Researchers Demonstrate Ethereum Transaction Censorship Vulnerability, Sparking Debate

In this post:

  • Researchers demonstrated a vulnerability in Ethereum’s censorship resistance by temporarily delaying transactions through the proposer-builder separation mechanism.
  • The proof of concept highlighted issues with fee calculations and raised concerns about Ethereum’s goal of being a neutral platform.

In a proof of concept that has raised concerns about the censorship resistance of Ethereum, a team of researchers known as the Special Mechanisms Group (SMG) has revealed a method to exploit the proposer-builder separation feature of the blockchain. By leveraging this feature, the team successfully forced an Ethereum block to contain only their transaction. 

This demonstration has ignited discussions about the core principles of Ethereum and the need for improved censorship resistance. While some argue that the current gas fee market would make it challenging to delay transactions significantly, the revelation highlights existing flaws in fee calculation methods used by certain Ethereum applications. This article delves into the details of the vulnerability, explores reactions from industry experts, and examines potential solutions.

The Exploited Vulnerability

The proposer-builder separation (PBS) mechanism was designed to enhance the censorship resistance of the Ethereum blockchain. Its purpose was to separate the roles of block builders and block proposers. However, the SMG team discovered a loophole within PBS that enabled them to manipulate the system. Their proof of concept involved including a transaction in a block with a URL pointing to their website, where they presented their research paper on the issue and proposed potential solutions. This single transaction block highlighted the vulnerability and raised concerns about the efficacy of censorship resistance on Ethereum.

Mixed Reactions and Challenges

The reaction to the SMG team’s demonstration has varied within the Ethereum community. Ryan Berckmans, a former software engineer at Augur, acknowledged the difficulties of leveraging this method for extended transaction delays due to Ethereum’s gas fee market. However, he emphasized that the situation revealed underlying problems with fee calculations for transaction inclusion. 

Censoring transactions, even temporarily, contradicts Ethereum’s goal of being “credibly neutral” and raises alarm bells within the community. Furthermore, other members of the Ethereum community have expressed concerns about the potential implications of this vulnerability. The demonstration has highlighted the need to address fee calculation methods to ensure fair and efficient transaction processing. 

The Need for Improved Censorship Resistance

While some argue that a short delay of 12 seconds may not cause significant issues, the SMG team asserts that even brief censorship periods can be problematic for certain applications and mechanisms. Auctions, for example, require fast and unbiased transaction processing to maintain system efficiency. The ability of participants to censor their competitors’ bids undermines the fairness and effectiveness of such auctions. 

Additionally, fraud proofs and Oracle updates can also be affected by censorship, limiting their functionality. The team believes that increasing censorship resistance on the base chain could lead to better user experiences in optimistic rollups, a layer-2 scaling solution.


The recent demonstration by the SMG team has raised important questions about the censorship resistance of Ethereum. While the 12-second delay may not appear significant, the potential impact on specific applications and mechanisms is cause for concern. Auctions, fraud proofs, and Oracle updates are just a few examples of use cases that require swift transaction processing to maintain their integrity. While some solutions, such as migrating to layer-2 scaling solutions, may alleviate the issue for certain applications, an overall improvement in censorship resistance on the Ethereum base chain is essential.

Disclaimer. The information provided is not trading advice. Cryptopolitan.com holds no liability for any investments made based on the information provided on this page. We strongly recommend independent research and/or consultation with a qualified professional before making any investment decisions.

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