CryptoDB
Streamlined Blockchains: A Simple and Elegant Approach (A Tutorial and Survey)
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| Abstract: | A blockchain protocol (also called state machine replication) allows a set of nodes to agree on an ever-growing, linearly ordered log of transactions. The classical consensus literature suggests two approaches for constructing a blockchain protocol: (1) through composition of single-shot consensus instances often called Byzantine Agreement; and (2) through direct construction of a blockchain where there is no clear-cut boundary between single-shot consensus instances. While conceptually simple, the former approach precludes cross-instance optimizations in a practical implementation. This perhaps explains why the latter approach has gained more traction in practice: specifically, well-known protocols such as Paxos and PBFT all follow the direct-construction approach.In this tutorial, we present a new paradigm called “streamlined blockchains” for directly constructing blockchain protocols. This paradigm enables a new family of protocols that are extremely simple and natural: every epoch, a proposer proposes a block extending from a notarized parent chain, and nodes vote if the proposal’s parent chain is not . Whenever a block gains votes, it becomes notarized. Whenever a node observes a notarized chain with blocks of consecutive epochs at the end, then the entire chain chopping off blocks at the end is final.By varying the parameters highlighted in , we illustrate two variants for the partially synchronous and synchronous settings respectively. We present very simple proofs of consistency and liveness. We hope that this tutorial provides a compelling argument why this new family of protocols should be used in lieu of classical candidates (e.g., PBFT, Paxos, and their variants), both in practical implementation and for pedagogical purposes. |
BibTeX
@article{asiacrypt-2019-30008,
title={Streamlined Blockchains: A Simple and Elegant Approach (A Tutorial and Survey)},
booktitle={Advances in Cryptology – ASIACRYPT 2019},
series={Advances in Cryptology – ASIACRYPT 2019},
publisher={Springer},
volume={11921},
pages={3-17},
doi={10.1007/978-3-030-34578-5_1},
author={Elaine Shi},
year=2019
}