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FOCIL: Restoring Ethereum’s Censorship Resistance

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Thomas Thiery

@soispoke

Robust Incentives Group, Ethereum Foundation

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ELI 5

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Validators

Builders

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ExecutionPayload

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Inclusion List 1

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Inclusion List 2

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FOCIL improves Ethereum’s censorship resistance by enabling multiple validators to ensure that any transaction valid under protocol rules is included in blocks.

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Beacon Block

FOCIL EIP-7805

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Step 1. Build and broadcast ILs

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Beacon Block

FOCIL EIP-7805

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Step 2. Include IL transactions in the block

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Beacon Block

FOCIL EIP-7805

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Step 3. Attesters enforce IL conditions are satisfied

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Beacon Block

FOCIL Properties ⚙️

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t = 0

Block

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Inclusion List

Slot N-1

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Payload

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IL txns

Same-slot

FOCIL provides real-time censorship resistance properties, with a one-out-of-N honesty assumption

One-out-of-N honesty assumption

Conditional

Block

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Anywhere-in-block

FOCIL is robust against MEV transactions crowding ILs

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💔

Centralized, Sophisticated�

2 builders build > 80% of all blocks

Geographically decentralized

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> 10,000 nodes

mevboost.pics, censorship.pics by Toni

Validators

Builders

Why it matters

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Benefits

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  • Improving censorship resistance of Ethereum�
  • Scaling Ethereum without imposing constraints on local block builders

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  • Improved user experience by reducing transaction inclusion time

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Beacon Block

Why now

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  • Builder market inherently centralized�
  • Observing how FOCIL behaves on mainnet allows us to make decisions on future protocol changes (e.g., Delayed Execution with zkVMs, APS)

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  • FOCIL needs to be included before we see significantly more censorship on the network

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Beacon Block

Technical Readiness

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Track progress on https://meetfocil.eth.limo/

  • Implemented by 5 client teams, successfully runs on a local devnet with Prysm, Lodestar, Teku, and Geth interoperability.

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  • 11 FOCIL breakout rooms�
  • ✅ Transaction invalidation, IL equivocation, consensus liveness, fork-choice related changes, commitment attacks�
  • Compatible with Account Abstraction, Delayed Execution, BALs, ePBS…

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https://meetfocil.eth.limo/

Thank you!