Permuting Transactions in Ethereum Blocks: An Empirical Study

TL;DR

This paper investigates the feasibility and implications of randomized intra-block transaction ordering in Ethereum. It empirically permutes and re-executes transactions from over 335,000 Mainnet blocks using a modified execution client and a Fisher-Yates-based permutation to study protocol violations, execution errors, and gas deviations. The study finds that 22% of permutations are invalid due to protocol violations (predominantly insufficient funds and near gas-limit conditions), about 6% of transactions exhibit gas deviations, and 98% of block permutations deviate by at most 10% in gas consumption, while execution errors rise under permutation but are largely tied to privately mined activity. The results suggest that randomized ordering is technically feasible with careful management of gas margins and avoidance of privately mined transactions, offering guidance for future designs that aim to reduce MEV centralization while highlighting practical challenges and policy considerations around private transactions.

Abstract

Several recent proposals implicitly or explicitly suggest making use of randomized transaction ordering within a block to mitigate centralization effects and to improve fairness in the Ethereum ecosystem. However, transactions and blocks are subject to gas limits and protocol rules. In a randomized transaction order, the behavior of transactions may change depending on other transactions in the same block, leading to invalid blocks and varying gas consumptions. In this paper, we quantify and characterize protocol violations, execution errors and deviations in gas consumption of blocks and transactions to examine technical deployability. For that, we permute and execute the transactions of over 335,000 Ethereum Mainnet blocks multiple times. About 22% of block permutations are invalid due to protocol violations caused by privately mined transactions or blocks close to their gas limit. Also, almost all transactions which show execution errors under permutation but not in the original order are privately mined transactions. Only 6% of transactions show deviations in gas consumption and 98% of block permutations deviate at most 10% from their original gas consumption. From a technical perspective, these results suggest that randomized transaction ordering may be feasible if transaction selection is handled carefully.

Figures (6)

• Figure 1: Components required for the experiment. Arrows represent communication between components. The execution client 'builder' and our own permutation software are the experiment's core components. Any standard consensus client is suitable for the experiment and the permutation software is database agnostic.
• Figure 2: Block processing workflow. Interaction between permutation software and Ethereum node use the standardized 'eth' API. Interaction between the permutation software and the execution client utilize the additional custom block functionality. In practice, the execution client is part of the Ethereum node as depicted in Fig. \ref{['figComponents']}.
• Figure 3: Distribution of blocks according to the fraction of core errors observed in their permutations. Note the log-scaled y-axis and x-axis interval ranges.
• Figure 4: Distribution of blocks (blue) and transactions (red) according to the fraction of deviating block / transaction permutations ($f^\mathrm{D}_B$ or $f^\mathrm{D}_T$) observed in their permutations. Note the log-scaled y-axis and x-axis interval ranges.
• Figure 5: Distribution of block permutations according to the gas deviation intensity $i^\mathrm{R}_{E_\mathrm{B}}$. Note the log-scaled y-axis and x-axis interval ranges. Orange-colored bars represent more than 98% together.