skip to main content

Explore Research Products in the NSF-PAR

Title: On Sharding Permissioned Blockchains.
Permissioned Blockchain systems rely mainly on Byzantine fault-tolerant protocols to establish consensus on the order of transactions. While Byzantine fault-tolerant protocols mostly guarantee consistency (safety) in an asynchronous network using 3f+1 machines to overcome the simultaneous malicious failure of any f nodes, in many systems, e.g., blockchain systems, the number of available nodes (resources) is much more than 3f + 1. To utilize such extra resources, in this paper we introduce a model that leverages transaction parallelism by partitioning the nodes into clusters (partitions) and processing independent transactions on different partitions simultaneously. The model also shards the blockchain ledger, assigns different shards of the blockchain ledger to different clusters, and includes both intra-shard and cross-shard transactions. Since more than one cluster is involved in each cross-shard transaction, the ledger is formed as a directed acyclic graph.  more » « less
Award ID(s):
1815733
NSF-PAR ID:
10113697
Author(s) / Creator(s):
Date Published:
Journal Name:
IEEE International Conference on Blockchain
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , 2021 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT))
    null (Ed.)
    The current centralized model of the electricity market is not efficient in performing distributed energy transactions required for the transactive smart grid. One of the prominent solutions to this issue is to integrate blockchain technologies, which promise transparent, tamper-proof, and secure transaction systems specifically suitable for the decentralized and distributed energy markets. Blockchain has already been shown to successfully operate in a microgrid peer-to-peer (P2P) energy market. The prime determinant of different blockchain implementations is the consensus algorithm they use to reach consensus on which blocks/transactions to accept as valid in a distributed environment. Although different blockchain implementations have been proposed independently for P2P energy market in the microgrid, quantitative experimental analyses and comparison of the consensus algorithms that the different blockchains may use for energy markets, has not been studied. Identifying the right consensus algorithm to use is essential for scalability and operation of the energy market. To this end, we evaluate three popular consensus algorithms: (i) proof of work (PoW), (ii) proof of authority (PoA), and (iii) Istanbul Byzantine fault tolerance (IBFT), running them on a network of nodes set up using a network of docker nodes to form a microgrid energy market. Using a series of double auctions, we assess each algorithm's viability using different metrics, such as time to reach consensus and scalability. The results indicate that PoA is the most efficient and scalable consensus algorithm to hold double auctions in the smart grid. We also identified the minimum hardware specification necessary for devices such as smart meters, which may run these consensus algorithms 
    more » « less
  2. ; ; ( , Innovative smart grid technologies)
    The current centralized model of the electricity market is not efficient in performing distributed energy transactions required for the transactive smart grid. One of the prominent solutions to this issue is to integrate blockchain technologies, which promise transparent, tamper-proof, and secure transaction systems specifically suitable for the decentralized and distributed energy markets. Blockchain has already been shown to successfully operate in a microgrid peer-to-peer (P2P) energy market. The prime determinant of different blockchain implementations is the consensus algorithm they use to reach consensus on which blocks/transactions to accept as valid in a distributed environment. Although different blockchain implementations have been proposed independently for P2P energy market in the microgrid, quantitative experimental analyses and comparison of the consensus algorithms that the different blockchains may use for energy markets, has not been studied. Identifying the right consensus algorithm to use is essential for scalability and operation of the energy market. To this end, we evaluate three popular consensus algorithms: (i) proof of work (PoW), (ii) proof of authority (PoA), and (iii) Istanbul Byzantine fault tolerance (IBFT), running them on a network of nodes set up using a network of docker nodes to form a microgrid energy market. Using a series of double auctions, we assess each algorithm’s viability using different metrics, such as time to reach consensus and scalability. The results indicate that PoA is the most efficient and scalable consensus algorithm to hold double auctions in the smart grid. We also identified the minimum hardware specification necessary for devices such as smart meters, which may run these consensus algorithms. 
    more » « less
  3. ; ; ; ( , Proceedings of the VLDB Endowment)
    Today's large-scale data management systems need to address distributed applications' confidentiality and scalability requirements among a set of collaborative enterprises. This paper presents Qanaat , a scalable multi-enterprise permissioned blockchain system that guarantees the confidentiality of enterprises in collaboration workflows. Qanaat presents data collections that enable any subset of enterprises involved in a collaboration workflow to keep their collaboration private from other enterprises. A transaction ordering scheme is also presented to enforce only the necessary and sufficient constraints on transaction order to guarantee data consistency. Furthermore, Qanaat supports data consistency across collaboration workflows where an enterprise can participate in different collaboration workflows with different sets of enterprises. Finally, Qanaat presents a suite of consensus protocols to support intra-shard and cross-shard transactions within or across enterprises. 
    more » « less
  4. ; ; ; ; ; ( , SoCC '19: Proceedings of the ACM Symposium on Cloud Computing)
    null (Ed.)
    Byzantine Fault Tolerant (BFT) protocols are designed to ensure correctness and eventual progress in the face of misbehaving nodes [1]. However, this does not prevent negative effects an adversary may have on performance: a faulty node may significantly affect the latency and throughput of the system without being detected. This is especially true in speculative protocols optimized for the best-case where a single leader can force the protocol into the worst case [3]. Systems like Aardvark [2] that are designed to maximize worst-case performance tolerate byzantine behavior without necessarily detecting who the perpetrator is. By forcing regular view changes, for example, they mitigate the effects of leaders who deliberately delay dissemination of messages, even if this behavior would be difficult to prove to a third party. Byzantine faults, by definition, can be difficult to detect. An error of 'commission', such as a message with a mismatching digest, can be proven. Errors of 'omission', such as delaying or failing to relay a message, as a rule cannot be proven, and the node responsible for these types of omission faults may not appear faulty to all observers. Nevertheless, we observe that they can reliably be detected. Designing protocols that detect and eject nodes is challenging for two reasons. First, some behaviors are observed by a subset of honest nodes and cannot be objectively proven to a third party. Second, any mechanism capable of ejecting nodes could be subverted by Byzantine nodes to eject honest nodes. This paper presents the Protocol for Ejecting All Corrupted Hosts (Peach, a mechanism for detecting and ejecting faulty nodes in Byzantine fault tolerant (BFT) protocols. Nodes submit votes to a trusted configuration manager that replaces faulty nodes once a threshold of votes are received. We implement Peach for two BFT protocol variants, a traditional pbft-style three-phase protocol and a speculative protocol, and evaluate its ability to respond to Byzantine behavior. This work makes the following contributions: (1) We present and prove a necessary and sufficient constraint on cluster membership guaranteeing that any nodes causing performance degradation via acts of omission will be detected. (2) We present an agreement protocol, PEACHes, in which replicas pass votes about their subjective local observations of possible omissions to a TTP. (3) We show how the separation of detection and effectuation allows fine-grained detection of malicious behavior that is compatible and easily integrated with existing systems. (4) We present DecentBFT, an extension of BFT-Smart to which we added a speculative fast path (similar to Zyzzva) and integrated PEACHes. (5) We show DecentBFT rapidly detects and mitigates a variety of performance attacks that would have gone undetected by the state of the art. 
    more » « less
  5. ; ; ( , The VLDB Journal)
    Abstract

    Modern distributed data management systems face a new challenge: how can autonomous, mutually distrusting parties cooperate safely and effectively? Addressing this challenge brings up familiar questions from classical distributed systems: how to combine multiple steps into a single atomic action, how to recover from failures, and how to synchronize concurrent access to data. Nevertheless, each of these issues requires rethinking when participants are autonomous and potentially adversarial. We propose the notion of across-chain deal, a new way to structure complex distributed computations that manage assets in an adversarial setting. Deals are inspired by classical atomic transactions, but are necessarily different, in important ways, to accommodate the decentralized and untrusting nature of the exchange. We describe novel safety and liveness properties, along with two alternative protocols for implementing cross-chain deals in a system of independent blockchain ledgers. One protocol, based on synchronous communication, is fully decentralized, while the other, based on semi-synchronous communication, requires a globally shared ledger. We also prove that some degree of centralization is required in the semi-synchronous communication model.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email