Vitalik's "Shelter Technology" Declaration: How Does Ethereum Incorporate Censorship Resistance into the Protocol?

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Written by: imToken

If one day Ethereum’s core development team collectively “disappears” or a sovereign country asks to censor a particular transaction, can Ethereum remain open?

These questions sound like extreme assumptions, but they are becoming an increasingly realistic frame of reference for Ethereum protocol design.

In early March, Vitalik Buterin proposed a new statement, bluntly stating that the Ethereum community should understand itself as part of the “sanctuary technologies” ecosystem: these free and open-source technologies allow people to live, work, communicate, manage risk, accumulate wealth, and collaborate towards a common goal, while maximizing their ability to resist external pressures.

This set of expressions may seem like an abstract value upgrade, but if you look at it in the context of Ereme’s recent protocol evolution, it actually corresponds to very specific engineering problems:

As block construction becomes more and more specialized, transaction ordering power becomes more and more concentrated, and public mempools are becoming more and more prone to being pinched and rushed, how can Ethereum continue to maintain the core bottom line of the “open network” - user transactions should not be easily blocked by a few people.

1. Vitalik coined a new word: “shelter technology”

Vitalik’s starting point this time comes with a rare frankness.

He did not continue to use the “change the world” style, but admitted that Ethereum’s improvement to the real life of ordinary people is still limited to this day, such as the improvement of on-chain financial efficiency and the richer application ecology, but many achievements are still stuck in the internal circulation of the crypto world.

Therefore, he proposed a new way of positioning, not understanding Ethereum as a mere financial network, but rather as part of a broader “sanctuary technology” ecosystem.

By his definition, these technologies usually have several common characteristics: they are open source, free, and can be used and copied by anyone; They help people communicate, collaborate, and manage risk and wealth; What’s more, they remain operational in the face of government pressure, corporate lockdowns, or other external intervention.

Vitalik even proposed an image metaphor - a true decentralized protocol should be more like a hammer than a subscription service. When you buy a hammer, it’s yours and it won’t suddenly lapse due to the manufacturer’s closure, and you won’t get a pop-up one day telling you that the feature is no longer available in your region.

In the final analysis, if a technology is to assume a shelter function, it cannot rely on a centralized organization to continue to exist, let alone put users in a position of passive service.

Source: CoinDesk

This is undoubtedly reminiscent of another criterion that Vitalik has often mentioned before to test the long-term value of Ethereum, namely the walkaway test, which asks a very simple question: if all the core developers of Ethereum disappear collectively tomorrow, will the protocol still function normally?

This is not a slogan, but an extremely strict decentralization standard, because what it really asks is not “is there a decentralized narrative now”, but “whether this system can still stand in the worst-case future”.

If you put this question at the block production level, the answer becomes very specific: if a chain wants to pass the walkaway test, it cannot allow transaction inclusion to be held in the hands of a few people for a long time, nor can it allow public transaction flows to be naturally exposed to the risks of rushing, pinching, and censorship.

This is the context behind which FOCIL and crypto mempools enter the Ethereum core discussion.

2. Anti-censorship Back to the protocol center: FOCIL + encrypted mempool

We need to break down the problems currently faced by Ethereum’s public mempool.

Over the past few years, Ethereum has continued to specialize at the block building level. In order to improve efficiency and MEV extraction capabilities, the role of builders is becoming more and more important, and block production is no longer an ideal state where each validator builds blocks locally and independently.

Once block building rights are concentrated in a small number of powerful participants, censorship is no longer just a theoretical risk. In theory, any mainstream builder could selectively reject transfers that include certain transactions, such as transfers from sanctioned Tornado Cash addresses.

In other words, the question facing Ethereum today is not just whether transaction fees are high or throughput, but whether the public transaction infrastructure is still worthy of the trust of ordinary users.

Therefore, FOCIL (Fork-Choice Enforced Inclusion Lists) is a positive response to the censorship issue of the Ethereum protocol layer, and its core idea is not complicated, that is, by introducing the Inclusion List mechanism, whether transactions can be included in blocks in a timely manner is no longer entirely dependent on the unilateral will of the proposer or builder.

Each slot selects an Inclusion List Committee from the validator set, and the committee members form a list of transactions to be included and broadcast it based on the mempool they see. The next slot’s proposer needs to build a block that satisfies these list constraints, while the attester will only vote for eligible blocks.

In other words, FOCIL does not eliminate builders, but provides stronger inclusion guarantees for valid transactions in the public mempool through fork selection rules, which means that builders can still do ordering optimization and can still improve efficiency and revenue around MEV, but they no longer have the power to decide whether a legitimate transaction is eligible to enter a block.

Although controversial, FOCIL has been confirmed as the Specification Freeze Included state for the next major upgrade to Hegotá, which is expected to go live in the second half of 2026 after the Glamsterdam upgrade.

However, FOCIL does not solve another equally critical problem: whether the transaction has been seen by the entire market before it actually enters the block, MEV Searcher can use this to run, pinch, and rearrange, especially DeFi transactions are the easiest to target, which means that even if they are not censored, they may still be targeted before entering the block.

This is where sandwich attacks come from.

The main solutions currently being discussed by the community are LUCID (proposed by Ethereum Foundation researchers Anders Elowsson, Julian Ma, and Justin Florentine) and EIP-8105 (Universal Enshrined Encrypted Mempool), which the EIP-8105 team has recently announced its full support for LUCID. The two teams are working together.

The core idea of encrypted mempools is:

When a user sends a transaction, the transaction content is encrypted;

Transactions are decrypted only after they are packaged into blocks and reach a certain confirmation.

Previously, the seeker could not see the intent to trade and could not perform a sandwich attack or run forward;

As a result, the public mempool becomes “safe to use” again;

As the researchers say, ePBS (execution layer proposer-builder separation) + FOCIL + cryptographic mempool, collectively known as the “Holy Trinity of Censorship Resistance”, is a complete solution that provides systemic defense from the entire transaction supply chain.

Currently, FOCIL has confirmed entry into Hegotá; The Encrypted Mempool Scheme (LUCID) is actively seeking inclusion as another headliner proposal from Hegotá.

3. What does all this mean?

If we zoom in a bit, FOCIL and crypto mempools are not just new terms in another round of Ethereum’s technical upgrade list, they are more like a signal:

Ethereum is putting “censorship-resistant” back at the center of protocol design.

After all, although the blockchain industry often talks about “decentralization”, when a transaction is actually censored, intercepted, and disappears from the network one day, most users will find that decentralization is never the default state, but something that needs to be fought for with protocol code.

As early as February 20, Vitalik stated that there is an important synergy between the FOCIL mechanism and Ethereum’s account abstraction proposal EIP-8141 (based on 7701), which elevates smart accounts (including multi-signature, quantum-resistant signatures, key changes, gas sponsorship, etc.) to “Type 1 citizens”, meaning that operations from this account can be directly packaged as on-chain transactions without additional encapsulation.

One might question: Is it worth the effort that FOCIL increases protocol complexity and the efficiency that encrypted mempools can incur?

This is the most noteworthy thing about “shelter technology”, the true unique value of blockchain may never be just the asset on the chain and the speed of transactions, but whether it can continue to provide people with a digital outlet that does not require permission, is not easy to shut down, and is not easy to be deprived in a high-pressure environment.

From this perspective, the significance of FOCIL and crypto mempools is clear, as they try to transform some things that originally relied on goodwill, spontaneous market equilibrium, and “hope nothing will happen” into harder protocol rules.

When countless users can freely live, work, communicate, manage risk, and accumulate wealth on this “digital stability island” without fear of being expelled or censored by any centralized entity - that’s when Ethereum truly passed the “Walkaway Test”.

And this is the ultimate meaning of shelter technology.