Key Takeaways
- Ethereum co-founder Vitalik Buterin released a detailed post exploring solutions to prevent excessive centralization in block construction
- Glamsterdam, the forthcoming upgrade, will deploy ePBS to separate block proposers and builders, though Buterin cautions centralization risks remain
- FOCIL is a proposed mechanism requiring randomly chosen validators to enforce transaction inclusion, blocking censorship from dominant builders
- An enhanced version dubbed “Big FOCIL” would manage all block transactions, limiting builders to MEV-specific operations only
- Encrypted mempools represent another solution aimed at eliminating harmful MEV practices such as frontrunning and sandwich attacks by concealing transactions pre-confirmation
On Monday, Vitalik Buterin released an extensive blog post detailing strategies to mitigate centralization threats within Ethereum’s transaction assembly infrastructure.
Transaction assembly, commonly known as block building, represents the critical process where transactions are organized before blockchain confirmation. According to Buterin, this mechanism has gradually evolved into a significant vulnerability for Ethereum’s decentralized architecture.
The primary issue centers on how a concentrated group of advanced operators tends to control block construction. These entities possess the capability to strategically arrange transactions for maximum value extraction, creating competitive advantages that smaller network participants cannot match.
Ethereum’s scheduled Glamsterdam upgrade, anticipated to launch during the first half of 2026, will implement enshrined Proposer-Builder Separation (ePBS). This protocol modification creates distinct roles for block proposers and builders by delegating construction responsibilities to a competitive marketplace.
While Buterin endorses the ePBS framework, he emphasizes it represents an incomplete solution. Despite marketplace competition, concentrated builder power could enable transaction censorship or allow excessive profit extraction from network users.
Exploring FOCIL and Its Expanded Version
To address these concerns, Glamsterdam will simultaneously deploy FOCIL—Forward Obligatory Commitment to Inclusion Lists. This mechanism operates by randomly selecting 16 network participants who each specify mandatory transactions for the subsequent block.
Blocks lacking these mandated transactions face automatic rejection. According to Buterin, this structure ensures that even complete control of block building by a single malicious entity cannot prevent specific transactions from executing.
Buterin further proposes “Big FOCIL,” an amplified implementation managing complete block transactions. This approach would restrict block builders exclusively to MEV-related transactions and state computations, effectively commoditizing the block construction process.
Privacy Through Encrypted Mempools
Buterin additionally examined “toxic MEV,” where traders leverage visibility into pending transactions to execute frontrunning strategies or sandwich attacks against other users.
His recommended solution involves encrypting the mempool—the holding area for unconfirmed transactions. With encryption maintained until block inclusion, exploitation opportunities disappear since transactions remain hidden from potential attackers.
Beyond mempool encryption, Buterin identified network-layer vulnerabilities. Transactions become observable to intermediary parties before reaching builders.
He referenced anonymization technologies like Tor and Ethereum-specific privacy networks such as Flashnet as viable protective measures. Additionally, he mentioned the Ethereum Foundation’s Kohaku privacy project as a relevant ongoing initiative.
This post represents one installment in an ongoing series of technical analyses Buterin has published recently. Previous entries 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 as the Ethereum Foundation began what he characterized as a “period of mild austerity.”
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