Ethereum Eyes BitTorrent-Style Block Building; Here’s What It Brings

Ethereum (ETH) is preparing structural changes to how blocks are built and who controls them. In a detailed post, Vitalik Buterin explained that the upcoming ‘Glamsterdam’ upgrade introduces ePBS (enshrined Proposer-Builder Separation). The goal is to prevent block builder centralization from creeping into validator centralization. 

As it happens, proposers can outsource block construction to a permissionless builder market, protecting staking decentralization. But that does not solve builder concentration itself, according to Buterin’s post shared on March 2.

FOCIL: A Censorship Backstop

To address this, Buterin highlighted FOCIL, a system that introduces multi-participant block building directly into the protocol. Under FOCIL, 16 randomly selected attesters each choose transactions that must be included in a block. If those transactions are excluded, the block is rejected.

This creates a safeguard. Even if a single builder dominates block production, they cannot fully censor transactions. Inclusion power becomes partially distributed. 

A more ambitious idea, dubbed ‘Big FOCIL,’ could expand this model further, potentially reducing builders’ roles mainly to MEV-related ordering and state execution. As Buterin explains:

“We avoid duplication by having the i’th FOCIL’er by default only include (i) txs whose sender address’s first hex char is i, and (ii) txs that were around but not included in the previous slot. So at the cost of one slot delay, only censored txs risk duplication. Taking this to its logical conclusion, the builder’s role could become reduced to ONLY including ‘MEV-relevant’ transactions (eg. DEX arbitrage), and computing the state transition.”

Encrypted Mempools And Toxic MEV

Another focus is toxic MEV, including sandwich attacks and frontrunning.

The team is exploring encrypted mempools as a defense. If transactions remain encrypted until inclusion, malicious actors can’t see and exploit them before finalization. The technical challenge is ensuring transactions remain valid and decrypt reliably at the right time.

The Network Layer Problem

Buterin also stressed one thing that many people often overlook: that the transaction ingress layer. Between sending a transaction and block inclusion, users remain exposed to surveillance and manipulation.

Proposals include Tor routing, Ethereum-specific mixnets, latency-optimized non-mixnet privacy networks like Flashnet, and the like.

The Long-Term Vision

Ultimately, Buterin described a broader goal: more distributed block building. One idea is creating transaction categories that don’t require full global synchronization, allowing Ethereum to scale without concentrating power in a single ordering actor.

“There is a dream, that we can make Ethereum truly like BitTorrent: able to process far more transactions than any single server needs to ever coalesce locally. The challenge with this vision is that Ethereum has (and indeed a core value proposition is) synchronous shared state, so any tx could in principle depend on any other tx. This centralizes block building.”

The direction is clear: reduce hidden centralization, limit MEV abuse, and strengthen censorship resistance at the protocol level, all part of new and expanded plans for the blockchain’s future.

Earlier, Ethereum Foundation (EF) introduced a new long-term roadmap called the ‘strawmap,’ outlining an ambitious vision for the network’s future, including multiple upgrade ideas stretching toward the end of the decade, sparking discussion about Ethereum’s long-term direction.

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