Research safe consensus finality parameters for mainnet chains

[nambrot]

Someone should give do a survey of safe finality parameters that stakeholders like developers and validators can use to consider transactions on a chain final.

[nambrot]

Competitor parameters:

• LayerZero https://layerzero.gitbook.io/docs/technical-reference/mainnet/default-config
• Nomad https://github.com/nomad-xyz/config/blob/main/production.json
• Wormhole (user specified) https://docs.wormholenetwork.com/wormhole/sending-messages/evm-on-chain-message (how would they slash?)
• Axelar ???

[nambrot]

Ethereum:

• Binance only does 2 confirmations for withdrawals https://www.binance.com/en/support/announcement/360030775291
• FTX does 10 for deposits and more for withdrawals https://help.ftx.us/hc/en-us/articles/360043065054-Crypto-Deposits-and-Withdrawals
• Coinbase does 35 confirmations https://help.coinbase.com/en/coinbase/getting-started/crypto-education/glossary/confirmations
• I would inclined to go with 20 which seems to be consensus

BSC:

• 15 as per https://github.com/abacus-network/abacus-monorepo/pull/671

Arbitrum:

• https://developer.offchainlabs.com/docs/tx_lifecycle
• https://developer.offchainlabs.com/docs/finality
• IIUC, Arbitrum runs in Sequencer mode and most RPCs that anyone has access to you trust either the sequencer, or the nodes interface to the sequencer for finality. Technically the "right" thing would be to observe the L2 tx data on L1, and wait confirmation there. It does not seem like that that is easily accessible or expressible. (Even then, you could argue its not actually finaly until the fraud period of a week is over) Thus my recommendation would be to go with instant finality with the understanding that one trusts the sequencer and RPC provider.
• 0 is thus value to recommend.

Avalanche:

• L0 specifies 12 blocks, Nomad 3. It's interesting that Avalanche is advertised as "fast" or "instant" finality, but always in terms of time, not in terms of blocks. It is fundamentally still probabilistic (https://docs.avax.network/overview/getting-started/avalanche-consensus#finality) and (https://docs.avax.network/quickstart/exchanges/integrate-exchange-with-avalanche#determining-finality), so Nomad's 3 is probably sufficient.

Celo:

• Celo is indeed instant finality via BFT, so 0 is the right value.

Optimism:

• Similarly to Arbitrum, you trust the sequencer and its eventual cryptoeconomic mechanism to keep it honest to consider your TX final. Technically, its not actually final until either 1) the sequencer has posted the tx data on ethereum or 2) the challenge period has elapsed. To be consistent with Arbitrum, I would suggest instant finality until it becomes more ergonomic to observe the tx data posted onto ethereum (and that tx's finality)

Polygon:

• Every 256 blocks, state gets written to ethereum, so 256 is the recommended period (even if its technically the number of blocks until checkpoint)

[tkporter]

I think we need to be wary of exchange confirmations (mostly thinking of Binance's move here, which feels extremely suspicious) because they have the ability to undo deposits or trades if a reorg does end up occurring

[nambrot]

Yeah I'm mostly trying to consider withdrawals which presumbly they can't undo

[tkporter]

Generally LGTM. I'm a bit surprised that LZ has gone with 20 for arbitrum / optimism and a higher value for Avalanche. Wondering if we should try to get in contact with the core devs at those chains for extra confirmation