Hi @alcercu. Thank you for joining the fray.
It’s a nice idea actually, especially as a cut the knot kind of solution.
I like the fact that you are forcing the miner to use a seed that you can prove they have seen. They cannot propose their block without admitting they have seen the previous block.
The drawbacks are:
- that you have a 1 block lag which is disruptive to existing user layers (as you pointed out)
- it mitigates transaction ordering attacks, but not transaction censorship attacks as the miners still pick txs and can still add their own (sadly thats a big deal as it means they can perform statistical frontrunning attacks while preventing anyone else from doing so/protecting themselves against it)
- you will be randomizing an entire block rather than chunks within the block
On a related note, Alex may suffer from worse statistical frontrunning attacks than I realized because more txs than I thought will fail making it cheaper for an attacker.
Alex is way fairer than what we have now and mitigates a lot of MEV, but the problem is tx bloat.
Essentially with random ordering an attacker can give themselves a better chance of a good outcome by adding n txs.
However if another attacker does the same thing, they end up with no better chance and higher tx fees.
If a third (or more) attacker does the same thing, they all end up losing big.
If the would be victim also splits their tx into multiple txs they can protect themselves again.
So Alex fixes inequality, but at the cost of increasing the tx rate (by approx: extra tx count = arb value / failed tx cost)
I don’t think the community is ready for a solution which leads to this level of tx bloat, and I’m not sure I’d want to be responsible for it.
That’s what got me thinking about encrypted mempool/fair ordering variants of Alex.
What finally turned me off random ordering (for L1- it could still work on L2) was being shown this issue #21350 where Geth randomly ordered txs with the same gas price.
Apparently it led to tx bloat from backrunning attacks, so is quite a good real world proxy for the kind of issues random ordering systems may have.