Pub Date : 2019-10-21DOI: 10.1163/2405-8262_rgg4_sim_024578
Patrick McCorry, Surya Bakshi, Iddo Bentov, S. Meiklejohn, Andrew Miller
{"title":"Pisa","authors":"Patrick McCorry, Surya Bakshi, Iddo Bentov, S. Meiklejohn, Andrew Miller","doi":"10.1163/2405-8262_rgg4_sim_024578","DOIUrl":"https://doi.org/10.1163/2405-8262_rgg4_sim_024578","url":null,"abstract":"","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123741993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to propagate transactions and blocks, today's blockchain systems rely on unstructured peer-to-peer overlay networks. In such networks, broadcast is known to be an inefficient operation in terms of message complexity and overhead. In addition to the impact on the system performance, inefficient or delayed block propagation may have severe consequences regarding security and fairness of the consensus layer. Therefore, we introduce Kadcast, a novel peer-to-peer protocol for block propagation in blockchain networks. Kadcast utilizes the well-known structured overlay topology of Kademlia to realize an efficient broadcast operation with tunable overhead. As our protocol is based on UDP, we incorporate forward error correction (FEC) to increase reliability while still maintaining its lightweight protocol architecture. To this end, we build a probabilistic model to analyze Kadcast's resilience to packet losses and node failures. Moreover, we evaluate Kadcast's block delivery performance, broadcast reliability, efficiency, and security based on advanced network simulations, which confirm the merits of the Kadcast protocol.
{"title":"Kadcast","authors":"Elias Rohrer, Florian Tschorsch","doi":"10.1145/3318041.3355469","DOIUrl":"https://doi.org/10.1145/3318041.3355469","url":null,"abstract":"In order to propagate transactions and blocks, today's blockchain systems rely on unstructured peer-to-peer overlay networks. In such networks, broadcast is known to be an inefficient operation in terms of message complexity and overhead. In addition to the impact on the system performance, inefficient or delayed block propagation may have severe consequences regarding security and fairness of the consensus layer. Therefore, we introduce Kadcast, a novel peer-to-peer protocol for block propagation in blockchain networks. Kadcast utilizes the well-known structured overlay topology of Kademlia to realize an efficient broadcast operation with tunable overhead. As our protocol is based on UDP, we incorporate forward error correction (FEC) to increase reliability while still maintaining its lightweight protocol architecture. To this end, we build a probabilistic model to analyze Kadcast's resilience to packet losses and node failures. Moreover, we evaluate Kadcast's block delivery performance, broadcast reliability, efficiency, and security based on advanced network simulations, which confirm the merits of the Kadcast protocol.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123033158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
While historically, economists have been primarily occupied with analyzing the behaviour of the markets, electronic trading gave rise to a new class of unprecedented problems associated with market fairness, transparency and manipulation. These problems stem from technical shortcomings that are not accounted for in the simple conceptual models used for theoretical market analysis. They, thus, call for more pragmatic market design methodologies that consider the various infrastructure complexities and their potential impact on the market procedures. First, we formally define temporal fairness and then explain why it is very difficult for order-matching policies to ensure it in continuous markets. Subsequently, we introduce a list of system requirements and evaluate existing "fair" market designs in various practical and adversarial scenarios. We conclude that they fail to retain their properties in the presence of infrastructure inefficiencies and sophisticated technical manipulation attacks. Based on these findings, we then introduce Libra, a "fair" policy that is resilient to gaming and tolerant of technical complications. Our security analysis shows that it is significantly more robust than existing designs, while Libra's deployment (in a live foreign currency exchange) validated both its considerably low impact on the operation of the market and its ability to reduce speed-based predatory trading.
{"title":"Libra","authors":"V. Mavroudis, H. Melton","doi":"10.1145/3318041.3355468","DOIUrl":"https://doi.org/10.1145/3318041.3355468","url":null,"abstract":"While historically, economists have been primarily occupied with analyzing the behaviour of the markets, electronic trading gave rise to a new class of unprecedented problems associated with market fairness, transparency and manipulation. These problems stem from technical shortcomings that are not accounted for in the simple conceptual models used for theoretical market analysis. They, thus, call for more pragmatic market design methodologies that consider the various infrastructure complexities and their potential impact on the market procedures. First, we formally define temporal fairness and then explain why it is very difficult for order-matching policies to ensure it in continuous markets. Subsequently, we introduce a list of system requirements and evaluate existing \"fair\" market designs in various practical and adversarial scenarios. We conclude that they fail to retain their properties in the presence of infrastructure inefficiencies and sophisticated technical manipulation attacks. Based on these findings, we then introduce Libra, a \"fair\" policy that is resilient to gaming and tolerant of technical complications. Our security analysis shows that it is significantly more robust than existing designs, while Libra's deployment (in a live foreign currency exchange) validated both its considerably low impact on the operation of the market and its ability to reduce speed-based predatory trading.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122218760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"SoK","authors":"G. Wang, Z. Shi, M. Nixon, Song Han","doi":"10.4328/derman.3816","DOIUrl":"https://doi.org/10.4328/derman.3816","url":null,"abstract":"","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114246721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick McCorry, Surya Bakshi, Iddo Bentov, Andrew K. Miller, S. Meiklejohn
State channels are a leading approach for improving the scalability of blockchains and cryptocurrencies. They allow a group of distrustful parties to optimistically execute an application-defined program amongst themselves, while the blockchain serves as a backstop in case of a dispute or abort. This effectively bypasses the congestion, fees and performance constraints of the underlying blockchain in the typical case. However, state channels introduce a new and undesirable assumption that a party must remain online and synchronised with the blockchain at all times to defend against execution fork attacks. An execution fork can revert a state channel's history, potentially causing financial damage to a party that is innocent except for having crashed. To provide security even to parties that may go offline for an extended period of time, we present Pisa, the first protocol to propose an accountable third party who can be hired by parties to cancel execution forks on their behalf. To evaluate Pisa, we provide a proof-of-concept implementation for a simplified Sprites and we demonstrate that it is cost-efficient to deploy on the Ethereum network.
{"title":"Pisa: Arbitration Outsourcing for State Channels","authors":"Patrick McCorry, Surya Bakshi, Iddo Bentov, Andrew K. Miller, S. Meiklejohn","doi":"10.1145/3318041.3355461","DOIUrl":"https://doi.org/10.1145/3318041.3355461","url":null,"abstract":"State channels are a leading approach for improving the scalability of blockchains and cryptocurrencies. They allow a group of distrustful parties to optimistically execute an application-defined program amongst themselves, while the blockchain serves as a backstop in case of a dispute or abort. This effectively bypasses the congestion, fees and performance constraints of the underlying blockchain in the typical case. However, state channels introduce a new and undesirable assumption that a party must remain online and synchronised with the blockchain at all times to defend against execution fork attacks. An execution fork can revert a state channel's history, potentially causing financial damage to a party that is innocent except for having crashed. To provide security even to parties that may go offline for an extended period of time, we present Pisa, the first protocol to propose an accountable third party who can be hired by parties to cancel execution forks on their behalf. To evaluate Pisa, we provide a proof-of-concept implementation for a simplified Sprites and we demonstrate that it is cost-efficient to deploy on the Ethereum network.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131211331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Khabbazian, Tejaswi Nadahalli, Roger Wattenhofer
In the context of second layer payments in Bitcoin, and specifically the Lightning Network, we propose a design for a lightweight watchtower that does not need to store signed justice transactions. We alter the structure of the opening and commitment transactions in Lightning channels to encode justice transactions as part of the commitment transactions. With that, a watchtower just needs to watch for specific cheating commitment transaction IDs on the blockchain and can extract signed justice transactions directly from these commitment transactions that appear on the blockchain. Our construction saves an order of magnitude in storage over existing watchtower designs. In addition, we let the watchtower prove to each channel that it has access to all the data required to do its job, and can therefore be paid-per-update.
{"title":"Outpost","authors":"M. Khabbazian, Tejaswi Nadahalli, Roger Wattenhofer","doi":"10.1145/3318041.3355464","DOIUrl":"https://doi.org/10.1145/3318041.3355464","url":null,"abstract":"In the context of second layer payments in Bitcoin, and specifically the Lightning Network, we propose a design for a lightweight watchtower that does not need to store signed justice transactions. We alter the structure of the opening and commitment transactions in Lightning channels to encode justice transactions as part of the commitment transactions. With that, a watchtower just needs to watch for specific cheating commitment transaction IDs on the blockchain and can extract signed justice transactions directly from these commitment transactions that appear on the blockchain. Our construction saves an order of magnitude in storage over existing watchtower designs. In addition, we let the watchtower prove to each channel that it has access to all the data required to do its job, and can therefore be paid-per-update.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121297151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Atomic Swap enables two parties to atomically exchange their own cryptocurrencies without trusted third parties. This paper provides the first quantitative analysis on the fairness of the Atomic Swap protocol, and proposes the first fair Atomic Swap protocol with implementations. In particular, we model the Atomic Swap as the American Call Option, and prove that an Atomic Swap is equivalent to an American Call Option without the premium. Thus, the Atomic Swap is unfair to the swap participant. Then, we quantify the fairness of the Atomic Swap and compare it with that of conventional financial assets (stocks and fiat currencies). The quantification results show that the the Atomic Swap is much more unfair on cryptocurrencies than on stocks and fiat currencies in the same setting. Moreover, we use the conventional Cox-Ross-Rubinstein option pricing model in Finance to estimate the premium, and show that the estimated premium for cryptocurrencies is 2% ~ 3% of the asset value, while the premium for stocks and fiat currencies is approximately 0.3%. Furthermore, we propose two fair Atomic Swap protocols, one is for currency exchange and the other is for American Call Options. Our protocols are based on the original Atomic Swap protocol, but implement the premium mechanism. Blockchains supporting smart contracts such as Ethereum support our protocols directly. Blockchains only supporting scripts such as Bitcoin can support our protocols by adding a simple opcode. Finally, we provide the reference implementation of our protocols in Solidity, and give detailed instructions on implementing our protocols with Bitcoin script.
{"title":"On the optionality and fairness of Atomic Swaps","authors":"Runchao Han, Haoyu Lin, Jiangshan Yu","doi":"10.1145/3318041.3355460","DOIUrl":"https://doi.org/10.1145/3318041.3355460","url":null,"abstract":"Atomic Swap enables two parties to atomically exchange their own cryptocurrencies without trusted third parties. This paper provides the first quantitative analysis on the fairness of the Atomic Swap protocol, and proposes the first fair Atomic Swap protocol with implementations. In particular, we model the Atomic Swap as the American Call Option, and prove that an Atomic Swap is equivalent to an American Call Option without the premium. Thus, the Atomic Swap is unfair to the swap participant. Then, we quantify the fairness of the Atomic Swap and compare it with that of conventional financial assets (stocks and fiat currencies). The quantification results show that the the Atomic Swap is much more unfair on cryptocurrencies than on stocks and fiat currencies in the same setting. Moreover, we use the conventional Cox-Ross-Rubinstein option pricing model in Finance to estimate the premium, and show that the estimated premium for cryptocurrencies is 2% ~ 3% of the asset value, while the premium for stocks and fiat currencies is approximately 0.3%. Furthermore, we propose two fair Atomic Swap protocols, one is for currency exchange and the other is for American Call Options. Our protocols are based on the original Atomic Swap protocol, but implement the premium mechanism. Blockchains supporting smart contracts such as Ethereum support our protocols directly. Blockchains only supporting scripts such as Bitcoin can support our protocols by adding a simple opcode. Finally, we provide the reference implementation of our protocols in Solidity, and give detailed instructions on implementing our protocols with Bitcoin script.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116819353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The spectacular success of Bitcoin and Blockchain Technology in recent years has provided enough evidence that a widespread adoption of a common cryptocurrency system is not merely a distant vision, but a scenario that might come true in the near future. However, the presence of Bitcoin's obvious shortcomings such as excessive electricity consumption, unsatisfying transaction throughput, and large validation time (latency) makes it clear that a new, more efficient system is needed. We propose a protocol in which a set of nodes maintains and updates a linear ordering of transactions that are being submitted by users. Virtually every cryptocurrency system has such a protocol at its core, and it is the efficiency of this protocol that determines the overall throughput and latency of the system. We develop our protocol on the grounds of the well-established field of Asynchronous Byzantine Fault Tolerant (ABFT) systems. This allows us to formally reason about correctness, efficiency, and security in the strictest possible model, and thus convincingly prove the overall robustness of our solution. Our protocol improves upon the state-of-the-art HoneyBadgerBFT by Miller et al. by reducing the asymptotic latency while matching the optimal communication complexity. Furthermore, in contrast to the above, our protocol does not require a trusted dealer thanks to a novel implementation of a trustless ABFT Randomness Beacon.
{"title":"Aleph","authors":"Adam Gagol, D. Lesniak, D. Straszak, M. Swietek","doi":"10.1145/3318041.3355467","DOIUrl":"https://doi.org/10.1145/3318041.3355467","url":null,"abstract":"The spectacular success of Bitcoin and Blockchain Technology in recent years has provided enough evidence that a widespread adoption of a common cryptocurrency system is not merely a distant vision, but a scenario that might come true in the near future. However, the presence of Bitcoin's obvious shortcomings such as excessive electricity consumption, unsatisfying transaction throughput, and large validation time (latency) makes it clear that a new, more efficient system is needed. We propose a protocol in which a set of nodes maintains and updates a linear ordering of transactions that are being submitted by users. Virtually every cryptocurrency system has such a protocol at its core, and it is the efficiency of this protocol that determines the overall throughput and latency of the system. We develop our protocol on the grounds of the well-established field of Asynchronous Byzantine Fault Tolerant (ABFT) systems. This allows us to formally reason about correctness, efficiency, and security in the strictest possible model, and thus convincingly prove the overall robustness of our solution. Our protocol improves upon the state-of-the-art HoneyBadgerBFT by Miller et al. by reducing the asymptotic latency while matching the optimal communication complexity. Furthermore, in contrast to the above, our protocol does not require a trusted dealer thanks to a novel implementation of a trustless ABFT Randomness Beacon.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123136647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fan Zhang, Philip Daian, Iddo Bentov, Ian Miers, A. Juels
The growing adoption of digital assets---including but not limited to cryptocurrencies, tokens, and even identities---calls for secure and robust digital assets custody. A common way to distribute the ownership of a digital asset is (M, N)-threshold access structures. However, traditional access structures leave users with a painful choice. Setting M = N seems attractive as it offers maximum resistance to share compromise, but it also causes maximum brittleness: A single lost share renders the asset permanently frozen, inducing paralysis. Lowering M improves availability, but degrades security. In this paper, we introduce techniques that address this impasse by making general cryptographic access structures dynamic. The core idea is what we call Paralysis Proofs, evidence that players or shares are provably unavailable. Using Paralysis Proofs, we show how to construct a Dynamic Access Structure System (DASS), which can securely and flexibly update target access structures without a trusted third party. We present DASS constructions that combine a trust anchor (a trusted execution environment or smart contract) with a censorship-resistant channel in the form of a blockchain. We offer a formal framework for specifying DASS policies, and show how to achieve critical security and usability properties (safety, liveness, and paralysis-freeness) in a DASS. To illustrate the wide range of applications, we present three use cases of DASSes for improving digital asset custody: a multi-signature scheme that can "downgrade" the threshold should players become unavailable; a hybrid scheme where the centralized custodian can't refuse service; and a smart-contract-based scheme that supports recovery from unexpected bugs.
{"title":"Paralysis Proofs: Secure Dynamic Access Structures for Cryptocurrency Custody and More","authors":"Fan Zhang, Philip Daian, Iddo Bentov, Ian Miers, A. Juels","doi":"10.1145/3318041.3355459","DOIUrl":"https://doi.org/10.1145/3318041.3355459","url":null,"abstract":"The growing adoption of digital assets---including but not limited to cryptocurrencies, tokens, and even identities---calls for secure and robust digital assets custody. A common way to distribute the ownership of a digital asset is (M, N)-threshold access structures. However, traditional access structures leave users with a painful choice. Setting M = N seems attractive as it offers maximum resistance to share compromise, but it also causes maximum brittleness: A single lost share renders the asset permanently frozen, inducing paralysis. Lowering M improves availability, but degrades security. In this paper, we introduce techniques that address this impasse by making general cryptographic access structures dynamic. The core idea is what we call Paralysis Proofs, evidence that players or shares are provably unavailable. Using Paralysis Proofs, we show how to construct a Dynamic Access Structure System (DASS), which can securely and flexibly update target access structures without a trusted third party. We present DASS constructions that combine a trust anchor (a trusted execution environment or smart contract) with a censorship-resistant channel in the form of a blockchain. We offer a formal framework for specifying DASS policies, and show how to achieve critical security and usability properties (safety, liveness, and paralysis-freeness) in a DASS. To illustrate the wide range of applications, we present three use cases of DASSes for improving digital asset custody: a multi-signature scheme that can \"downgrade\" the threshold should players become unavailable; a hybrid scheme where the centralized custodian can't refuse service; and a smart-contract-based scheme that supports recovery from unexpected bugs.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122036391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Blockchain is a distributed and decentralized ledger for recording transactions. It is maintained and shared among the participating nodes by utilizing cryptographic primitives. A consensus protocol ensures that all nodes agree on a unique order in which records are appended. However, current blockchain solutions are facing scalability issues. Many methods, such as Off-chain and Directed Acyclic Graph (DAG) solutions, have been proposed to address the issue. However, they have inherent drawbacks, e.g., forming parasite chains. Performance, such as throughput and latency, is also important to a blockchain system. Sharding has emerged as a good candidate that can overcome both the scalability and performance problems in blockchain. To date, there is no systematic work that analyzes the sharding protocols. To bridge this gap, this paper provides a systematic and comprehensive review on blockchain sharding techniques. We first present a general design flow of sharding protocols and then discuss key design challenges. For each challenge, we analyze and compare the techniques in state-of-the-art solutions. Finally, we discuss several potential research directions in blockchain sharding.
{"title":"SoK: Sharding on Blockchain","authors":"Gang Wang, Z. Shi, M. Nixon, Song Han","doi":"10.1145/3318041.3355457","DOIUrl":"https://doi.org/10.1145/3318041.3355457","url":null,"abstract":"Blockchain is a distributed and decentralized ledger for recording transactions. It is maintained and shared among the participating nodes by utilizing cryptographic primitives. A consensus protocol ensures that all nodes agree on a unique order in which records are appended. However, current blockchain solutions are facing scalability issues. Many methods, such as Off-chain and Directed Acyclic Graph (DAG) solutions, have been proposed to address the issue. However, they have inherent drawbacks, e.g., forming parasite chains. Performance, such as throughput and latency, is also important to a blockchain system. Sharding has emerged as a good candidate that can overcome both the scalability and performance problems in blockchain. To date, there is no systematic work that analyzes the sharding protocols. To bridge this gap, this paper provides a systematic and comprehensive review on blockchain sharding techniques. We first present a general design flow of sharding protocols and then discuss key design challenges. For each challenge, we analyze and compare the techniques in state-of-the-art solutions. Finally, we discuss several potential research directions in blockchain sharding.","PeriodicalId":326009,"journal":{"name":"Proceedings of the 1st ACM Conference on Advances in Financial Technologies","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132173027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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