TLDR
- Ethereum co-founder Vitalik Buterin released a detailed blog post addressing centralization concerns in the network’s block building infrastructure
- The Glamsterdam upgrade scheduled for early 2026 will deploy ePBS to separate proposer and builder functions, though centralization risks persist
- FOCIL (Forward Obligatory Commitment to Inclusion Lists) mandates transaction inclusion through randomly selected validators to prevent censorship
- An enhanced version called “Big FOCIL” would process all block transactions, limiting builders to MEV-focused operations only
- Buterin advocates for encrypted mempools as a defense against harmful MEV practices including frontrunning and sandwich attacks
On Monday, Ethereum co-founder Vitalik Buterin shared a comprehensive blog post exploring solutions to centralization threats within Ethereum’s block construction infrastructure.
The block building mechanism determines how transactions are organized and packaged before being permanently recorded on the blockchain. According to Buterin, this critical function has emerged as a significant vulnerability for the Ethereum network.
The fundamental issue centers on the reality that a limited group of advanced participants typically control block building operations. These entities possess the capability to sequence transactions strategically for maximum value extraction, creating an inherent advantage against less sophisticated players.
The Glamsterdam network upgrade, targeted for the first six months of 2026, will deploy enshrined Proposer-Builder Separation (ePBS) to Ethereum. This protocol change distinguishes block proposers from builders by establishing a competitive marketplace for block construction.
While Buterin endorses the ePBS implementation, he cautions that it does not completely eliminate centralization concerns. A competitive market environment could still result in a handful of powerful builders censoring specific transactions or capturing disproportionate value from network users.
FOCIL and Big FOCIL
As a countermeasure, Glamsterdam will simultaneously introduce FOCIL—an acronym for Forward Obligatory Commitment to Inclusion Lists. Under this framework, 16 validators chosen at random will each specify transactions that must be incorporated into the subsequent block.
Blocks lacking these designated transactions face automatic rejection. According to Buterin’s analysis, this mechanism ensures that even complete block builder monopolization cannot enable transaction censorship.
Buterin further introduces “Big FOCIL,” a comprehensive extension that would manage the entirety of block transactions. This architectural shift would confine block builders exclusively to MEV-related transaction ordering and state calculations, essentially commodifying the block building process.
Encrypted Mempools and Network Privacy
Buterin’s post also tackles “toxic MEV,” where sophisticated traders leverage advance knowledge of pending transactions to execute frontrunning or sandwich attacks against other network participants.
His recommended solution involves mempool encryption—the staging area where transactions await confirmation. Encrypting transactions until block inclusion would eliminate the information asymmetry that enables these exploitative strategies.
Buterin additionally identifies vulnerabilities at the network transport layer. Transactions can be intercepted and analyzed by intermediary nodes before reaching block builders.
He referenced privacy-preserving routing systems such as Tor and specialized Ethereum mixnets like Flashnet as viable protection mechanisms. The Ethereum Foundation’s Kohaku privacy project also received mention as a relevant development effort.
This latest post represents one installment in an extensive series of technical analyses Buterin has released recently. Previous publications have examined quantum resistance strategies and execution layer modifications.
Earlier this year, Buterin announced plans to liquidate ETH holdings to support open source development initiatives while the Ethereum Foundation navigates what he characterized as “a period of mild austerity.”
Get 3 Free Stock Ebooks
Discover top-performing stocks in AI, Crypto, and Technology with expert analysis.
- Top 10 AI Stocks - Leading AI companies
- Top 10 Crypto Stocks - Blockchain leaders
- Top 10 Tech Stocks - Tech giants
