TLDR

  • Vitalik Buterin released a detailed blog post examining solutions for Ethereum block building centralization concerns
  • Glamsterdam upgrade will deploy ePBS to separate block proposers and builders, though Buterin cautions about potential builder concentration
  • FOCIL mechanism mandates randomly chosen validators to enforce transaction inclusion, blocking censorship even with dominant builders
  • Big FOCIL extends this approach to manage all transactions in blocks, limiting builders to MEV-specific operations
  • Encrypted mempool technology aims to eliminate toxic MEV practices including frontrunning and sandwich attacks by concealing transactions until finalization

Vitalik Buterin released a comprehensive blog post on Monday detailing strategies to mitigate centralization threats within Ethereum’s block building infrastructure.

The block building process determines how transactions get organized before receiving blockchain confirmation. According to Buterin, this mechanism has emerged as a critical vulnerability point for Ethereum’s architecture.

The primary challenge stems from a concentrated group of advanced operators who typically control block building activities. These entities can manipulate transaction sequencing to maximize value extraction, creating competitive advantages over smaller network participants.

Ethereum’s Glamsterdam upgrade, scheduled for the first half of 2026, will deploy enshrined Proposer-Builder Separation (ePBS). This framework divides block proposer responsibilities from builder functions by delegating construction work to competitive market forces.

While Buterin endorses ePBS, he emphasizes that it represents an incomplete solution. Despite market openness, concentrated builder power could enable transaction censorship or excessive profit extraction from users.

FOCIL and Big FOCIL

Addressing these concerns, the Glamsterdam upgrade will implement FOCIL (Forward Obligatory Commitment to Inclusion Lists). This protocol requires 16 randomly chosen participants to specify transactions that must appear in subsequent blocks.

Blocks lacking these designated transactions face rejection. According to Buterin, this design ensures that even total control over block building by a single malicious entity cannot enable transaction censorship.

Buterin advances a more comprehensive approach called Big FOCIL, which would manage every transaction within blocks. This evolution would restrict builders to handling only MEV-related transactions and state calculations, essentially commodifying block construction.

Encrypted Mempools and Network Privacy

Buterin examined toxic MEV, where traders exploit pending transaction visibility to execute frontrunning or sandwich attacks against other users.

His recommended solution involves encrypting the mempool—the holding area for pending transactions. Encryption prevents exploitation by concealing transaction details until block inclusion.

Buterin also identified vulnerabilities at the network infrastructure level. Intermediaries can monitor transactions before they reach block builders.

He referenced anonymized routing solutions like Tor and Ethereum-specific mixnet tools like Flashnet as protective measures. He mentioned the Ethereum Foundation’s Kohaku privacy project as an active development effort in this space.

Buterin’s analysis forms part of an extended series of technical assessments he has shared recently. These publications have examined subjects ranging from quantum resistance strategies to execution layer modifications.

Earlier this year, Buterin announced plans to sell ETH to support open source development funding as the Ethereum Foundation began what he characterized as a period of mild austerity.