DROPS

Volume

OASIcs, Volume 101

5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

FAB 2022, June 3, 2022, Berkeley, CA, USA

Editors: Sara Tucci-Piergiovanni and Natacha Crooks

Volume

OASIcs, Volume 71

International Conference on Blockchain Economics, Security and Protocols (Tokenomics 2019)

Tokenomics 2019, May 6-7, 2019, Paris, France

Editors: Vincent Danos, Maurice Herlihy, Maria Potop-Butucaru, Julien Prat, and Sara Tucci-Piergiovanni

Document

DOI: 10.4230/LITES.8.2.2

Swarms of Mobile Robots: Towards Versatility with Safety

Authors: Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain

Published in: LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2

Abstract

We present Pactole, a formal framework to design and prove the correctness of protocols (or the impossibility of their existence) that target mobile robotic swarms. Unlike previous approaches, our methodology unifies in a single formalism the execution model, the problem specification, the protocol, and its proof of correctness. The Pactole framework makes use of the Coq proof assistant, and is specially targeted at protocol designers and problem specifiers, so that a common unambiguous language is used from the very early stages of protocol development. We stress the underlying framework design principles to enable high expressivity and modularity, and provide concrete examples about how the Pactole framework can be used to tackle actual problems, some previously addressed by the Distributed Computing community, but also new problems, while being certified correct.

Cite as

Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain. Swarms of Mobile Robots: Towards Versatility with Safety. In LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2, pp. 02:1-02:36, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@Article{courtieu_et_al:LITES.8.2.2,
  author =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  title =	{{Swarms of Mobile Robots: Towards Versatility with Safety}},
  booktitle =	{LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems},
  pages =	{02:1--02:36},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2022},
  volume =	{8},
  number =	{2},
  editor =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.8.2.2},
  doi =		{10.4230/LITES.8.2.2},
  annote =	{Keywords: distributed algorithm, mobile autonomous robots, formal proof}
}

Document

Complete Volume

DOI: 10.4230/OASIcs.FAB.2022

OASIcs, Volume 101, FAB 2022, Complete Volume

Authors: Sara Tucci-Piergiovanni and Natacha Crooks

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

OASIcs, Volume 101, FAB 2022, Complete Volume

Cite as

Sara Tucci-Piergiovanni and Natacha Crooks. OASIcs, Volume 101, FAB 2022, Complete Volume. In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 1-66, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@Proceedings{tuccipiergiovanni_et_al:OASIcs.FAB.2022,
  title =	{{OASIcs, Volume 101, FAB 2022, Complete Volume}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{1--66},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022},
  URN =		{urn:nbn:de:0030-drops-162666},
  doi =		{10.4230/OASIcs.FAB.2022},
  annote =	{Keywords: OASIcs, Volume 101, FAB 2022, Complete Volume}
}

Document

Front Matter

DOI: 10.4230/OASIcs.FAB.2022.0

Front Matter, Table of Contents, Preface, Conference Organization

Authors: Sara Tucci-Piergiovanni and Natacha Crooks

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

Front Matter, Table of Contents, Preface, Conference Organization

Cite as

Sara Tucci-Piergiovanni and Natacha Crooks. Front Matter, Table of Contents, Preface, Conference Organization. In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 0:i-0:viii, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{tuccipiergiovanni_et_al:OASIcs.FAB.2022.0,
  author =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{0:i--0:viii},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.0},
  URN =		{urn:nbn:de:0030-drops-162678},
  doi =		{10.4230/OASIcs.FAB.2022.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}

Document

Invited Talk

DOI: 10.4230/OASIcs.FAB.2022.1

Reflections on the Past, Present and Future of Blockchain Foundations and Applications (Invited Talk)

Authors: Ittai Abraham

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

We survey some of the amazing progress in Blockchain technology in the last 5 years: from foundations like consensus protocols, execution models, and zero-knowledge proofs, to why these foundations are critical for applications like decentralized finance and web3. The main part of the talk will try to envision the future of Blockchains: how will the "Endgame" look like? What foundations are we still missing? We argue that for Blockchains to thrive and reach Billions of users, we should expect a much more regulated landscape to emerge and discuss some exciting opportunities in reg-crypto and RegDeFi. An example of this direction is our new work on UTT which is a decentralized Ecash system with accountable privacy.

Cite as

Ittai Abraham. Reflections on the Past, Present and Future of Blockchain Foundations and Applications (Invited Talk). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 1:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{abraham:OASIcs.FAB.2022.1,
  author =	{Abraham, Ittai},
  title =	{{Reflections on the Past, Present and Future of Blockchain Foundations and Applications}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{1:1--1:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.1},
  URN =		{urn:nbn:de:0030-drops-162686},
  doi =		{10.4230/OASIcs.FAB.2022.1},
  annote =	{Keywords: Blockchain}
}

Document

Invited Talk

DOI: 10.4230/OASIcs.FAB.2022.2

Some Insights on Open Problems in Blockchains: Explorative Tracks for Tezos (Invited Talk)

Authors: Sylvain Conchon

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

Blockchain is an emerging field that started with the advent of Bitcoin, the first cryptocurrency launched in 2008. Since then, new distributed applications (DApps) based on blockchain have emerged, such as non-fungible tokens (NFT) or decentralized finance (DeFi). All this contributes to an ever-increasing use of blockchains and poses many technological and scientific challenges. The first challenge is related to scalability, usually measured by the number of transactions per second (TPS) that a blockchain can process. Recent solutions, such as Rollups, implement the concept of Layer 2, a secondary framework built on top of an existing blockchain that allows transactions to be managed off-chain for efficiency. The primary blockchain is used to secure the exchanges of the second layer by regularly recording its exchanges and its current state. A first experiment of Optimistic Rollups has been implemented in the Blockchain Tezos. The TORUs (Transaction Optimistic Rollups) allow efficient financial assets exchanges in the form of Michelson tickets. A generalization to Smart contracts Optimistic Rollups (SCORU) is currently under development. Another challenge is to improve the efficiency of the data structures used in blockchain implementations. The main explorative tracks are to reduce and improve disk usage (compact representations, serialization of big data, sharing, ...), increase the speed of access operations (efficient caching strategies, asynchronous I/O, ...). For example, recent improvements to the storage layer of Octez, Tezos' most popular node implementation, have shown that it is possible to significantly speed up transactions, stabilize average transaction latency, and significantly reduce memory usage. The security issues associated with blockchains also raise many challenges. Indeed, the economic protocols or consensus algorithms implemented in blockchains use incentive mechanisms to discourage nodes from engaging in bad behavior or in launching attacks. A fine tuning of these incentives is difficult in situations where decision makers interact. Game theory can be used to develop incentives, in particular its integration into verification tools (model-checkers, proof assistants, deductive program verification) or machine-learning tools could be very promising. Finally, given the financial amounts managed by blockchains, it is essential to have a very precise specification of the algorithms, protocols and data structures used in blockchain implementations in order to guarantee the reliability of these very complex software. Whether it is for the programming of smart contracts, consensus algorithms or the P2P layer, the introduction of formal methods in the development cycle of blockchains is a major challenge in this domain. A lot of work in formal methods has been done for the Tezos blockchain. Among others, the formalization in TLA+ of Tenderbake, a PBFT-style consensus algorithm which offers deterministic finality to Tezos. Author Bio. Sylvain Conchon is Professor in Computer Science at University Paris-Saclay since 2013. He is a member of LMF (Formal Methods Laboratory) and his research focuses on automatic deduction and model-checking, using techniques based on SMT (Satisfiabilty Modulo Theories) solvers. He is one of the designers of the SMT solver Alt-Ergo and the model-checker Cubicle. In collaboration with Nomadic-Labs, he is currently working on the use of formal methods to design and verify several aspects related to the blockchain Tezos, such as Michelson smart contracts or the Tenderbake consensus algorithm.

Cite as

Sylvain Conchon. Some Insights on Open Problems in Blockchains: Explorative Tracks for Tezos (Invited Talk). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 2:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{conchon:OASIcs.FAB.2022.2,
  author =	{Conchon, Sylvain},
  title =	{{Some Insights on Open Problems in Blockchains: Explorative Tracks for Tezos}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{2:1--2:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.2},
  URN =		{urn:nbn:de:0030-drops-162696},
  doi =		{10.4230/OASIcs.FAB.2022.2},
  annote =	{Keywords: Blockchain, Tezos, Scalability, Efficiency, Security, Reliability}
}

Document

Invited Talk

DOI: 10.4230/OASIcs.FAB.2022.3

Hierarchical Consensus: A Horizontal Scaling Framework for Blockchains (Invited Talk)

Authors: Alfonso de la Rocha

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

In this talk we present the Filecoin Hierarchical Consensus framework, which aims to overcome the throughput challenges of blockchain consensus by horizontally scaling the network. Unlike traditional sharding designs, based on partitioning the state of the network, our solution centers on the concept of subnets –which are organized hierarchically– and can be spawned on-demand to manage new state. Child subnets are firewalled from parent subnets, have their own specific policies, and run a different consensus algorithm, increasing the network capacity and enabling new applications. Moreover, they benefit from the security of parent subnets by periodically checkpointing state. In this paper, we introduce the overall system architecture, our detailed designs for cross-net transaction handling, and the open questions that we are still exploring. Author Bio. Before joining Protocol Labs, Alfonso worked as a blockchain expert at Telefónica R&D, where he was responsible for the design and development of core technology based on blockchains, distributed systems, and advanced cryptography. Alfonso’s involvement in research and development began at Universidad Politécnica de Madrid, where he worked on topics related to energy efficiency in data centers. His broad R&D experience also includes research into the compression efficiency of video coding standards at Ericsson Research and projects related to securing interdomain routing protocols at KTH Royal Institute of Technology in Stockholm. https://research.protocol.ai/authors/alfonso-delarocha/

Cite as

Alfonso de la Rocha. Hierarchical Consensus: A Horizontal Scaling Framework for Blockchains (Invited Talk). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 3:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{delarocha:OASIcs.FAB.2022.3,
  author =	{de la Rocha, Alfonso},
  title =	{{Hierarchical Consensus: A Horizontal Scaling Framework for Blockchains}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{3:1--3:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.3},
  URN =		{urn:nbn:de:0030-drops-162709},
  doi =		{10.4230/OASIcs.FAB.2022.3},
  annote =	{Keywords: blockchain, consensus, distributed systems, P2P, scalability, sharding}
}

Document

Invited Talk

DOI: 10.4230/OASIcs.FAB.2022.4

Efficient DAG-Based Consensus (Invited Talk)

Authors: Alberto Sonnino

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

This talk shows how to build high-performant Byzantine fault-tolerant (BFT) quorum-based consensus cores. The talks starts by challenging the common misconception that the overall communication complexity of the protocol is the key factor determining performance. We instead argue that the bottleneck of many state-of-the-art consensus protocols is their sequential use of the machine’s resources (network, storage, CPU), and that data dissemination is the most resource-intensive task. In light of the above considerations, the first insight to build performant BFT-based consensus cores is to separate the task of reliable transaction dissemination from transaction ordering. We show how to design a new DAG-based mempool protocol, called Narwhal, specialising in high-throughput reliable dissemination and storage of causal histories of transactions. Narwhal tolerates an asynchronous network and maintains high performance despite failures. It is designed to easily scale-out using multiple workers at each validator to concurrently use the machine’s resources (network, storage, CPU), and demonstrates that there is no foreseeable limit to the throughput we can achieve. We then present two ways to leverage Narwhal to achieve consensus. We first (i) present Tusk, a zero-message overhead asynchronous consensus protocol designed to work with Narwhal. Tusk achieves an unprecedented 160,000 tx/s with about 3 seconds latency in a geo-replicated environment. We then (ii) show how any partially-synchronous consensus, such as HotStuff (PODC 19), can be composed with Narwhal to drastically improve its performance. HotStuff running over Narwhal sees its throughput increase from about 2,000 tx/s to over 130,000 tx/s without noticeable latency increase. The talk concludes by illustrating how to properly evaluate performance of BFT-based consensus cores. It highlights the most common mistakes seen in the literature, such as benchmarks with empty transactions (empty load), performance approximation based on LAN-only benchmarks, and using a single burst of input transactions. We then show how to analyse benchmark results using latency-throughput graphs (L-graphs) and SLA-based throughput graphs. Author Bio. I am a system researcher at Mysten Labs, based in London (UK). I previously was a research scientist at Facebook (now called Meta) in the blockchain and cryptography team. Before joining Facebook, I co-founded chainspace.io which built a scalable smart contract platform; the team was then acquired by Facebook. My research interests are in systems security and privacy engineering. My main areas of research include distributed systems, blockchains, and privacy enhancing technologies. I have a special interest in cryptography, and I spend most of my time designing, implementing and evaluating high-performance distributed systems.

Cite as

Alberto Sonnino. Efficient DAG-Based Consensus (Invited Talk). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 4:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{sonnino:OASIcs.FAB.2022.4,
  author =	{Sonnino, Alberto},
  title =	{{Efficient DAG-Based Consensus}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{4:1--4:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.4},
  URN =		{urn:nbn:de:0030-drops-162712},
  doi =		{10.4230/OASIcs.FAB.2022.4},
  annote =	{Keywords: Consensus protocol, Byzantine Fault Tolerant}
}

Document

DOI: 10.4230/OASIcs.FAB.2022.5

Fork Accountability in Tenderbake

Authors: Antonella Del Pozzo and Thibault Rieutord

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

This work investigates the Fork Accountability problem in the BFT-Consensus-based Blockchain context. When there are more attackers than the tolerated ones, BFT-Consensus may fail in delivering safety. When this occurs, Fork Accountability aims to account for the responsible processes for that safety violation. As a case study, we consider Tenderbake when the assumption on the maximum number of Byzantine validators - participants involved in creating the next block - does not hold anymore. When a fork occurs, there are more than one-third of Byzantine validators, and we aim to account for the responsible validators to remove them from the system. In this work, we compare three different approaches to implementing accountability in the case of a fork. In particular, we show that in the case of a fork, if we do not modify Tenderbake or we enrich it with a reliable broadcast communication abstraction, then we can account Byzantine processes only in particular scenarios. Contrarily, if we change Tenderbake such that the exchanged messages also carry extra information (which size is proportional to the duration of the current consensus computation), then we can account for Byzantine processes in all kinds of scenarios; however, at the cost of unbounded message size and unbounded local memory.

Cite as

Antonella Del Pozzo and Thibault Rieutord. Fork Accountability in Tenderbake. In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 5:1-5:22, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{delpozzo_et_al:OASIcs.FAB.2022.5,
  author =	{Del Pozzo, Antonella and Rieutord, Thibault},
  title =	{{Fork Accountability in Tenderbake}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{5:1--5:22},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.5},
  URN =		{urn:nbn:de:0030-drops-162723},
  doi =		{10.4230/OASIcs.FAB.2022.5},
  annote =	{Keywords: Blockchain, BFT-Consensus, Fork Accountability}
}

Document

DOI: 10.4230/OASIcs.FAB.2022.6

Dynamic Blockchain Sharding

Authors: Deepal Tennakoon and Vincent Gramoli

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

By supporting decentralized applications (DApps), modern blockchains have become the technology of choice for the Web3, a decentralized way for people to interact with each other. As the popularity of DApps is growing, the challenge is now to allocate shard or subnetwork resources to face the associated demand of individual DApps. Unfortunately, most sharding proposals are inherently static as they cannot be adjusted at runtime. Given that blockchains are expected to run for years without interruption, these proposals are insufficient to cope with the upcoming demand. In this paper, we present dynamic blockchain sharding, a new way to create and close shards on-demand, and adjust their size at runtime without requiring to hard fork (i.e., creating duplicated instances of the same blockchain). The novel idea is to reconfigure sharding through dedicated smart contract invocations: not only does it strengthen the security of the sharding reconfiguration, it also makes it inherently transparent as any other blockchain data. Similarly to classic sharding, our protocol relies on randomness to cope with shard-takeover attacks and on rotating nodes to cope with the bribery of a slowly-adaptive adversary. By contrast, however, our protocol is ideally suited for open networks as it does not require fully synchronous communications. To demonstrate its efficiency, we deploy it in 10 countries over 5 continents and demonstrate that its performance increases quasi-linearly with the number of shards as it reaches close to 14,000 TPS on only 8 shards.

Cite as

Deepal Tennakoon and Vincent Gramoli. Dynamic Blockchain Sharding. In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 6:1-6:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{tennakoon_et_al:OASIcs.FAB.2022.6,
  author =	{Tennakoon, Deepal and Gramoli, Vincent},
  title =	{{Dynamic Blockchain Sharding}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{6:1--6:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.6},
  URN =		{urn:nbn:de:0030-drops-162733},
  doi =		{10.4230/OASIcs.FAB.2022.6},
  annote =	{Keywords: Reconfiguration, smart contract, transparency, shard}
}

Document

Poster

DOI: 10.4230/OASIcs.FAB.2022.7

Analyzing Soft and Hard Partitions of Global-Scale Blockchain Systems (Poster)

Authors: Kevin Bruhwiler, Fayzah Alshammari, Farzad Habibi, Juncheng Fang, and Faisal Nawab

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

Partitioning attacks have been a known threat since the invention of cryptocurrencies. Attackers could deliberately fork the chain by re-routing network traffic into two or more separate chains and spend money on each piece, effectively spending multiples of their money. Apostolaki et. al. [{Apostolaki and {Laurent Vanbever}, 2017] were among the first to quantify the threats of such attacks on Bitcoin. They suggest a number of ways to mitigate this risk which were combined into a tool named SABRE. Jyothi explored the possibility that a solar superstorm could damage the undersea fiber-optic cables that connect the Internets of different continents, and considered the mostly likely ramifications of the damage. She concluded that such an event would likely cause major connectivity issues across the northern hemisphere and may disconnect much of North America’s internet from the eastern hemisphere for weeks. There is also concern that undersea cables could be deliberately destroyed as acts of terrorism or war or by natural disasters such as earthquakes. In this work, we construct a simulation to properly quantify the effects of a global-scale network partition on the blockchain. We hope to provide the groundwork for preventative measures to be taken to minimize the harm that such partitions might cause in the future. We do this by modifying SimBlock [{Yusuke, 2019], a blockchain simulator created to study the effect of different network topologies, to allow initiating and recovering from partitions and also add metrics to capture their effects. To quantify the severity of partitions we use a number of metrics, including the rate of agreement improvement after a new block has been minted and the average rate of block propagation across regions. We also examine the number of forks in the blockchain that result from partitions and identify the break-points at which forks begin to appear. Finally, we quantify the duration that partitions of various sizes can persist before they begin to generate forks and measure the how long it takes for the system to recover once the partition has been resolved.

Cite as

Kevin Bruhwiler, Fayzah Alshammari, Farzad Habibi, Juncheng Fang, and Faisal Nawab. Analyzing Soft and Hard Partitions of Global-Scale Blockchain Systems (Poster). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 7:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bruhwiler_et_al:OASIcs.FAB.2022.7,
  author =	{Bruhwiler, Kevin and Alshammari, Fayzah and Habibi, Farzad and Fang, Juncheng and Nawab, Faisal},
  title =	{{Analyzing Soft and Hard Partitions of Global-Scale Blockchain Systems}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{7:1--7:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.7},
  URN =		{urn:nbn:de:0030-drops-162741},
  doi =		{10.4230/OASIcs.FAB.2022.7},
  annote =	{Keywords: Blockchain, Partitioning, Resilience, Simulation}
}

Document

Poster

DOI: 10.4230/OASIcs.FAB.2022.8

A Modular Approach for the Analysis of Blockchain Consensus Protocol Under Churn (Poster)

Authors: Floris Ciprian Dinu and Silvia Bonomi

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

Blockchain is an emerging technology that gained a lot of attention in the last years. Many different consensus protocols have been proposed to improve both the scalability and the resilience of existing blockchain. However, all these solutions have been defined for rather static settings. We propose a modular approach for analysing and comparing different consensus protocols used in blockchain under churn.

Cite as

Floris Ciprian Dinu and Silvia Bonomi. A Modular Approach for the Analysis of Blockchain Consensus Protocol Under Churn (Poster). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 8:1-8:2, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{dinu_et_al:OASIcs.FAB.2022.8,
  author =	{Dinu, Floris Ciprian and Bonomi, Silvia},
  title =	{{A Modular Approach for the Analysis of Blockchain Consensus Protocol Under Churn}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{8:1--8:2},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.8},
  URN =		{urn:nbn:de:0030-drops-162754},
  doi =		{10.4230/OASIcs.FAB.2022.8},
  annote =	{Keywords: Blockchain Dependability, Dynamic Distributed Systems, Simulation}
}

Document

Poster

DOI: 10.4230/OASIcs.FAB.2022.9

Improving Blockchain Resilience to Network Partitioning by Sharding (Poster)

Authors: Juncheng Fang, Farzad Habibi, Kevin Bruhwiler, Fayzah Alshammari, and Faisal Nawab

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

Blockchain plays a significant role in cryptocurrencies and growing applications like smart contracts. However, prior blockchain algorithms did not consider large-scale network partitioning a considerable concern while relying heavily on a reliable global network. Previous works have shown a possibility of a massive disruption on the Internet. The author in [Jyothi, 2021] discusses the case of Internet disorder due to solar superstorms, which can disconnect different geographical regions from each other for months. Partitioning attacks are also notable concerns that should be considered, in which their goal is to cut connections between a set of nodes and the rest of the network. In the case of network partitioning, the main chain will fork into branches, and miners in different disconnected regions will create multiple blocks in parallel. The longest chain rule in current blockchain systems accepts only one of the branches after the network is recovered, and because of that, all blocks in other branches will be pruned. Losing a considerable number of mined blocks is not tolerable and significantly impacts the reliability of the ledger and miners' benefit. In this work, we aim to improve blockchain resilience by designing a partition-tolerance blockchain system that: (1) split into branches when network partition happens. (2) merge existing branches into one when the network goes back to normal. (3) ensure the safety and integrity of the blockchain. Newly mined blocks will be collectively signed by a group of miners with a BFT protocol similar to ByzCoin[Kogias et al., 2016], where the consensus group is formed by the miners of the previous w blocks. When a network partition happens, only part of the consensus group can be reached; thus the number of signers w_b of the new block will be less than w. If a block with w_b signers is published, every node in the partition learns that they are now in a branch with around w_b/w of the total hashing power, and it can be identified by the signature of the block. After the network recovers, miners will receive multiple branches, and they mine on a merging block which points to the last block of each branch as the parent blocks. The consensus group will be selected from each branch according to the branch size. Transactions in each partition are preserved after merging.

Cite as

Juncheng Fang, Farzad Habibi, Kevin Bruhwiler, Fayzah Alshammari, and Faisal Nawab. Improving Blockchain Resilience to Network Partitioning by Sharding (Poster). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, p. 9:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{fang_et_al:OASIcs.FAB.2022.9,
  author =	{Fang, Juncheng and Habibi, Farzad and Bruhwiler, Kevin and Alshammari, Fayzah and Nawab, Faisal},
  title =	{{Improving Blockchain Resilience to Network Partitioning by Sharding}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{9:1--9:1},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.9},
  URN =		{urn:nbn:de:0030-drops-162762},
  doi =		{10.4230/OASIcs.FAB.2022.9},
  annote =	{Keywords: resilience, partitioning, blockchain, collective signing}
}

Document

Poster

DOI: 10.4230/OASIcs.FAB.2022.10

Why General Collective Intelligence Must Be the Future of the Blockchain (Poster)

Authors: Andy E. Williams

Published in: OASIcs, Volume 101, 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)

Abstract

General Collective Intelligence or GCI is predicted to radically increase the speed and scale at which blockchain technology can be designed, developed, and deployed as well as being predicted to radically increase demand for those new blockchain based products and services where they don’t involve consumption of limited physical resources. Therefore, if a GCI can be implemented, it is predicted that GCI based platforms will quickly come to dominate the blockchain marketplace and that GCI is the future of the blockchain. But it also must be the case that GCI is the future of the blockchain because without it, through an effect called the "technology gravity well" blockchain and other technologies have the possibility of introducing an unprecedented degree of centralization, control, and abuse.

Cite as

Andy E. Williams. Why General Collective Intelligence Must Be the Future of the Blockchain (Poster). In 5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022). Open Access Series in Informatics (OASIcs), Volume 101, pp. 10:1-10:3, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{williams:OASIcs.FAB.2022.10,
  author =	{Williams, Andy E.},
  title =	{{Why General Collective Intelligence Must Be the Future of the Blockchain}},
  booktitle =	{5th International Symposium on Foundations and Applications of Blockchain 2022 (FAB 2022)},
  pages =	{10:1--10:3},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-248-8},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{101},
  editor =	{Tucci-Piergiovanni, Sara and Crooks, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.FAB.2022.10},
  URN =		{urn:nbn:de:0030-drops-162774},
  doi =		{10.4230/OASIcs.FAB.2022.10},
  annote =	{Keywords: General Collective Intelligence, Human-Centric Functional Modeling, functional state space, conceptual space, blockchain state space, cooperation state space}
}

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