Censorship resistance is now a builder problem. The Ethereum merge and PBS outsourced block construction to a new class of actors, specialized block builders. This centralizes transaction ordering power, creating a single point of failure for censorship.
mev-the-hidden-tax-of-crypto
Blog
The Future of Censorship Resistance in Block Construction
Consensus-layer decentralization is insufficient. This analysis argues that censorship resistance is now a block construction problem, requiring decentralized builders and sequencers to prevent transaction blacklisting and ensure credible neutrality.
introduction
THE STAKES
Introduction
The shift to proposer-builder separation (PBS) creates a new, centralized attack surface that threatens the core value proposition of blockchains.
Builders are not validators. Their incentives diverge. A validator's primary goal is protocol compliance for rewards. A profit-maximizing builder will filter transactions based on MEV and regulatory pressure, not neutrality.
The threat is active, not theoretical. In 2022, OFAC-compliant builders like Flashbots censored Tornado Cash transactions, controlling over 90% of Ethereum blocks. This demonstrated that protocol-level decentralization fails if the builder layer centralizes.
The solution requires new primitives. Relying on altruism or competition is insufficient. The future requires cryptoeconomic mechanisms like inclusion lists, encrypted mempools, and protocols like SUAVE to enforce neutrality at the builder level.
thesis-statement
THE ARCHITECTURAL SHIFT
Thesis: Censorship is a Block Construction Problem
Censorship resistance depends on who controls the ordering and inclusion of transactions, moving from a validator-level to a builder-level design challenge.
Censorship is an ordering problem. The validator who proposes a block decides transaction sequence. This centralizes power, enabling MEV extraction and compliance with OFAC lists. The solution is separating block proposal from block construction.
Proposer-Builder Separation (PBS) is the architectural fix. It creates a competitive market where specialized block builders like Flashbots and bloXroute compete to sell bundles to proposers. This shifts censorship power from a single entity to a competitive landscape.
Builder dominance creates new risks. A single builder like Flashbots can capture >40% of Ethereum blocks, creating a centralized censorship point. The protocol must enforce credible neutrality at the builder layer through mechanisms like inclusion lists.
In-protocol PBS (ePBS) is the endgame. Ethereum's roadmap integrates PBS directly, using builder commitments and consensus-level slashing to prevent censorship. This makes resistance a protocol property, not a market assumption.
key-trends
THE FUTURE OF CENSORSHIP RESISTANCE
Key Trends: The Centralization of Block Construction
The rise of specialized block builders and MEV relays has created a new centralization vector, challenging the foundational principle of permissionless block production.
01
The Problem: Builder Oligopoly
A handful of professional builders like Flashbots and bloXroute dominate block production, controlling >80% of Ethereum blocks post-Merge. This creates a single point of failure for censorship and transaction filtering.
- Centralized Control: Reliance on a few entities for >90% of MEV revenue.
- Regulatory Risk: Builders can be compelled to censor OFAC-sanctioned addresses.
>80%
Blocks Controlled
>90%
MEV Revenue
02
The Solution: Permissionless Builders & SUAVE
Decentralizing the builder layer itself is the only credible path to long-term censorship resistance. This requires open-source, competitive builder software and shared infrastructure.
- SUAVE's Vision: A decentralized mempool and block builder network to commoditize the role.
- Builder Diversity: Projects like EigenLayer's EigenDA and Astria aim to lower the capital/technical barriers to becoming a builder.
0
Trust Assumptions
100%
Uptime Goal
03
The Solution: Enshrined Proposer-Builder Separation (PBS)
Ethereum's roadmap explicitly calls for enshrining PBS at the protocol level, moving the auction mechanism from off-chain relays to on-chain contracts.
- Protocol-Level Guarantees: Builders compete in a credibly neutral, permissionless marketplace.
- Force-Inclusion Lists: Validators can mandate the inclusion of specific transactions, overriding builder censorship.
~2025
Target Timeline
100%
On-Chain
04
The Problem: Relayer Centralization
Even with decentralized builders, the relay layer remains a bottleneck. Most validators connect to a single dominant relay, which can filter blocks before they reach the chain.
- Single Point of Failure: Flashbots Relay historically processed the vast majority of MEV-boost blocks.
- Gatekeeper Risk: Relays can impose arbitrary rules on block validity beyond consensus.
1
Primary Relay
High
Gatekeeper Risk
05
The Solution: MEV-Boost++ & Relay Diversity
The next evolution of MEV infrastructure pushes competition and redundancy into the relay layer, preventing any single entity from controlling the pipeline.
- Multi-Relay Architecture: Validators connecting to >3 relays significantly reduce censorship risk.
- Open Sourcing: Initiatives to standardize relay APIs and open-source relay software to foster competition.
>3
Relays Needed
0
Proprietary Code
06
The Wildcard: Intent-Based Architectures
A paradigm shift from transaction-based to intent-based systems, as seen in UniswapX and CowSwap, could bypass the builder/relay problem entirely. Users express a desired outcome, and a decentralized network of solvers competes to fulfill it.
- Solver Networks: Decentralized actors (Across, Anoma) compete on execution quality, not just block space.
- Reduced MEV Surface: Intents abstract away transaction ordering, reducing the value extractable by centralized builders.
~$1B+
Intent Volume
Low
MEV Leakage
THE POST-MEV-BOOST LANDSCAPE
Builder & Sequencer Censorship Risk Matrix
Comparative analysis of censorship resistance mechanisms across dominant block production and sequencing architectures.
| Censorship Vector | PBS w/ Enshrined Commitments (e.g., Ethereum) | Centralized Sequencer (e.g., OP Stack, Arbitrum) | Decentralized Sequencer Set (e.g., Espresso, Astria, Shared) |
|---|---|---|---|
Block Withholding / Reordering | Mitigated via crLists & PBS, Builder can still censor | High Risk: Single operator controls tx ordering & inclusion | Low Risk: Leader election & attestation prevent single-point control |
Transaction Filtering (OFAC) | Relay-level risk persists; ~30% of blocks compliant | Extreme Risk: Operator can enforce any filter list | Protocol-level resistance via stake-weighted consensus |
Time-to-Inclusion Guarantee | ~12s (Slot time) for next builder opportunity | Indefinite: At sole discretion of sequencer | Bounded by protocol-defined slot/round time |
Force-Inclusion Mechanism | crLists (enshrined), ~2-block delay | L1 L2Output/State Root Challenge (6+ hour delay) | Built-in challenge period or slashing for non-inclusion |
Architectural Centralization | Builder market (semi-decentralized), ~5 dominant builders | Single corporate entity (e.g., Offchain Labs, OP Labs) | Permissionless validator set, similar to L1 PoS |
Cost to Censor (Attack Cost) | High: Requires dominating builder market & relay compliance | Low: Operational cost of running a sequencer node | Very High: Requires >33% stake slashing or takeover |
Recovery/Exit Path for Users | Direct L1 submission (always available) | Forced via L1 bridge (slow, expensive, technical) | Direct submission to honest sequencer node in set |
deep-dive
THE POST-MEV FUTURE
Deep Dive: Architectures for Credibly Neutral Construction
Censorship resistance shifts from transaction ordering to credibly neutral block construction, requiring new architectural primitives.
Credible neutrality is architectural. It is a property enforced by protocol design, not validator goodwill. The PBS (Proposer-Builder Separation) model, pioneered by Ethereum, creates a market for block space but outsources censorship power to builders.
Enshrined PBS solves nothing. Moving PBS on-chain, as with Ethereum's ePBS, formalizes the builder role but does not guarantee its neutrality. The censorship vector simply shifts from proposers to a new, potentially centralized, builder cartel.
The solution is competitive construction. Networks like Solana and Sui rely on Jito-style auction queues and parallel execution to make censorship unprofitable. Their high throughput and low latency create a market where excluding transactions forfeits revenue.
Intent-based architectures bypass the problem. Protocols like UniswapX and CowSwap abstract execution to a solver network. Users submit intents; solvers compete to fulfill them, making transaction-level censorship impossible by design.
The endpoint is sovereign rollups. The final architecture for neutrality is a rollup with a decentralized sequencer set, like dYdX v4 or Espresso Systems. Credible neutrality is enforced at the sequencer layer, not the settlement layer.
protocol-spotlight
THE POST-MEV FUTURE
Protocol Spotlight: The Builders of Censorship Resistance
The MEV supply chain is the new attack surface for censorship. These protocols are re-architecting block construction to neutralize it.
01
Flashbots SUAVE: Decentralizing the Mempool
The Problem: Centralized block builders (like Flashbots themselves) create a single point of failure for OFAC compliance. The Solution: A decentralized, chain-agnostic mempool and block-building network. Validators commit to building blocks from SUAVE, which auctions order flow in a trust-minimized environment.
- Key Benefit: Separates block building from proposing, breaking builder monopolies.
- Key Benefit: Enables cross-domain MEV capture (Ethereum → Arbitrum, etc.) via its own execution layer.
100%
Decentralized Goal
Multi-Chain
Scope
02
MEV-Boost Relay Bypass: PBS at the Validator
The Problem: Relays in the MEV-Boost ecosystem can (and do) censor transactions, acting as regulatory gatekeepers. The Solution: Validator-side software that enables proposer-builder separation (PBS) without a trusted relay. Builders send full block contents directly; validators verify and sign headers.
- Key Benefit: Eliminates the relay as a censorship vector. The builder's signature is the guarantee.
- Key Benefit: Preserves MEV revenue for validators while maximizing credibly neutral inclusion.
0 Relays
Trust Assumption
~100%
Uptime
03
Shutterized Auctions: Encrypted Mempools for dApps
The Problem: Frontrunning and malicious MEV extract value and censor users on application layers like DeFi. The Solution: A network of Keypers (distributed key holders) that encrypt transaction payloads until a block is finalized. Pioneered by Shutter Network and integrated by CowSwap and Gnosis Auction.
- Key Benefit: Makes frontrunning and targeted censorship economically impossible for that application.
- Key Benefit: Preserves transparency post-execution, maintaining blockchain auditability.
Threshold
Encryption
Application-Layer
Defense
04
The Enshrined PBS Endgame
The Problem: Even advanced PBS designs introduce new intermediaries (builders, relays) with their own profit motives. The Solution: Protocol-level, enshrined proposer-builder separation. This is Ethereum's long-term roadmap, baking anti-censorship and fair ordering directly into the consensus layer.
- Key Benefit: Censorship resistance becomes a cryptoeconomic property of the chain, not an add-on.
- Key Benefit: Radically simplifies the stack, reducing latency and complexity for builders like Jito Labs and BloXroute.
L1 Native
Solution
2025+
Timeline
counter-argument
THE INCENTIVE MISMATCH
Counter-Argument: Is Decentralized Building Even Possible?
The economic and technical forces that created MEV searchers are the same forces that will centralize block building.
Decentralized building is economically irrational. The specialized hardware and capital required for optimal MEV extraction creates a natural oligopoly. This is not a bug; it is the Nash equilibrium of a permissionless, profit-maximizing system.
The builder role centralizes by design. The winner-take-all auction model for block space (e.g., Flashbots MEV-Boost) inherently favors the entity with the best data, fastest connections, and most sophisticated algorithms. This is a centralizing force, not a distributing one.
Evidence from Ethereum's PBS rollout. Post-merge, a handful of builders (e.g., bloXroute, Builder0x69, beaverbuild) consistently win over 80% of blocks. This concentration proves the economic gravity of block production, even with a decentralized validator set.
risk-analysis
CENSORSHIP RESISTANCE
Risk Analysis: What Could Go Wrong?
The shift to proposer-builder separation and MEV extraction creates new vectors for transaction censorship and manipulation.
01
The Builder Cartel Problem
A small group of dominant builders (e.g., Flashbots, bloXroute, Titan) could collude to blacklist addresses or transactions, effectively re-introducing centralized control. This is not theoretical; builders already control >80% of Ethereum blocks.
- Risk: OFAC compliance becomes a de facto network rule.
- Impact: Neutral protocols like Tornado Cash become unusable, breaking core crypto promises.
>80%
Builder Share
OFAC
Compliance Risk
02
Enshrined PBS & SUAVE
The proposed long-term solution is to enshrine Proposer-Builder Separation (PBS) into the protocol and leverage systems like SUAVE for decentralized block building. This separates trust from economic incentives.
- Mechanism: Validators commit to blocks from a competitive, permissionless builder marketplace.
- Goal: Eliminate the trusted relay layer, making censorship a costly, detectable deviation.
Protocol
Level Fix
SUAVE
Key Entity
03
The CrList Compromise
A stop-gap proposal before enshrined PBS. Validators provide a "Censorship Resistance List" (crList) of transactions they want included. Builders must include these txns or face penalties, preserving some liveness guarantees.
- Trade-off: Adds complexity and may reduce builder revenue, potentially lowering bids.
- Status: Actively debated for inclusion in future Ethereum hard forks.
Interim
Solution
crList
Mechanism
04
Inclusion Lists & MEV-Boost++
Client teams (e.g., Teku, Prysm) are implementing inclusion lists at the validator client level. This allows validators to force specific transactions into blocks, bypassing builder censorship. The next iteration of MEV-Boost must support this.
- Execution: Validator software overrides builder's block proposal for listed txns.
- Limitation: Reduces MEV extraction efficiency, creating an economic disincentive.
Client
Level Fix
MEV-Boost++
Upgrade Path
05
The Economic Attack: Time-Bandit Reorgs
If censorship becomes profitable, sophisticated actors could execute time-bandit chain reorganizations to censor transactions after the fact. This attacks the blockchain's finality.
- Vector: A builder withhold a profitable block, then reorg the chain to claim its MEV.
- Defense: Requires stronger single-slot finality and cryptographic commitments.
Finality
Attack Vector
Reorg
Risk
06
The Regulatory Capture Endgame
The ultimate risk is legal pressure forcing all major infrastructure providers (builders, relays, RPCs) to implement blacklists. This turns the decentralized stack into a global surveillance tool.
- Precedent: The Tornado Cash sanctions set the stage.
- Countermeasure: True decentralization requires geographically and jurisdictionally distributed operators, which is currently not the case.
Global
Regulatory Risk
Sanctions
Precedent
future-outlook
THE CENSORSHIP RESISTANCE FRONTIER
Future Outlook: The 24-Month Horizon
The next two years will define whether block construction becomes a permissioned service or a credibly neutral public good.
Permissioned block builders win unless PBS is forced. The economic reality of MEV extraction creates a natural monopoly for sophisticated searcher-builder firms. Without proposer-builder separation (PBS) enforced at the protocol layer, validators will outsource to the most profitable, centralized builders like Flashbots, Jito, and bloXroute.
Enshrined PBS is the only solution. Counter-intuitively, the path to decentralization requires protocol-level mandates, not market forces. Ethereum's enshrined PBS roadmap and Solana's Jito-driven evolution demonstrate that credible neutrality must be hard-coded to prevent validator-builder collusion and censorship vectors.
Cross-domain MEV complicates the landscape. The rise of intent-based architectures (UniswapX, CowSwap) and shared sequencers (Espresso, Astria) shifts censorship risk upstream. The battle for neutrality moves from the block builder to the intent solver network and cross-chain messaging layer (LayerZero, Axelar).
Evidence: Flashbots controls >80% of Ethereum's MEV-Boost relay market. Jito processes over 50% of Solana blocks. This concentration proves the market's failure to decentralize block construction organically.
takeaways
THE FUTURE OF CENSORSHIP RESISTANCE
Key Takeaways for CTOs & Architects
MEV centralization is the new attack vector. The builder market is the battleground for credible neutrality.
01
The Problem: Builder Centralization
A handful of builders like Flashbots, BloXroute, and Titan dominate block production, creating a single point of censorship failure. Regulatory pressure can be applied at this layer.
- >80% of Ethereum blocks are built by a few entities
- Creates a soft fork risk if builders collude
- Undermines the foundational promise of permissionless access
>80%
Builder Dominance
1
Critical Chokepoint
02
The Solution: Enshrined PBS & SUAVE
Protocol-level Proposer-Builder Separation (PBS) and shared sequencers like SUAVE decentralize the builder role itself. This moves the trust from off-chain cartels to on-chain, verifiable auctions.
- Ethereum's PBS roadmap aims to enshrine neutrality
- SUAVE creates a decentralized block building marketplace
- Forces competition on execution quality, not relationships
On-Chain
Verifiable Auctions
Multi-Chain
SUAVE Scope
03
The Hedge: Intent-Based Architectures
Bypass the builder problem entirely. Protocols like UniswapX, CowSwap, and Across let users express outcomes, not transactions. Solvers compete to fulfill the intent, abstracting away block construction.
- Removes transaction ordering as a vulnerability
- ~30% better prices via solver competition
- Future-proofs against any single layer's failure
~30%
Price Improvement
0
MEV Exposure
04
The Metric: Censorship Resistance Score
You can't manage what you don't measure. Architect a real-time dashboard tracking inclusion latency for OFAC-sanctioned addresses and transactions. Use relays like Ultra Sound, Aestus, and agnostic.
- Monitor inclusion delay for flagged addresses
- Track builder market share of censoring vs. non-censoring entities
- Set automated alerts for resistance degradation
<2s
Target Latency
100%
Required Uptime
05
The Fallback: Private Mempools & Encryption
When public mempools fail, encryption is the last line of defense. Shutter Network and threshold encryption schemes (like in EigenLayer) prevent frontrunning and ensure transaction privacy until block inclusion.
- 0 visibility for searchers/block builders
- Requires decentralized key management
- Adds ~100-200ms of latency overhead
0
Mempool Leaks
~150ms
Latency Cost
06
The Reality: Economic Incentives Win
Censorship is expensive. Design systems where bypassing censorship is more profitable than complying. This is the core thesis behind MEV burn, MEV smoothing, and proposer rewards for including censored tx.
- EIP-1559 burns base fee, reducing builder profit from exclusion
- Proposer rewards can be slashed for censorship
- Aligns validator economics with network health
EIP-1559
Burn Mechanism
Slashing
Enforcement Lever
ENQUIRY
Get In Touch
today.
Our experts will offer a free quote and a 30min call to discuss your project.
NDA Protected
Confidentiality24h Response
Time to ValueDirectly to Engineering Team
No Sales Fluff10+
Protocols Shipped
$20M+
TVL Overall