Specify how Fuel synchronizes with L1

[adlerjohn]

Leader Selection

Leader should be assigned for a slot: range of Ethereum blocks. (Maybe 10 minutes?) Happens entirely off-chain.

• fuel-bft should return leader given Fuel height, round, and validator set/voting power

1. If missed slot, increment round, and/or
2. If missed slot, next leader can submit missed block.

If there's a Commit, then don't re-org, instead submit later. If there's no Commit, then increment round.

Batch submission

If validator set hasn't changed by >1/3, then can submit a range of block with only a single Commit. (Have to look up exact details. https://arxiv.org/abs/2010.07031)

Deposits and valset updates

After some parameter (100 Ethereum blocks?) and Fuel block has Ethereum block number at least that, then deposit poofs into deposit set and can be spent.

How to sync Ethereum block number (and timestamp) in header

Suggestion: contract checks timestamp and block number is (non-strictly) monotonic and within some tolerance (some parameter).

Tolerance (checked by contract could just not check under honest majority assumption):

1. Timestamp can't be in the future at all.
2. Ethereum block number can't be in the future at all.
3. Timestamp must be within [some parameter >0 number of slots] of current Ethereum time.
4. Ethereum block number must be within [some parameter >0 number of slots] of current Ethereum block number.

[simonr0204]

If validator set hasn't changed by >1/3

I'm concerned about the gas cost of verifying this on ethereum.

[Voxelot]

Closing this for now, the approach has changed a lot since this was written.