Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Let Leaders Play Games: Improving Timing in Leader-based Consensus

Rasheed M, Parth Desai, Sujit Gujar

TL;DR

2-Prop is proposed, a double-block proposal mechanism that selects two proposers per slot to propose blocks and confirms one of them and a reward-sharing policy for proposers based on how quickly their blocks propagate to avoid strategic deviations.

Abstract

Propagation latency is inherent to any distributed network, including blockchains. Typically, blockchain protocols provide a timing buffer for block propagation across the network. In leader-based blockchains, the leader -- block proposer -- is known in advance for each slot. A fast (or low-latency) proposer may delay the block proposal in anticipation of more rewards from the transactions that would otherwise be included in the subsequent block. Deploying such a strategy by manipulating the timing is known as timing games. It increases the risk of missed blocks due to reduced time for other nodes to vote on the block, affecting the overall efficiency of the blockchain. Moreover, proposers who play timing games essentially appropriate MEV (additional rewards over transaction fees and the block reward) that would otherwise accrue to the next block, making it unfair to subsequent block proposers. We propose a double-block proposal mechanism, 2-Prop, to curtail timing games. 2-Prop selects two proposers per slot to propose blocks and confirms one of them. We design a reward-sharing policy for proposers based on how quickly their blocks propagate to avoid strategic deviations. In the induced game, which we call the Latency Game, we show that it is a Nash Equilibrium for the proposers to propose the block without delay under homogeneous network settings. Under heterogeneous network settings, we study many configurations, and our analysis shows that a faster proposer would prefer not to delay unless the other proposer is extremely slow. Thus, we show the efficacy of 2-Prop in mitigating the effect of timing games.

Let Leaders Play Games: Improving Timing in Leader-based Consensus

TL;DR

2-Prop is proposed, a double-block proposal mechanism that selects two proposers per slot to propose blocks and confirms one of them and a reward-sharing policy for proposers based on how quickly their blocks propagate to avoid strategic deviations.

Abstract

Propagation latency is inherent to any distributed network, including blockchains. Typically, blockchain protocols provide a timing buffer for block propagation across the network. In leader-based blockchains, the leader -- block proposer -- is known in advance for each slot. A fast (or low-latency) proposer may delay the block proposal in anticipation of more rewards from the transactions that would otherwise be included in the subsequent block. Deploying such a strategy by manipulating the timing is known as timing games. It increases the risk of missed blocks due to reduced time for other nodes to vote on the block, affecting the overall efficiency of the blockchain. Moreover, proposers who play timing games essentially appropriate MEV (additional rewards over transaction fees and the block reward) that would otherwise accrue to the next block, making it unfair to subsequent block proposers. We propose a double-block proposal mechanism, 2-Prop, to curtail timing games. 2-Prop selects two proposers per slot to propose blocks and confirms one of them. We design a reward-sharing policy for proposers based on how quickly their blocks propagate to avoid strategic deviations. In the induced game, which we call the Latency Game, we show that it is a Nash Equilibrium for the proposers to propose the block without delay under homogeneous network settings. Under heterogeneous network settings, we study many configurations, and our analysis shows that a faster proposer would prefer not to delay unless the other proposer is extremely slow. Thus, we show the efficacy of 2-Prop in mitigating the effect of timing games.
Paper Structure (36 sections, 7 theorems, 27 equations, 17 figures, 7 tables)

This paper contains 36 sections, 7 theorems, 27 equations, 17 figures, 7 tables.

Table of Contents

  1. Introduction
  2. The Model and Preliminaries
  3. Blockchain
  4. Blockchains.
  5. Leader-based Consensus Protocol for Blockchains.
  6. Objectives of Proposers
  7. Practical Parameters
  8. Network Model
  9. Game Theory
  10. Timing Game
  11. Our Approach
  12. Proposed Solution 2-Prop
  13. Latency Game in 2-Prop
  14. Analysis of Latency Game,
  15. Basic Results
  16. ...and 21 more sections

Key Result

Lemma 1

$\forall i \in \{0,1\}, q_i(\delta_i)$ is monotonically decreasing with $\delta_i$

Figures (17)

  • Figure 1: Progression within Slot
  • Figure 2: Average Cumulative Block Valuation across three Consecutive Slots
  • Figure 3: Proposer ($P_0$) Utility in Homogeneous Setting against an Honest Proposer ($P_1$) for $\mu =0.16$
  • Figure 4: Equilibrium strategies for $\Gamma^{\mathscr{D}}$ for $\zeta=0.05$, $c = 1$
  • Figure 5: $U_0(\delta_0,\delta_1=0)$ vs $\delta_0$ in Homogenous Settings
  • ...and 12 more figures

Theorems & Definitions (19)

  • Definition 1: Restricted $L^2$ norm
  • Definition 2: Nash Equilibrium nash1950equilibrium
  • Lemma 1
  • proof
  • Lemma 2
  • proof
  • Lemma 3
  • proof : Proof Sketch
  • Theorem 1
  • proof : Proof Intuition
  • ...and 9 more