Conference：IEEE International Conference on Computer Communications (INFOCOM)
CCF level：CCF A
Categories：computer network
Year：2023
Num：5
1
Title:
CoChain: High Concurrency Blockchain Sharding via Consensus on Consensus
CoChain：通过共识上的共识实现高并发区块链分片
Authors:****
Abstract:****
Sharding is an effective technique to improve the scalability of blockchain. It splits nodes into multiple groups so that they can process transactions in parallel. To achieve higher parallelism and concurrency at large scales, it is desirable to maintain a large number of small shards. However, simply configuring small shards easily results in a higher fraction of malicious nodes inside shards, causing shard corruption and compromising system security. Existing sharding techniques hence demand large shards, at the expense of limited concurrency. To address this limitation, we propose CoChain: a blockchain sharding system that can securely configure small shards for enhanced concurrency. CoChain allows some shards to be corrupted. For security, each shard is monitored by multiple other shards. The latter reach a cross-shard Consensus on the Consensus results of their monitored shard. Once a corrupted shard is found, its subsequent consensus will be taken over by another shard, hence recovering the system. Via Consensus on Consensus, CoChain allows the existence of shards with more fraction of malicious nodes (<2/3) while securing the system, thus reducing the shard size safely. We implement CoChain based on Harmony and conduct extensive experiments. Compared with Harmony, CoChain achieves 35x throughput gain with 6,000+ nodes.
分片是一种提高区块链可扩展性的有效技术。它将节点分成多个组，以便并行处理交易。为了在大规模情况下实现更高的并行性和并发性，最好维护大量的小型分片。然而，简单地配置小型分片很容易导致分片内恶意节点的比例增加，从而造成分片损坏，危及系统安全。因此，现有的分片技术需要大型分片，但其代价是有限的并发性。为了解决这一局限性，我们提出了 CoChain：一种区块链分片系统，可以安全地配置小型分片以增强并发性。CoChain 允许某些分片被破坏。为了安全起见，每个分片都受到多个其他分片的监控。其他分块根据其监控分块的共识结果达成跨分块共识。一旦发现损坏的分块，其后续共识将由其他分块接管，从而恢复系统。通过共识上的共识，CoChain 允许存在更多恶意节点（<2/3）的分片，同时确保系统安全，从而安全地缩小分片规模。我们基于 Harmony 实现了 CoChain，并进行了大量实验。与 Harmony 相比，CoChain 在 6000 多个节点上的吞吐量提高了 35 倍。
Pdf link:
https://ieeexplore.ieee.org/document/10228892
2
Title:
Prophet: Conflict-Free Sharding Blockchain via Byzantine-Tolerant Deterministic Ordering
Prophet: 通过拜占庭容错确定性排序实现无冲突分片区块链
Authors:****
Abstract:****
Sharding scales throughput by splitting blockchain nodes into parallel groups. However, different shards' independent and random scheduling for cross-shard transactions results in numerous conflicts and aborts, since cross-shard transactions from different shards may access the same account. A deterministic ordering can eliminate conflicts by determining a global order for transactions before processing, as proved in the database field. Unfortunately, due to the intertwining of the Byzantine environment and information isolation among shards, there is no trusted party able to predetermine such an order for cross-shard transactions. To tackle this challenge, this paper proposes Prophet, a conflict-free sharding blockchain based on Byzantine-tolerant deterministic ordering. It first depends on untrusted self-organizing coalitions of nodes from different shards to pre-execute cross-shard transactions for prerequisite information about ordering. It then determines a trusted global order based on stateless ordering and post-verification for pre-executed results, through shard cooperation. Following the order, the shards thus orderly execute and commit transactions without conflicts. Prophet orchestrates the pre-execution, ordering, and execution processes in the sharding consensus for minimal overhead. We rigorously prove the determinism and serializability of transactions under the Byzantine and sharded environment. An evaluation of our prototype shows that Prophet improves the throughput by 3.11× and achieves nearly no aborts on 1 million Ethereum transactions compared with state-of-the-art sharding.
分片通过将区块链节点分成并行组来提高吞吐量。然而，由于不同分片的跨分片交易可能会访问同一个账户，因此不同分片对跨分片交易的独立和随机排序会导致大量冲突和中止。确定性排序可以在处理前确定事务的全局顺序，从而消除冲突，这一点已在数据库领域得到证实。遗憾的是，由于拜占庭环境的相互交织和分片之间的信息隔离，没有可信的一方能够为跨分片事务预先确定这样的顺序。为了应对这一挑战，本文提出了基于拜占庭容忍确定性排序的无冲突分片区块链--Prophet。它首先依靠来自不同分片的节点组成的不可信任的自组织联盟，预先执行跨分片交易，以获取有关排序的前提信息。然后，通过分片合作，基于无状态排序和对预执行结果的事后验证，确定可信的全局排序。这样，分片就能按照顺序有序地执行和提交事务，而不会发生冲突。Prophet 在分片共识中协调了预执行、排序和执行过程，将开销降至最低。我们严格证明了拜占庭和分片环境下事务的确定性和可序列化性。对我们原型的评估表明，与最先进的分片技术相比，Prophet 将吞吐量提高了 3.11 倍，在 100 万个以太坊交易中几乎没有中止。
Pdf link:
https://ieeexplore.ieee.org/document/10228939
3
Title:
Mercury: Fast Transaction Broadcast in High Performance Blockchain Systems
Mercury: 高性能区块链系统中的快速交易广播
Authors:****
Abstract:****
Blockchain systems must be secure and offer high performance. These systems rely on transaction broadcast mechanisms to provide both of these features. Unfortunately, in today's systems, the broadcast mechanisms are highly inefficient.We present Mercury, a new transaction broadcast protocol designed for high performance blockchains. Mercury shortens the transaction propagation delay using two techniques: a virtual coordinate system and an early outburst strategy. Simulation results show that Mercury outperforms prior propagation schemes and decreases overall propagation latency by up to 44%. When implemented in Conflux, an open-source high-throughput blockchain system, Mercury reduces transaction propagation latency by over 50% with less than 5% bandwidth overhead.
区块链系统必须安全并提供高性能。这些系统依赖交易广播机制来提供这两个特性。不幸的是，在当今的系统中，广播机制的效率非常低。我们提出了Mercury，一种专为高性能区块链设计的新交易广播协议。Mercury 采用两种技术缩短交易传播延迟：虚拟坐标系和提前爆发策略。仿真结果表明，Mercury 优于之前的传播方案，可将整体传播延迟降低 44%。在开源高吞吐量区块链系统 Conflux 中实施时，Mercury 将交易传播延迟减少了 50%以上，而带宽开销不到 5%。
Pdf link:
https://ieeexplore.ieee.org/document/10228972
4
Title:
Latency-First Smart Contract: Overclock the Blockchain for a while
延迟优先智能合约：区块链超频一段时间
Authors:****
Abstract:****
Blockchain systems can become overwhelmed by a large number of transactions, leading to increased latency. As a consequence, latency-sensitive users must bid against each other and pay higher fees to ensure that their transactions are processed in priority. However, most of the time of a blockchain system (78% in Ethereum), there is still a lot of unused computational power, with few users sending transactions. To address this issue and reduce latency for users, we propose the latency-first smart contract model in this paper, which optimistically accepts committed transactions. This allows users to submit a commitment during times of high demand, and then complete the rest of the work at a lower priority. From the perspective of the blockchain, this temporarily "overclocks" the system. We have developed a programming tool for our model, and our experiments show that the proposed latency-first smart contract model can greatly reduce latency during the periods of high demand.
区块链系统可能会因大量交易而不堪重负，导致延迟增加。因此，对延迟敏感的用户必须相互竞价并支付更高的费用，以确保其交易得到优先处理。然而，在区块链系统的大部分时间里（以太坊为 78%），仍有大量未使用的计算能力，很少有用户发送交易。为了解决这个问题并减少用户的延迟，我们在本文中提出了延迟优先的智能合约模型，该模型以乐观的态度接受已承诺的交易。这样，用户就可以在需求量大的时候提交承诺，然后以较低的优先级完成其他工作。从区块链的角度来看，这可以使系统暂时 "超频"。我们为我们的模型开发了一个编程工具，我们的实验表明，所提出的延迟优先智能合约模型可以大大减少高需求时期的延迟。
Pdf link:
https://ieeexplore.ieee.org/document/10228992
5
Title:
A Decentralized Truth Discovery Approach to the Blockchain Oracle Problem
区块链预言机问题的去中心化真相发现方法
Authors:****
Abstract:****
When a blockchain application runs on data from the real world, it relies on an oracle mechanism that transports data from external sources to the blockchain. The blockchain oracle problem arises around the need to procure trustworthy data from external sources. Previous works have addressed data authenticity/integrity by building a secure channel between blockchain and external sources while employing a decentralized oracle network to avoid a single point of failure. However, the truthful data challenge, which emerges when legitimate external sources submit fraudulent or deceitful data, remains unsolved. In this paper, we introduce a new decentralized truth-discovering oracle architecture called DecenTruth to address the truthful data challenge using a data-centric approach. DecenTruth aims to elevate the "truthfulness" of external data input by enabling decentralized oracle nodes to discover and reach consensus on truthful values of common data objects from multi-sourced inputs in an off-chain manner. It harmonizes techniques in both the data plane and consensus plane---truth discovery (TD) and asynchronous BFT consensus---and enables nodes to finalize the same estimated truths on data objects with high accuracy, amid the harsh asynchronous network condition and presence of Byzantine sources and nodes. We implemented DecenTruth and evaluated its performance in a simulated oracle service scenario. The results demonstrate significantly higher Byzantine resilience and long-term data feed accuracy of DecenTruth, compared to existing median-based aggregation methods.
当区块链应用在现实世界的数据上运行时，它依赖于一种将数据从外部来源传输到区块链的预言机机制。区块链预言机问题围绕着从外部来源获取可信数据的需求而产生。以前的工作通过在区块链和外部来源之间建立安全通道来解决数据真实性/完整性问题，同时采用去中心化的预言机网络来避免单点故障。然而，当合法外部来源提交欺诈性或欺骗性数据时出现的真实数据挑战仍未解决。在本文中，我们介绍了一种名为 DecenTruth 的新型去中心化真相发现预言机架构，利用以数据为中心的方法来应对真实数据挑战。DecenTruth 旨在提高外部数据输入的 "真实性"，其方法是使分散式预言机节点能够以链外方式从多来源输入中发现共同数据对象的真实值并达成共识。它协调了数据平面和共识平面的技术--真相发现（TD）和异步 BFT 共识--并使节点能够在苛刻的异步网络条件和拜占庭来源与节点存在的情况下，高精度地最终确定数据对象的相同估计真相。我们实现了 DecenTruth，并在模拟的预言机服务场景中对其性能进行了评估。结果表明，与现有的基于中值的聚合方法相比，DecenTruth 的拜占庭恢复能力和长期数据馈送准确性明显更高。
Pdf link:
https://ieeexplore.ieee.org/document/10229019
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