Why the 'Censorship Resistance' of Your Rollup Is a Mirage

A single entity controls transaction ordering and inclusion. This creates a de facto censor.\n- State-level pressure can force the sequencer to blacklist addresses.\n- No forced inclusion for most rollups means censored users have no L1 escape hatch.\n- Real-world precedent: OFAC sanctions on Tornado Cash demonstrate this vector.

Theoretical 'escape to L1' mechanisms are often impractical or non-functional.\n- High latency & cost: Submitting a tx directly to L1 can take 7 days and cost 100x more.\n- Implementation gaps: Many rollups lack robust, user-friendly force inclusion.\n- Market reality: Protocols like Aave and Uniswap default to the sequencer's chain, not the L1.

Projects like Espresso, Astria, and Shared Sequencer networks are building alternatives.\n- Proof-of-Stake validator sets for ordering, similar to L1s.\n- MEV resistance via encrypted mempools or fair ordering.\n- Interoperability enables atomic cross-rollup composability, a key unlock for EigenLayer and AltLayer.

Even with a decentralized sequencer set, stake concentration and MEV create new attack vectors.\n- Staking cartels: Lido-like dominance can re-emerge, controlling the proposer set.\n- MEV extraction can bias ordering, censoring low-fee transactions.\n- Cost of entry: Running a sequencer node may require $1M+ in stake, limiting participation.

A single, centralized sequencer is a single point of failure. The operator can unilaterally halt block production or censor transactions, rendering the L2 unusable.\n- Arbitrum & Optimism initially launched with sole, centralized sequencers.\n- Transaction Finality depends entirely on a single entity's honesty and liveness.

Most rollups use upgradeable proxy contracts controlled by a multi-sig. This council can change any rule of the system without user consent.\n- Arbitrum's Security Council holds a 9-of-12 multi-sig over the core contracts.\n- This allows for code changes, fee extraction, or logic overrides at will, breaking immutability guarantees.

If a rollup posts its data to a centralized data availability (DA) layer, that provider can censor by withholding data. Validators cannot reconstruct the chain state, breaking withdrawals and security.\n- Ethereum is the only credibly neutral DA layer today.\n- Relying on a Celestia validator set or a Polygon Avail committee reintroduces trust assumptions.

In proof-based bridging (e.g., Optimistic Rollups), a centralized proponent can withhold state root updates to L1, freezing funds. While there is a challenge period, users cannot force a resolution.\n- Optimism's initial design had a single proposer.\n- This creates a 7-day liquidity freeze risk if the sole actor is malicious or offline.

Application access is mediated by RPC endpoints. If infrastructure providers like Alchemy or Infura censor access, dApps and wallets are blind. This is a replay of Ethereum's pre-merge client diversity issue.\n- Most dApps default to centralized RPCs for reliability.\n- Censorship at this layer is invisible to the core protocol but effective for users.

Centralized sequencers have perfect visibility into the mempool, enabling maximal value extraction. They can front-run, back-run, or sandwich user transactions without competition.\n- This creates a regulated, rent-seeking financial market controlled by one entity.\n- True resistance requires a decentralized sequencer set with fair ordering, like Espresso or Astria.

A single, centralized sequencer is a kill switch. It can front-run, reorder, or censor transactions at will. Decentralization is a roadmap promise, not a guarantee.

• Current State: >90% of major rollups use a single, centralized sequencer.
• Risk: The sequencer can be compelled by regulators to block addresses.
• Reality: Your 'L2 security' is irrelevant if the entry gate is controlled.

The bridge that posts data/state roots to L1 is a centralized proposer. If it stops, your rollup halts. If it's malicious, your state can be corrupted.

• Bottleneck: A single proposer key is a single point of failure.
• Example: Early Optimism had a 2-of-2 multisig for state roots.
• Solution Path: Requires decentralized validator sets, like Espresso or Astria.

Users and apps rely on centralized RPC endpoints (Alchemy, Infura, QuickNode). These gateways can filter transactions before they even reach the sequencer.

• Vector: Infrastructure providers comply with OFAC sanctions lists.
• Impact: Creates a 'soft censorship' layer invisible to the protocol.
• Mitigation: Requires self-hosted nodes or decentralized RPC networks like POKT.

Force-inclusion via L1 is the theoretical backstop. In practice, it's economically non-viable for users, creating a 'censorship tax'.

• Cost: A forced L1 transaction can cost $100+ vs. a $0.01 L2 tx.
• Delay: Requires a 7-day challenge window (Optimism) or similar.
• Result: A powerful deterrent that makes censorship resistance a premium feature.

Shared sequencers (Espresso, Astria) decentralize sequencing but create new systemic risks. You trade one central point for a cartel or a new, untested consensus layer.

• Risk: Replaces operator risk with consensus risk.
• Adoption: Still nascent; major rollups have not fully committed.
• Trade-off: Introduces latency and complexity for cross-rollup composability.

Using a centralized Data Availability (DA) layer like a single committee or an external chain (Celestia, EigenDA) moves the trust assumption. Censorship can occur by withholding data.

• Shifted Problem: You're now trusting the liveness of another system.
• Cost vs. Security: Cheaper DA often means weaker guarantees.
• Audit Question: Who ensures the DA layer's data is available and uncensored?