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Quick Order Fairness: Implementation and Evaluation

Christian Cachin, Jovana Micic

TL;DR

This paper revisits the QOF protocol and describes a modular implementation that uses a generic consensus component and also connects this with similar fairness-imposing protocols like Themis and Pompē.

Abstract

Decentralized finance revolutionizes traditional financial systems by leveraging blockchain technology to reduce trust. However, some vulnerabilities persist, notably front-running by malicious actors who exploit transaction information to gain financial advantage. Consensus with a fair order aims at preventing such attacks, and in particular, the differential order fairness property addresses this problem and connects fair ordering to the validity of consensus. The notion is implemented by the Quick Order-Fair Atomic Broadcast (QOF) protocol (Cachin et al., FC '22). This paper revisits the QOF protocol and describes a modular implementation that uses a generic consensus component. Moreover, an empirical evaluation is performed to compare the performance of QOF to a consensus protocol without fairness. Measurements show that the increased complexity comes at a cost, throughput decreases by at most 5%, and latency increases by roughly 50ms, using an emulated ideal network. This paper contributes to a comprehensive understanding of practical aspects regarding differential order fairness with the QOF protocol and also connects this with similar fairness-imposing protocols like Themis and Pompe.

Quick Order Fairness: Implementation and Evaluation

TL;DR

This paper revisits the QOF protocol and describes a modular implementation that uses a generic consensus component and also connects this with similar fairness-imposing protocols like Themis and Pompē.

Abstract

Decentralized finance revolutionizes traditional financial systems by leveraging blockchain technology to reduce trust. However, some vulnerabilities persist, notably front-running by malicious actors who exploit transaction information to gain financial advantage. Consensus with a fair order aims at preventing such attacks, and in particular, the differential order fairness property addresses this problem and connects fair ordering to the validity of consensus. The notion is implemented by the Quick Order-Fair Atomic Broadcast (QOF) protocol (Cachin et al., FC '22). This paper revisits the QOF protocol and describes a modular implementation that uses a generic consensus component. Moreover, an empirical evaluation is performed to compare the performance of QOF to a consensus protocol without fairness. Measurements show that the increased complexity comes at a cost, throughput decreases by at most 5%, and latency increases by roughly 50ms, using an emulated ideal network. This paper contributes to a comprehensive understanding of practical aspects regarding differential order fairness with the QOF protocol and also connects this with similar fairness-imposing protocols like Themis and Pompe.
Paper Structure (27 sections, 2 equations, 10 figures, 2 tables)

This paper contains 27 sections, 2 equations, 10 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related work
  3. Causal order.
  4. Receive-order fairness.
  5. Randomized order.
  6. Overviews.
  7. Quick Order Fairness Protocol
  8. Broadcast and consensus
  9. Building a graph
  10. Implementation
  11. Byzantine Consistent Broadcast Channel
  12. Implementation details
  13. Validated Byzantine Consensus
  14. Implementation details
  15. Graph Building
  16. ...and 12 more sections

Figures (10)

  • Figure 1: Execution of the protocol shows the first (consensus) phase of the protocol.
  • Figure 2: Example execution of building a graph starting from the first round.
  • Figure 3: Continuation of the execution from Figure \ref{['fig:execution0']}.
  • Figure 4: A stack of modules for implementing Byzantine consistent broadcast channel in Quick Order Fairness protocol.
  • Figure 5: A stack of modules for implementing validated Byzantine consensus in Quick Order Fairness protocol.
  • ...and 5 more figures

Theorems & Definitions (1)

  • Definition 1: $\kappa$-Differentially Order-Fair Atomic Broadcast