Ethereum’s EIP-7917 Proposal
Ethereum developers Lin Oshitani (@linoscope) and Justin Drake (@JustinDrake) have jointly drafted the EIP-7917 proposal, titled Deterministic proposer lookahead, to address the uncertainty in the existing proposer election system.
> Excited to share EIP-7917 by me & @drakefjustin! It introduces deterministic proposer lookahead to the Beacon chain—a natural simplification that removes proposer unpredictability, which is crucial for preconfirmation protocols. Link to tweet
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> — Lin Oshitani (@linoscope) March 26, 2025
Currently, the Ethereum consensus mechanism selects a validator as the block proposer for each slot from an active set of validators using a random sampling algorithm based on random numbers (like RANDAO) and their effective balance. Although the RANDAO seed can be accessed in advance, the effective balance of validators may fluctuate over the epoch, making it hard to predict the proposer, which poses risks for on-chain applications that rely on the pre-confirmation protocol.
Excerpt of EIP 7917
EIP-7917 addresses the uncertainty in proposer arrangement caused by the dynamic changes in validator effective balance by pre-calculating and storing a deterministic proposer list at the start of each epoch. This approach enhances the security of the system, prevents validator manipulation, and simplifies on-chain protocol implementation while ensuring backward compatibility and scalability.
The authors have provided a rationale considering alternatives, stating: “An alternative approach would be to cache the effective balances at the start of epoch N to calculate the proposer lookahead at the beginning of epoch N+MIN_SEED_LOOKAHEAD. However, this would increase the burden on the beacon state and wouldn’t offer proposer lookahead to the EVM via the beacon root.”
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