InProceedings{chan_et_al:LIPIcs.ITC.2021.8,
  author =	{Chan, T-H. Hubert and Shi, Elaine and Lin, Wei-Kai and Nayak, Kartik},
  title =	{{Perfectly Oblivious (Parallel) RAM Revisited, and Improved Constructions}},
  booktitle =	{2nd Conference on Information-Theoretic Cryptography (ITC 2021)},
  pages =	{8:1--8:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-197-9},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{199},
  editor =	{Tessaro, Stefano},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2021.8},
  URN =		{urn:nbn:de:0030-drops-143271},
  doi =		{10.4230/LIPIcs.ITC.2021.8},
  annote =	{Keywords: perfect oblivious RAM, oblivious PRAM}
}
Document
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
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
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
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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