TLDR
- Ethereum co-founder Vitalik Buterin released a detailed blog post exploring solutions to block building centralization concerns
- The Glamsterdam network upgrade will deploy ePBS, separating block proposers and builders, though centralization risks remain
- FOCIL represents a mechanism requiring randomly chosen validators to mandate specific transaction inclusion, blocking censorship attempts
- An enhanced “Big FOCIL” version would manage all block transactions, limiting builders primarily to MEV-focused operations
- Encrypted mempool technology aims to eliminate “toxic MEV” practices including frontrunning and sandwich attacks by concealing transaction data
Ethereum co-founder Vitalik Buterin released a comprehensive blog post this Monday detailing strategies to combat centralization threats within Ethereum’s transaction assembly infrastructure.
Transaction assembly refers to the mechanism through which pending transactions are organized before receiving blockchain confirmation. According to Buterin, this component has quietly emerged as a critical vulnerability within Ethereum’s architecture.
The primary issue stems from sophisticated entities gaining disproportionate control over block construction. These actors leverage advanced optimization techniques to arrange transactions for maximum value extraction, creating significant competitive advantages over smaller network participants.
Ethereum’s forthcoming Glamsterdam upgrade, scheduled for deployment during the first half of 2026, will implement enshrined Proposer-Builder Separation (ePBS). This protocol modification divides block proposal duties from construction responsibilities by establishing an open marketplace for builders.
While Buterin endorses the ePBS approach, he emphasizes it represents an incomplete solution. An open marketplace alone cannot prevent a concentrated group of dominant builders from censoring specific transactions or extracting excessive value from network users.
FOCIL and Big FOCIL
Addressing these concerns, the Glamsterdam implementation will incorporate FOCIL—Forward Obligatory Commitment to Inclusion Lists. This system designates 16 randomly selected validators to specify mandatory transactions for subsequent blocks.
Blocks lacking these required transactions face automatic rejection. According to Buterin, this architecture ensures that even complete block builder monopolization cannot enable transaction censorship.
Buterin advances an ambitious “Big FOCIL” proposal that expands this framework to encompass all block transactions. This modification would restrict block builders primarily to MEV-relevant transaction handling and state computation tasks, effectively commoditizing the block construction process.
Encrypted Mempools and Network Privacy
Buterin additionally examined “toxic MEV” exploitation, where traders leverage pending transaction visibility to execute frontrunning strategies or sandwich attacks against other users.
His recommended solution involves mempool encryption, targeting the staging area where transactions await confirmation. Encrypting transactions until block inclusion eliminates opportunities for advance exploitation.
Beyond mempool considerations, Buterin identified network layer vulnerabilities. Transactions remain observable by network intermediaries before reaching block builders.
He referenced anonymization technologies like Tor and Ethereum-specific mixnet solutions such as Flashnet as viable protective measures. He also acknowledged the Ethereum Foundation’s Kohaku privacy initiative as relevant ongoing development work.
Buterin’s latest publication continues a series of technical analyses he has released throughout recent days. Previous installments have examined quantum resistance strategies and execution layer modifications.
Earlier this year, Buterin announced plans to liquidate ETH holdings to finance open source development initiatives as the Ethereum Foundation transitioned into what he characterized as a “period of mild austerity.”
